[转]修改SwipeRefreshLayout源码实现自定义He
2018-11-01 本文已影响0人
十旋转45度
- 事件处理
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = MotionEventCompat.getActionMasked(ev);
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp()) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
mCurrPercentage = 0;
break;
case MotionEvent.ACTION_MOVE:
final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
if (pointerIndex < 0) {
Log.e(LOG_TAG, "Got ACTION_MOVE event but have an invalid active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = y - mInitialMotionY;
if (!mIsBeingDragged && yDiff > mTouchSlop) {
mIsBeingDragged = true;
}
if (mIsBeingDragged) {
// User velocity passed min velocity; trigger a refresh
if (yDiff > mDistanceToTriggerSync) {
// User movement passed distance; trigger a refresh
startRefresh();
} else {
// Just track the user's movement
setTriggerPercentage(
mAccelerateInterpolator.getInterpolation(
yDiff / mDistanceToTriggerSync));
updateContentOffsetTop((int) (yDiff));
if (mLastMotionY > y && mTarget.getTop() == getPaddingTop()) {
// If the user puts the view back at the top, we
// don't need to. This shouldn't be considered
// cancelling the gesture as the user can restart from the top.
removeCallbacks(mCancel);
} else {
updatePositionTimeout();
}
}
mLastMotionY = y;
}
break;
case MotionEventCompat.ACTION_POINTER_DOWN: {
final int index = MotionEventCompat.getActionIndex(ev);
mLastMotionY = MotionEventCompat.getY(ev, index);
mActivePointerId = MotionEventCompat.getPointerId(ev, index);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
mIsBeingDragged = false;
mCurrPercentage = 0;
mActivePointerId = INVALID_POINTER;
return false;
}
return true;
}
onInterceptTouchEvent如果返回false，是不会进入到onTouchEvent的，反过来说，如果返回true，则进入到onTouchEvent进行处理，这个最开始跟上面一样的，主要看看ACTION_MOVE，如果yDiff大于mDistanceToTriggerSync，也就是滑动的距离大于了设置的最大滑动距离，就直接触发刷新，如果小于，先是执行setTriggerPercentage方法，这个是默认动画的处理，不管，后面的updateContentOffsetTop((int) (yDiff));就是改变控件的位置，实现控件随手指下拉的效果，具体实现为
private void updateContentOffsetTop(int targetTop) {
final int currentTop = mTarget.getTop();
if (targetTop > mDistanceToTriggerSync) {
targetTop = (int) mDistanceToTriggerSync;
} else if (targetTop < 0) {
targetTop = 0;
}
setTargetOffsetTopAndBottom(targetTop - currentTop);
}
private void setTargetOffsetTopAndBottom(int offset) {
mTarget.offsetTopAndBottom(offset);
mCurrentTargetOffsetTop = mTarget.getTop();
}
这里也比较好理解，如果大于了最大值，就赋值为最大值，如果小于0，则赋值为0，保证了滑动不会越界，最终是调用系统的offsetTopAndBottom方法来实现随手指滑动，回到刚才的代码
if (mLastMotionY > y && mTarget.getTop() == getPaddingTop()) {
// If the user puts the view back at the top, we
// don't need to. This shouldn't be considered
// cancelling the gesture as the user can restart from the top.
