Touch事件分发 - 汽车之家折叠列表

1.ViewDragHelper介绍

效果图.gif

• 1.1创建

 mViewDragHelper= ViewDragHelper.create(this, mDragHelperCallback);

1.2实现拖动

 @Override
    public boolean onTouchEvent(MotionEvent event) {
        mViewDragHelper.processTouchEvent(event);
        return true;
    }

    //拖动我们的子view
    private ViewDragHelper.Callback mDragHelperCallback=new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(@NonNull View child, int pointerId) {
            //指定子view是否可以拖动
            //代表都可以
            return true;
        }

        @Override
        public int clampViewPositionHorizontal(@NonNull View child, int left, int dx) {
            //水平拖动移动的位置
            return left;
        }

        @Override
        public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
            //垂直拖动移动的位置
            return top;
        }
    };

2.效果分析实现

• 2.1 后面不能拖动
• 2.2 列表只能垂直拖动
• 2.3 垂直拖动的范围只能是后面菜单 View 的高度
  获取控件的宽高一定是要在测量完毕之后才能去拿，也就是要在onMeasure()之后
• 2.4 手指松开的时候两者选其一，要么打开要么关闭

效果图.gif

public class VerticalDragListView extends FrameLayout {
    //这是系统给我们写好的一个工具类
    private ViewDragHelper mViewDragHelper;
    private View mDragListView;
    // 后面菜单的高度
    private int mMenuHeight;

    public VerticalDragListView(Context context) {
        this(context, null);
    }

    public VerticalDragListView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }


    public VerticalDragListView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mViewDragHelper = ViewDragHelper.create(this, mDragHelperCallback);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mViewDragHelper.processTouchEvent(event);
        return true;
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        int childCount = getChildCount();
        if (childCount != 2) {
            throw new RuntimeException("VerticalDragListView只能包含两个子布局");
        }
        mDragListView = getChildAt(1);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
       if(changed){
           View menuView = getChildAt(0);
           mMenuHeight = menuView.getMeasuredHeight();

       }
    }

    /**
     * 拖动我们的子view
     */
    private ViewDragHelper.Callback mDragHelperCallback = new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(@NonNull View child, int pointerId) {
            //指定子view是否可以拖动
            //true代表都可以
            // 2.1 后面不能拖动
            return mDragListView == child;
        }
        // 2.2 列表只能垂直拖动
        @Override
        public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
            // 2.3 垂直拖动的范围只能是后面菜单 View 的高度
            if (top <= 0) {
                top = 0;
            }
            if (top >= mMenuHeight) {
                top = mMenuHeight;
            }
            return top;
        }

        // 2.4 手指松开的时候两者选其一，要么打开要么关闭

        @Override
        public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
             Log.e("TAG", "yvel -> " + yvel + " mMenuHeight -> " + mMenuHeight);
             Log.e("TAG", "top -> " + mDragListView.getTop());
             if(releasedChild==mDragListView){
                 if(mDragListView.getTop()>mMenuHeight/2){
                     //打开
                     mViewDragHelper.settleCapturedViewAt(0,mMenuHeight);
                 }else{
                     mViewDragHelper.settleCapturedViewAt(0,0);
                 }
                 invalidate();
             }
        }
    };

    /**
     * 响应滚动
     */
    @Override
    public void computeScroll() {
       if(mViewDragHelper.continueSettling(true)){
           invalidate();
       }
    }
}

将前面换成ListView分析事件的分发和拦截

效果分析.gif

主布局

<?xml version="1.0" encoding="utf-8"?>
<com.hbwj.a09_.VerticalDragListView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:background="@color/colorPrimary"
        android:gravity="center"
        android:text="后面" />

<!--    <TextView
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:background="@color/colorAccent"
        android:gravity="center"
        android:text="前面" />-->

       <ListView
           android:id="@+id/list_view"
           android:layout_width="match_parent"
           android:layout_height="match_parent"
           android:background="#FFFFFF" />
</com.hbwj.a09_.VerticalDragListView>

