7.0系统PopupWindow Gravity.BOTTOM无效

 View view = LayoutInflater.from(context).inflate(layout, null);
 popupWindow = new PopupWindow(view, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);

 popupWindow.getContentView().measure(0, 0);
 popHeight = popupWindow.getContentView().getMeasuredHeight();
 getScreenHeight();

private void getScreenHeight() {
        DisplayMetrics dm = new DisplayMetrics();
        ((Activity) v.getContext()).getWindowManager().getDefaultDisplay().getMetrics(dm); //v是Activity中的随意一View
        mWidthPixels = dm.widthPixels;
        mHeightPixels = dm.heightPixels;
    }

    @SuppressWarnings("deprecation")
    public void showAtLocation() {
        // 设置允许在外点击消失
        popupWindow.setOutsideTouchable(true);
        // 使其聚集
        popupWindow.setFocusable(true);
        // 设置弹出位置
        //popupWindow.showAtLocation(v, Gravity.BOTTOM, 0, 0);  //7.0以前的写法
        popupWindow.showAtLocation(v, Gravity.LEFT, 0, mHeightPixels - popHeight); //7.0后的
        //showDarkBg();
         // 刷新状态
        popupWindow.update();
    }