不能簡單的WPF拖放工作

Question

對於一個簡單的測試，我想將一個按鈕拖到一個文本框。我可以開始拖動按鈕，但不會引發Drop事件。我錯過了什麼？

的XAML：

<Window x:Class="DayPlanner.View.DnDTest" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="DnDTest" Height="200" Width="200"> 
    <StackPanel> 
     <Button Name="button" 
       Content="OK" 
       PreviewMouseLeftButtonDown="button_PreviewMouseLeftButtonDown" 
       PreviewMouseMove="button_PreviewMouseMove"/> 
     <TextBox Name="textBox" 
       AllowDrop="True" 
       DragEnter="textBox_DragEnter" 
       Drop="textBox_Drop"/> 
    </StackPanel> 
</Window> 

代碼：

public partial class DnDTest : Window 
{ 
    public DnDTest() 
    { 
     InitializeComponent(); 
    } 

    private Point dragStartPoint; 

    private void button_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) 
    { 
     dragStartPoint = e.GetPosition(null); 
    } 

    private static bool IsDragging(Point dragStartPoint, MouseEventArgs e) 
    { 
     var diff = e.GetPosition(null) - dragStartPoint; 
     return 
      e.LeftButton == MouseButtonState.Pressed && 
      (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance || 
       Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance); 
    } 

    private void button_PreviewMouseMove(object sender, MouseEventArgs e) 
    { 
     if (IsDragging(dragStartPoint, e)) 
     { 
      DragDrop.DoDragDrop(button, new DataObject("Button", button), DragDropEffects.Move); 
      e.Handled = true; 
     } 
    } 

    private void textBox_DragEnter(object sender, DragEventArgs e) 
    { 
     e.Handled = true; 
    } 

    private void textBox_Drop(object sender, DragEventArgs e) 
    { 
     var button = (Button)e.Data.GetData("Button"); 
     textBox.Text = string.Format("[0]", button.Content.ToString()); 
     e.Handled = true; 
    } 
} 

Answer 1

這可能是一些奇怪的情況，但要解決它，我需要處理或拖動事件，包括預覽版本。

以下是如何使其工作。

的XAML：

<Window x:Class="DayPlanner.View.DnDTestBasic" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="DnDTestBasic" Height="200" Width="200"> 
    <StackPanel> 
     <Button Name="button" 
       Content="OK" 
       PreviewMouseLeftButtonDown="button_PreviewMouseLeftButtonDown" 
       PreviewMouseMove="button_PreviewMouseMove"/> 
     <TextBox Name="textBox" 
       AllowDrop="True" 
       PreviewDragEnter="textBox_Dragging" 
       DragEnter="textBox_Dragging" 
       PreviewDragOver="textBox_Dragging" 
       DragOver="textBox_Dragging" 
       Drop="textBox_Drop"/> 
     <TextBlock Name="status" 
        Text="No dragging"/> 
    </StackPanel> 
</Window> 

代碼：

public partial class DnDTestBasic : Window 
{ 
    public DnDTestBasic() 
    { 
     InitializeComponent(); 
    } 

    private Point dragStartPoint; 

    private void button_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) 
    { 
     dragStartPoint = e.GetPosition(null); 
     status.Text = "New drag start position"; 
    } 

    private static bool IsDragging(Point dragStartPoint, MouseEventArgs e) 
    { 
     var diff = e.GetPosition(null) - dragStartPoint; 
     return 
      e.LeftButton == MouseButtonState.Pressed && 
      (Math.Abs(diff.X) > SystemParameters.MinimumHorizontalDragDistance || 
      Math.Abs(diff.Y) > SystemParameters.MinimumVerticalDragDistance); 
    } 

    private void button_PreviewMouseMove(object sender, MouseEventArgs e) 
    { 
     if (IsDragging(dragStartPoint, e)) 
     { 
      status.Text = "Starting drag..."; 
      DragDrop.DoDragDrop(button, new DataObject("Button", button), DragDropEffects.Copy); 
      status.Text = "Dragging done."; 
      e.Handled = true; 
     } 
    } 

    private void textBox_Dragging(object sender, DragEventArgs e) 
    { 
     if (e.Data.GetDataPresent("Button")) 
      e.Effects = DragDropEffects.Copy; 
     else 
      e.Effects = DragDropEffects.None; 
     e.Handled = true; 
    } 

    private void textBox_Drop(object sender, DragEventArgs e) 
    { 
     var button = (Button)e.Data.GetData("Button"); 
     textBox.Text = string.Format("[{0}]", button.Content.ToString()); 
     e.Handled = true; 
    } 
} 

Answer 2

我相信這是與事實，當你開始拖動事件，按鈕控制捕獲鼠標輸入的事情。後註冊到該按鈕，而不是到應用

你做任何的鼠標動作其實我也有類似的問題，並最終使用的MouseEnter/Leave事件，而不是建立在WPF拖/放框架。