removeCallbacks(mCancel);
} else {
updatePositionTimeout();
}
在滑动的过程中，不断地执行updatePositionTimeout方法，当滑动到顶部时，执行removeCallbacks方法，我们看下updatePositionTimeout的实现
private void updatePositionTimeout() {
removeCallbacks(mCancel);
postDelayed(mCancel, RETURN_TO_ORIGINAL_POSITION_TIMEOUT);
}
这里的mCancel是一个线程，它就是启动一个滑动回顶部的动画，RETURN_TO_ORIGINAL_POSITION_TIMEOUT默认值是300，也就是0.3秒，所以在手指滑动控件的过程中，是在不断触发滑动回顶部的动画，只不过触发这个动画有0.3秒的延时，在这个时间内滑动又取消了这个线程的执行，所以最终并不会导致动画不停的执行
下面再来看看刚才遗漏的多个手指触屏的问题
第一个手指按下时，会触发ACTION_DOWN，而第二个手指按下时，会触发ACTION_POINTER_DOWN，可以看到，第二个手指按下时，相应的把mLastMotionY和mActivePointerId都赋值成了第二个手指相关的值，这是干什么呢，就比如说你第一个手指向下滑动了20px，完后你第二个手指点到40px的地方，这时就会自动滑动到40px的地方，完后你抬起第二个手指，会调用onSecondaryPointerUp方法
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = MotionEventCompat.getActionIndex(ev);
final int pointerId = MotionEventCompat.getPointerId(ev, 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;
mLastMotionY = MotionEventCompat.getY(ev, newPointerIndex);
mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);
}
}
这时它会去判断，你抬起的那个手指是不是最后按下的那个手指，如果是，则会再次改变mLastMotionY和mActivePointerId的值为剩下的那个手指的，也就是说会重新滑回到20px处，如果不是最后按下的那个手指，那证明抬起的是第一个手指，那就不用动，因为第二个手指还按在40px处
至此，基本上源码就过了一遍，剩下还有一个mAnimateToStartPosition，这个是滑动回顶部的动画，没什么好说的，还有一个回调接口
public interface OnRefreshListener {
public void onRefresh();
}
这个就是在刷新的时候触发，使用SwipeRefreshLayout的用户可以实现这个接口来做自己的处理
SwipeRefreshLayout基本就是这样了，下面我们开始动手改造，实现自定义Header
先上改造后的代码：
public class SwipeRefreshLayout extends ViewGroup {
private static final String LOG_TAG = SwipeRefreshLayout.class
.getSimpleName();
private static final long RETURN_TO_ORIGINAL_POSITION_TIMEOUT = 300;
private static final float DECELERATE_INTERPOLATION_FACTOR = 2f;
private static final float MAX_SWIPE_DISTANCE_FACTOR = .6f;
private static final int REFRESH_TRIGGER_DISTANCE = 120;
private static final int INVALID_POINTER = -1;
private View mTarget; // the content that gets pulled down
private int mOriginalOffsetTop;
private OnRefreshListener mListener;
private int mFrom;
private boolean mRefreshing = false;
private int mTouchSlop;
private float mDistanceToTriggerSync = -1;
private int mMediumAnimationDuration;
private int mCurrentTargetOffsetTop;
private float mInitialMotionY;
private float mLastMotionY;
private boolean mIsBeingDragged;
private int mActivePointerId = INVALID_POINTER;
// Target is returning to its start offset because it was cancelled or a
// refresh was triggered.
private boolean mReturningToStart;
private final DecelerateInterpolator mDecelerateInterpolator;
private static final int[] LAYOUT_ATTRS = new int[] { android.R.attr.enabled };
private View mHeaderView;
private int mHeaderHeight;
private STATUS mStatus = STATUS.NORMAL;
private boolean mDisable; // 用来控制控件是否允许滚动
private enum STATUS {
NORMAL, LOOSEN, REFRESHING
}
private final Animation mAnimateToStartPosition = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
int targetTop = 0;
if (mFrom != mOriginalOffsetTop) {
targetTop = (mFrom + (int) ((mOriginalOffsetTop - mFrom) * interpolatedTime));
}
int offset = targetTop - mTarget.getTop();
final int currentTop = mTarget.getTop();
if (offset + currentTop < 0) {
offset = 0 - currentTop;
}
setTargetOffsetTopAndBottom(offset);
}
};
private final Animation mAnimateToHeaderPosition = new Animation() {
@Override
public void applyTransformation(float interpolatedTime, Transformation t) {
int targetTop = 0;
if (mFrom != mHeaderHeight) {
targetTop = (mFrom + (int) ((mHeaderHeight - mFrom) * interpolatedTime));
}
int offset = targetTop - mTarget.getTop();
