修改ViewPager源码控制滑动响应范围
2018-04-24 本文已影响353人
贝贝beibei96
需求： 指定范围响应滑动切换Fragment（红色线toRightOf="parent"可以滑动， 其它范围不能滑动）
做Android的都知道ViewPager滑动的响应范围是一整个View的大小， 想要控制这个响应范围的话， 唯有修改源码， 不然就自定义一个ViewGroup
查看一下源码， ViewPager本来就是一个ViewGroup
public class ViewPager extends ViewGroup {
效果图如下：
修改ViewPager源码效果
1.Copy ViewPager的所有代码到自己的文件夹里面
必须包含ViewPager、 FragmentPagerAdapter、 PagerAdapter这三个类， 其中HomeVpAdapter忽略是我的适配器代码
ViewPager 源码结构
2.修改ViewPager类的源码
定义一些自定义属性
///////////////////////////////////WebbLin定义的属性///////////////////////////////////
/**
* 在上线前记得改为fase
*/
private static final boolean DEBUG = true;
/**
* 屏幕宽高
*/
private int screenWidth;
private int screenHeight;
/**
* 辅助线画笔
*/
private Paint mPaint;
/**
* 手指按下点的x坐标
*/
private float actionDownX;
/**
* 第一次进入第一个页面
*/
private boolean isFirstEnter = false;
/**
* 响应滑动的范围
*/
private int slidingRange = 50;
private ViewPager.onPageSelecting mOnPageSelecting;
public int getSlidingRange() {
return slidingRange;
}
public void setSlidingRange(int slidingRange) {
this.slidingRange = slidingRange;
}
public void setOnPageSelecting(onPageSelecting onPageSelecting) {
mOnPageSelecting = onPageSelecting;
}
自定义一个PagSelecting接口， 用于监听当前选中的页
public interface onPageSelecting {
/**
* 自定义Pag选择回调
*/
void onMyPageSelected(int position);
}
private void dispatchOnPageSelected(int position)方法
private void dispatchOnPageSelected(int position) {
if (mOnPageSelecting != null) {
mOnPageSelecting.onMyPageSelected(position);
}
}
在onDraw()方法里面画一条辅助线
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (DEBUG) {
// 辅助线
canvas.drawLine(screenWidth - slidingRange, 0, screenWidth - slidingRange, screenHeight, mPaint);
}
......
}
最核心最核心的就是修改onTouchEvent方法， 因为代码太多， 我直接贴上源码
package cn.startrails.webblintestdemo.homemodule.viewpager;
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.SystemClock;
import android.support.annotation.CallSuper;
import android.support.annotation.DrawableRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.AbsSavedState;
import android.support.v4.view.AccessibilityDelegateCompat;
import android.support.v4.view.PagerTitleStrip;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.WindowInsetsCompat;
import android.support.v4.view.accessibility.AccessibilityEventCompat;
import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.FocusFinder;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.animation.Interpolator;
import android.widget.EdgeEffect;
import android.widget.Scroller;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Layout manager that allows the user to flip left and right
* through pages of data. You supply an implementation of a
* {@link PagerAdapter} to generate the pages that the view shows.
* <p>
* <p>ViewPager is most often used in conjunction with {@link android.app.Fragment},
* which is a convenient way to supply and manage the lifecycle of each page.
* There are standard adapters implemented for using fragments with the ViewPager,
* which cover the most common use cases. These are
* {@link android.support.v4.app.FragmentPagerAdapter} and
* {@link android.support.v4.app.FragmentStatePagerAdapter}; each of these
* classes have simple code showing how to build a full user interface
* with them.
* <p>
* <p>Views which are annotated with the {@link ViewPager.DecorView} annotation are treated as
* part of the view pagers 'decor'. Each decor view's position can be controlled via
* its {@code android:layout_gravity} attribute. For example:
* <p>
* <pre>
* <android.support.v4.view.ViewPager
* android:layout_width="match_parent"
* android:layout_height="match_parent">
*
* <android.support.v4.view.PagerTitleStrip
* android:layout_width="match_parent"
* android:layout_height="wrap_content"
* android:layout_gravity="top" />
*
* </android.support.v4.view.ViewPager>
* </pre>
* <p>
* <p>For more information about how to use ViewPager, read <a
* href="{@docRoot}training/implementing-navigation/lateral.html">Creating Swipe Views with
* Tabs</a>.</p>
* <p>
* <p>You can find examples of using ViewPager in the API 4+ Support Demos and API 13+ Support Demos
* sample code.
*
* @author Ai（陈祥林）
* @date 2018/1/27 15:11
* @email Webb@starcc.cc
*/
public class ViewPager extends ViewGroup {
private static final String TAG = "ViewPager";
private static final boolean DEBUG = true;
private static final boolean USE_CACHE = false;
private static final int DEFAULT_OFFSCREEN_PAGES = 1;
/**
* ms
*/
private static final int MAX_SETTLE_DURATION = 600;
/**
* dips
*/
private static final int MIN_DISTANCE_FOR_FLING = 25;
/**
* dips
*/
private static final int DEFAULT_GUTTER_SIZE = 16;
/**
* dips
*/
private static final int MIN_FLING_VELOCITY = 400;
static final int[] LAYOUT_ATTRS = new int[]{
android.R.attr.layout_gravity
};
/**
* Used to track what the expected number of items in the adapter should be.
* If the app changes this when we don't expect it, we'll throw a big obnoxious exception.
*/
private int mExpectedAdapterCount;
static class ItemInfo {
Object object;
int position;
boolean scrolling;
float widthFactor;
float offset;
}
private static final Comparator<ItemInfo> COMPARATOR = (lhs, rhs) -> lhs.position - rhs.position;
private static final Interpolator S_INTERPOLATOR = t -> {
t -= 1.0f;
return t * t * t * t * t + 1.0f;
};
private final ArrayList<ItemInfo> mItems = new ArrayList<>();
private final ViewPager.ItemInfo mTempItem = new ViewPager.ItemInfo();
private final Rect mTempRect = new Rect();
PagerAdapter mAdapter;
/**
* Index of currently displayed page.
*/
int mCurItem;
private int mRestoredCurItem = -1;
private Parcelable mRestoredAdapterState = null;
private ClassLoader mRestoredClassLoader = null;
private Scroller mScroller;
private boolean mIsScrollStarted;
private ViewPager.PagerObserver mObserver;
private int mPageMargin;
private Drawable mMarginDrawable;
private int mTopPageBounds;
private int mBottomPageBounds;
/**
* Offsets of the first and last items, if known.
* Set during population, used to determine if we are at the beginning
* or end of the pager data set during touch scrolling.
*/
private float mFirstOffset = -Float.MAX_VALUE;
private float mLastOffset = Float.MAX_VALUE;
private int mChildWidthMeasureSpec;
private int mChildHeightMeasureSpec;
private boolean mInLayout;
private boolean mScrollingCacheEnabled;
private boolean mPopulatePending;
private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;
private boolean mIsBeingDragged;
private boolean mIsUnableToDrag;
private int mDefaultGutterSize;
private int mGutterSize;
private int mTouchSlop;
/**
* 最后一个运动事件的位置
* Position of the last motion event.
*/
private float mLastMotionX;
private float mLastMotionY;
private float mInitialMotionX;
private float mInitialMotionY;
/**
* 活跃的ID指针。这是用来保持一致性在拖/将如果使用多个指针。
* ID of the active pointer. This is used to retain consistency during
* drags/flings if multiple pointers are used.
*/
private int mActivePointerId = INVALID_POINTER;
/**
* Sentinel value for no current active pointer.
* Used by {@link #mActivePointerId}.
*/
private static final int INVALID_POINTER = -1;
/**
* Determines speed during touch scrolling
*/
private VelocityTracker mVelocityTracker;
private int mMinimumVelocity;
private int mMaximumVelocity;
private int mFlingDistance;
private int mCloseEnough;
/*
* If the pager is at least this close to its final position, complete the scroll
* on touch down and let the user interact with the content inside instead of
* "catching" the flinging pager.
*/
/**
* dp
*/
private static final int CLOSE_ENOUGH = 2;
private boolean mFakeDragging;
private long mFakeDragBeginTime;
private EdgeEffect mLeftEdge;
private EdgeEffect mRightEdge;
private boolean mFirstLayout = true;
private boolean mNeedCalculatePageOffsets = false;
private boolean mCalledSuper;
private int mDecorChildCount;
private List<OnPageChangeListener> mOnPageChangeListeners;
private ViewPager.OnPageChangeListener mOnPageChangeListener;
private ViewPager.onPageSelecting mOnPageSelecting;
private ViewPager.OnPageChangeListener mInternalPageChangeListener;
private List<OnAdapterChangeListener> mAdapterChangeListeners;
private ViewPager.PageTransformer mPageTransformer;
private int mPageTransformerLayerType;
private static final int DRAW_ORDER_DEFAULT = 0;
private static final int DRAW_ORDER_FORWARD = 1;
private static final int DRAW_ORDER_REVERSE = 2;
private int mDrawingOrder;
private ArrayList<View> mDrawingOrderedChildren;
private static final ViewPager.ViewPositionComparator S_POSITION_COMPARATOR = new ViewPager.ViewPositionComparator();
/**
* Indicates that the pager is in an idle, settled state. The current page
* is fully in view and no animation is in progress.
*/
public static final int SCROLL_STATE_IDLE = 0;
/**
* Indicates that the pager is currently being dragged by the user.
*/
public static final int SCROLL_STATE_DRAGGING = 1;
/**
* Indicates that the pager is in the process of settling to a final position.
*/
public static final int SCROLL_STATE_SETTLING = 2;
private final Runnable mEndScrollRunnable = () -> {
setScrollState(SCROLL_STATE_IDLE);
populate();
};
private int mScrollState = SCROLL_STATE_IDLE;
///////////////////////////////////WebbLin定义的属性///////////////////////////////////
/**
* 屏幕宽高
*/
private int screenWidth;
private int screenHeight;
/**
* 辅助线画笔
*/
private Paint mPaint;
/**
* 手指按下点的x坐标
*/
private float actionDownX;
/**
* 第一次进入第一个页面
*/
private boolean isFirstEnter = false;
/**
* 响应滑动的范围
*/
private int slidingRange = 50;
public int getSlidingRange() {
return slidingRange;
}
public void setSlidingRange(int slidingRange) {
this.slidingRange = slidingRange;
}
public interface onPageSelecting {
/**
* 自定义Pag选择回调
*/
void onMyPageSelected(int position);
}
/**
* Callback interface for responding to changing state of the selected page.
*/
public interface OnPageChangeListener {
/**
* This method will be invoked when the current page is scrolled, either as part
* of a programmatically initiated smooth scroll or a user initiated touch scroll.
*
* @param position Position index of the first page currently being displayed.
* Page position+1 will be visible if positionOffset is nonzero.
* @param positionOffset Value from [0, 1) indicating the offset from the page at position.
* @param positionOffsetPixels Value in pixels indicating the offset from position.
*/
void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);
/**
* This method will be invoked when a new page becomes selected. Animation is not
* necessarily complete.
*
* @param position Position index of the new selected page.
*/
void onPageSelected(int position);
/**
* Called when the scroll state changes. Useful for discovering when the user
* begins dragging, when the pager is automatically settling to the current page,
* or when it is fully stopped/idle.
*
* @param state The new scroll state.
* @see ViewPager#SCROLL_STATE_IDLE
* @see ViewPager#SCROLL_STATE_DRAGGING
* @see ViewPager#SCROLL_STATE_SETTLING
*/
void onPageScrollStateChanged(int state);
}
/**
* Simple implementation of the {@link ViewPager.OnPageChangeListener} interface with stub
* implementations of each method. Extend this if you do not intend to override
* every method of {@link ViewPager.OnPageChangeListener}.
*/
public static class SimpleOnPageChangeListener implements ViewPager.OnPageChangeListener {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// This space for rent
}
@Override
public void onPageSelected(int position) {
// This space for rent
}
@Override
public void onPageScrollStateChanged(int state) {
// This space for rent
}
}
/**
* A PageTransformer is invoked whenever a visible/attached page is scrolled.
* This offers an opportunity for the application to apply a custom transformation
* to the page views using animation properties.
* <p>
* <p>As property animation is only supported as of Android 3.0 and forward,
* setting a PageTransformer on a ViewPager on earlier platform versions will
* be ignored.</p>
*/
public interface PageTransformer {
/**
* Apply a property transformation to the given page.
*
* @param page Apply the transformation to this page
* @param position Position of page relative to the current front-and-center
* position of the pager. 0 is front and center. 1 is one full
* page position to the right, and -1 is one page position to the left.
