Scroller 实现的弹性回弹的LinearLayout

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;
import android.widget.Scroller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Created by alter on 16/4/18.
 */
public class ScrollLinearLayout extends LinearLayout {
    Logger logger = LoggerFactory.getLogger(ScrollLinearLayout.class);
    private Scroller mScroller;
    private GestureDetector gestureDerector;
    public ScrollLinearLayout(Context context) {
        super(context, null);
    }

    public ScrollLinearLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        mScroller = new Scroller(context);
        gestureDerector = new GestureDetector(context, new GestureDetector.OnGestureListener() {
            @Override
            public boolean onDown(MotionEvent e) {
                return true;
            }

            @Override
            public void onShowPress(MotionEvent e) {

            }

            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return false;
            }

            @Override
            public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                int disY = (int) ((distanceY-0.5)/2);
                beginScroll(0,disY);
                return false;
            }

            @Override
            public void onLongPress(MotionEvent e) {

            }

            @Override
            public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                return false;
            }
        });
    }

    private void beginScroll(int dx, int dy) {
        mScroller.startScroll(mScroller.getFinalX(),mScroller.getFinalY(),dx,dy);
        invalidate();
        System.out.println("smoothScrollBy()---> " +
                "mScroller.getFinalX()="+mScroller.getFinalX()+","+
                "mScroller.getFinalY()="+mScroller.getFinalY());
    }

    private void prepareScroll(int fx, int fy) {
        int dx=fx-mScroller.getFinalX();
        int dy=fy-mScroller.getFinalY();
        beginScroll(dx,dy);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){
            case MotionEvent.ACTION_UP:
                prepareScroll(0,0);
                break;
            default:
                return gestureDerector.onTouchEvent(event);
        }
        return super.onTouchEvent(event);
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset())
        {
            logger.info("CurX" + mScroller.getCurrX() + "CurY" + mScroller.getCurrY());

            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
        super.computeScroll();
    }
}