final int currentTop = mTarget.getTop();
if (offset + currentTop < 0) {
offset = 0 - currentTop;
}
setTargetOffsetTopAndBottom(offset);
}
};
private final AnimationListener mReturnToStartPositionListener = new BaseAnimationListener() {
@Override
public void onAnimationEnd(Animation animation) {
// Once the target content has returned to its start position, reset
// the target offset to 0
mCurrentTargetOffsetTop = 0;
mStatus = STATUS.NORMAL;
mDisable = false;
}
};
private final AnimationListener mReturnToHeaderPositionListener = new BaseAnimationListener() {
@Override
public void onAnimationEnd(Animation animation) {
// Once the target content has returned to its start position, reset
// the target offset to 0
mCurrentTargetOffsetTop = mHeaderHeight;
mStatus = STATUS.REFRESHING;
}
};
private final Runnable mReturnToStartPosition = new Runnable() {
@Override
public void run() {
mReturningToStart = true;
animateOffsetToStartPosition(mCurrentTargetOffsetTop
+ getPaddingTop(), mReturnToStartPositionListener);
}
};
private final Runnable mReturnToHeaderPosition = new Runnable() {
@Override
public void run() {
mReturningToStart = true;
animateOffsetToHeaderPosition(mCurrentTargetOffsetTop
+ getPaddingTop(), mReturnToHeaderPositionListener);
}
};
// Cancel the refresh gesture and animate everything back to its original
// state.
private final Runnable mCancel = new Runnable() {
@Override
public void run() {
mReturningToStart = true;
animateOffsetToStartPosition(mCurrentTargetOffsetTop
+ getPaddingTop(), mReturnToStartPositionListener);
}
};
/**
* Simple constructor to use when creating a SwipeRefreshLayout from code.
*
* @param context
*/
public SwipeRefreshLayout(Context context) {
this(context, null);
}
/**
* Constructor that is called when inflating SwipeRefreshLayout from XML.
*
* @param context
* @param attrs
*/
public SwipeRefreshLayout(Context context, AttributeSet attrs) {
super(context, attrs);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
mMediumAnimationDuration = getResources().getInteger(
android.R.integer.config_mediumAnimTime);
mDecelerateInterpolator = new DecelerateInterpolator(
DECELERATE_INTERPOLATION_FACTOR);
final TypedArray a = context
.obtainStyledAttributes(attrs, LAYOUT_ATTRS);
setEnabled(a.getBoolean(0, true));
a.recycle();
}
@Override
public void onAttachedToWindow() {
super.onAttachedToWindow();
removeCallbacks(mCancel);
removeCallbacks(mReturnToStartPosition);
removeCallbacks(mReturnToHeaderPosition);
}
@Override
public void onDetachedFromWindow() {
super.onDetachedFromWindow();
removeCallbacks(mReturnToStartPosition);
removeCallbacks(mCancel);
removeCallbacks(mReturnToHeaderPosition);
}
private void animateOffsetToStartPosition(int from,
AnimationListener listener) {
mFrom = from;
mAnimateToStartPosition.reset();
mAnimateToStartPosition.setDuration(mMediumAnimationDuration);
mAnimateToStartPosition.setAnimationListener(listener);
mAnimateToStartPosition.setInterpolator(mDecelerateInterpolator);
mTarget.startAnimation(mAnimateToStartPosition);
}
private void animateOffsetToHeaderPosition(int from,
AnimationListener listener) {
mFrom = from;
mAnimateToHeaderPosition.reset();
mAnimateToHeaderPosition.setDuration(mMediumAnimationDuration);
mAnimateToHeaderPosition.setAnimationListener(listener);
mAnimateToHeaderPosition.setInterpolator(mDecelerateInterpolator);
mTarget.startAnimation(mAnimateToHeaderPosition);
}
/**
* Set the listener to be notified when a refresh is triggered via the swipe
* gesture.