*/
void transformPage(@NonNull View page, float position);
}
/**
* Callback interface for responding to adapter changes.
*/
public interface OnAdapterChangeListener {
/**
* Called when the adapter for the given view pager has changed.
*
* @param viewPager ViewPager where the adapter change has happened
* @param oldAdapter the previously set adapter
* @param newAdapter the newly set adapter
*/
void onAdapterChanged(@NonNull ViewPager viewPager,
@Nullable PagerAdapter oldAdapter, @Nullable PagerAdapter newAdapter);
}
/**
* Annotation which allows marking of views to be decoration views when added to a view
* pager.
* <p>
* <p>Views marked with this annotation can be added to the view pager with a layout resource.
* An example being {@link PagerTitleStrip}.</p>
* <p>
* <p>You can also control whether a view is a decor view but setting
* {@link ViewPager.LayoutParams#isDecor} on the child's layout params.</p>
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Inherited
public @interface DecorView {
}
public ViewPager(@NonNull Context context) {
super(context);
initViewPager();
initPaint();
}
public ViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
initViewPager();
initPaint();
}
private void initPaint() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(8);
}
void initViewPager() {
setWillNotDraw(false);
setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
setFocusable(true);
final Context context = getContext();
mScroller = new Scroller(context, S_INTERPOLATOR);
final ViewConfiguration configuration = ViewConfiguration.get(context);
final float density = context.getResources().getDisplayMetrics().density;
mTouchSlop = configuration.getScaledPagingTouchSlop();
mMinimumVelocity = (int) (MIN_FLING_VELOCITY * density);
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
mLeftEdge = new EdgeEffect(context);
mRightEdge = new EdgeEffect(context);
mFlingDistance = (int) (MIN_DISTANCE_FOR_FLING * density);
mCloseEnough = (int) (CLOSE_ENOUGH * density);
mDefaultGutterSize = (int) (DEFAULT_GUTTER_SIZE * density);
ViewCompat.setAccessibilityDelegate(this, new ViewPager.MyAccessibilityDelegate());
if (ViewCompat.getImportantForAccessibility(this)
== ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
ViewCompat.setImportantForAccessibility(this,
ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
ViewCompat.setOnApplyWindowInsetsListener(this,
new android.support.v4.view.OnApplyWindowInsetsListener() {
private final Rect mTempRect = new Rect();
@Override
public WindowInsetsCompat onApplyWindowInsets(final View v,
final WindowInsetsCompat originalInsets) {
// First let the ViewPager itself try and consume them...
final WindowInsetsCompat applied =
ViewCompat.onApplyWindowInsets(v, originalInsets);
if (applied.isConsumed()) {
// If the ViewPager consumed all insets, return now
return applied;
}
// Now we'll manually dispatch the insets to our children. Since ViewPager
// children are always full-height, we do not want to use the standard
// ViewGroup dispatchApplyWindowInsets since if child 0 consumes them,
// the rest of the children will not receive any insets. To workaround this
// we manually dispatch the applied insets, not allowing children to
// consume them from each other. We do however keep track of any insets
// which are consumed, returning the union of our children's consumption
final Rect res = mTempRect;
res.left = applied.getSystemWindowInsetLeft();
res.top = applied.getSystemWindowInsetTop();
res.right = applied.getSystemWindowInsetRight();
res.bottom = applied.getSystemWindowInsetBottom();
for (int i = 0, count = getChildCount(); i < count; i++) {
final WindowInsetsCompat childInsets = ViewCompat
.dispatchApplyWindowInsets(getChildAt(i), applied);
// Now keep track of any consumed by tracking each dimension's min
// value
res.left = Math.min(childInsets.getSystemWindowInsetLeft(),
res.left);
res.top = Math.min(childInsets.getSystemWindowInsetTop(),
res.top);
res.right = Math.min(childInsets.getSystemWindowInsetRight(),
res.right);
res.bottom = Math.min(childInsets.getSystemWindowInsetBottom(),
res.bottom);
}
// Now return a new WindowInsets, using the consumed window insets
return applied.replaceSystemWindowInsets(
res.left, res.top, res.right, res.bottom);
}
});
}
@Override
protected void onDetachedFromWindow() {
removeCallbacks(mEndScrollRunnable);
// To be on the safe side, abort the scroller
if ((mScroller != null) && !mScroller.isFinished()) {
mScroller.abortAnimation();
}
super.onDetachedFromWindow();
}
void setScrollState(int newState) {
if (mScrollState == newState) {
return;
}
mScrollState = newState;
if (mPageTransformer != null) {
// PageTransformers can do complex things that benefit from hardware layers.
enableLayers(newState != SCROLL_STATE_IDLE);
}
dispatchOnScrollStateChanged(newState);
}
/**
* Set a PagerAdapter that will supply views for this pager as needed.
*
* @param adapter Adapter to use
*/
public void setAdapter(@Nullable PagerAdapter adapter) {
if (mAdapter != null) {
mAdapter.setViewPagerObserver(null);
mAdapter.startUpdate(this);
for (int i = 0; i < mItems.size(); i++) {
final ViewPager.ItemInfo ii = mItems.get(i);
mAdapter.destroyItem(this, ii.position, ii.object);
}
mAdapter.finishUpdate(this);
mItems.clear();
removeNonDecorViews();
mCurItem = 0;
scrollTo(0, 0);
}
final PagerAdapter oldAdapter = mAdapter;
mAdapter = adapter;
mExpectedAdapterCount = 0;
if (mAdapter != null) {
if (mObserver == null) {
mObserver = new ViewPager.PagerObserver();
}
mAdapter.setViewPagerObserver(mObserver);
mPopulatePending = false;
final boolean wasFirstLayout = mFirstLayout;
mFirstLayout = true;
mExpectedAdapterCount = mAdapter.getCount();
if (mRestoredCurItem >= 0) {
mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);
setCurrentItemInternal(mRestoredCurItem, false, true);
mRestoredCurItem = -1;
mRestoredAdapterState = null;
mRestoredClassLoader = null;
} else if (!wasFirstLayout) {
populate();
} else {
requestLayout();
}
}
// Dispatch the change to any listeners
if (mAdapterChangeListeners != null && !mAdapterChangeListeners.isEmpty()) {
for (int i = 0, count = mAdapterChangeListeners.size(); i < count; i++) {
mAdapterChangeListeners.get(i).onAdapterChanged(this, oldAdapter, adapter);
}
}
}
private void removeNonDecorViews() {
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (!lp.isDecor) {
removeViewAt(i);
i--;
}
}
}
/**
* Retrieve the current adapter supplying pages.
*
* @return The currently registered PagerAdapter
*/
@Nullable
public PagerAdapter getAdapter() {
return mAdapter;
}
/**
* Add a listener that will be invoked whenever the adapter for this ViewPager changes.
*
* @param listener listener to add
*/
public void addOnAdapterChangeListener(@NonNull ViewPager.OnAdapterChangeListener listener) {
if (mAdapterChangeListeners == null) {
mAdapterChangeListeners = new ArrayList<>();
}
mAdapterChangeListeners.add(listener);
}
/**
* Remove a listener that was previously added via
* {@link #addOnAdapterChangeListener(ViewPager.OnAdapterChangeListener)}.
*
* @param listener listener to remove
*/
public void removeOnAdapterChangeListener(@NonNull ViewPager.OnAdapterChangeListener listener) {
if (mAdapterChangeListeners != null) {
mAdapterChangeListeners.remove(listener);
}
}
private int getClientWidth() {
return getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
}
/**
* Set the currently selected page. If the ViewPager has already been through its first
* layout with its current adapter there will be a smooth animated transition between
* the current item and the specified item.
*
* @param item Item index to select
*/
public void setCurrentItem(int item) {
mPopulatePending = false;
setCurrentItemInternal(item, !mFirstLayout, false);
}
/**
* Set the currently selected page.
*
* @param item Item index to select
* @param smoothScroll True to smoothly scroll to the new item, false to transition immediately
*/
public void setCurrentItem(int item, boolean smoothScroll) {
mPopulatePending = false;
setCurrentItemInternal(item, smoothScroll, false);
}
public int getCurrentItem() {
return mCurItem;
}
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
setCurrentItemInternal(item, smoothScroll, always, 0);
}
/**
* 实现页面切换，切换到哪个页面时由determineTargetPage(....)返回的值决定
*
* @param item i
* @param smoothScroll s
* @param always a
* @param velocity v
*/
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always, int velocity) {
if (mAdapter == null || mAdapter.getCount() <= 0) {
setScrollingCacheEnabled(false);
return;
}
if (!always && mCurItem == item && mItems.size() != 0) {
setScrollingCacheEnabled(false);
return;
}
if (item < 0) {
item = 0;
} else if (item >= mAdapter.getCount()) {
item = mAdapter.getCount() - 1;
}
final int pageLimit = mOffscreenPageLimit;
if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {
// We are doing a jump by more than one page. To avoid
// glitches, we want to keep all current pages in the view
// until the scroll ends.
for (int i = 0; i < mItems.size(); i++) {
mItems.get(i).scrolling = true;
}
}
final boolean dispatchSelected = mCurItem != item;
if (mFirstLayout) {
// We don't have any idea how big we are yet and shouldn't have any pages either.
// Just set things up and let the pending layout handle things.
mCurItem = item;
if (dispatchSelected) {
dispatchOnPageSelected(item);
}
requestLayout();
} else {
populate(item);
scrollToItem(item, smoothScroll, velocity, dispatchSelected);
}
if (item != 0) {
isFirstEnter = true;
}
if (item == 0) {
isFirstEnter = false;
}
}
private void scrollToItem(int item, boolean smoothScroll, int velocity,
boolean dispatchSelected) {
final ViewPager.ItemInfo curInfo = infoForPosition(item);
int destX = 0;
if (curInfo != null) {
final int width = getClientWidth();
destX = (int) (width * Math.max(mFirstOffset,
Math.min(curInfo.offset, mLastOffset)));
}
if (smoothScroll) {
smoothScrollTo(destX, 0, velocity);
if (dispatchSelected) {
dispatchOnPageSelected(item);
}
} else {
if (dispatchSelected) {
dispatchOnPageSelected(item);
}
completeScroll(false);
scrollTo(destX, 0);
pageScrolled(destX);
}
}
/**
* Set a listener that will be invoked whenever the page changes or is incrementally
* scrolled. See {@link ViewPager.OnPageChangeListener}.
*
* @param listener Listener to set
* @deprecated Use {@link #addOnPageChangeListener(ViewPager.OnPageChangeListener)}
* and {@link #removeOnPageChangeListener(ViewPager.OnPageChangeListener)} instead.
*/
@Deprecated
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
mOnPageChangeListener = listener;
}
public void setOnPageSelecting(onPageSelecting onPageSelecting) {
mOnPageSelecting = onPageSelecting;
}
/**
* Add a listener that will be invoked whenever the page changes or is incrementally
* scrolled. See {@link ViewPager.OnPageChangeListener}.
* <p>
* <p>Components that add a listener should take care to remove it when finished.
* Other components that take ownership of a view may call {@link #clearOnPageChangeListeners()}
* to remove all attached listeners.</p>
*
* @param listener listener to add
*/
public void addOnPageChangeListener(@NonNull ViewPager.OnPageChangeListener listener) {
if (mOnPageChangeListeners == null) {
mOnPageChangeListeners = new ArrayList<>();
}
mOnPageChangeListeners.add(listener);
}
/**
* Remove a listener that was previously added via
* {@link #addOnPageChangeListener(ViewPager.OnPageChangeListener)}.
*
* @param listener listener to remove
*/
public void removeOnPageChangeListener(@NonNull ViewPager.OnPageChangeListener listener) {
if (mOnPageChangeListeners != null) {
mOnPageChangeListeners.remove(listener);
}
}
/**
* Remove all listeners that are notified of any changes in scroll state or position.
*/
public void clearOnPageChangeListeners() {
if (mOnPageChangeListeners != null) {
mOnPageChangeListeners.clear();
}
}
/**
* Sets a {@link ViewPager.PageTransformer} that will be called for each attached page whenever
* the scroll position is changed. This allows the application to apply custom property
* transformations to each page, overriding the default sliding behavior.
