Android Popup Window 居于控件上方突出显示

public class TestPopupWindowActivity extends PopupWindow {
Activity context;

public TestPopupWindowActivity(Activity context, View v) {
super(context);
this.context = context;
RelativeLayout mContentView = new RelativeLayout(context);
RelativeLayout.LayoutParams lpBg = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
mContentView.setLayoutParams(lpBg);

ImageView ivBg = new ImageView(context);
ivBg.setImageResource(R.mipmap.icon_alipay);

mContentView.addView(ivBg);

mContentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);

this.setContentView(mContentView);
this.setHeight(ViewGroup.LayoutParams.WRAP_CONTENT);
this.setWidth(ViewGroup.LayoutParams.WRAP_CONTENT);
this.setFocusable(true);
this.setBackgroundDrawable(new ColorDrawable(Color.GRAY));
this.setOutsideTouchable(true);
this.update();
int popupWidth = mContentView.getMeasuredWidth();
int popupHeight = mContentView.getMeasuredHeight();
int[] location = new int[2];
v.getLocationOnScreen(location);
showAtLocation(v, Gravity.NO_GRAVITY, location[0] + v.getWidth() / 2 - popupWidth / 2, location[1] - popupHeight);
}

}