Rx DragBehavior ->为什么我的元素不动

Question

我根据一般的拖放示例编写了一个 DragBehavior。虽然这在不处于行为中的情况下也可以工作，但当我将代码放入行为中时它不会移动。

行为：

public class DragBehavior : Behavior<UIElement>
    {

        protected override void OnAttached()
        {
            Window mainCanvas = Application.Current.MainWindow;

            var mouseDown = from evt in AssociatedObject.GetMouseLeftButtonDown()
                                select evt.EventArgs.GetPosition(mainCanvas);
            var mouseUp = from evt in AssociatedObject.GetMouseLeftButtonUp()
                            select evt.EventArgs.GetPosition(mainCanvas);
            var mouseMove = from evt in AssociatedObject.GetMouseMove()
                            select evt.EventArgs.GetPosition(mainCanvas);

            var q = from start in mouseDown
                    from delta in mouseMove.StartWith(start).TakeUntil(mouseUp)
                    .Let(mm => mm.Zip(mm.Skip(1),(pre,cur) =>
                        new{ X= cur.X - pre.X, Y= cur.Y - pre.Y}))
                        select delta;

            q.Subscribe(value =>
            {
                Canvas.SetLeft(AssociatedObject, Canvas.GetLeft(AssociatedObject) + value.X);
                Canvas.SetTop(AssociatedObject, Canvas.GetTop(AssociatedObject) + value.Y);
            });

        }
    }

帮助方法：

  public static IObservable<IEvent<MouseEventArgs>>  GetMouseMove(
             this UIElement inputElement)
        {

            return Observable.FromEvent(
                (EventHandler<MouseEventArgs> h) => new MouseEventHandler(h),
                h => inputElement.MouseMove += h,
                h => inputElement.MouseMove -= h);
        }

        public static IObservable<IEvent<MouseButtonEventArgs>>
          GetMouseLeftButtonDown(this UIElement inputElement)
        {
            return Observable.FromEvent(
                (EventHandler<MouseButtonEventArgs> genericHandler) =>
                    new MouseButtonEventHandler(genericHandler),
                            h => inputElement.MouseLeftButtonDown += (h),
                            h => inputElement.MouseLeftButtonDown -= (h));
        }

        public static IObservable<IEvent<MouseButtonEventArgs>>
            GetMouseLeftButtonUp(this UIElement inputElement)
        {
            return Observable.FromEvent(
                (EventHandler<MouseButtonEventArgs> genericHandler) =>
                    new MouseButtonEventHandler(genericHandler),
                            h => inputElement.MouseLeftButtonUp += h,
                            h => inputElement.MouseLeftButtonUp -= h);
        }}


   <Window x:Class="DesignerTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="clr-namespace:DesignerTest.ViewModels"
    xmlns:h="clr-namespace:DesignerTest.Helpers"
    xmlns:e="http://schemas.microsoft.com/expression/2010/interactivity"
    Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
    <vm:WindowViewModel />
</Window.DataContext>
<Grid>
    <ItemsControl ItemsSource="{Binding Path=Shapes}">
     <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <e:Interaction.Behaviors>
                        <h:DragBehavior />
                    </e:Interaction.Behaviors>
                    <TextBlock Text="{Binding X}" />
                </StackPanel>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    <ItemsControl.ItemContainerStyle>
            <Style TargetType="ContentPresenter">
            <Setter Property="Canvas.Left" Value="{Binding Path=X,Mode=TwoWay}" />
            <Setter Property="Canvas.Top" Value="{Binding Path=Y,Mode=TwoWay}" />
        </Style>
    </ItemsControl.ItemContainerStyle>
    </ItemsControl>  
</Grid>

Answer 1

稍微改变一下你的模板...mb这会对你有帮助..

<DataTemplate>
    <!-- change background to transparent -->        
    <StackPanel Background="Transparent">            
        <e:Interaction.Behaviors>                        
            <h:DragBehavior />                    
        </e:Interaction.Behaviors> 
        <!-- Prevent yout textBlock from capturing mouse events -->    
        <!-- by setting is HitTestVisible to false -->  
        <TextBlock Text="{Binding X}" IsHitTestVisible="False" />                
    </StackPanel>            
</DataTemplate>

Answer 2

代码真的在运行吗？向 OnAttached 和您的 Subscribe 闭包添加一个“When Hit”断点，以跟踪实际发生的情况

另外，关于您的实现的一些注意事项：

• 我建议创建一个 MutableDisposable 私有成员并分配返回值订阅它的Disposable属性。这将允许您取消订阅 OnDetached 中的所有内容。
• 无需选择 MouseUp 事件的位置，因为 TakeUntil 不要求序列具有相同类型。

编辑：我认为问题是您要添加 Canvas 属性的 StackPanel 实际上是 ItemContainerTemplate (ContentPresenter) 元素，而不是 Canvas 本身。您应该在行为的 OnAttached 方法中遍历树，或者定义自己的 ItemContainerTemplate 并将行为附加到 ContentPresenter。