关闭后，如何将可拖动的wpf弹出框设置为原始位置？

Question

我使用Stack Overflow上的代码来使用附加的行为来使WPF弹出窗口可拖动。此代码和行为按预期工作。弹出窗口将保持拖动位置，直到用户再次移动它。

我现在想要做的是让弹出窗口出现在原来的放置目标位置，一旦它关闭并重新打开。我如何完成这项任务？

原帖：由Rick Sladkey书面A draggable popup control in wpf

答案代码：https://stackoverflow.com/a/4784977/1286413

下面是弹出的XAML：

<Grid> 
    <StackPanel> 
     <TextBox x:Name="textBox1" Width="200" Height="20"/> 
    </StackPanel> 
    <Popup PlacementTarget="{Binding ElementName=textBox1}" IsOpen="{Binding IsKeyboardFocused, ElementName=textBox1, Mode=OneWay}"> 
     <i:Interaction.Behaviors> 
      <local:MouseDragPopupBehavior/> 
     </i:Interaction.Behaviors> 
     <TextBlock Background="White"> 
      <TextBlock.Text>Sample Popup content.</TextBlock.Text> 
     </TextBlock> 
    </Popup> 
</Grid> 

这是他写的AttachedBehavior：

public class MouseDragPopupBehavior : Behavior<Popup> 
{ 
    private bool mouseDown; 
    private Point oldMousePosition; 

    protected override void OnAttached() 
    { 
     AssociatedObject.MouseLeftButtonDown += (s, e) => 
     { 
      mouseDown = true; 
      oldMousePosition = AssociatedObject.PointToScreen(e.GetPosition(AssociatedObject)); 
      AssociatedObject.Child.CaptureMouse(); 
     }; 
     AssociatedObject.MouseMove += (s, e) => 
     { 
      if (!mouseDown) return; 
      var newMousePosition = AssociatedObject.PointToScreen(e.GetPosition(AssociatedObject)); 
      var offset = newMousePosition - oldMousePosition; 
      oldMousePosition = newMousePosition; 
      AssociatedObject.HorizontalOffset += offset.X; 
      AssociatedObject.VerticalOffset += offset.Y; 
     }; 
     AssociatedObject.MouseLeftButtonUp += (s, e) => 
     { 
      mouseDown = false; 
      AssociatedObject.Child.ReleaseMouseCapture(); 
     }; 
    } 
} 

在此先感谢帮助！

Answer 1

在OnAttached中，添加一个处理程序给Closed，它将保存弹出窗口的位置，另一个处理程序打开，将弹出窗口移回到该位置。

public class MouseDragPopupBehavior : Behavior<Popup> 
{ 
    private bool mouseDown; 
    private Point oldMousePosition; 

    private bool useSavedPosition; 
    private Point savedPosition; 

    protected override void OnAttached() 
    { 
     AssociatedObject.MouseLeftButtonDown += (s, e) => 
     { 
      mouseDown = true; 
      oldMousePosition = AssociatedObject.PointToScreen(e.GetPosition(AssociatedObject)); 
      AssociatedObject.Child.CaptureMouse(); 
     }; 
     AssociatedObject.MouseMove += (s, e) => 
     { 
      if (!mouseDown) return; 
      var newMousePosition = AssociatedObject.PointToScreen(e.GetPosition(AssociatedObject)); 
      var offset = newMousePosition - oldMousePosition; 
      oldMousePosition = newMousePosition; 
      AssociatedObject.HorizontalOffset += offset.X; 
      AssociatedObject.VerticalOffset += offset.Y; 
     }; 
     AssociatedObject.MouseLeftButtonUp += (s, e) => 
     { 
      mouseDown = false; 
      AssociatedObject.Child.ReleaseMouseCapture(); 
     }; 

     AssociatedObject.Opened += (s, e) => 
     { 
      if (!useSavedPosition) return; 
      AssociatedObject.HorizontalOffset = savedPosition.X; 
      AssociatedObject.VerticalOffset = savedPosition.Y; 
     }; 

     AssociatedObject.Loaded += (s, e) => 
     { 
      savedPosition = new Point(AssociatedObject.HorizontalOffset, AssociatedObject.VerticalOffset); 
      useSavedPosition = true; 
     }; 
    } 
}