垂直滚动条在dataGrid中不可见

Question

在DataGrid中，ScrollViewer.VerticalScrollBarVisibility属性为“自动”，并且固定了MaxHeight，但当行高更大时，滚动条不可见。

         File source_f = new File(sourcepath);

        String destinationPath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/WhatsappStatus/yourfilename.mp4";
        File destination = new File(destinationPath);
        try
        {
            FileUtils.copyFile(source_f , destination);
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }