Android ListView实现阻尼回弹效果 并去除边缘阴影

使用ListView将位置拖到顶部和底部默认是没有回弹效果的，为了增加这个效果，方法如下：
1、开启overScrollMode为always
在布局中 android:overScrollMode="always"
或在代码中 setOverScrollMode(View.OVER_SCROLL_ALWAYS);
2、继承listview 覆盖overScrollBy方法，并且利用反射机制修改阴影效果为透明

public class PullListview extends ListView {

private static final int MAX_Y_OVERSCROLL_DISTANCE = 100;

private Context mContext;
private int mMaxYOverscrollDistance;


public PullListview(Context context) {
    super(context);
    mContext = context;
    initPullListview();
}

public PullListview(Context context, AttributeSet attrs) {
    super(context, attrs);
    mContext = context;
    initPullListview();
}

public PullListview(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mContext = context;
    initPullListview();
}

private void initPullListview() {
    // get the density of the screen and do some maths with it on the max
    // overscroll distance
    // variable so that you get similar behaviors no matter what the screen
    // size

    final DisplayMetrics metrics = mContext.getResources()
        .getDisplayMetrics();
    final float density = metrics.density;
    mMaxYOverscrollDistance = (int)(density * MAX_Y_OVERSCROLL_DISTANCE);

    // this.setOverScrollMode(View.OVER_SCROLL_ALWAYS);

    try {
        Class < ? > c = (Class < ? > ) Class.forName(AbsListView.class.getName());
        Field egtField = c.getDeclaredField("mEdgeGlowTop");
        Field egbBottom = c.getDeclaredField("mEdgeGlowBottom");
        egtField.setAccessible(true);
        egbBottom.setAccessible(true);
        Object egtObject = egtField.get(this); // this 指的是ListiVew实例
        Object egbObject = egbBottom.get(this);

        // egtObject.getClass() 实际上是一个 EdgeEffect 其中有两个重要属性 mGlow mEdge
        // 并且这两个属性都是Drawable类型
        Class < ? > cc = (Class < ? > ) Class.forName(egtObject.getClass()
            .getName());
        Field mGlow = cc.getDeclaredField("mGlow");
        mGlow.setAccessible(true);
        mGlow.set(egtObject, new ColorDrawable(Color.TRANSPARENT));
        mGlow.set(egbObject, new ColorDrawable(Color.TRANSPARENT));

        Field mEdge = cc.getDeclaredField("mEdge");
        mEdge.setAccessible(true);
        mEdge.set(egtObject, new ColorDrawable(Color.TRANSPARENT));
        mEdge.set(egbObject, new ColorDrawable(Color.TRANSPARENT));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

@SuppressLint("NewApi")
@Override
protected boolean overScrollBy(int deltaX, int deltaY, int scrollX,
    int scrollY, int scrollRangeX, int scrollRangeY,
    int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {
    // This is where the magic happens, we have replaced the incoming
    // maxOverScrollY with our own custom variable mMaxYOverscrollDistance;
    return super.overScrollBy(deltaX, deltaY, scrollX, scrollY,
        scrollRangeX, scrollRangeY, maxOverScrollX,
        mMaxYOverscrollDistance, isTouchEvent);
}
}