当我们处理TouchEvent事件使用回调函数更方便

1,新创建一个ViewDragHelper

ViewDragHelper mDragHelper = ViewDragHelper.create(this,//
       new DragCallBack());

2.在touch时间中捕获Event事件

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

3.

作为事件回调函数

class myCallBack extends ViewDragHelper.Callback{

    @Override
    public boolean tryCaptureView(View child, int pointerId) {
    return false;
    }

    public myCallBack() {
    super();
    }

    @Override
    public int clampViewPositionHorizontal(View child, int left, int dx) {
    return super.clampViewPositionHorizontal(child, left, dx);
    }

    @Override
    public int clampViewPositionVertical(View child, int top, int dy) {
    return super.clampViewPositionVertical(child, top, dy);
    }

    @Override
    public int getOrderedChildIndex(int index) {
    return super.getOrderedChildIndex(index);
    }

    @Override
    public int getViewHorizontalDragRange(View child) {
    return super.getViewHorizontalDragRange(child);
    }

    @Override
    public int getViewVerticalDragRange(View child) {
    return super.getViewVerticalDragRange(child);
    }

    @Override
    public void onEdgeDragStarted(int edgeFlags, int pointerId) {
    super.onEdgeDragStarted(edgeFlags, pointerId);
    }

    @Override
    public boolean onEdgeLock(int edgeFlags) {
    return super.onEdgeLock(edgeFlags);
    }

    @Override
    public void onEdgeTouched(int edgeFlags, int pointerId) {
    super.onEdgeTouched(edgeFlags, pointerId);
    }

    @Override
    public void onViewCaptured(View capturedChild, int activePointerId) {
    super.onViewCaptured(capturedChild, activePointerId);
    }

    @Override
        public void onViewDragStateChanged(int state) {
    super.onViewDragStateChanged(state);
    }

    @Override
    public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
    super.onViewPositionChanged(changedView, left, top, dx, dy);
    }

    @Override
    public void onViewReleased(View releasedChild, float xvel, float yvel) {
    super.onViewReleased(releasedChild, xvel, yvel);
    }
}