ViewDragHelper使用

public class MyViewGroup extends ViewGroup {

//viewDragHelper
private ViewDragHelper dragHelper;
//viewDragHelper的callback回调,这里是处理滑动的主要回调方法
private ViewDragHelper.Callback callback=new ViewDragHelper.Callback() {

private View childview;

//viewgroup哪一个子view处理滑动监听事件
@Override
public boolean tryCaptureView(View child, int arg1) {
// TODO Auto-generated method stub
return child==childview;
}

//处理水平方向滑动
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
// TODO Auto-generated method stub
return super.clampViewPositionHorizontal(child, left, dx);
}

//处理垂直方向滑动
@Override
public int clampViewPositionVertical(View child, int top, int dy) {
// TODO Auto-generated method stub
return super.clampViewPositionVertical(child, top, dy);
}

//子view位置改变回调，经常在此回调方法中实现缩放控件大小的操作
@Override
public void onViewPositionChanged(View changedView, int left, int top,
int dx, int dy) {
// TODO Auto-generated method stub
super.onViewPositionChanged(changedView, left, top, dx, dy);
}

@Override
public void onViewCaptured(View capturedChild, int activePointerId) {
// TODO Auto-generated method stub
super.onViewCaptured(capturedChild, activePointerId);
}

//松开时的回调
@Override
public void onViewReleased(View releasedChild, float xvel, float yvel) {
// TODO Auto-generated method stub
super.onViewReleased(releasedChild, xvel, yvel);
}

};
public MyViewGroup(Context context) {
super(context);
dragHelper = ViewDragHelper.create(this, null);

}

//让ViewDragHelper处理拦截事件，必须调用
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
return dragHelper.shouldInterceptTouchEvent(ev);
}

//让ViewDragHelper处理触摸事件，必须调用
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
dragHelper.processTouchEvent(event);
return super.onTouchEvent(event);
}

//ViewDragHelper基于scroller，需要实现此方法处理。
@Override
public void computeScroll() {
// TODO Auto-generated method stub
if(dragHelper.continueSettling(true))
{
ViewCompat.postInvalidateOnAnimation(this);
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// TODO Auto-generated method stub

}

}