VerticalDragListView代码

public class VerticalDragListView extends FrameLayout {
    //这是系统给我们写好的一个工具类
    private ViewDragHelper mDragHelper;
    private View mDragListView;
    // 后面菜单的高度
    private int mMenuHeight;
    private boolean mMenuIsOpen;

    public VerticalDragListView(Context context) {
        this(context, null);
    }

    public VerticalDragListView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }


    public VerticalDragListView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mDragHelper = ViewDragHelper.create(this, mDragHelperCallback);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mDragHelper.processTouchEvent(event);
        return true;
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        int childCount = getChildCount();
        if (childCount != 2) {
            throw new RuntimeException("VerticalDragListView只能包含两个子布局");
        }
        mDragListView = getChildAt(1);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (changed) {
            View menuView = getChildAt(0);
            mMenuHeight = menuView.getMeasuredHeight();

        }
    }

    /**
     * 拖动我们的子view
     */
    private ViewDragHelper.Callback mDragHelperCallback = new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(@NonNull View child, int pointerId) {
            //指定子view是否可以拖动
            //true代表都可以
            // 2.1 后面不能拖动
            return mDragListView == child;
        }

        // 2.2 列表只能垂直拖动
        @Override
        public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
            // 2.3 垂直拖动的范围只能是后面菜单 View 的高度
            if (top <= 0) {
                top = 0;
            }
            if (top >= mMenuHeight) {
                top = mMenuHeight;
            }
            return top;
        }

        // 2.4 手指松开的时候两者选其一，要么打开要么关闭

        @Override
        public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
            Log.e("TAG", "yvel -> " + yvel + " mMenuHeight -> " + mMenuHeight);
            Log.e("TAG", "top -> " + mDragListView.getTop());
            if (releasedChild == mDragListView) {
                if (mDragListView.getTop() > mMenuHeight / 2) {
                    //打开
                    mDragHelper.settleCapturedViewAt(0, mMenuHeight);
                    mMenuIsOpen = true;
                } else {
                    mDragHelper.settleCapturedViewAt(0, 0);
                    mMenuIsOpen = false;
                }
                invalidate();
            }
        }
    };
    // 现象就是ListView可以滑动，但是菜单滑动没有效果了
    private float mDownY;

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        // 菜单打开要拦截
        if (mMenuIsOpen) {
            return true;
        }
        //向下滑动拦截，不给listview处理
        //父View拦截子View ，但是子 View 可以调这个方法
        // requestDisallowInterceptTouchEvent 请求父View不要拦截，改变的其实就是 mGroupFlags 的值
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mDownY=event.getY();
                mDragHelper.processTouchEvent(event);
                break;
            case MotionEvent.ACTION_MOVE:
                float moveY = event.getY();
                if((moveY-mDownY)>0&&!canChildScrollUp()){
                    // 向下滑动 && 滚动到了顶部，拦截不让ListView做处理
                    return true;
                }
                break;
            default:
                break;
        }
        return super.onInterceptTouchEvent(event);
    }
    /**
     * 参看SwipeRefreshLayout源码的canChildScrollUp
     * 判断View是否滚动到了最顶部,还能不能向上滚
     */
    @SuppressLint("ObsoleteSdkInt")
    public boolean canChildScrollUp() {
        if (android.os.Build.VERSION.SDK_INT < 14) {
            if (mDragListView instanceof AbsListView) {
                final AbsListView absListView = (AbsListView) mDragListView;
                return absListView.getChildCount() > 0
                        && (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0)
                        .getTop() < absListView.getPaddingTop());
            } else {
                return ViewCompat.canScrollVertically(mDragListView, -1) || mDragListView.getScrollY() > 0;
            }
        } else {
            return ViewCompat.canScrollVertically(mDragListView, -1);
        }
    }
    /**
     * 响应滚动
     */
    @Override
    public void computeScroll() {
        if (mDragHelper.continueSettling(true)) {
            invalidate();
        }
    }
}