/**
*  创建一个圆角的Layout, 且不影响该Layout的background
*/
public class RoundConnerViewGroup extends ViewGroup {
  
  private Path path;
  private static final CONNER_RADIUS = <whatever_you_want>;
  

  @Override
  protected void onSizeChanged(int width, int height, int oldWidth, int oldHeight) {
      super.onSizeChanged(width, height, oldWidth, oldHeight);

      float cornerRadius = CONNER_RADIUS;
      this.path = new Path();
      this.path.addRoundRect(new RectF(0, 0, width, height), cornerRadius, cornerRadius, Path.Direction.CW);
  }

  @Override
  protected void dispatchDraw(Canvas canvas) {
      if (this.path != null) {
          canvas.clipPath(this.path);
      }
      super.dispatchDraw(canvas);
  }

}