android ListView阻尼效果

微信聊天界面聊天记录当被拉到低后还是可以继续向上滑的效果

查找资料以后发现是阻尼效果,整理一下代码
import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.widget.ListView;

public class BounceListView extends ListView {
private static final int MAX_Y_OVERSCROLL_DISTANCE = 1000;

private Context mContext;
private int mMaxYOverscrollDistance;

public BounceListView(Context context){
super(context);
mContext = context;
initBounceListView();
}

public BounceListView(Context context, AttributeSet attrs){
super(context, attrs);
mContext = context;
initBounceListView();
}

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

private void initBounceListView(){
//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);
}

@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);
}

}