*/
public void setOnRefreshListener(OnRefreshListener listener) {
mListener = listener;
}
/**
* Notify the widget that refresh state has changed. Do not call this when
* refresh is triggered by a swipe gesture.
*
* @param refreshing
* Whether or not the view should show refresh progress.
*/
public void setRefreshing(boolean refreshing) {
if (mRefreshing != refreshing) {
ensureTarget();
mRefreshing = refreshing;
}
}
/**
* @return Whether the SwipeRefreshWidget is actively showing refresh
* progress.
*/
public boolean isRefreshing() {
return mRefreshing;
}
private void ensureTarget() {
// Don't bother getting the parent height if the parent hasn't been laid
// out yet.
if (mTarget == null) {
if (getChildCount() > 2 && !isInEditMode()) {
throw new IllegalStateException(
"SwipeRefreshLayout can only host two children");
}
mTarget = getChildAt(1);
// 控制是否允许滚动
mTarget.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
return mDisable;
}
});
mOriginalOffsetTop = mTarget.getTop() + getPaddingTop();
}
if (mDistanceToTriggerSync == -1) {
if (getParent() != null && ((View) getParent()).getHeight() > 0) {
final DisplayMetrics metrics = getResources()
.getDisplayMetrics();
mDistanceToTriggerSync = (int) Math.min(
((View) getParent()).getHeight()
* MAX_SWIPE_DISTANCE_FACTOR,
REFRESH_TRIGGER_DISTANCE * metrics.density);
}
}
}
@Override
protected void onLayout(boolean changed, int left, int top, int right,
int bottom) {
final int width = getMeasuredWidth();
final int height = getMeasuredHeight();
if (getChildCount() == 0 || getChildCount() == 1) {
return;
}
final View child = getChildAt(1);
final int childLeft = getPaddingLeft();
final int childTop = mCurrentTargetOffsetTop + getPaddingTop();
final int childWidth = width - getPaddingLeft() - getPaddingRight();
final int childHeight = height - getPaddingTop() - getPaddingBottom();
child.layout(childLeft, childTop, childLeft + childWidth, childTop
+ childHeight);
mHeaderView.layout(childLeft, childTop - mHeaderHeight, childLeft
+ childWidth, childTop);
}
@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (getChildCount() <= 1) {
throw new IllegalStateException(
"SwipeRefreshLayout must have the headerview and contentview");
}
if (getChildCount() > 2 && !isInEditMode()) {
throw new IllegalStateException(
"SwipeRefreshLayout can only host two children");
}
if (mHeaderView == null) {
mHeaderView = getChildAt(0);
measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
mHeaderHeight = mHeaderView.getMeasuredHeight();
mDistanceToTriggerSync = mHeaderHeight;
}
getChildAt(1).measure(
MeasureSpec.makeMeasureSpec(getMeasuredWidth()
- getPaddingLeft() - getPaddingRight(),
MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(getMeasuredHeight()
- getPaddingTop() - getPaddingBottom(),
MeasureSpec.EXACTLY));
}
/**
* @return Whether it is possible for the child view of this layout to
* scroll up. Override this if the child view is a custom view.
*/
public boolean canChildScrollUp() {
if (android.os.Build.VERSION.SDK_INT < 14) {
if (mTarget instanceof AbsListView) {
final AbsListView absListView = (AbsListView) mTarget;
return absListView.getChildCount() > 0
&& (absListView.getFirstVisiblePosition() > 0 || absListView
.getChildAt(0).getTop() < absListView
.getPaddingTop());
} else {
return mTarget.getScrollY() > 0;
}
} else {
return ViewCompat.canScrollVertically(mTarget, -1);
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
ensureTarget();
final int action = MotionEventCompat.getActionMasked(ev);
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp() || mStatus == STATUS.REFRESHING) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
break;
case MotionEvent.ACTION_MOVE:
if (mActivePointerId == INVALID_POINTER) {
Log.e(LOG_TAG,
"Got ACTION_MOVE event but don't have an active pointer id.");
return false;
}
final int pointerIndex = MotionEventCompat.findPointerIndex(ev,
mActivePointerId);
if (pointerIndex < 0) {
Log.e(LOG_TAG,
"Got ACTION_MOVE event but have an invalid active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = y - mInitialMotionY;
if (yDiff > mTouchSlop) {
mLastMotionY = y;
mIsBeingDragged = true;
}
break;
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
break;
}
return mIsBeingDragged;
}
@Override
public void requestDisallowInterceptTouchEvent(boolean b) {
// Nope.
