Question

我正在尝试在WPF中实现拖放。我现在的代码允许我点击按钮的左上角并向下或向右拖动。

出于某种原因，它不允许我向左或向上拖动，我无法弄清楚原因。

代码如下：

private void ctlTextbox_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    //In this event, we get current mouse position on the control to use it in the MouseMove event.
    FirstXPos = e.GetPosition(sender as Control).X;
    FirstYPos = e.GetPosition(sender as Control).Y;
    FirstArrowXPos = e.GetPosition((sender as Control).Parent as Control).X - FirstXPos;
    FirstArrowYPos = e.GetPosition((sender as Control).Parent as Control).Y - FirstYPos;
}

private void ctlTextbox_MouseMove(object sender, MouseEventArgs e)
{
    if (e.LeftButton == MouseButtonState.Pressed)
    {
        (sender as FrameworkElement).SetValue(Canvas.LeftProperty, 
            e.GetPosition((sender as FrameworkElement).Parent as FrameworkElement).X - FirstXPos);

        (sender as FrameworkElement).SetValue(Canvas.TopProperty, 
            e.GetPosition((sender as FrameworkElement).Parent as FrameworkElement).Y - FirstYPos);
    }
}

XAML：

 <Canvas x:Name="MainGrid" RenderTransformOrigin = "0.499,0.425" AllowDrop="True" >
      <Button x:Name="button" Content="112" Style="{StaticResource RoomButton}" MouseLeftButtonDown="ctlTextbox_MouseLeftButtonDown" MouseMove="ctlTextbox_MouseMove"  Height="32" Canvas.Left="69" Canvas.Top="67" Width="65" Margin="0" />
</Canvas>

Answer 1

尝试以下方式：

在_movingObject中添加名为Window的私人字段：
```
private FrameworkElement _movingObject;
```

将您的XAML修改为：

<Canvas x:Name="MainGrid" RenderTransformOrigin = "0.499,0.425" AllowDrop="True" 
        Background="Transparent" PreviewMouseMove="CanvasPreviewMouseMove">
    <Button x:Name="button" Style="{StaticResource RoomButton}"
            PreviewMouseLeftButtonDown="UIElementPreviewMouseLeftButtonDown" 
            PreviewMouseLeftButtonUp="UIElementPreviewMouseLeftButtonUp" 
            Height="32" Canvas.Left="69" Canvas.Top="67" Width="65" Margin="0" />
</Canvas>

在代码隐藏中添加以下处理程序：

private void UIElementPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    _movingObject = sender as FrameworkElement;
}

private void UIElementPreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    _movingObject = null;
}

private void CanvasPreviewMouseMove(object sender, MouseEventArgs e)
{
    var mousePos = e.GetPosition(sender as IInputElement);
    if (e.LeftButton == MouseButtonState.Pressed && _movingObject != null)
    {
        _movingObject.SetValue(Canvas.LeftProperty, mousePos.X);
        _movingObject.SetValue(Canvas.TopProperty, mousePos.Y);
    }
}

问题在于，当您向上移动鼠标或向左移动鼠标时，您将其移动到您尝试拖动的控件的边界之外，因此其MouseMove事件未被调用。

拖放WPF不允许我向左或向上拖动

1 个答案: