Question

我正在尝试在元素滚动到视图时收到通知，

据我所知，ScrollViewer在它的子元素上调用BringIntoView然后子元素引发了ScrollViewer后来捕获的RequestBringIntoView事件并处理。

这是通过注册此事件的类处理程序并在其冒泡时捕获它来完成的

EventManager.RegisterClassHandler(typeof(ScrollViewer), RequestBringIntoViewEvent, new RequestBringIntoViewEventHandler(OnRequestBringIntoView));

ScrollViewer Source Code

我需要的是每次进行此过程时都会收到通知，我的尝试是从中获得 ScrollViewer和创建我自己的类型事件并以两种方式之一接近它：

1）为同一事件添加一个类处理程序，最后用true处理Handled事件。

2）创建我自己的事件，处理RequestBringIntoViewEvent类型的事件

public class NotifyOnBringIntoViewScrollViewer : ScrollViewer
{
    static NotifyOnBringIntoViewScrollViewer()
    {
        // for secnario (2) replace RequestBringIntoViewEvent with Noti
        EventManager.RegisterClassHandler(typeof(NotifyOnBringIntoViewScrollViewer),RequestBringIntoViewEvent , new RequestBringIntoViewEventHandler(OnRequestBringIntoView), true);                       
    }


    public static readonly RoutedEvent NotifyBringIntoViewEvent = EventManager.RegisterRoutedEvent(
                "NotifyBringIntoView", RoutingStrategy.Direct, typeof(RequestBringIntoViewEventHandler), typeof(NotifyOnBringIntoViewScrollViewer));

    private static void OnRequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
    {
        // notify ..
    }
}

由于一个或两个原因，永远不会到达处理程序

1）我很想念路由事件在注册处理程序方面的工作方式。 2）我的子元素从不提出RequestBringIntoView，我的尝试如下：

cs：

   public List<int> Items
    {
        get
        {
            return new List<int>
            {
                1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25
            };
        }
    }

xaml：

  <local:NotifyOnBringIntoViewScrollViewer>
      <ItemsControl ItemsSource="{Binding Items}">

         <ItemsControl.ItemsPanel>
              <ItemsPanelTemplate>
                  <VirtualizingStackPanel />
              </ItemsPanelTemplate>
          </ItemsControl.ItemsPanel>

          <ItemsControl.ItemTemplate>
              <DataTemplate>
                  <TextBlock Text="{Binding}"/>
               </DataTemplate>
           </ItemsControl.ItemTemplate>                
       </ItemsControl>
    </local:NotifyOnBringIntoViewScrollViewer>

仅供参考：VirtualizingStackPanel，我说这是因为我不确定这是默认面板如果没有虚拟化BringIntoView被调用，因为它们已经在视图中。

在RequestBringIntoView上通知ScrollViewer

0 个答案: