DragEventArgs 类

参考

定义

命名空间:: System.Windows.Forms

程序集:: System.Windows.Forms.dll

重要

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public ref class DragEventArgs : EventArgs

[System.Runtime.InteropServices.ComVisible(true)]
public class DragEventArgs : EventArgs

public class DragEventArgs : EventArgs

[<System.Runtime.InteropServices.ComVisible(true)>]
type DragEventArgs = class
    inherit EventArgs

type DragEventArgs = class
    inherit EventArgs

Public Class DragEventArgs
Inherits EventArgs

继承: Object

EventArgs
DragEventArgs

派生: System.Workflow.ComponentModel.Design.ActivityDragEventArgs

属性: ComVisibleAttribute

示例

以下示例演示两个 ListBox 控件之间的拖放操作。该示例在拖动操作启动时调用 DoDragDrop 方法。如果鼠标在 MouseDown 事件期间从鼠标位置移动了超过 SystemInformation.DragSize，则拖动操作将启动。 IndexFromPoint 方法用于确定在 MouseDown 事件期间要拖动的项的索引。

该示例还演示如何对拖放操作使用自定义游标。该示例假定两个游标文件（3dwarro.cur 和 3dwno.cur）分别存在于应用程序目录中，分别用于自定义拖放游标。如果选中 UseCustomCursorsCheckCheckBox，将使用自定义游标。自定义游标在 GiveFeedback 事件处理程序中设置。

键盘状态在右侧 ListBox的 DragOver 事件处理程序中进行评估，以确定拖动操作将基于 SHIFT、Ctrl、Alt 或 Ctrl+Alt 键的状态。在 DragOver 事件期间，也会确定 ListBox 发生放置的位置。如果要删除的数据不是 String，则 DragEventArgs.Effect 设置为 DragDropEffects.None。最后，删除状态显示在 DropLocationLabelLabel中。

要删除的右 ListBox 的数据在 DragDrop 事件处理程序中确定，并在 ListBox的适当位置添加 String 值。如果拖动操作在窗体边界之外移动，则拖放操作在 QueryContinueDrag 事件处理程序中取消。

此代码摘录演示了如何使用 DragEventArgs 类。有关完整的代码示例，请参阅 DoDragDrop 方法。

void ListDragTarget_DragOver( Object^ /*sender*/, System::Windows::Forms::DragEventArgs^ e )
{
   // Determine whether string data exists in the drop data. If not, then
   // the drop effect reflects that the drop cannot occur.
   if (  !e->Data->GetDataPresent( System::String::typeid ) )
   {
      e->Effect = DragDropEffects::None;
      DropLocationLabel->Text = "None - no string data.";
      return;
   }

   // Set the effect based upon the KeyState.
   if ( (e->KeyState & (8 + 32)) == (8 + 32) && ((e->AllowedEffect & DragDropEffects::Link) == DragDropEffects::Link) )
   {
      // KeyState 8 + 32 = CTRL + ALT
      // Link drag-and-drop effect.
      e->Effect = DragDropEffects::Link;
   }
   else
   if ( (e->KeyState & 32) == 32 && ((e->AllowedEffect & DragDropEffects::Link) == DragDropEffects::Link) )
   {
      // ALT KeyState for link.
      e->Effect = DragDropEffects::Link;
   }
   else
   if ( (e->KeyState & 4) == 4 && ((e->AllowedEffect & DragDropEffects::Move) == DragDropEffects::Move) )
   {
      // SHIFT KeyState for move.
      e->Effect = DragDropEffects::Move;
   }
   else
   if ( (e->KeyState & 8) == 8 && ((e->AllowedEffect & DragDropEffects::Copy) == DragDropEffects::Copy) )
   {
      // CTRL KeyState for copy.
      e->Effect = DragDropEffects::Copy;
   }
   else
   if ( (e->AllowedEffect & DragDropEffects::Move) == DragDropEffects::Move )
   {
      // By default, the drop action should be move, if allowed.
      e->Effect = DragDropEffects::Move;
   }
   else
            e->Effect = DragDropEffects::None;





   
   // Get the index of the item the mouse is below.
   // The mouse locations are relative to the screen, so they must be
   // converted to client coordinates.
   indexOfItemUnderMouseToDrop = ListDragTarget->IndexFromPoint( ListDragTarget->PointToClient( Point(e->X,e->Y) ) );
   