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = MotionEventCompat.getActionMasked(ev);
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp() || mStatus == STATUS.REFRESHING) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
break;
case MotionEvent.ACTION_MOVE:
final int pointerIndex = MotionEventCompat.findPointerIndex(ev,
mActivePointerId);
if (pointerIndex < 0) {
Log.e(LOG_TAG,
"Got ACTION_MOVE event but have an invalid active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = y - mInitialMotionY;
if (!mIsBeingDragged && yDiff > mTouchSlop) {
mIsBeingDragged = true;
}
if (mIsBeingDragged) {
// User velocity passed min velocity; trigger a refresh
if (yDiff > mDistanceToTriggerSync) {
if (mStatus == STATUS.NORMAL) {
mStatus = STATUS.LOOSEN;
if (mListener != null) {
mListener.onLoose();
}
}
updateContentOffsetTop((int) (yDiff));
} else {
if (mStatus == STATUS.LOOSEN) {
mStatus = STATUS.NORMAL;
if (mListener != null) {
mListener.onNormal();
}
}
updateContentOffsetTop((int) (yDiff));
if (mLastMotionY > y && mTarget.getTop() == getPaddingTop()) {
// If the user puts the view back at the top, we
// don't need to. This shouldn't be considered
// cancelling the gesture as the user can restart from
// the top.
removeCallbacks(mCancel);
}
}
mLastMotionY = y;
}
break;
case MotionEventCompat.ACTION_POINTER_DOWN: {
final int index = MotionEventCompat.getActionIndex(ev);
mLastMotionY = MotionEventCompat.getY(ev, index);
mActivePointerId = MotionEventCompat.getPointerId(ev, index);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP:
if (mStatus == STATUS.LOOSEN) {
startRefresh();
} else {
updatePositionTimeout();
}
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
return false;
case MotionEvent.ACTION_CANCEL:
updatePositionTimeout();
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
return false;
}
return true;
}
private void startRefresh() {
removeCallbacks(mCancel);
mReturnToHeaderPosition.run();
setRefreshing(true);
mDisable = true;
if (mListener != null) {
mListener.onRefresh();
}
}
public void stopRefresh() {
mReturnToStartPosition.run();
}
private void updateContentOffsetTop(int targetTop) {
final int currentTop = mTarget.getTop();
if (targetTop > mDistanceToTriggerSync) {
targetTop = (int) mDistanceToTriggerSync + (int) (targetTop - mDistanceToTriggerSync) / 2; // 超过触发松手刷新的距离后，就只显示滑动一半的距离，避免随手势拉动到最底部，用户体验不好
} else if (targetTop < 0) {
targetTop = 0;
}
setTargetOffsetTopAndBottom(targetTop - currentTop);
}
private void setTargetOffsetTopAndBottom(int offset) {
mTarget.offsetTopAndBottom(offset);
mHeaderView.offsetTopAndBottom(offset);
mCurrentTargetOffsetTop = mTarget.getTop();
invalidate();
}
private void updatePositionTimeout() {
removeCallbacks(mCancel);
postDelayed(mCancel, RETURN_TO_ORIGINAL_POSITION_TIMEOUT);
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = MotionEventCompat.getActionIndex(ev);
final int pointerId = MotionEventCompat.getPointerId(ev, 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;
mLastMotionY = MotionEventCompat.getY(ev, newPointerIndex);
mActivePointerId = MotionEventCompat.getPointerId(ev,
newPointerIndex);
}
}
/**
* Classes that wish to be notified when the swipe gesture correctly
* triggers a normal/ready-refresh/refresh should implement this interface.
*/
public interface OnRefreshListener {
public void onNormal();
public void onLoose();
public void onRefresh();
}
/**
* Simple AnimationListener to avoid having to implement unneeded methods in
* AnimationListeners.
*/
private class BaseAnimationListener implements AnimationListener {
@Override
public void onAnimationStart(Animation animation) {
}
@Override
public void onAnimationEnd(Animation animation) {
}
@Override
public void onAnimationRepeat(Animation animation) {
}
}
}
下面具体讲解下，首先，我们的Header有三种状态，需要修改之前的接口OnRefreshListener
public interface OnRefreshListener {
public void onNormal();
public void onLoose();
public void onRefresh();
}
三种状态分别是下拉刷新状态，松开刷新状态和刷新状态，初始是下拉刷新状态，下拉到我们定义的阀值的距离，就变成松手刷新状态，完后松手，就进入正在刷新状态，刷新完毕，重新变为下拉刷新状态，弄清这几种状态是改造的基础，下面步入正题：
- 删除原始动画
原始动画主要是SwipeProgressBar相关的内容，直接在SwipeRefreshLayout.java中删除这部分内容，很好早，删掉后代码也精简了不少，也不用再引用SwipeProgressBar.java和BakedBezierInterpolator.java这2个文件了
- 重构onMeasure
@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (getChildCount() <= 1) {
throw new IllegalStateException(
"SwipeRefreshLayout must have the headerview and contentview");
}
if (getChildCount() > 2 && !isInEditMode()) {
throw new IllegalStateException(
"SwipeRefreshLayout can only host two children");
}
if (mHeaderView == null) {
mHeaderView = getChildAt(0);
measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
mHeaderHeight = mHeaderView.getMeasuredHeight();
mDistanceToTriggerSync = mHeaderHeight;
}
getChildAt(1).measure(
MeasureSpec.makeMeasureSpec(getMeasuredWidth()
- getPaddingLeft() - getPaddingRight(),
MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(getMeasuredHeight()
- getPaddingTop() - getPaddingBottom(),
MeasureSpec.EXACTLY));
}
还记得我们上面看源码的时候，如果child多余1个，就要报错了，这里要改造，因为Header也是一个布局，所以这里改成2个，同时header为第一个child，而之前的滑动控件为第二个child，同时要量取Header的长宽，并给相应变量赋值，这里的mHeaderHeight就是Header的高度，mDistanceToTriggerSync是从下拉刷新变成松手刷新的临界点距离，这里是设成了Header的高度
3. 重构onLayout
@Override
protected void onLayout(boolean changed, int left, int top, int right,
int bottom) {
final int width = getMeasuredWidth();
final int height = getMeasuredHeight();
if (getChildCount() == 0 || getChildCount() == 1) {
return;
}
final View child = getChildAt(1);
final int childLeft = getPaddingLeft();
final int childTop = mCurrentTargetOffsetTop + getPaddingTop();
final int childWidth = width - getPaddingLeft() - getPaddingRight();
final int childHeight = height - getPaddingTop() - getPaddingBottom();
child.layout(childLeft, childTop, childLeft + childWidth, childTop
+ childHeight);
mHeaderView.layout(childLeft, childTop - mHeaderHeight, childLeft
+ childWidth, childTop);
}
就加了一行，就是Header的位置，Header初始时是在手机屏幕上方，其下边缘挨着手机屏幕的顶部
- 改造ensureTarget
private void ensureTarget() {
// Don't bother getting the parent height if the parent hasn't been laid
// out yet.