* <p>
* <p><em>Note:</em> By default, calling this method will cause contained pages to use
* {@link View#LAYER_TYPE_HARDWARE}. This layer type allows custom alpha transformations,
* but it will cause issues if any of your pages contain a {@link android.view.SurfaceView}
* and you have not called {@link android.view.SurfaceView#setZOrderOnTop(boolean)} to put that
* {@link android.view.SurfaceView} above your app content. To disable this behavior, call
* {@link #setPageTransformer(boolean, ViewPager.PageTransformer, int)} and pass
* {@link View#LAYER_TYPE_NONE} for {@code pageLayerType}.</p>
*
* @param reverseDrawingOrder true if the supplied PageTransformer requires page views
* to be drawn from last to first instead of first to last.
* @param transformer PageTransformer that will modify each page's animation properties
*/
public void setPageTransformer(boolean reverseDrawingOrder,
@Nullable ViewPager.PageTransformer transformer) {
setPageTransformer(reverseDrawingOrder, transformer, View.LAYER_TYPE_HARDWARE);
}
/**
* Sets a {@link android.support.v4.view.ViewPager.PageTransformer} that will be called for each attached page whenever
* the scroll position is changed. This allows the application to apply custom property
* transformations to each page, overriding the default sliding behavior.
*
* @param reverseDrawingOrder true if the supplied PageTransformer requires page views
* to be drawn from last to first instead of first to last.
* @param transformer PageTransformer that will modify each page's animation properties
* @param pageLayerType View layer type that should be used for ViewPager pages. It should be
* either {@link View#LAYER_TYPE_HARDWARE},
* {@link View#LAYER_TYPE_SOFTWARE}, or
* {@link View#LAYER_TYPE_NONE}.
*/
public void setPageTransformer(boolean reverseDrawingOrder,
@Nullable ViewPager.PageTransformer transformer, int pageLayerType) {
final boolean hasTransformer = transformer != null;
final boolean needsPopulate = hasTransformer != (mPageTransformer != null);
mPageTransformer = transformer;
setChildrenDrawingOrderEnabled(hasTransformer);
if (hasTransformer) {
mDrawingOrder = reverseDrawingOrder ? DRAW_ORDER_REVERSE : DRAW_ORDER_FORWARD;
mPageTransformerLayerType = pageLayerType;
} else {
mDrawingOrder = DRAW_ORDER_DEFAULT;
}
if (needsPopulate) {
populate();
}
}
@Override
protected int getChildDrawingOrder(int childCount, int i) {
final int index = mDrawingOrder == DRAW_ORDER_REVERSE ? childCount - 1 - i : i;
return ((LayoutParams) mDrawingOrderedChildren.get(index).getLayoutParams()).childIndex;
}
/**
* Set a separate OnPageChangeListener for internal use by the support library.
*
* @param listener Listener to set
* @return The old listener that was set, if any.
*/
ViewPager.OnPageChangeListener setInternalPageChangeListener(ViewPager.OnPageChangeListener listener) {
ViewPager.OnPageChangeListener oldListener = mInternalPageChangeListener;
mInternalPageChangeListener = listener;
return oldListener;
}
/**
* Returns the number of pages that will be retained to either side of the
* current page in the view hierarchy in an idle state. Defaults to 1.
*
* @return How many pages will be kept offscreen on either side
* @see #setOffscreenPageLimit(int)
*/
public int getOffscreenPageLimit() {
return mOffscreenPageLimit;
}
/**
* Set the number of pages that should be retained to either side of the
* current page in the view hierarchy in an idle state. Pages beyond this
* limit will be recreated from the adapter when needed.
* <p>
* <p>This is offered as an optimization. If you know in advance the number
* of pages you will need to support or have lazy-loading mechanisms in place
* on your pages, tweaking this setting can have benefits in perceived smoothness
* of paging animations and interaction. If you have a small number of pages (3-4)
* that you can keep active all at once, less time will be spent in layout for
* newly created view subtrees as the user pages back and forth.</p>
* <p>
* <p>You should keep this limit low, especially if your pages have complex layouts.
* This setting defaults to 1.</p>
*
* @param limit How many pages will be kept offscreen in an idle state.
*/
public void setOffscreenPageLimit(int limit) {
if (limit < DEFAULT_OFFSCREEN_PAGES) {
Log.w(TAG, "Requested offscreen page limit " + limit + " too small; defaulting to "
+ DEFAULT_OFFSCREEN_PAGES);
limit = DEFAULT_OFFSCREEN_PAGES;
}
if (limit != mOffscreenPageLimit) {
mOffscreenPageLimit = limit;
populate();
}
}
/**
* 设置页面之间的差距
* Set the margin between pages.
*
* @param marginPixels Distance between adjacent pages in pixels
* @see #getPageMargin()
* @see #setPageMarginDrawable(Drawable)
* @see #setPageMarginDrawable(int)
*/
public void setPageMargin(int marginPixels) {
final int oldMargin = mPageMargin;
mPageMargin = marginPixels;
final int width = getWidth();
recomputeScrollPosition(width, width, marginPixels, oldMargin);
requestLayout();
}
/**
* Return the margin between pages.
*
* @return The size of the margin in pixels
*/
public int getPageMargin() {
return mPageMargin;
}
/**
* Set a drawable that will be used to fill the margin between pages.
*
* @param d Drawable to display between pages
*/
public void setPageMarginDrawable(@Nullable Drawable d) {
mMarginDrawable = d;
if (d != null) {
refreshDrawableState();
}
setWillNotDraw(d == null);
invalidate();
}
/**
* Set a drawable that will be used to fill the margin between pages.
*
* @param resId Resource ID of a drawable to display between pages
*/
public void setPageMarginDrawable(@DrawableRes int resId) {
setPageMarginDrawable(ContextCompat.getDrawable(getContext(), resId));
}
@Override
protected boolean verifyDrawable(@NonNull Drawable who) {
return super.verifyDrawable(who) || who == mMarginDrawable;
}
@Override
protected void drawableStateChanged() {
super.drawableStateChanged();
final Drawable d = mMarginDrawable;
if (d != null && d.isStateful()) {
d.setState(getDrawableState());
}
}
/**
* We want the duration of the page snap animation to be influenced by the distance that
* the screen has to travel, however, we don't want this duration to be effected in a
* purely linear fashion. Instead, we use this method to moderate the effect that the distance
* of travel has on the overall snap duration.
*/
float distanceInfluenceForSnapDuration(float f) {
// center the values about 0.
f -= 0.5f;
f *= 0.3f * (float) Math.PI / 2.0f;
return (float) Math.sin(f);
}
/**
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param x the number of pixels to scroll by on the X axis
* @param y the number of pixels to scroll by on the Y axis
*/
void smoothScrollTo(int x, int y) {
smoothScrollTo(x, y, 0);
}
/**
* 平滑滚动到
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param x the number of pixels to scroll by on the X axis
* @param y the number of pixels to scroll by on the Y axis
* @param velocity the velocity associated with a fling, if applicable. (0 otherwise)
*/
void smoothScrollTo(int x, int y, int velocity) {
if (getChildCount() == 0) {
// Nothing to do.
setScrollingCacheEnabled(false);
return;
}
int sx;
boolean wasScrolling = (mScroller != null) && !mScroller.isFinished();
if (wasScrolling) {
// We're in the middle of a previously initiated scrolling. Check to see
// whether that scrolling has actually started (if we always call getStartX
// we can get a stale value from the scroller if it hadn't yet had its first
// computeScrollOffset call) to decide what is the current scrolling position.
sx = mIsScrollStarted ? mScroller.getCurrX() : mScroller.getStartX();
// And abort the current scrolling.
mScroller.abortAnimation();
setScrollingCacheEnabled(false);
} else {
sx = getScrollX();
}
int sy = getScrollY();
int dx = x - sx;
int dy = y - sy;
if (dx == 0 && dy == 0) {
completeScroll(false);
populate();
setScrollState(SCROLL_STATE_IDLE);
return;
}
setScrollingCacheEnabled(true);
setScrollState(SCROLL_STATE_SETTLING);
final int width = getClientWidth();
final int halfWidth = width / 2;
final float distanceRatio = Math.min(1f, 1.0f * Math.abs(dx) / width);
final float distance = halfWidth + halfWidth
* distanceInfluenceForSnapDuration(distanceRatio);
int duration;
velocity = Math.abs(velocity);
if (velocity > 0) {
duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
} else {
final float pageWidth = width * mAdapter.getPageWidth(mCurItem);
final float pageDelta = (float) Math.abs(dx) / (pageWidth + mPageMargin);
duration = (int) ((pageDelta + 1) * 100);
}
duration = Math.min(duration, MAX_SETTLE_DURATION);
// Reset the "scroll started" flag. It will be flipped to true in all places
// where we call computeScrollOffset().
mIsScrollStarted = false;
mScroller.startScroll(sx, sy, dx, dy, duration);
ViewCompat.postInvalidateOnAnimation(this);
}
ViewPager.ItemInfo addNewItem(int position, int index) {
ViewPager.ItemInfo ii = new ViewPager.ItemInfo();
ii.position = position;
ii.object = mAdapter.instantiateItem(this, position);
ii.widthFactor = mAdapter.getPageWidth(position);
if (index < 0 || index >= mItems.size()) {
mItems.add(ii);
} else {
mItems.add(index, ii);
}
return ii;
}
/**
* 数据集变化
*/
void dataSetChanged() {
// This method only gets called if our observer is attached, so mAdapter is non-null.
final int adapterCount = mAdapter.getCount();
mExpectedAdapterCount = adapterCount;
boolean needPopulate = mItems.size() < mOffscreenPageLimit * 2 + 1
&& mItems.size() < adapterCount;
int newCurrItem = mCurItem;
boolean isUpdating = false;
for (int i = 0; i < mItems.size(); i++) {
final ViewPager.ItemInfo ii = mItems.get(i);
final int newPos = mAdapter.getItemPosition(ii.object);
if (newPos == PagerAdapter.POSITION_UNCHANGED) {
continue;
}
if (newPos == PagerAdapter.POSITION_NONE) {
mItems.remove(i);
i--;
if (!isUpdating) {
mAdapter.startUpdate(this);
isUpdating = true;
}
mAdapter.destroyItem(this, ii.position, ii.object);
needPopulate = true;
if (mCurItem == ii.position) {
// Keep the current item in the valid range
newCurrItem = Math.max(0, Math.min(mCurItem, adapterCount - 1));
needPopulate = true;
}
continue;
}
if (ii.position != newPos) {
if (ii.position == mCurItem) {
// Our current item changed position. Follow it.
newCurrItem = newPos;
}
ii.position = newPos;
needPopulate = true;
}
}
if (isUpdating) {
mAdapter.finishUpdate(this);
}
Collections.sort(mItems, COMPARATOR);
if (needPopulate) {
// Reset our known page widths; populate will recompute them.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (!lp.isDecor) {
lp.widthFactor = 0.f;
}
}
setCurrentItemInternal(newCurrItem, false, true);
requestLayout();
}
}
void populate() {
populate(mCurItem);
}
void populate(int newCurrentItem) {
ViewPager.ItemInfo oldCurInfo = null;
if (mCurItem != newCurrentItem) {
oldCurInfo = infoForPosition(mCurItem);
mCurItem = newCurrentItem;
}
if (mAdapter == null) {
sortChildDrawingOrder();
return;
}
// Bail now if we are waiting to populate. This is to hold off
// on creating views from the time the user releases their finger to
// fling to a new position until we have finished the scroll to
// that position, avoiding glitches from happening at that point.
if (mPopulatePending) {
if (DEBUG) {
Log.i(TAG, "populate is pending, skipping for now...");
}
sortChildDrawingOrder();
return;
}
// Also, don't populate until we are attached to a window. This is to
// avoid trying to populate before we have restored our view hierarchy
// state and conflicting with what is restored.
if (getWindowToken() == null) {
return;
}
mAdapter.startUpdate(this);
final int pageLimit = mOffscreenPageLimit;
final int startPos = Math.max(0, mCurItem - pageLimit);
final int n = mAdapter.getCount();
final int endPos = Math.min(n - 1, mCurItem + pageLimit);
if (n != mExpectedAdapterCount) {
String resName;
try {
resName = getResources().getResourceName(getId());
} catch (Resources.NotFoundException e) {
resName = Integer.toHexString(getId());
}
throw new IllegalStateException("The application's PagerAdapter changed the adapter's"
+ " contents without calling PagerAdapter#notifyDataSetChanged!"
+ " Expected adapter item count: " + mExpectedAdapterCount + ", found: " + n
+ " Pager id: " + resName
+ " Pager class: " + getClass()
+ " Problematic adapter: " + mAdapter.getClass());
}
// Locate the currently focused item or add it if needed.
int curIndex;
ViewPager.ItemInfo curItem = null;
for (curIndex = 0; curIndex < mItems.size(); curIndex++) {
final ViewPager.ItemInfo ii = mItems.get(curIndex);
if (ii.position >= mCurItem) {
if (ii.position == mCurItem) {
curItem = ii;
}
break;
}
}
if (curItem == null && n > 0) {
curItem = addNewItem(mCurItem, curIndex);
}
// Fill 3x the available width or up to the number of offscreen
// pages requested to either side, whichever is larger.
// If we have no current item we have no work to do.
if (curItem != null) {
float extraWidthLeft = 0.f;
int itemIndex = curIndex - 1;
ViewPager.ItemInfo ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
final int clientWidth = getClientWidth();
final float leftWidthNeeded = clientWidth <= 0 ? 0 :
2.f - curItem.widthFactor + (float) getPaddingLeft() / (float) clientWidth;
for (int pos = mCurItem - 1; pos >= 0; pos--) {
if (extraWidthLeft >= leftWidthNeeded && pos < startPos) {
if (ii == null) {
break;
}
if (pos == ii.position && !ii.scrolling) {
mItems.remove(itemIndex);
mAdapter.destroyItem(this, pos, ii.object);
if (DEBUG) {
Log.i(TAG, "populate() - destroyItem() with pos: " + pos
+ " view: " + ii.object);
}
itemIndex--;
curIndex--;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
}
} else if (ii != null && pos == ii.position) {
extraWidthLeft += ii.widthFactor;
itemIndex--;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
} else {
ii = addNewItem(pos, itemIndex + 1);
extraWidthLeft += ii.widthFactor;
curIndex++;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
}
}
float extraWidthRight = curItem.widthFactor;
itemIndex = curIndex + 1;
if (extraWidthRight < 2.f) {
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
final float rightWidthNeeded = clientWidth <= 0 ? 0 :
(float) getPaddingRight() / (float) clientWidth + 2.f;
for (int pos = mCurItem + 1; pos < n; pos++) {
if (extraWidthRight >= rightWidthNeeded && pos > endPos) {
if (ii == null) {
break;
}
if (pos == ii.position && !ii.scrolling) {
mItems.remove(itemIndex);
mAdapter.destroyItem(this, pos, ii.object);
if (DEBUG) {
Log.i(TAG, "populate() - destroyItem() with pos: " + pos
+ " view: " + ii.object);
}
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
}
} else if (ii != null && pos == ii.position) {
extraWidthRight += ii.widthFactor;
itemIndex++;
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
} else {
ii = addNewItem(pos, itemIndex);
itemIndex++;
extraWidthRight += ii.widthFactor;
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
}
}
}
calculatePageOffsets(curItem, curIndex, oldCurInfo);
}
if (DEBUG) {
Log.i(TAG, "Current page list:");
for (int i = 0; i < mItems.size(); i++) {
Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);
}
}
mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);
mAdapter.finishUpdate(this);
// Check width measurement of current pages and drawing sort order.
// Update LayoutParams as needed.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
lp.childIndex = i;
if (!lp.isDecor && lp.widthFactor == 0.f) {
// 0 means requery the adapter for this, it doesn't have a valid width.
final ViewPager.ItemInfo ii = infoForChild(child);
if (ii != null) {
lp.widthFactor = ii.widthFactor;
lp.position = ii.position;
}
}
}
sortChildDrawingOrder();
if (hasFocus()) {
View currentFocused = findFocus();
ViewPager.ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused) : null;
if (ii == null || ii.position != mCurItem) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
if (child.requestFocus(View.FOCUS_FORWARD)) {
break;
}
}
}
}
}
}
private void sortChildDrawingOrder() {
if (mDrawingOrder != DRAW_ORDER_DEFAULT) {
if (mDrawingOrderedChildren == null) {
mDrawingOrderedChildren = new ArrayList<>();
} else {
mDrawingOrderedChildren.clear();
}
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
mDrawingOrderedChildren.add(child);
}
Collections.sort(mDrawingOrderedChildren, S_POSITION_COMPARATOR);
}
}
private void calculatePageOffsets(ViewPager.ItemInfo curItem, int curIndex, ViewPager.ItemInfo oldCurInfo) {
final int n = mAdapter.getCount();
final int width = getClientWidth();
final float marginOffset = width > 0 ? (float) mPageMargin / width : 0;
// Fix up offsets for later layout.
if (oldCurInfo != null) {
final int oldCurPosition = oldCurInfo.position;
// Base offsets off of oldCurInfo.
if (oldCurPosition < curItem.position) {
int itemIndex = 0;
ViewPager.ItemInfo ii;
float offset = oldCurInfo.offset + oldCurInfo.widthFactor + marginOffset;
for (int pos = oldCurPosition + 1;
pos <= curItem.position && itemIndex < mItems.size(); pos++) {
ii = mItems.get(itemIndex);
while (pos > ii.position && itemIndex < mItems.size() - 1) {
itemIndex++;
ii = mItems.get(itemIndex);
}
while (pos < ii.position) {
// We don't have an item populated for this,
// ask the adapter for an offset.
offset += mAdapter.getPageWidth(pos) + marginOffset;
pos++;
}
ii.offset = offset;
offset += ii.widthFactor + marginOffset;
}
} else if (oldCurPosition > curItem.position) {
int itemIndex = mItems.size() - 1;
ViewPager.ItemInfo ii;
float offset = oldCurInfo.offset;
for (int pos = oldCurPosition - 1;
pos >= curItem.position && itemIndex >= 0; pos--) {
ii = mItems.get(itemIndex);
while (pos < ii.position && itemIndex > 0) {
itemIndex--;
ii = mItems.get(itemIndex);
}
while (pos > ii.position) {
// We don't have an item populated for this,
// ask the adapter for an offset.
offset -= mAdapter.getPageWidth(pos) + marginOffset;
pos--;
}
offset -= ii.widthFactor + marginOffset;
ii.offset = offset;
}
}
}
// Base all offsets off of curItem.
final int itemCount = mItems.size();
float offset = curItem.offset;
int pos = curItem.position - 1;
mFirstOffset = curItem.position == 0 ? curItem.offset : -Float.MAX_VALUE;
mLastOffset = curItem.position == n - 1
? curItem.offset + curItem.widthFactor - 1 : Float.MAX_VALUE;
// Previous pages
for (int i = curIndex - 1; i >= 0; i--, pos--) {
final ViewPager.ItemInfo ii = mItems.get(i);
while (pos > ii.position) {
offset -= mAdapter.getPageWidth(pos--) + marginOffset;
}
offset -= ii.widthFactor + marginOffset;
ii.offset = offset;
if (ii.position == 0) {
mFirstOffset = offset;
}
}
offset = curItem.offset + curItem.widthFactor + marginOffset;
pos = curItem.position + 1;
// Next pages
for (int i = curIndex + 1; i < itemCount; i++, pos++) {
final ViewPager.ItemInfo ii = mItems.get(i);
while (pos < ii.position) {
offset += mAdapter.getPageWidth(pos++) + marginOffset;
}
if (ii.position == n - 1) {
mLastOffset = offset + ii.widthFactor - 1;
}
ii.offset = offset;
offset += ii.widthFactor + marginOffset;
}
mNeedCalculatePageOffsets = false;
}
/**
* This is the persistent state that is saved by ViewPager. Only needed
* if you are creating a sublass of ViewPager that must save its own
* state, in which case it should implement a subclass of this which
* contains that state.
*/
public static class SavedState extends AbsSavedState {
int position;
Parcelable adapterState;
ClassLoader loader;
public SavedState(@NonNull Parcelable superState) {
super(superState);
}
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeInt(position);
out.writeParcelable(adapterState, flags);
}
@Override
public String toString() {
return "FragmentPager.SavedState{"
+ Integer.toHexString(System.identityHashCode(this))
+ " position=" + position + "}";
}
public static final Creator<SavedState> CREATOR = new ClassLoaderCreator<SavedState>() {
@Override
public ViewPager.SavedState createFromParcel(Parcel in, ClassLoader loader) {
return new ViewPager.SavedState(in, loader);
}
@Override
public ViewPager.SavedState createFromParcel(Parcel in) {
return new ViewPager.SavedState(in, null);
}
@Override
public ViewPager.SavedState[] newArray(int size) {
return new ViewPager.SavedState[size];
}
};
SavedState(Parcel in, ClassLoader loader) {
super(in, loader);
if (loader == null) {
loader = getClass().getClassLoader();
}
position = in.readInt();
adapterState = in.readParcelable(loader);
this.loader = loader;
}
}
@Override
public Parcelable onSaveInstanceState() {
Parcelable superState = super.onSaveInstanceState();
ViewPager.SavedState ss = new ViewPager.SavedState(superState);
ss.position = mCurItem;
if (mAdapter != null) {
ss.adapterState = mAdapter.saveState();
}
return ss;
}
/**
* 回复实例状态
*
* @param state s
*/
@Override
public void onRestoreInstanceState(Parcelable state) {
if (!(state instanceof ViewPager.SavedState)) {
super.onRestoreInstanceState(state);
return;
}
ViewPager.SavedState ss = (ViewPager.SavedState) state;
super.onRestoreInstanceState(ss.getSuperState());
if (mAdapter != null) {
mAdapter.restoreState(ss.adapterState, ss.loader);
setCurrentItemInternal(ss.position, false, true);
} else {
mRestoredCurItem = ss.position;
mRestoredAdapterState = ss.adapterState;
mRestoredClassLoader = ss.loader;
}
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if (!checkLayoutParams(params)) {
params = generateLayoutParams(params);
}
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) params;
// Any views added via inflation should be classed as part of the decor
lp.isDecor |= isDecorView(child);
if (mInLayout) {
if (lp != null && lp.isDecor) {
throw new IllegalStateException("Cannot add pager decor view during layout");
}
lp.needsMeasure = true;
addViewInLayout(child, index, params);
} else {
super.addView(child, index, params);
}
if (USE_CACHE) {
if (child.getVisibility() != GONE) {
child.setDrawingCacheEnabled(mScrollingCacheEnabled);
} else {
child.setDrawingCacheEnabled(false);
}
}
}
private static boolean isDecorView(@NonNull View view) {
Class<?> clazz = view.getClass();
return clazz.getAnnotation(ViewPager.DecorView.class) != null;
}
@Override
public void removeView(View view) {
if (mInLayout) {
removeViewInLayout(view);
} else {
super.removeView(view);
}
}
ViewPager.ItemInfo infoForChild(View child) {
for (int i = 0; i < mItems.size(); i++) {
ViewPager.ItemInfo ii = mItems.get(i);
if (mAdapter.isViewFromObject(child, ii.object)) {
return ii;
}
}
return null;
}
ViewPager.ItemInfo infoForAnyChild(View child) {
ViewParent parent;
while ((parent = child.getParent()) != this) {
if (parent == null || !(parent instanceof View)) {
return null;
}
child = (View) parent;
}
return infoForChild(child);
}
ViewPager.ItemInfo infoForPosition(int position) {
for (int i = 0; i < mItems.size(); i++) {
ViewPager.ItemInfo ii = mItems.get(i);
if (ii.position == position) {
return ii;
}
}
return null;
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
mFirstLayout = true;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// For simple implementation, our internal size is always 0.
// We depend on the container to specify the layout size of
// our view. We can't really know what it is since we will be
// adding and removing different arbitrary views and do not
// want the layout to change as this happens.
setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),
getDefaultSize(0, heightMeasureSpec));
final int measuredWidth = getMeasuredWidth();
final int maxGutterSize = measuredWidth / 10;
mGutterSize = Math.min(maxGutterSize, mDefaultGutterSize);
// Children are just made to fill our space.
int childWidthSize = measuredWidth - getPaddingLeft() - getPaddingRight();
int childHeightSize = getMeasuredHeight() - getPaddingTop() - getPaddingBottom();
/*
* Make sure all children have been properly measured. Decor views first.
* Right now we cheat and make this less complicated by assuming decor
* views won't intersect. We will pin to edges based on gravity.