   // Updates the label text.
   if ( indexOfItemUnderMouseToDrop != ListBox::NoMatches )
   {
      DropLocationLabel->Text = String::Concat( "Drops before item # ", (indexOfItemUnderMouseToDrop + 1) );
   }
   else
            DropLocationLabel->Text = "Drops at the end.";
}

private void ListDragTarget_DragOver(object sender, DragEventArgs e)
{
    // Determine whether string data exists in the drop data. If not, then
    // the drop effect reflects that the drop cannot occur.
    if (!e.Data.GetDataPresent(typeof(System.String)))
    {
        e.Effect = DragDropEffects.None;
        DropLocationLabel.Text = "None - no string data.";
        return;
    }

    // Set the effect based upon the KeyState.
    if ((e.KeyState & (8 + 32)) == (8 + 32) &&
        (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link)
    {
        // KeyState 8 + 32 = CTRL + ALT

        // Link drag-and-drop effect.
        e.Effect = DragDropEffects.Link;
    }
    else if ((e.KeyState & 32) == 32 &&
        (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link)
    {
        // ALT KeyState for link.
        e.Effect = DragDropEffects.Link;
    }
    else if ((e.KeyState & 4) == 4 &&
        (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)
    {
        // SHIFT KeyState for move.
        e.Effect = DragDropEffects.Move;
    }
    else if ((e.KeyState & 8) == 8 &&
        (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy)
    {
        // CTRL KeyState for copy.
        e.Effect = DragDropEffects.Copy;
    }
    else if ((e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)
    {
        // By default, the drop action should be move, if allowed.
        e.Effect = DragDropEffects.Move;
    }
    else
    {
        e.Effect = DragDropEffects.None;
    }

    // Get the index of the item the mouse is below. 

    // The mouse locations are relative to the screen, so they must be 
    // converted to client coordinates.

    indexOfItemUnderMouseToDrop =
        ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(new Point(e.X, e.Y)));

    // Updates the label text.
    if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
    {
        DropLocationLabel.Text = "Drops before item #" + (indexOfItemUnderMouseToDrop + 1);
    }
    else
    {
        DropLocationLabel.Text = "Drops at the end.";
    }
}

Private Sub ListDragTarget_DragOver(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragOver
    ' Determine whether string data exists in the drop data. If not, then
    ' the drop effect reflects that the drop cannot occur.
    If Not (e.Data.GetDataPresent(GetType(System.String))) Then

        e.Effect = DragDropEffects.None
        DropLocationLabel.Text = "None - no string data."
        Return
    End If

    ' Set the effect based upon the KeyState.
    If ((e.KeyState And (8 + 32)) = (8 + 32) And
        (e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
        ' KeyState 8 + 32 = CTRL + ALT

        ' Link drag-and-drop effect.
        e.Effect = DragDropEffects.Link

    ElseIf ((e.KeyState And 32) = 32 And
        (e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then

        ' ALT KeyState for link.
        e.Effect = DragDropEffects.Link

    ElseIf ((e.KeyState And 4) = 4 And
        (e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then

        ' SHIFT KeyState for move.
        e.Effect = DragDropEffects.Move

    ElseIf ((e.KeyState And 8) = 8 And
        (e.AllowedEffect And DragDropEffects.Copy) = DragDropEffects.Copy) Then

        ' CTRL KeyState for copy.
        e.Effect = DragDropEffects.Copy

    ElseIf ((e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then

        ' By default, the drop action should be move, if allowed.
        e.Effect = DragDropEffects.Move

    Else
        e.Effect = DragDropEffects.None
    End If

    ' Gets the index of the item the mouse is below. 

