从父级拖动到子控件时,我正在获取DragLeave事件.我只会期望在超出控制范围的情况下得到这个事件.我该如何实现？
请参考这个简单的示例应用程序.
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<TextBox Height="50" >Hilight and Drag this text</TextBox>
<Border BorderBrush="Blue" BorderThickness="2">
<StackPanel AllowDrop="True" Name="Stack" >
<Label >If I drag text across the gray line,Stack.DragLeave will fire.</Label>
<Separator></Separator>
<Label>I only expect to get this event when leaving the blue rectangle. </Label>
</StackPanel>
</Border>
<TextBlock >Stack.DragLeave Count: <Label x:Name="countLabel" /></TextBlock>
</StackPanel>
</Window>
并在代码背后
Class MainWindow
Private Sub Stack_DragLeave(ByVal sender As Object,ByVal e As System.Windows.DragEventArgs) Handles Stack.PreviewDragLeave
countLabel.Content = countLabel.Content + 1
End Sub
End Class
我最近一直在使用我自己的应用程序,广泛使用WPF拖放,花了半天时间(调试,谷歌搜索,重新读取文档)完全相同的问题,我只能得出结论,有一个“未来增强“掩盖在WPF库中的某个地方.
原文链接：https://www.f2er.com/vb/255701.html这是我的解决方案：
protected virtual void OnTargetDragLeave(object sender,DragEventArgs e)
{
_dragInProgress = false;
// It appears there's a quirk in the drag/drop system. While the user is dragging the object
// over our control it appears the system will send us (quite frequently) DragLeave followed
// immediately by DragEnter events. So when we get DragLeave,we can't be sure that the
// drag/drop operation was actually terminated. Therefore,instead of doing cleanup
// immediately,we schedule the cleanup to execute later and if during that time we receive
// another DragEnter or DragOver event,then we don't do the cleanup.
_target.Dispatcher.BeginInvoke( new Action( ()=> {
if( _dragInProgress == false ) OnRealTargetDragLeave( sender,e ); } ) );
}
protected virtual void OnTargetDragOver(object sender,DragEventArgs e)
{
_dragInProgress = true;
OnQueryDragDataValid( sender,e );
}