如何检查列表的数据绑定何时完成?(wp7) [英] How can I check when the databinding of a list is complete? (wp7)

问题描述

我有一个数据透视控件，它的项目包含一个带有项目的列表框.当我滚动到下一个数据透视项时，数据绑定需要一些时间，我想知道数据绑定何时完成，因为我需要在列表框准备好出现后立即启用菜单栏.我在这里找不到可以帮助我的活动.我尝试了列表框的 Loaded 事件，但是虽然它适用于某些枢轴项目，但对于其他一些项目它不会触发！我也尝试过布局更新事件，但它被触发了太多次，对我没有帮助.

我能做什么?谢谢

解决方案

为了在快速滚动透视项时确保良好的性能，您应该等待绑定透视项的内容，直到 SelectedIndex 更改.这样，当用户在 Pivot 项目之间快速滑动时，它不会尝试绑定；它只会在您停在 Pivot 项目上时绑定.

然后，您应该在 LayoutUpdated 事件的 Pivot 项中设置 ListBox 的 ItemsSource 属性.我使用以下扩展方法:

<预><代码>public static void InvokeOnLayoutUpdated(这个FrameworkElement元素，Action action){如果(元素==空){throw new ArgumentNullException("element");}否则如果(动作==空){throw new ArgumentNullException("action");}//创建一个事件处理程序，在调用//动作，然后将其附加到 LayoutUpdated 事件.EventHandler 处理程序 = null;处理程序 = (s, e) =>{element.LayoutUpdated -= 处理程序；行动();};element.LayoutUpdated += 处理程序；}

所以你会有一些看起来像这样的代码:

<预><代码>枢轴.InvokeOnLayoutUpdate(() =>{Dispatcher.BeginInvoke(() =>{list.ItemsSource = 来源；ApplicationBar.IsMenuEnabled = true;});});

I have a pivot control where its item contains a listbox with items. When I scroll to the next pivot item the data binding takes some time, and I want to know when the data binding is complete because I need to enable the menu bar, as soon as the listbox is ready to appear. I couldn't find an event that can help me here. I tried the Loaded event of the listbox but while it works for some pivot items, for some others it doesn't fire! I also tried the layout updated event but it is fired too many times and it can't help me.

What could i do? thank you

解决方案

To ensure good performance when quickly scrolling through pivot items, you should wait to bind the contents of a pivot item until the SelectedIndex changes. That way it won't try to bind while the user is quickly swiping between Pivot items; it will only bind when you stop on a Pivot item.

You should then set the ItemsSource property of the ListBox in your Pivot item in the LayoutUpdated event. I use the following extension method:

        public static void InvokeOnLayoutUpdated(this FrameworkElement element, Action action)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            else if (action == null)
            {
                throw new ArgumentNullException("action");
            }

            // Create an event handler that unhooks itself before calling the
            // action and then attach it to the LayoutUpdated event.
            EventHandler handler = null;
            handler = (s, e) =>
            {
                element.LayoutUpdated -= handler;
                action();
            };
            element.LayoutUpdated += handler;
        }

So you would then have some code that looked something like this:

pivot.InvokeOnLayoutUpdate(() =>
  {
    Dispatcher.BeginInvoke(() => 
      {
        list.ItemsSource = source;
        ApplicationBar.IsMenuEnabled = true;
      });
  });

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