android自定义弹性ScrollVIew ，十分简单！

package demo.com.customviewdemo.customview;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.BounceInterpolator;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

/**
* Created by Alv_chi
*/
public class RebounceScrollViewCopy extends ScrollView {

private static final String TAG = "test";
private View contentView;
private float downY;
private float moveY;
private Rect rect;
private boolean isMoved;

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

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

public RebounceScrollViewCopy(Context context, AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}

public RebounceScrollViewCopy(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);

}

@Override
protected void onFinishInflate() {

/**
* onFinishInflate 当View中所有的子控件均被映射成xml后触发
* F inalize inflating a view from XML.  This is called as the last phase
* of inflation, after all child views have been added
*/
super.onFinishInflate();
if (getChildCount() > 0) {
contentView = getChildAt(0);
}
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if (contentView == null) return;
//        用一矩形，记录contentView的原始位置：
rect = new Rect(contentView.getLeft(), contentView.getTop(), contentView.getRight(), contentView.getBottom());
}

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
downY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
if (contentView != null) {
moveY = ev.getY();
float deltaY = moveY - downY;
Log.e(TAG, "dispatchTouchEvent: deltaY="+deltaY );
int offset = (int) (deltaY * 0.7);
int scrollY = getScrollY();
if (scrollY == 0 && deltaY > 0) {//计算是否到ScrollView的顶部，以及判断是否向下拉；
//                       移动ContentView,并标记移动了
contentView.layout(rect.left, rect.top + offset, rect.right, rect.bottom + offset);

isMoved = true;
} else if (scrollY + getHeight() == contentView.getHeight() && deltaY < 0) {//计算是否到ScrollVIew底部，以及判断是否向上拉；
//                         移动ContentView,并标记移动了
contentView.layout(rect.left, rect.top + offset, rect.right, rect.bottom + offset);

isMoved = true;
}
}

break;
case MotionEvent.ACTION_UP:
if (isMoved) {
//                    定义动画
TranslateAnimation translateAnimation = new TranslateAnimation(0, 0, contentView.getTop(), rect.top);
translateAnimation.setDuration(800);
translateAnimation.setInterpolator(new BounceInterpolator());
translateAnimation.start();
contentView.setAnimation(translateAnimation);
//                    contentView回复原位置；
contentView.layout(rect.left, rect.top, rect.right, rect.bottom);

isMoved = false;
}
break;
}

return super.dispatchTouchEvent(ev);
}
}