*/
int size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (lp != null && lp.isDecor) {
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
int widthMode = MeasureSpec.AT_MOST;
int heightMode = MeasureSpec.AT_MOST;
boolean consumeVertical = vgrav == Gravity.TOP || vgrav == Gravity.BOTTOM;
@SuppressLint("RtlHardcoded")
boolean consumeHorizontal = hgrav == Gravity.LEFT || hgrav == Gravity.RIGHT;
if (consumeVertical) {
widthMode = MeasureSpec.EXACTLY;
} else if (consumeHorizontal) {
heightMode = MeasureSpec.EXACTLY;
}
int widthSize = childWidthSize;
int heightSize = childHeightSize;
if (lp.width != ViewPager.LayoutParams.WRAP_CONTENT) {
widthMode = MeasureSpec.EXACTLY;
if (lp.width != ViewPager.LayoutParams.MATCH_PARENT) {
widthSize = lp.width;
}
}
if (lp.height != ViewPager.LayoutParams.WRAP_CONTENT) {
heightMode = MeasureSpec.EXACTLY;
if (lp.height != ViewPager.LayoutParams.MATCH_PARENT) {
heightSize = lp.height;
}
}
final int widthSpec = MeasureSpec.makeMeasureSpec(widthSize, widthMode);
final int heightSpec = MeasureSpec.makeMeasureSpec(heightSize, heightMode);
child.measure(widthSpec, heightSpec);
if (consumeVertical) {
childHeightSize -= child.getMeasuredHeight();
} else if (consumeHorizontal) {
childWidthSize -= child.getMeasuredWidth();
}
}
}
}
mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(childWidthSize, MeasureSpec.EXACTLY);
mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(childHeightSize, MeasureSpec.EXACTLY);
// Make sure we have created all fragments that we need to have shown.
mInLayout = true;
populate();
mInLayout = false;
// Page views next.
size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
if (DEBUG) {
Log.v(TAG, "Measuring #" + i + " " + child + ": " + mChildWidthMeasureSpec);
}
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (lp == null || !lp.isDecor) {
final int widthSpec = MeasureSpec.makeMeasureSpec(
(int) (childWidthSize * lp.widthFactor), MeasureSpec.EXACTLY);
child.measure(widthSpec, mChildHeightMeasureSpec);
}
}
}
}
/**
* 获取控件的宽高
*/
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// 显示指标
DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
screenWidth = displayMetrics.widthPixels;
screenHeight = displayMetrics.heightPixels;
if (DEBUG) {
Log.v("screenWidth", String.valueOf(screenWidth));
Log.v("screenHeight", String.valueOf(screenHeight));
}
// Make sure scroll position is set correctly.
if (w != oldw) {
recomputeScrollPosition(w, oldw, mPageMargin, mPageMargin);
}
}
private void recomputeScrollPosition(int width, int oldWidth, int margin, int oldMargin) {
if (oldWidth > 0 && !mItems.isEmpty()) {
if (!mScroller.isFinished()) {
mScroller.setFinalX(getCurrentItem() * getClientWidth());
} else {
final int widthWithMargin = width - getPaddingLeft() - getPaddingRight() + margin;
final int oldWidthWithMargin = oldWidth - getPaddingLeft() - getPaddingRight()
+ oldMargin;
final int xpos = getScrollX();
final float pageOffset = (float) xpos / oldWidthWithMargin;
final int newOffsetPixels = (int) (pageOffset * widthWithMargin);
scrollTo(newOffsetPixels, getScrollY());
}
} else {
final ViewPager.ItemInfo ii = infoForPosition(mCurItem);
final float scrollOffset = ii != null ? Math.min(ii.offset, mLastOffset) : 0;
final int scrollPos =
(int) (scrollOffset * (width - getPaddingLeft() - getPaddingRight()));
if (scrollPos != getScrollX()) {
completeScroll(false);
scrollTo(scrollPos, getScrollY());
}
}
}
/**
* 确定控件的位置
*/
@SuppressLint("RtlHardcoded")
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
final int count = getChildCount();
int width = r - l;
int height = b - t;
int paddingLeft = getPaddingLeft();
int paddingTop = getPaddingTop();
int paddingRight = getPaddingRight();
int paddingBottom = getPaddingBottom();
final int scrollX = getScrollX();
int decorCount = 0;
// First pass - decor views. We need to do this in two passes so that
// we have the proper offsets for non-decor views later.
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
int childLeft;
int childTop;
if (lp.isDecor) {
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
switch (hgrav) {
default:
childLeft = paddingLeft;
break;
case Gravity.LEFT:
childLeft = paddingLeft;
paddingLeft += child.getMeasuredWidth();
break;
case Gravity.CENTER_HORIZONTAL:
childLeft = Math.max((width - child.getMeasuredWidth()) / 2,
paddingLeft);
break;
case Gravity.RIGHT:
childLeft = width - paddingRight - child.getMeasuredWidth();
paddingRight += child.getMeasuredWidth();
break;
}
switch (vgrav) {
default:
childTop = paddingTop;
break;
case Gravity.TOP:
childTop = paddingTop;
paddingTop += child.getMeasuredHeight();
break;
case Gravity.CENTER_VERTICAL:
childTop = Math.max((height - child.getMeasuredHeight()) / 2,
paddingTop);
break;
case Gravity.BOTTOM:
childTop = height - paddingBottom - child.getMeasuredHeight();
paddingBottom += child.getMeasuredHeight();
break;
}
childLeft += scrollX;
child.layout(childLeft, childTop,
childLeft + child.getMeasuredWidth(),
childTop + child.getMeasuredHeight());
decorCount++;
}
}
}
final int childWidth = width - paddingLeft - paddingRight;
// Page views. Do this once we have the right padding offsets from above.
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
ViewPager.ItemInfo ii;
if (!lp.isDecor && (ii = infoForChild(child)) != null) {
int loff = (int) (childWidth * ii.offset);
int childLeft = paddingLeft + loff;
if (lp.needsMeasure) {
// This was added during layout and needs measurement.
// Do it now that we know what we're working with.
lp.needsMeasure = false;
final int widthSpec = MeasureSpec.makeMeasureSpec(
(int) (childWidth * lp.widthFactor),
MeasureSpec.EXACTLY);
final int heightSpec = MeasureSpec.makeMeasureSpec(
height - paddingTop - paddingBottom,
MeasureSpec.EXACTLY);
child.measure(widthSpec, heightSpec);
}
if (DEBUG) {
Log.v(TAG, "Positioning #" + i + " " + child + " f=" + ii.object
+ ":" + childLeft + "," + paddingTop + " " + child.getMeasuredWidth()
+ "x" + child.getMeasuredHeight());
}
child.layout(childLeft, paddingTop,
childLeft + child.getMeasuredWidth(),
paddingTop + child.getMeasuredHeight());
}
}
}
mTopPageBounds = paddingTop;
mBottomPageBounds = height - paddingBottom;
mDecorChildCount = decorCount;
if (mFirstLayout) {
scrollToItem(mCurItem, false, 0, false);
}
mFirstLayout = false;
}
@Override
public void computeScroll() {
mIsScrollStarted = true;
if (!mScroller.isFinished() && mScroller.computeScrollOffset()) {
int oldX = getScrollX();
int oldY = getScrollY();
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (oldX != x || oldY != y) {
scrollTo(x, y);
if (!pageScrolled(x)) {
mScroller.abortAnimation();
scrollTo(0, y);
}
}
// 继续画， 直到动画完成
// Keep on drawing until the animation has finished.
ViewCompat.postInvalidateOnAnimation(this);
return;
}
// Done with scroll, clean up state.
completeScroll(true);
}
private boolean pageScrolled(int xpos) {
if (mItems.size() == 0) {
if (mFirstLayout) {
// If we haven't been laid out yet, we probably just haven't been populated yet.
// Let's skip this call since it doesn't make sense in this state
return false;
}
mCalledSuper = false;
onPageScrolled(0, 0, 0);
if (!mCalledSuper) {
throw new IllegalStateException(
"onPageScrolled did not call superclass implementation");
}
return false;
}
final ViewPager.ItemInfo ii = infoForCurrentScrollPosition();
final int width = getClientWidth();
final int widthWithMargin = width + mPageMargin;
final float marginOffset = (float) mPageMargin / width;
final int currentPage = ii.position;
final float pageOffset = (((float) xpos / width) - ii.offset)
/ (ii.widthFactor + marginOffset);
final int offsetPixels = (int) (pageOffset * widthWithMargin);
mCalledSuper = false;
onPageScrolled(currentPage, pageOffset, offsetPixels);
if (!mCalledSuper) {
throw new IllegalStateException(
"onPageScrolled did not call superclass implementation");
}
return true;
}
/**
* This method will be invoked when the current page is scrolled, either as part
* of a programmatically initiated smooth scroll or a user initiated touch scroll.
* If you override this method you must call through to the superclass implementation
* (e.g. super.onPageScrolled(position, offset, offsetPixels)) before onPageScrolled
* returns.
*
* @param position Position index of the first page currently being displayed.
* Page position+1 will be visible if positionOffset is nonzero.
* @param offset Value from [0, 1) indicating the offset from the page at position.
* @param offsetPixels Value in pixels indicating the offset from position.
*/
@SuppressLint("RtlHardcoded")
@CallSuper
protected void onPageScrolled(int position, float offset, int offsetPixels) {
// Offset any decor views if needed - keep them on-screen at all times.
if (mDecorChildCount > 0) {
final int scrollX = getScrollX();
int paddingLeft = getPaddingLeft();
int paddingRight = getPaddingRight();
final int width = getWidth();
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (!lp.isDecor) {
continue;
}
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
int childLeft;
switch (hgrav) {
default:
childLeft = paddingLeft;
break;
case Gravity.LEFT:
childLeft = paddingLeft;
paddingLeft += child.getWidth();
break;
case Gravity.CENTER_HORIZONTAL:
childLeft = Math.max((width - child.getMeasuredWidth()) / 2,
paddingLeft);
break;
case Gravity.RIGHT:
childLeft = width - paddingRight - child.getMeasuredWidth();
paddingRight += child.getMeasuredWidth();
break;
}
childLeft += scrollX;
final int childOffset = childLeft - child.getLeft();
if (childOffset != 0) {
child.offsetLeftAndRight(childOffset);
}
}
}
dispatchOnPageScrolled(position, offset, offsetPixels);
if (mPageTransformer != null) {
final int scrollX = getScrollX();
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();
if (lp.isDecor) {
continue;
}
final float transformPos = (float) (child.getLeft() - scrollX) / getClientWidth();
mPageTransformer.transformPage(child, transformPos);
}
}
mCalledSuper = true;
}
/**
* 调度页滚动
*
* @param position p
* @param offset o
* @param offsetPixels op
*/
private void dispatchOnPageScrolled(int position, float offset, int offsetPixels) {
if (mOnPageChangeListener != null) {
mOnPageChangeListener.onPageScrolled(position, offset, offsetPixels);
}
if (mOnPageChangeListeners != null) {
for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
ViewPager.OnPageChangeListener listener = mOnPageChangeListeners.get(i);
if (listener != null) {
listener.onPageScrolled(position, offset, offsetPixels);
}
}
}
if (mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageScrolled(position, offset, offsetPixels);
}
}
/**
* 调度选中的页
*
* @param position p
*/
private void dispatchOnPageSelected(int position) {
if (mOnPageChangeListener != null) {
mOnPageChangeListener.onPageSelected(position);
}
if (mOnPageSelecting != null) {
mOnPageSelecting.onMyPageSelected(position);
}
if (mOnPageChangeListeners != null) {
for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
ViewPager.OnPageChangeListener listener = mOnPageChangeListeners.get(i);
if (listener != null) {
listener.onPageSelected(position);
}
}
}
if (mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageSelected(position);
}
}
private void dispatchOnScrollStateChanged(int state) {
if (mOnPageChangeListener != null) {
mOnPageChangeListener.onPageScrollStateChanged(state);
}
if (mOnPageChangeListeners != null) {
for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
ViewPager.OnPageChangeListener listener = mOnPageChangeListeners.get(i);
if (listener != null) {
listener.onPageScrollStateChanged(state);
}
}
}
if (mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageScrollStateChanged(state);
}
}
private void completeScroll(boolean postEvents) {
boolean needPopulate = mScrollState == SCROLL_STATE_SETTLING;
if (needPopulate) {
// Done with scroll, no longer want to cache view drawing.
setScrollingCacheEnabled(false);
boolean wasScrolling = !mScroller.isFinished();
if (wasScrolling) {
mScroller.abortAnimation();
int oldX = getScrollX();
int oldY = getScrollY();
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (oldX != x || oldY != y) {
scrollTo(x, y);
if (x != oldX) {
pageScrolled(x);
}
}
}
}
mPopulatePending = false;
for (int i = 0; i < mItems.size(); i++) {
ViewPager.ItemInfo ii = mItems.get(i);
if (ii.scrolling) {
needPopulate = true;
ii.scrolling = false;
}
}
if (needPopulate) {
if (postEvents) {
ViewCompat.postOnAnimation(this, mEndScrollRunnable);
} else {
mEndScrollRunnable.run();
}
}
}
private boolean isGutterDrag(float x, float dx) {
return (x < mGutterSize && dx > 0) || (x > getWidth() - mGutterSize && dx < 0);
}
private void enableLayers(boolean enable) {
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final int layerType = enable
? mPageTransformerLayerType : View.LAYER_TYPE_NONE;
getChildAt(i).setLayerType(layerType, null);
}
}
/**
* 拦截触摸事件
*/
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onMotionEvent will be called and we do the actual
* scrolling there.