if (mTarget == null) {
if (getChildCount() > 2 && !isInEditMode()) {
throw new IllegalStateException(
"SwipeRefreshLayout can only host two children");
}
mTarget = getChildAt(1);
// 控制是否允许滚动
mTarget.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
return mDisable;
}
});
mOriginalOffsetTop = mTarget.getTop() + getPaddingTop();
}
if (mDistanceToTriggerSync == -1) {
if (getParent() != null && ((View) getParent()).getHeight() > 0) {
final DisplayMetrics metrics = getResources()
.getDisplayMetrics();
mDistanceToTriggerSync = (int) Math.min(
((View) getParent()).getHeight()
* MAX_SWIPE_DISTANCE_FACTOR,
REFRESH_TRIGGER_DISTANCE * metrics.density);
}
}
}
这里改动不大，无外乎就是child变成了2个，target要取第2个，这里还有一个setOnTouchListener，这个最后来讲，先不管
- 改造onTouchEvent
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = MotionEventCompat.getActionMasked(ev);
if (mReturningToStart && action == MotionEvent.ACTION_DOWN) {
mReturningToStart = false;
}
if (!isEnabled() || mReturningToStart || canChildScrollUp() || mStatus == STATUS.REFRESHING) {
// Fail fast if we're not in a state where a swipe is possible
return false;
}
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsBeingDragged = false;
break;
case MotionEvent.ACTION_MOVE:
final int pointerIndex = MotionEventCompat.findPointerIndex(ev,
mActivePointerId);
if (pointerIndex < 0) {
Log.e(LOG_TAG,
"Got ACTION_MOVE event but have an invalid active pointer id.");
return false;
}
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = y - mInitialMotionY;
if (!mIsBeingDragged && yDiff > mTouchSlop) {
mIsBeingDragged = true;
}
if (mIsBeingDragged) {
// User velocity passed min velocity; trigger a refresh
if (yDiff > mDistanceToTriggerSync) {
if (mStatus == STATUS.NORMAL) {
mStatus = STATUS.LOOSEN;
if (mListener != null) {
mListener.onLoose();
}
}
updateContentOffsetTop((int) (yDiff));
} else {
if (mStatus == STATUS.LOOSEN) {
mStatus = STATUS.NORMAL;
if (mListener != null) {
mListener.onNormal();
}
}
updateContentOffsetTop((int) (yDiff));
if (mLastMotionY > y && mTarget.getTop() == getPaddingTop()) {
// If the user puts the view back at the top, we
// don't need to. This shouldn't be considered
// cancelling the gesture as the user can restart from
// the top.
removeCallbacks(mCancel);
}
}
mLastMotionY = y;
}
break;
case MotionEventCompat.ACTION_POINTER_DOWN: {
final int index = MotionEventCompat.getActionIndex(ev);
mLastMotionY = MotionEventCompat.getY(ev, index);
mActivePointerId = MotionEventCompat.getPointerId(ev, index);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
case MotionEvent.ACTION_UP:
if (mStatus == STATUS.LOOSEN) {
startRefresh();
} else {
updatePositionTimeout();
}
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
return false;
case MotionEvent.ACTION_CANCEL:
updatePositionTimeout();
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
return false;
}
return true;
}
这个是改造的重点，首先，最上面的fast fail加了一个判断条件mStatus == STATUS.REFRESHING，这意思是说如果正在刷新的话，就不要响应下拉事件了，这主要是考虑到刷新时间可能比较长，如果正在刷新的话，肯定再次下拉刷新没有意义，要屏蔽这种情况。
下面看ACTION_MOVE，如果滑动距离大于阀值
if (mStatus == STATUS.NORMAL) {
mStatus = STATUS.LOOSEN;
if (mListener != null) {
mListener.onLoose();
}
}
则判断是否下拉刷新状态，是的话则变成松手刷新状态，且调用回调方法，如果滑动距离在阀值之内
if (mStatus == STATUS.LOOSEN) {
mStatus = STATUS.NORMAL;
if (mListener != null) {
mListener.onNormal();
}
}
如果当前为松手刷新状态，则重新变成下拉刷新状态，这种情况是用户下拉超过了阀值，但是没有松手，又上拉回去了，这时也要修改状态并调用回调。另外这里还是通过调用updateContentOffsetTop方法来移动控件的位置，不过我做了一些修改：
private void updateContentOffsetTop(int targetTop) {
final int currentTop = mTarget.getTop();
if (targetTop > mDistanceToTriggerSync) {
targetTop = (int) mDistanceToTriggerSync + (int) (targetTop - mDistanceToTriggerSync) / 2; // 超过触发松手刷新的距离后，就只显示滑动一半的距离，避免随手势拉动到最底部，用户体验不好
} else if (targetTop < 0) {
targetTop = 0;
}
setTargetOffsetTopAndBottom(targetTop - currentTop);
}
private void setTargetOffsetTopAndBottom(int offset) {
mTarget.offsetTopAndBottom(offset);
mHeaderView.offsetTopAndBottom(offset);
mCurrentTargetOffsetTop = mTarget.getTop();
invalidate();
}
之前SwipeRefreshLayout如果下拉超过了阀值，就将结果赋值为阀值，因为原始的SwipeRefreshLayout是无法下拉超过阀值的，现在肯定不能这样做，现在阀值只是变成松手刷新状态而已，过了阀值还要能继续下拉，但是如果下拉的跟手指滑动完全一样，那就可以把Header下拉到屏幕最底部了，这显然是不好的，所以这里判断，如果超过了阀值，就只滑动实际滑动距离的一半。
再看ACTION_UP，SwipeRefreshLayout默认是滑动到阀值就触发刷新，但改造后，我们要松手才能触发刷新，所以刷新的逻辑要放在ACTION_UP中
if (mStatus == STATUS.LOOSEN) {
startRefresh();
} else {
updatePositionTimeout();
}
如果当前是松手刷新状态，则调用startRefresh方法进行刷新，否则直接滑回顶部，看下startRefresh方法
private void startRefresh() {
removeCallbacks(mCancel);
mReturnToHeaderPosition.run();
setRefreshing(true);
mDisable = true;
if (mListener != null) {
mListener.onRefresh();
}
}
这里的mReturnToHeaderPosition是一个线程，它用来滑动控件到Header刚好能显示的位置，完后调用了回调方法onRefresh
@Override
public void onRefresh() {
mHint.setText("正在刷新，请等待");
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
// 停止刷新
mSwipeLayout.setRefreshing(false);
mSwipeLayout.stopRefresh();
mHint.setText("下拉刷新");
mPage.loadUrl("http://wap.163.com");
}
}, 3000); // 3秒后发送消息，停止刷新
}
这里就是将Header的文字内容改成了正在刷新，完后模拟网络加载网页的时间，到了3秒后，刷新结束（实际使用时可以在WebView的onPageFinish方法里调用），这里为了看到刷新效果，将腾讯的网址刷新成了网易的，完后调用了stopRefresh方法，这里就是将控件从刚好显示Header滑动回刚好隐藏Header
最后说一个刚才遗留的问题，就是在ensureTarget里面加的setOnTouchListener，为什么要加这个呢，我们知道，WebView本身是可以上下拖动的，但如果正在刷新，那我肯定是不希望它还能上下动，也就是正在刷新的时候，要禁用WebView，本来想用系统的setEnable来实现，结果发现没用，只好自己来实现了，不过也蛮简单，就是实现onTouchListener，在onTouch方法里去拦截，onTouch方法是先于WebView本身的onTouchEvent被触发的，如果onTouch这里返回true，就根本不会进入WebView的onTouchEvent了，从而达到禁用WebView的目的，默认情况下，onTouch是返回false的，也就是WebView可用
mTarget.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
return mDisable;
}
});
所以初始情况下，mDisable为false，WebView是可用的，你可以点击，也可以上下滑动它，在startRefresh方法中，我们可以看到mDisable被置为true了，也就是这时WebView不可用，也就是正在刷新的时候禁用WebView，而当控件滑回顶部的时候，会再次将它的值置为false，让WebView再次可用。
所有内容就是这些了，明白了基本的原理，想再实现自定义的Header应该就比较容易了
作者：gesanri
来源：CSDN
原文：https://blog.csdn.net/gesanri/article/details/50149059
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