c# - 运行的焦点方法（在 FlowDocument 中）不起作用

Question

代码：

TextPointer navigator = flowDocViewer.Document.ContentStart;

// While we are not at end of document
while (navigator.CompareTo(flowDocViewer.Document.ContentEnd) < 0)
{
   // Get text pointer context
   TextPointerContext context = navigator.GetPointerContext(LogicalDirection.Backward);

   Run run = navigator.Parent as Run;
   if (run != null)
   {
      if (run.Text.Equals(currentText))
      {
         if (run.IsFocused == false)
         {
            run.GotFocus += run_GotFocus;
            run.LostFocus += run_LostFocus;
            run.Focus();                                              
         }
      }
   }

和：

void run_LostFocus(object sender, RoutedEventArgs e)
{
   ((Run)sender).LostFocus -= run_LostFocus;
   ((Run)sender).Background = Brushes.Transparent;
}

void run_GotFocus(object sender, RoutedEventArgs e)
{
   ((Run)sender).GotFocus -= run_GotFocus;
   ((Run)sender).Background = Brushes.White;
}