*/
final int action = ev.getAction() & MotionEvent.ACTION_MASK;
// Always take care of the touch gesture being complete.
if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
// Release the drag.
if (DEBUG) {
Log.v(TAG, "Intercept done!");
}
resetTouch();
return false;
}
// Nothing more to do here if we have decided whether or not we
// are dragging.
if (action != MotionEvent.ACTION_DOWN) {
if (mIsBeingDragged) {
if (DEBUG) {
Log.v(TAG, "Intercept returning true!");
}
return true;
}
if (mIsUnableToDrag) {
if (DEBUG) {
Log.v(TAG, "Intercept returning false!");
}
return false;
}
}
switch (action) {
case MotionEvent.ACTION_MOVE: {
if (actionDownX >= (screenWidth - slidingRange)) {
/*
* mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
* whether the user has moved far enough from his original down touch.
*/
/*
* Locally do absolute value. mLastMotionY is set to the y value
* of the down event.
*/
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
// If we don't have a valid id, the touch down wasn't on content.
break;
}
final int pointerIndex = ev.findPointerIndex(activePointerId);
final float x = ev.getX(pointerIndex);
final float dx = x - mLastMotionX;
final float xDiff = Math.abs(dx);
final float y = ev.getY(pointerIndex);
final float yDiff = Math.abs(y - mInitialMotionY);
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
}
if (dx != 0 && !isGutterDrag(mLastMotionX, dx)
&& canScroll(this, false, (int) dx, (int) x, (int) y)) {
// Nested view has scrollable area under this point. Let it be handled there.
mLastMotionX = x;
mLastMotionY = y;
mIsUnableToDrag = true;
return false;
}
if (xDiff > mTouchSlop && xDiff * 0.5f > yDiff) {
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Starting drag!");
}
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
mLastMotionX = dx > 0
? mInitialMotionX + mTouchSlop : mInitialMotionX - mTouchSlop;
mLastMotionY = y;
setScrollingCacheEnabled(true);
} else if (yDiff > mTouchSlop) {
// The finger has moved enough in the vertical
// direction to be counted as a drag... abort
// any attempt to drag horizontally, to work correctly
// with children that have scrolling containers.
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Starting unable to drag!");
}
mIsUnableToDrag = true;
}
if (mIsBeingDragged) {
// Scroll to follow the motion event
if (performDrag(x)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
} else if (isFirstEnter) {
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
// If we don't have a valid id, the touch down wasn't on content.
break;
}
final int pointerIndex = ev.findPointerIndex(activePointerId);
final float x = ev.getX(pointerIndex);
final float dx = x - mLastMotionX;
final float xDiff = Math.abs(dx);
final float y = ev.getY(pointerIndex);
final float yDiff = Math.abs(y - mInitialMotionY);
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
}
if (dx != 0 && !isGutterDrag(mLastMotionX, dx)
&& canScroll(this, false, (int) dx, (int) x, (int) y)) {
// Nested view has scrollable area under this point. Let it be handled there.
mLastMotionX = x;
mLastMotionY = y;
mIsUnableToDrag = true;
return false;
}
if (xDiff > mTouchSlop && xDiff * 0.5f > yDiff) {
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Starting drag!");
}
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
mLastMotionX = dx > 0
? mInitialMotionX + mTouchSlop : mInitialMotionX - mTouchSlop;
mLastMotionY = y;
setScrollingCacheEnabled(true);
} else if (yDiff > mTouchSlop) {
// The finger has moved enough in the vertical
// direction to be counted as a drag... abort
// any attempt to drag horizontally, to work correctly
// with children that have scrolling containers.
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Starting unable to drag!");
}
mIsUnableToDrag = true;
}
if (mIsBeingDragged) {
// Scroll to follow the motion event
if (performDrag(x)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
}
break;
}
case MotionEvent.ACTION_DOWN: {
actionDownX = ev.getX();
if (actionDownX >= (screenWidth - slidingRange)) {
/*
* Remember location of down touch.
* ACTION_DOWN always refers to pointer index 0.
*/
mLastMotionX = mInitialMotionX = ev.getX();
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = ev.getPointerId(0);
mIsUnableToDrag = false;
mIsScrollStarted = true;
mScroller.computeScrollOffset();
if (mScrollState == SCROLL_STATE_SETTLING
&& Math.abs(mScroller.getFinalX() - mScroller.getCurrX()) > mCloseEnough) {
// Let the user 'catch' the pager as it animates.
mScroller.abortAnimation();
mPopulatePending = false;
populate();
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
} else {
completeScroll(false);
}
mIsBeingDragged = false;
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Down at " + mLastMotionX + "," + mLastMotionY
+ " mIsBeingDragged=" + mIsBeingDragged
+ "mIsUnableToDrag=" + mIsUnableToDrag);
}
} else if (isFirstEnter) {
mLastMotionX = mInitialMotionX = ev.getX();
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = ev.getPointerId(0);
mIsUnableToDrag = false;
mIsScrollStarted = true;
mScroller.computeScrollOffset();
if (mScrollState == SCROLL_STATE_SETTLING
&& Math.abs(mScroller.getFinalX() - mScroller.getCurrX()) > mCloseEnough) {
// Let the user 'catch' the pager as it animates.
mScroller.abortAnimation();
mPopulatePending = false;
populate();
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
} else {
completeScroll(false);
}
mIsBeingDragged = false;
if (DEBUG) {
Log.v("onInterceptTouchEvent", "Down at " + mLastMotionX + "," + mLastMotionY
+ " mIsBeingDragged=" + mIsBeingDragged
+ "mIsUnableToDrag=" + mIsUnableToDrag);
}
}
break;
}
case MotionEvent.ACTION_POINTER_UP:
if (actionDownX >= (screenWidth - slidingRange)) {
onSecondaryPointerUp(ev);
} else if (isFirstEnter) {
onSecondaryPointerUp(ev);
}
break;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
/*
* The only time we want to intercept motion events is if we are in the
* drag mode.
*/
return mIsBeingDragged;
}
@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (mFakeDragging) {
// A fake drag is in progress already, ignore this real one
// but still eat the touch events.
// (It is likely that the user is multi-touching the screen.)
return true;
}
if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {
// Don't handle edge touches immediately -- they may actually belong to one of our
// descendants.
return false;
}
if (mAdapter == null || mAdapter.getCount() == 0) {
// Nothing to present or scroll; nothing to touch.
return false;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
boolean needsInvalidate = false;
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
actionDownX = ev.getX();
if (actionDownX >= (screenWidth - slidingRange)) {
onTouchEventDown(ev);
} else if (isFirstEnter) {
onTouchEventDown(ev);
}
break;
}
case MotionEvent.ACTION_MOVE:
if (actionDownX >= (screenWidth - slidingRange)) {
if (!mIsBeingDragged) {
// 给定一个指针标识符,找到事件的索引数据
// 传入指针Id
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
if (pointerIndex == -1) {
// A child has consumed some touch events and put us into an inconsistent
// state.
needsInvalidate = resetTouch();
break;
}
final float x = ev.getX(pointerIndex);
final float xDiff = Math.abs(x - mLastMotionX);
final float y = ev.getY(pointerIndex);
final float yDiff = Math.abs(y - mLastMotionY);
if (DEBUG) {
Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
}
if (xDiff > mTouchSlop && xDiff > yDiff) {
if (DEBUG) {
Log.v(TAG, "Starting drag!");
}
// 是否被拖
mIsBeingDragged = true;
// 请求父类不允许拦截触摸事件;
requestParentDisallowInterceptTouchEvent(true);
mLastMotionX = x - mInitialMotionX > 0 ? mInitialMotionX + mTouchSlop :
mInitialMotionX - mTouchSlop;
mLastMotionY = y;
setScrollState(SCROLL_STATE_DRAGGING);
setScrollingCacheEnabled(true);
// 不允许父类拦截， 以备不时之需
ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
}
// Not else! Note that mIsBeingDragged can be set above.
if (mIsBeingDragged) {
// 滚动运动事件
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(activePointerIndex);
// a |= b a和b按位或后赋值给a， 按位或：ab转换成二进制然后移位运算
needsInvalidate |= performDrag(x);
}
} else if (isFirstEnter) {
if (!mIsBeingDragged) {
// 给定一个指针标识符,找到事件的索引数据
// 传入指针Id
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
if (pointerIndex == -1) {
// A child has consumed some touch events and put us into an inconsistent
// state.
needsInvalidate = resetTouch();
break;
}
final float x = ev.getX(pointerIndex);
final float xDiff = Math.abs(x - mLastMotionX);
final float y = ev.getY(pointerIndex);
final float yDiff = Math.abs(y - mLastMotionY);
if (DEBUG) {
Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
}
if (xDiff > mTouchSlop && xDiff > yDiff) {
if (DEBUG) {
Log.v(TAG, "Starting drag!");
}
// 是否被拖
mIsBeingDragged = true;
// 请求父类不允许拦截触摸事件;
requestParentDisallowInterceptTouchEvent(true);
mLastMotionX = x - mInitialMotionX > 0 ? mInitialMotionX + mTouchSlop :
mInitialMotionX - mTouchSlop;
mLastMotionY = y;
setScrollState(SCROLL_STATE_DRAGGING);
setScrollingCacheEnabled(true);
// 不允许父类拦截， 以备不时之需
ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
}
// Not else! Note that mIsBeingDragged can be set above.
if (mIsBeingDragged) {
// 滚动运动事件
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(activePointerIndex);
// a |= b a和b按位或后赋值给a， 按位或：ab转换成二进制然后移位运算
needsInvalidate |= performDrag(x);
}
}
break;
case MotionEvent.ACTION_UP:
if (actionDownX >= (screenWidth - slidingRange)) {
if (mIsBeingDragged) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId);
mPopulatePending = true;
final int width = getClientWidth();
final int scrollX = getScrollX();
final ViewPager.ItemInfo ii = infoForCurrentScrollPosition();
final float marginOffset = (float) mPageMargin / width;
final int currentPage = ii.position;
final float pageOffset = (((float) scrollX / width) - ii.offset)
/ (ii.widthFactor + marginOffset);
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(activePointerIndex);
final int totalDelta = (int) (x - mInitialMotionX);
// 确定切换到目标页
int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
totalDelta);
// 切换页
setCurrentItemInternal(nextPage, true, true, initialVelocity);
if (DEBUG) {
Log.i("onTouchEvent", "执行了setCurrentItemInternal");
}
needsInvalidate = resetTouch();
}
} else if (isFirstEnter) {
if (mIsBeingDragged) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId);
mPopulatePending = true;
final int width = getClientWidth();
final int scrollX = getScrollX();
final ViewPager.ItemInfo ii = infoForCurrentScrollPosition();
final float marginOffset = (float) mPageMargin / width;
final int currentPage = ii.position;
final float pageOffset = (((float) scrollX / width) - ii.offset)
/ (ii.widthFactor + marginOffset);
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(activePointerIndex);
final int totalDelta = (int) (x - mInitialMotionX);
// 确定切换到目标页
int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
totalDelta);
// 切换页
setCurrentItemInternal(nextPage, true, true, initialVelocity);
if (DEBUG) {
Log.i("onTouchEvent", "执行了setCurrentItemInternal");
}
needsInvalidate = resetTouch();
}
}
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged) {
scrollToItem(mCurItem, true, 0, false);
needsInvalidate = resetTouch();
}
break;
case MotionEvent.ACTION_POINTER_DOWN: {
final int index = ev.getActionIndex();
mLastMotionX = ev.getX(index);
mActivePointerId = ev.getPointerId(index);
break;
}
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
mLastMotionX = ev.getX(ev.findPointerIndex(mActivePointerId));
break;
}
if (needsInvalidate) {
ViewCompat.postInvalidateOnAnimation(this);
}
return true;
}
private void onTouchEventDown(MotionEvent ev) {
mScroller.abortAnimation();
mPopulatePending = false;
populate();
System.out.println("X : " + ev.getX());
// 记住运动事件开始的地方
mLastMotionX = mInitialMotionX = ev.getX();
mLastMotionY = mInitialMotionY = ev.getY();
// 返回的指针标识符关联到一个特定的指针数据指数在这个事件
// 标识符告诉你实际的指针与数据相关联,占个人指针上下开始以来的当前姿态
// 传入指针索引
mActivePointerId = ev.getPointerId(0);
}
/**
* 重置触摸
*/
private boolean resetTouch() {
boolean needsInvalidate;
mActivePointerId = INVALID_POINTER;
endDrag();
mLeftEdge.onRelease();
mRightEdge.onRelease();
needsInvalidate = mLeftEdge.isFinished() || mRightEdge.isFinished();
return needsInvalidate;
}
private void requestParentDisallowInterceptTouchEvent(boolean disallowIntercept) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
/**
* 执行拖
*/
private boolean performDrag(float x) {
boolean needsInvalidate = false;
final float deltaX = mLastMotionX - x;
mLastMotionX = x;
float oldScrollX = getScrollX();
float scrollX = oldScrollX + deltaX;
final int width = getClientWidth();
float leftBound = width * mFirstOffset;
float rightBound = width * mLastOffset;
boolean leftAbsolute = true;
boolean rightAbsolute = true;
final ViewPager.ItemInfo firstItem = mItems.get(0);
final ViewPager.ItemInfo lastItem = mItems.get(mItems.size() - 1);
if (firstItem.position != 0) {
leftAbsolute = false;
leftBound = firstItem.offset * width;
}
if (lastItem.position != mAdapter.getCount() - 1) {
rightAbsolute = false;
rightBound = lastItem.offset * width;
}
if (scrollX < leftBound) {
if (leftAbsolute) {
float over = leftBound - scrollX;
mLeftEdge.onPull(Math.abs(over) / width);
needsInvalidate = true;
}
scrollX = leftBound;
} else if (scrollX > rightBound) {
if (rightAbsolute) {
float over = scrollX - rightBound;
mRightEdge.onPull(Math.abs(over) / width);
needsInvalidate = true;
}
scrollX = rightBound;
}
// Don't lose the rounded component
mLastMotionX += scrollX - (int) scrollX;
scrollTo((int) scrollX, getScrollY());
pageScrolled((int) scrollX);
return needsInvalidate;
}
/**
* @return Info about the page at the current scroll position.
