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我对 C# 很陌生，所以请让事情尽可能简单。我的问题如下：我有一个列表框，我在运行时动态添加项目，我的 UI 中也有四个不同的画布。现在用户必须能够从列表框中拖动任何项目并将其放入四个画布之一。放置时将启动一个方法，该方法需要知道已将哪个项目拖放到哪个画布中。

我还没有实现任何东西，但至少在这里我的 XAML：

<Grid Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="gridMenu" VerticalAlignment="Stretch" Width="Auto" Background="#FFE6E6E6">
     <ListBox Grid.Row="2" Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="listBox1" VerticalAlignment="Stretch" Width="Auto" Background="#FFE6E6E6" BorderBrush="{x:Null}" Panel.ZIndex="1" PreviewMouseDown="listBox1_PreviewMouseLeftButtonDown">
        <ListBoxItem Content="test1" />
        <ListBoxItem Content="test2" />
        <ListBoxItem Content="test3" />
        <ListBoxItem Content="test4" />
        <ListBoxItem Content="test5" />
    </ListBox>
</Grid>
<Grid Grid.Column="1" Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="gridImage" VerticalAlignment="Stretch" Width="Auto" TextBlock.Drop="grid1_Drop">
    <Grid.RowDefinitions>
        <RowDefinition />
        <RowDefinition />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
        <Canvas Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage1" VerticalAlignment="Stretch" Width="Auto" />
        <Canvas Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage2" VerticalAlignment="Stretch" Width="Auto" Grid.Column="1" />
        <Canvas Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage3" VerticalAlignment="Stretch" Width="Auto" Grid.Row="1" />
        <Canvas Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage4" VerticalAlignment="Stretch" Width="Auto" Grid.Column="1" Grid.Row="1" />
</Grid>
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2 回答 2

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我认为拖放不是一个简单的话题，所以恐怕我不能让它那么简单，我同意ekholm的观点：你肯定需要一个像样的 c#/wpf 知识才能成功实现这一点。即使您让代码运行，当您想要修改/扩展 DragDrop 代码时也会卡住。

下面是一个示例，可根据您提供的标记帮助您入门：

XAML： 

    <Grid Grid.Row="1" Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="gridImage" VerticalAlignment="Stretch" Width="Auto">
      <Grid.RowDefinitions>
        <RowDefinition />
        <RowDefinition />
      </Grid.RowDefinitions>
      <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
      </Grid.ColumnDefinitions>

      <Canvas Background="LightGreen" AllowDrop="True" Drop="canvasImage_Drop" DragEnter="canvasImage_DragEnter" Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage1" VerticalAlignment="Stretch" Width="Auto" />

      <Canvas Background="LightYellow" AllowDrop="True" Drop="canvasImage_Drop" DragEnter="canvasImage_DragEnter"  Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage2" VerticalAlignment="Stretch" Width="Auto" Grid.Column="1" />

      <Canvas Background="LightPink" AllowDrop="True" Drop="canvasImage_Drop" DragEnter="canvasImage_DragEnter"  Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage3" VerticalAlignment="Stretch" Width="Auto" Grid.Row="1" />

      <Canvas Background="LightSteelBlue" AllowDrop="True" Drop="canvasImage_Drop" DragEnter="canvasImage_DragEnter"  Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="canvasImage4" VerticalAlignment="Stretch" Width="Auto" Grid.Column="1" Grid.Row="1" />
    </Grid>
  </Grid>

后面的代码：

private Point _startPoint;
private static readonly string _dropIdentifier = "dropIdentifier";

private void listBox_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
  // The initial mouse position
  _startPoint = e.GetPosition(null);
}

private void listBox_PreviewMouseMove(object sender, MouseEventArgs e)
{
  // Get the current mouse position
  Point mousePos = e.GetPosition(null);
  Vector diff = _startPoint - mousePos;

  if (e.LeftButton == MouseButtonState.Pressed &&
      (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance ||
      Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance))
  {
    // Get the dragged ListBoxItem
    var listBox = sender as ListBox;
    var listBoxItem = listBox.SelectedItem;

    // Initialize the drag & drop operation
    DataObject dragData = new DataObject(_dropIdentifier, listBoxItem);
    DragDrop.DoDragDrop(listBox, dragData, DragDropEffects.Move);
  } 
}

private void canvasImage_Drop(object sender, DragEventArgs e)
{
  if (e.Data.GetDataPresent(_dropIdentifier))
  {
    var item = e.Data.GetData(_dropIdentifier) as ListBoxItem;
    DropOnCanvas(sender as Canvas, item);
  }
}

private void canvasImage_DragEnter(object sender, DragEventArgs e)
{
  if (!e.Data.GetDataPresent(_dropIdentifier) ||
    sender == e.Source)
  {
    e.Effects = DragDropEffects.None;
  }
}

public void DropOnCanvas(Canvas targetCanvas, ListBoxItem item)
{
  // do your stuff here ...
  int textHeight = 20;
  var text = new TextBlock() { Text = item.Content.ToString(), Height = textHeight };
  Canvas.SetTop(text, targetCanvas.Children.Count * textHeight);
  targetCanvas.Children.Add(text);
}
于 2012-06-26T08:44:52.630 回答
2

本教程应该可以帮助您入门：http ://wpftutorial.net/DragAndDrop.html

于 2012-06-25T19:31:57.547 回答