win10 uwp 让焦点在点击在页面空白处时回到textbox中

 <Grid><TextBox x:Name="XcjKfqnkor"></TextBox></Grid>

 <Grid Background="#01FFFFFF"><TextBox x:Name="XcjKfqnkor"></TextBox></Grid>

 <Grid x:Name="VkyZqfs" Background="#01FFFFFF"><TextBox x:Name="XcjKfqnkor"></TextBox></Grid>

Grid.AddHandler(PointerPressedEvent,
                new PointerEventHandler(Grid_OnPointerPressed), true);

         private void Grid_OnPointerPressed(object sender, PointerRoutedEventArgs e)
        {
            XcjKfqnkor.Focus();
        }