* This can be synthetic for a missing middle page; the 'object' field can be null.
*/
private ViewPager.ItemInfo infoForCurrentScrollPosition() {
final int width = getClientWidth();
final float scrollOffset = width > 0 ? (float) getScrollX() / width : 0;
final float marginOffset = width > 0 ? (float) mPageMargin / width : 0;
int lastPos = -1;
float lastOffset = 0.f;
float lastWidth = 0.f;
boolean first = true;
ViewPager.ItemInfo lastItem = null;
for (int i = 0; i < mItems.size(); i++) {
ViewPager.ItemInfo ii = mItems.get(i);
float offset;
if (!first && ii.position != lastPos + 1) {
// Create a synthetic item for a missing page.
ii = mTempItem;
ii.offset = lastOffset + lastWidth + marginOffset;
ii.position = lastPos + 1;
ii.widthFactor = mAdapter.getPageWidth(ii.position);
i--;
}
offset = ii.offset;
final float leftBound = offset;
final float rightBound = offset + ii.widthFactor + marginOffset;
if (first || scrollOffset >= leftBound) {
if (scrollOffset < rightBound || i == mItems.size() - 1) {
return ii;
}
} else {
return lastItem;
}
first = false;
lastPos = ii.position;
lastOffset = offset;
lastWidth = ii.widthFactor;
lastItem = ii;
}
return lastItem;
}
/**
* 最小可切换Page的偏移量
**/
private float minPageOffset = 0.6f;
public void setMinPageOffset(float pageOffset) {
minPageOffset = pageOffset;
}
// /**
// * 确定目标页面
// *
// * @param currentPage 当前页
// * @param pageOffset 用户滑动的页面偏移量
// * @param velocity 滑动速度
// * @param deltaX x方向移动的距离
// */
// private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaX) {
// // 滑动的目标页， 这个方法在MotionEvent.ACTION_UP下调用
// int targetPage;
// if (Math.abs(deltaX) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {
// targetPage = velocity > 0 ? currentPage : currentPage + 1;
// } else {
// final float truncator = currentPage >= mCurItem ? 1.0f - minPageOffset : minPageOffset;
// targetPage = (int) (currentPage + pageOffset + truncator);
// }
//
// if (mItems.size() > 0) {
// final ItemInfo firstItem = mItems.get(0);
// final ItemInfo lastItem = mItems.get(mItems.size() - 1);
//
// // Only let the user target pages we have items for
// targetPage = Math.max(firstItem.position, Math.min(targetPage, lastItem.position));
// }
//
// return targetPage;
// }
private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaX) {
int targetPage;
if (Math.abs(deltaX) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {
targetPage = velocity > 0 ? currentPage : currentPage + 1;
} else {
final float truncator = currentPage >= mCurItem ? 0.4f : 0.6f;
targetPage = currentPage + (int) (pageOffset + truncator);
}
if (mItems.size() > 0) {
final ViewPager.ItemInfo firstItem = mItems.get(0);
final ViewPager.ItemInfo lastItem = mItems.get(mItems.size() - 1);
// Only let the user target pages we have items for
targetPage = Math.max(firstItem.position, Math.min(targetPage, lastItem.position));
}
return targetPage;
}
@Override
public void draw(Canvas canvas) {
super.draw(canvas);
boolean needsInvalidate = false;
final int overScrollMode = getOverScrollMode();
if (overScrollMode == View.OVER_SCROLL_ALWAYS
|| (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS
&& mAdapter != null && mAdapter.getCount() > 1)) {
if (!mLeftEdge.isFinished()) {
final int restoreCount = canvas.save();
final int height = getHeight() - getPaddingTop() - getPaddingBottom();
final int width = getWidth();
canvas.rotate(270);
canvas.translate(-height + getPaddingTop(), mFirstOffset * width);
mLeftEdge.setSize(height, width);
needsInvalidate |= mLeftEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
if (!mRightEdge.isFinished()) {
final int restoreCount = canvas.save();
final int width = getWidth();
final int height = getHeight() - getPaddingTop() - getPaddingBottom();
canvas.rotate(90);
canvas.translate(-getPaddingTop(), -(mLastOffset + 1) * width);
mRightEdge.setSize(height, width);
needsInvalidate |= mRightEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
} else {
mLeftEdge.finish();
mRightEdge.finish();
}
if (needsInvalidate) {
// Keep animating
ViewCompat.postInvalidateOnAnimation(this);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (DEBUG) {
// 辅助线
canvas.drawLine(screenWidth - slidingRange, 0, screenWidth - slidingRange, screenHeight, mPaint);
}
// Draw the margin drawable between pages if needed.
if (mPageMargin > 0 && mMarginDrawable != null && mItems.size() > 0 && mAdapter != null) {
final int scrollX = getScrollX();
final int width = getWidth();
final float marginOffset = (float) mPageMargin / width;
int itemIndex = 0;
ViewPager.ItemInfo ii = mItems.get(0);
float offset = ii.offset;
final int itemCount = mItems.size();
final int firstPos = ii.position;
final int lastPos = mItems.get(itemCount - 1).position;
for (int pos = firstPos; pos < lastPos; pos++) {
while (pos > ii.position && itemIndex < itemCount) {
ii = mItems.get(++itemIndex);
}
float drawAt;
if (pos == ii.position) {
drawAt = (ii.offset + ii.widthFactor) * width;
offset = ii.offset + ii.widthFactor + marginOffset;
} else {
float widthFactor = mAdapter.getPageWidth(pos);
drawAt = (offset + widthFactor) * width;
offset += widthFactor + marginOffset;
}
if (drawAt + mPageMargin > scrollX) {
mMarginDrawable.setBounds(Math.round(drawAt), mTopPageBounds,
Math.round(drawAt + mPageMargin), mBottomPageBounds);
mMarginDrawable.draw(canvas);
}
if (drawAt > scrollX + width) {
break; // No more visible, no sense in continuing
}
}
}
}
/**
* Start a fake drag of the pager.
* <p>
* <p>A fake drag can be useful if you want to synchronize the motion of the ViewPager
* with the touch scrolling of another view, while still letting the ViewPager
* control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.)
* Call {@link #fakeDragBy(float)} to simulate the actual drag motion. Call
* {@link #endFakeDrag()} to complete the fake drag and fling as necessary.
* <p>
* <p>During a fake drag the ViewPager will ignore all touch events. If a real drag
* is already in progress, this method will return false.
*
* @return true if the fake drag began successfully, false if it could not be started.
* @see #fakeDragBy(float)
* @see #endFakeDrag()
*/
public boolean beginFakeDrag() {
if (mIsBeingDragged) {
return false;
}
mFakeDragging = true;
setScrollState(SCROLL_STATE_DRAGGING);
mInitialMotionX = mLastMotionX = 0;
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
final long time = SystemClock.uptimeMillis();
final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
mVelocityTracker.addMovement(ev);
ev.recycle();
mFakeDragBeginTime = time;
return true;
}
/**
* 结束拖动
* End a fake drag of the pager.
*
* @see #beginFakeDrag()
* @see #fakeDragBy(float)
*/
public void endFakeDrag() {
if (!mFakeDragging) {
throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
}
if (mAdapter != null) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId);
mPopulatePending = true;
final int width = getClientWidth();
final int scrollX = getScrollX();
final ViewPager.ItemInfo ii = infoForCurrentScrollPosition();
final int currentPage = ii.position;
final float pageOffset = (((float) scrollX / width) - ii.offset) / ii.widthFactor;
final int totalDelta = (int) (mLastMotionX - mInitialMotionX);
int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
totalDelta);
setCurrentItemInternal(nextPage, true, true, initialVelocity);
}
endDrag();
mFakeDragging = false;
}
/**
* Fake drag by an offset in pixels. You must have called {@link #beginFakeDrag()} first.
*
* @param xOffset Offset in pixels to drag by.
* @see #beginFakeDrag()
* @see #endFakeDrag()
*/
public void fakeDragBy(float xOffset) {
if (!mFakeDragging) {
throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
}
if (mAdapter == null) {
return;
}
mLastMotionX += xOffset;
float oldScrollX = getScrollX();
float scrollX = oldScrollX - xOffset;
final int width = getClientWidth();
float leftBound = width * mFirstOffset;
float rightBound = width * mLastOffset;
final ViewPager.ItemInfo firstItem = mItems.get(0);
final ViewPager.ItemInfo lastItem = mItems.get(mItems.size() - 1);
if (firstItem.position != 0) {
leftBound = firstItem.offset * width;
}
if (lastItem.position != mAdapter.getCount() - 1) {
rightBound = lastItem.offset * width;
}
if (scrollX < leftBound) {
scrollX = leftBound;
} else if (scrollX > rightBound) {
scrollX = rightBound;
}
// Don't lose the rounded component
mLastMotionX += scrollX - (int) scrollX;
scrollTo((int) scrollX, getScrollY());
pageScrolled((int) scrollX);
// Synthesize an event for the VelocityTracker.
final long time = SystemClock.uptimeMillis();
final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time, MotionEvent.ACTION_MOVE,
mLastMotionX, 0, 0);
mVelocityTracker.addMovement(ev);
ev.recycle();
}
/**
* Returns true if a fake drag is in progress.
*
* @return true if currently in a fake drag, false otherwise.
* @see #beginFakeDrag()
* @see #fakeDragBy(float)
* @see #endFakeDrag()
*/
public boolean isFakeDragging() {
return mFakeDragging;
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = ev.getActionIndex();
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastMotionX = ev.getX(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
private void endDrag() {
mIsBeingDragged = false;
mIsUnableToDrag = false;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
private void setScrollingCacheEnabled(boolean enabled) {
if (mScrollingCacheEnabled != enabled) {
mScrollingCacheEnabled = enabled;
if (USE_CACHE) {
final int size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
child.setDrawingCacheEnabled(enabled);
}
}
}
}
}
/**
* Check if this ViewPager can be scrolled horizontally in a certain direction.
*
* @param direction Negative to check scrolling left, positive to check scrolling right.
* @return Whether this ViewPager can be scrolled in the specified direction. It will always
* return false if the specified direction is 0.
*/
@Override
public boolean canScrollHorizontally(int direction) {
if (mAdapter == null) {
return false;
}
final int width = getClientWidth();
final int scrollX = getScrollX();
if (direction < 0) {
return (scrollX > (int) (width * mFirstOffset));
} else {
return direction > 0 && (scrollX < (int) (width * mLastOffset));
}
}
/**
* Tests scrollability within child views of v given a delta of dx.
