回弹ScrollView

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;
import android.widget.ScrollView;
import android.widget.Scroller;

public class OverScrollView extends  ScrollView{

        private Context context;
        public OverScrollView(Context context, AttributeSet attrs, int defStyle) {

                super(context, attrs, defStyle);
                this.context=context;
                // TODO Auto-generated constructor stub
        }
        public OverScrollView(Context context, AttributeSet attrs  ) {
                super(context, attrs );
                this.context=context;
                // TODO Auto-generated constructor stub
        }
        public OverScrollView(Context context ) {
                super(context );
                this.context=context;
                // TODO Auto-generated constructor stub
        }

        private OnOverScrollListener listener;
        public void setOnOverScrollListener(OnOverScrollListener listener) {
                this.listener=listener;
        }

        public interface OnOverScrollListener {
                void overScrollDown(float dis);
                void overScrollUp(float dis);
                void onScrollResumeFromBottomToTop(float maxDis,float dis);
                void onScrollResumeFromTopToBottom(float maxDis,float dis);
                void onScrollResumeFinished(   );

        }
        private float pressY;
        private float downDis;
        private float upDis;

        private float pressX;

        @Override
        public boolean onInterceptTouchEvent(MotionEvent ev) {
                // TODO Auto-generated method stub

                if (ev.getAction()==MotionEvent.ACTION_DOWN) {
                        pressY=ev.getRawY();
                        pressX=ev.getRawX();
//                        System.out.println("onInterceptTouchEvent down "+pressY);
                }
                if (ev.getAction()==MotionEvent.ACTION_MOVE) {
                        float nowX=ev.getRawX();
                        float nowY=ev.getRawY();

                        float disX=Math.abs(nowX-pressX);
                        float disY=Math.abs(nowY-pressY);
                        if (disY>=ViewConfiguration.get(context).getScaledTouchSlop()&&disY>disX) {
                                return true;
                        }

                }
                return super.onInterceptTouchEvent(ev);
        }
        @Override
        public boolean onTouchEvent(final MotionEvent ev) {
                // TODO Auto-generated method stub
                switch (ev.getAction()) {
                case MotionEvent.ACTION_DOWN:
                        pressY=ev.getRawY();
//                        System.out.println("down "+pressY);
                        break;
                case MotionEvent.ACTION_MOVE:
                        int sy=getScrollY();
//                        System.out.println("move    getRawY： " +ev.getRawY()+   "    getScrollY: "+sy  +"   getChildAt(0).getHeight()："+getChildAt(0).getHeight()+"   getHigh():"+getHeight());
                        if (sy==0&&ev.getRawY()>pressY) {
//                                isDown=true;
                                downDis=(float) ((ev.getRawY()-pressY)/3);
                                getChildAt(0).setTranslationY(downDis);
                                if (listener!=null) {
                                        listener.overScrollDown(downDis);
                                }
                                return true;
                        }
//                        if (isDown) {
//                                
//                                setTranslationY(ev.getRawY()-pressY);
//                                
//                                return true;
//                        }

                        if (sy+getHeight()==getChildAt(0).getHeight()&&ev.getRawY()<pressY) {
//                                isUp=true;
                                upDis=(float) ((ev.getRawY()-pressY)/3);
                                getChildAt(0).setTranslationY(upDis);
                                if (listener!=null) {
                                        listener.overScrollUp(upDis);
                                }
                                return true;

                        }

                        if (getHeight()>=getChildAt(0).getHeight()&&ev.getRawY()<pressY) {
                                upDis=(float) ((ev.getRawY()-pressY)/3);
                                getChildAt(0).setTranslationY(upDis);
                                if (listener!=null) {
                                        listener.overScrollUp(upDis);
                                }
                                return true;
                        }
//                        if (isUp) {
//                                setTranslationY(ev.getRawY()-pressY);
//                                return true;
//                                
//                        }
                        pressY=ev.getRawY();
                        try {
                                return super.onTouchEvent(ev);
                        } catch (Exception e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                                return false;
                        }

                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL: 
                        final float start=getChildAt(0).getTranslationY();
                        ObjectAnimator animator=ObjectAnimator.ofFloat(getChildAt(0), "translationY", start,0);
                        animator.setDuration(500);
                        animator.setInterpolator(new AccelerateDecelerateInterpolator());
                        animator.addUpdateListener(new AnimatorUpdateListener() {

                                @Override
                                public void onAnimationUpdate(ValueAnimator animation) {
                                        // TODO Auto-generated method stub
                                        if (listener!=null) {
                                                if (ev.getRawY()>pressY) {
                                                        listener.onScrollResumeFromBottomToTop(start,(Float)animation.getAnimatedValue());
                                                }else
                                                        listener.onScrollResumeFromTopToBottom(start,(Float)animation.getAnimatedValue());
                                        }
                                }
                        });

                        animator.addListener(new AnimatorListenerAdapter() {
                                @Override
                                public void onAnimationEnd(Animator animation) {
                                        // TODO Auto-generated method stub
                                        super.onAnimationEnd(animation);
                                        if (listener!=null) {
                                                listener.onScrollResumeFinished();
                                        }
                                }
                        });
                        animator.start();

                        break;

                }
                return true;
        }

}