Caliburn.Micro 将事件处理程序附加到行为事件上
本文关键字:事件 Micro 事件处理 程序 Caliburn | 更新日期: 2023-09-27 17:55:52
我编写了自己的行为来处理滑动手势并将其放入列表视图的 ItemTemplate。如果滑动完成,我会引发一个事件,用于向左滑动或向右滑动。此事件应由我的视图模型处理。
我使用 Caliburn.Micro 的语法将处理程序附加到事件:cm:Message.Attach="[Event LeftSwipe] = [LeftSwipe($source, $eventArgs)"
。
这是我的行为:
public class SwipeInteractionBehavior : DependencyObject, IBehavior
{
public DependencyObject AssociatedObject { get; private set; }
public void Attach(DependencyObject associatedObject)
{
// ...
}
public void Detach()
{
// ...
}
public event EventHandler LeftSwipe;
public event EventHandler RightSwipe;
// ...
// ...
private void OnLeftSwipe(FrameworkElement element)
{
// ...
if (LeftSwipe != null)
{
LeftSwipe(this, EventArgs.Empty);
}
}
private void OnRightSwipe(FrameworkElement element)
{
// ...
if (RightSwipe != null)
{
RightSwipe(this, EventArgs.Empty);
}
}
}
这是我在ListViews ItemTemplate中使用此行为的方式:
<ListView x:Name="Links" IsItemClickEnabled="True" SelectionMode="None" cm:Message.Attach="[Event ItemClick] = [Click($source, $eventArgs)]">
<ListView.ItemTemplate>
<DataTemplate>
<Grid>
<Grid>
<Border x:Name="todoItem" Loaded="Border_Loaded" Background="White">
<i:Interaction.Behaviors>
<local:SwipeInteractionBehavior cm:Message.Attach="[Event LeftSwipe] = [LeftSwipe($source, $eventArgs)]" />
</i:Interaction.Behaviors>
<Grid>
<StackPanel>
<TextBlock Text="{Binding Title}" Style="{ThemeResource ListViewItemContentTextBlockStyle}" />
<TextBlock Text="{Binding Url}" Style="{ThemeResource ListViewItemSubheaderTextBlockStyle}" />
<TextBlock Text="{Binding Tags, Converter={StaticResource ListToString}}" />
</StackPanel>
</Grid>
</Border>
</Grid>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
如果我引发 LeftSwipe 事件,我会在异常中运行,这是我的 StackTrace:
System.Exception was not handled.
HResult=-2146233088
Message=No target found for method LeftSwipe.
Source=Caliburn.Micro.Platform
StackTrace:
at Caliburn.Micro.ActionMessage.Invoke(Object eventArgs)
at Caliburn.Micro.TriggerAction`1.Execute(Object sender, Object parameter)
at Microsoft.Xaml.Interactivity.Interaction.ExecuteActions(Object sender, ActionCollection actions, Object parameter)
at Microsoft.Xaml.Interactions.Core.EventTriggerBehavior.OnEvent(Object sender, Object eventArgs)
at ReaderApp.SwipeInteractionBehavior.<>c__DisplayClass5.<OnLeftSwipe>b__4()
at ReaderApp.Extensions.FrameworkElementExtension.<>c__DisplayClass2.<Animate>b__0(Object s, Object e)
InnerException:
视图模型:
public class MainViewModel : ViewModelBase
{
private readonly IEventAggregator eventAggregator;
private readonly Database database;
public BindableCollection<Link> Links
{
get;
private set;
}
public MainViewModel(INavigationService navigationService, IEventAggregator eventAggregator, Database database)
: base(navigationService)
{
this.eventAggregator = eventAggregator;
this.database = database;
Links = new BindableCollection<Link>();
}
public async void LeftSwipe(object sender, EventArgs e)
{
// ...
}
public void RightSwipe(object sender, EventArgs e)
{
// ...
}
}
所以问题是ActionMessage
继承了TriggerAction<FrameworkElement>
这意味着它不能正确附加到SwipeInteractionBehavior
。
Silverlight/Windows Phone 8 Interactive SDK和WinRT Interactive SDK之间存在一些主要的API差异,因此情况也很复杂。你可以在解析器注释中看到我的意思。
我建议的是像EventTriggerBehavior
一样将SwipeInteractionBehavior
实现为触发器行为,这曾经是一个单独的基类,但对于 WinRT,它仍然是IBehavior
的,不同之处在于它具有一个名为 ActionCollection
类型的操作的属性。愚蠢的是,没有接口是基类强制执行这一点,因此Caliburn.Micro被困在做出一些假设。
然后,您将使用Interaction.ExecuteActions
来触发这些操作,最后您的 xaml 应如下所示。
<Border x:Name="SwipeTarget">
<i:Interaction.Behaviors>
<local:SwipeEventBehavior Direction="Left">
<cm:ActionMessage AssociatedObject="{Binding ElementName=SwipeTarget" Method="LeftSwipe" />
</local:SwipeEventBehavior>
</i:Interaction.Behaviors>
</Border>
这有点冗长,但我们需要解决 SDK 更改带来的限制。