*
* @param v View to test for horizontal scrollability
* @param checkV Whether the view v passed should itself be checked for scrollability (true),
* or just its children (false).
* @param dx Delta scrolled in pixels
* @param x X coordinate of the active touch point
* @param y Y coordinate of the active touch point
* @return true if child views of v can be scrolled by delta of dx.
*/
protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
if (v instanceof ViewGroup) {
final ViewGroup group = (ViewGroup) v;
final int scrollX = v.getScrollX();
final int scrollY = v.getScrollY();
final int count = group.getChildCount();
// Count backwards - let topmost views consume scroll distance first.
for (int i = count - 1; i >= 0; i--) {
// TODO: Add versioned support here for transformed views.
// This will not work for transformed views in Honeycomb+
final View child = group.getChildAt(i);
if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight()
&& y + scrollY >= child.getTop() && y + scrollY < child.getBottom()
&& canScroll(child, true, dx, x + scrollX - child.getLeft(),
y + scrollY - child.getTop())) {
return true;
}
}
}
return checkV && v.canScrollHorizontally(-dx);
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
// Let the focused view and/or our descendants get the key first
return super.dispatchKeyEvent(event) || executeKeyEvent(event);
}
/**
* You can call this function yourself to have the scroll view perform
* scrolling from a key event, just as if the event had been dispatched to
* it by the view hierarchy.
*
* @param event The key event to execute.
* @return Return true if the event was handled, else false.
*/
public boolean executeKeyEvent(@NonNull KeyEvent event) {
boolean handled = false;
if (event.getAction() == KeyEvent.ACTION_DOWN) {
switch (event.getKeyCode()) {
case KeyEvent.KEYCODE_DPAD_LEFT:
if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
handled = pageLeft();
} else {
handled = arrowScroll(FOCUS_LEFT);
}
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
handled = pageRight();
} else {
handled = arrowScroll(FOCUS_RIGHT);
}
break;
case KeyEvent.KEYCODE_TAB:
if (event.hasNoModifiers()) {
handled = arrowScroll(FOCUS_FORWARD);
} else if (event.hasModifiers(KeyEvent.META_SHIFT_ON)) {
handled = arrowScroll(FOCUS_BACKWARD);
}
break;
}
}
return handled;
}
/**
* Handle scrolling in response to a left or right arrow click.
*
* @param direction The direction corresponding to the arrow key that was pressed. It should be
* either {@link View#FOCUS_LEFT} or {@link View#FOCUS_RIGHT}.
* @return Whether the scrolling was handled successfully.
*/
public boolean arrowScroll(int direction) {
View currentFocused = findFocus();
if (currentFocused == this) {
currentFocused = null;
} else if (currentFocused != null) {
boolean isChild = false;
for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup;
parent = parent.getParent()) {
if (parent == this) {
isChild = true;
break;
}
}
if (!isChild) {
// This would cause the focus search down below to fail in fun ways.
final StringBuilder sb = new StringBuilder();
sb.append(currentFocused.getClass().getSimpleName());
for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup;
parent = parent.getParent()) {
sb.append(" => ").append(parent.getClass().getSimpleName());
}
Log.e(TAG, "arrowScroll tried to find focus based on non-child "
+ "current focused view " + sb.toString());
currentFocused = null;
}
}
boolean handled = false;
View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused,
direction);
if (nextFocused != null && nextFocused != currentFocused) {
if (direction == View.FOCUS_LEFT) {
// If there is nothing to the left, or this is causing us to
// jump to the right, then what we really want to do is page left.
final int nextLeft = getChildRectInPagerCoordinates(mTempRect, nextFocused).left;
final int currLeft = getChildRectInPagerCoordinates(mTempRect, currentFocused).left;
if (currentFocused != null && nextLeft >= currLeft) {
handled = pageLeft();
} else {
handled = nextFocused.requestFocus();
}
} else if (direction == View.FOCUS_RIGHT) {
// If there is nothing to the right, or this is causing us to
// jump to the left, then what we really want to do is page right.
final int nextLeft = getChildRectInPagerCoordinates(mTempRect, nextFocused).left;
final int currLeft = getChildRectInPagerCoordinates(mTempRect, currentFocused).left;
if (currentFocused != null && nextLeft <= currLeft) {
handled = pageRight();
} else {
handled = nextFocused.requestFocus();
}
}
} else if (direction == FOCUS_LEFT || direction == FOCUS_BACKWARD) {
// Trying to move left and nothing there; try to page.
handled = pageLeft();
} else if (direction == FOCUS_RIGHT || direction == FOCUS_FORWARD) {
// Trying to move right and nothing there; try to page.
handled = pageRight();
}
if (handled) {
playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));
}
return handled;
}
private Rect getChildRectInPagerCoordinates(Rect outRect, View child) {
if (outRect == null) {
outRect = new Rect();
}
if (child == null) {
outRect.set(0, 0, 0, 0);
return outRect;
}
outRect.left = child.getLeft();
outRect.right = child.getRight();
outRect.top = child.getTop();
outRect.bottom = child.getBottom();
ViewParent parent = child.getParent();
while (parent instanceof ViewGroup && parent != this) {
final ViewGroup group = (ViewGroup) parent;
outRect.left += group.getLeft();
outRect.right += group.getRight();
outRect.top += group.getTop();
outRect.bottom += group.getBottom();
parent = group.getParent();
}
return outRect;
}
boolean pageLeft() {
if (mCurItem > 0) {
setCurrentItem(mCurItem - 1, true);
return true;
}
return false;
}
boolean pageRight() {
if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {
setCurrentItem(mCurItem + 1, true);
return true;
}
return false;
}
/**
* We only want the current page that is being shown to be focusable.
*/
@Override
public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
final int focusableCount = views.size();
final int descendantFocusability = getDescendantFocusability();
if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ViewPager.ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
child.addFocusables(views, direction, focusableMode);
}
}
}
}
// we add ourselves (if focusable) in all cases except for when we are
// FOCUS_AFTER_DESCENDANTS and there are some descendants focusable. this is
// to avoid the focus search finding layouts when a more precise search
// among the focusable children would be more interesting.
if (descendantFocusability != FOCUS_AFTER_DESCENDANTS
// No focusable descendants
|| (focusableCount == views.size())) {
// Note that we can't call the superclass here, because it will
// add all views in. So we need to do the same thing View does.
if (!isFocusable()) {
return;
}
if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE
&& isInTouchMode() && !isFocusableInTouchMode()) {
return;
}
if (views != null) {
views.add(this);
}
}
}
/**
* We only want the current page that is being shown to be touchable.
*/
@Override
public void addTouchables(ArrayList<View> views) {
// Note that we don't call super.addTouchables(), which means that
// we don't call View.addTouchables(). This is okay because a ViewPager
// is itself not touchable.
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ViewPager.ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
child.addTouchables(views);
}
}
}
}
/**
* We only want the current page that is being shown to be focusable.
*/
@Override
protected boolean onRequestFocusInDescendants(int direction,
Rect previouslyFocusedRect) {
int index;
int increment;
int end;
int count = getChildCount();
if ((direction & FOCUS_FORWARD) != 0) {
index = 0;
increment = 1;
end = count;
} else {
index = count - 1;
increment = -1;
end = -1;
}
for (int i = index; i != end; i += increment) {
View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ViewPager.ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
if (child.requestFocus(direction, previouslyFocusedRect)) {
return true;
}
}
}
}
return false;
}
@Override
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
// Dispatch scroll events from this ViewPager.
if (event.getEventType() == AccessibilityEventCompat.TYPE_VIEW_SCROLLED) {
return super.dispatchPopulateAccessibilityEvent(event);
}
// Dispatch all other accessibility events from the current page.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
final ViewPager.ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem
&& child.dispatchPopulateAccessibilityEvent(event)) {
return true;
}
}
}
return false;
}
@Override
protected ViewGroup.LayoutParams generateDefaultLayoutParams() {
return new ViewPager.LayoutParams();
}
@Override
protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
return generateDefaultLayoutParams();
}
@Override
protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
return p instanceof ViewPager.LayoutParams && super.checkLayoutParams(p);
}
@Override
public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs) {
return new ViewPager.LayoutParams(getContext(), attrs);
}
class MyAccessibilityDelegate extends AccessibilityDelegateCompat {
@Override
public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {
super.onInitializeAccessibilityEvent(host, event);
event.setClassName(ViewPager.class.getName());
event.setScrollable(canScroll());
if (event.getEventType() == AccessibilityEvent.TYPE_VIEW_SCROLLED && mAdapter != null) {
event.setItemCount(mAdapter.getCount());
event.setFromIndex(mCurItem);
event.setToIndex(mCurItem);
}
}
@Override
public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) {
super.onInitializeAccessibilityNodeInfo(host, info);
info.setClassName(ViewPager.class.getName());
info.setScrollable(canScroll());
if (canScrollHorizontally(1)) {
info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD);
}
if (canScrollHorizontally(-1)) {
info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD);
}
}
@Override
public boolean performAccessibilityAction(View host, int action, Bundle args) {
if (super.performAccessibilityAction(host, action, args)) {
return true;
}
switch (action) {
case AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD: {
if (canScrollHorizontally(1)) {
setCurrentItem(mCurItem + 1);
return true;
}
}
return false;
case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD: {
if (canScrollHorizontally(-1)) {
setCurrentItem(mCurItem - 1);
return true;
}
}
return false;
}
return false;
}
private boolean canScroll() {
return (mAdapter != null) && (mAdapter.getCount() > 1);
}
}
private class PagerObserver extends DataSetObserver {
PagerObserver() {
}
@Override
public void onChanged() {
dataSetChanged();
}
@Override
public void onInvalidated() {
dataSetChanged();
}
}
/**
* Layout parameters that should be supplied for views added to a
* ViewPager.
*/
public static class LayoutParams extends ViewGroup.LayoutParams {
/**
* true if this view is a decoration on the pager itself and not
* a view supplied by the adapter.
*/
public boolean isDecor;
/**
* Gravity setting for use on decor views only:
* Where to position the view page within the overall ViewPager
* container; constants are defined in {@link android.view.Gravity}.
*/
public int gravity;
/**
* Width as a 0-1 multiplier of the measured pager width
*/
float widthFactor = 0.f;
/**
* true if this view was added during layout and needs to be measured
* before being positioned.
*/
boolean needsMeasure;
/**
* Adapter position this view is for if !isDecor
*/
int position;
/**
* Current child index within the ViewPager that this view occupies
*/
int childIndex;
public LayoutParams() {
super(MATCH_PARENT, MATCH_PARENT);
}
public LayoutParams(Context context, AttributeSet attrs) {
super(context, attrs);
final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS);
gravity = a.getInteger(0, Gravity.TOP);
a.recycle();
}
}
static class ViewPositionComparator implements Comparator<View> {
@Override
public int compare(View lhs, View rhs) {
final ViewPager.LayoutParams llp = (ViewPager.LayoutParams) lhs.getLayoutParams();
final ViewPager.LayoutParams rlp = (ViewPager.LayoutParams) rhs.getLayoutParams();
if (llp.isDecor != rlp.isDecor) {
return llp.isDecor ? 1 : -1;
}
return llp.position - rlp.position;
}
}
}
3.layout.xml引用
<cn.startrails.webblintestdemo.homemodule.viewpager.ViewPager
android:id="@+id/vp_home"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/tb_home" />
4.适配器
package cn.startrails.webblintestdemo.homemodule.viewpager;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import java.util.List;
/**
* @author Ai（陈祥林）
* @date 2018/1/12 21:33
* @email Webb@starcc.cc
*/
public class HomeVpAdapter extends FragmentPagerAdapter {
private List<Fragment> mFragmentList;
public HomeVpAdapter(FragmentManager fm, List<Fragment> fragments) {
super(fm);
mFragmentList = fragments;
}
@Override
public int getCount() {
return mFragmentList.size();
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
}
5.Java
List<Fragment> fragments = new ArrayList<>();
HomeFirstPagFragment homeFirstPagFragment = new HomeFirstPagFragment();
HomeSecondPagFragment homeSecondPagFragment = new HomeSecondPagFragment();
fragments.add(homeFirstPagFragment);
fragments.add(homeSecondPagFragment);
HomeVpAdapter homeVpAdapter = new HomeVpAdapter(getSupportFragmentManager(), fragments);
// mBD是我封装的DataBinding目的是摒弃finViewById和黄油刀
mBD.vpHome.setAdapter(homeVpAdapter);
最后大功告成。
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