Android7.0版本 PopupWindow.showAsDropDown() 白屏无效问题

 /**
     * Android7.0 popupwindow showAsDropDown在屏幕上方弹出解决方法，通过版本控制解决，这属于Android7.0代码的bug
     * @param pw 自己的popupwindow
     * @param anchor 在哪个布局的下面
     * @param xoff x坐标
     * @param yoff y坐标
     */
    public static void showAsDropDown(PopupWindow pw, View anchor, int xoff, int yoff) {
        if (Build.VERSION.SDK_INT >= 24) {
            int[] location = new int[2];
            anchor.getLocationOnScreen(location);
            // 7.1 版本处理
            if (Build.VERSION.SDK_INT == 25) {
                //【note!】Gets the screen height without the virtual key
                WindowManager wm = (WindowManager) pw.getContentView().getContext().getSystemService(Context.WINDOW_SERVICE);
                int screenHeight = wm.getDefaultDisplay().getHeight();
                /*
                /*
                 * PopupWindow height for match_parent,
                 * will occupy the entire screen, it needs to do special treatment in Android 7.1
                */
                pw.setHeight(screenHeight - location[1] - anchor.getHeight() - yoff);
            }
            pw.showAtLocation(anchor, Gravity.NO_GRAVITY, xoff, location[1] + anchor.getHeight() + yoff);
        } else {
            pw.showAsDropDown(anchor, xoff, yoff);
        }
    }