    ' The mouse locations are relative to the screen, so they must be 
    ' converted to client coordinates.

    indexOfItemUnderMouseToDrop =
        ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(New Point(e.X, e.Y)))

    ' Updates the label text.
    If (indexOfItemUnderMouseToDrop <> ListBox.NoMatches) Then
        DropLocationLabel.Text = "Drops before item #" & (indexOfItemUnderMouseToDrop + 1)
    Else
        DropLocationLabel.Text = "Drops at the end."
    End If

End Sub

以下示例演示如何在拖放操作的源和目标之间传递 DragEventArgs。在此示例中，ListBox 控件是数据源，RichTextBox 控件是目标。该示例假定 ListBox 控件已填充有效文件名列表。当用户将其中一个显示文件名从 ListBox 控件拖动到 RichTextBox 控件上时，将打开文件名中引用的文件。

操作在 ListBox 控件的 MouseDown 事件中启动。在 DragEnter 事件处理程序中，该示例使用 GetDataPresent 方法验证数据的格式是否为 RichTextBox 控件可以显示的格式，然后设置 DragDropEffects 属性以指定应将数据从源代码管理复制到目标控件。最后，RichTextBox 控件的 DragDrop 事件处理程序使用 GetData 方法检索要打开的文件名。

private:
   void Form1_Load( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      // Sets the AllowDrop property so that data can be dragged onto the control.
      richTextBox1->AllowDrop = true;

      // Add code here to populate the ListBox1 with paths to text files.
   }

   void listBox1_MouseDown( Object^ sender, System::Windows::Forms::MouseEventArgs^ e )
   {
      // Determines which item was selected.
      ListBox^ lb = (dynamic_cast<ListBox^>(sender));
      Point pt = Point(e->X,e->Y);
      int index = lb->IndexFromPoint( pt );

      // Starts a drag-and-drop operation with that item.
      if ( index >= 0 )
      {
         lb->DoDragDrop( lb->Items[ index ], DragDropEffects::Link );
      }
   }

   void richTextBox1_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
   {
      // If the data is text, copy the data to the RichTextBox control.
      if ( e->Data->GetDataPresent( "Text" ) )
            e->Effect = DragDropEffects::Copy;
   }

   void richTextBox1_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
   {
      // Loads the file into the control.
      richTextBox1->LoadFile( dynamic_cast<String^>(e->Data->GetData( "Text" )), System::Windows::Forms::RichTextBoxStreamType::RichText );
   }

private void Form1_Load(object sender, EventArgs e) 
{
   // Sets the AllowDrop property so that data can be dragged onto the control.
   richTextBox1.AllowDrop = true;

   // Add code here to populate the ListBox1 with paths to text files.
}

private void listBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
   // Determines which item was selected.
   ListBox lb =( (ListBox)sender);
   Point pt = new Point(e.X,e.Y);
   int index = lb.IndexFromPoint(pt);

   // Starts a drag-and-drop operation with that item.
   if(index>=0) 
   {
      lb.DoDragDrop(lb.Items[index].ToString(), DragDropEffects.Link);
   }
}

private void richTextBox1_DragEnter(object sender, DragEventArgs e) 
{
   // If the data is text, copy the data to the RichTextBox control.
   if(e.Data.GetDataPresent("Text"))
      e.Effect = DragDropEffects.Copy;
}

private void richTextBox1_DragDrop(object sender, DragEventArgs e) 
{
   // Loads the file into the control. 
   richTextBox1.LoadFile((String)e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText);
}

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
   ' Sets the AllowDrop property so that data can be dragged onto the control.
   RichTextBox1.AllowDrop = True

   ' Add code here to populate the ListBox1 with paths to text files.

End Sub

Private Sub RichTextBox1_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragEnter
   ' If the data is text, copy the data to the RichTextBox control.
   If (e.Data.GetDataPresent("Text")) Then
      e.Effect = DragDropEffects.Copy
   End If
End Sub


Private Overloads Sub RichTextBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragDrop
   ' Loads the file into the control. 
   RichTextBox1.LoadFile(e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText)
End Sub

Private Sub ListBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListBox1.MouseDown
   Dim Lb As ListBox
   Dim Pt As New Point(e.X, e.Y)
   Dim Index As Integer

   ' Determines which item was selected.
   Lb = sender
   Index = Lb.IndexFromPoint(Pt)

   ' Starts a drag-and-drop operation with that item.
   If Index >= 0 Then
      Lb.DoDragDrop(Lb.Items(Index), DragDropEffects.Link)
   End If
End Sub

注解

当用户通过将对象拖动到控件上，然后通过释放鼠标按钮将其拖放到控件上，从而完成拖放操作时，会发生 DragDrop 事件。当用户在使用鼠标拖动对象时将鼠标指针移到控件上时，会发生 DragEnter 事件。当用户使用鼠标拖动对象时将鼠标指针移到控件上时，会发生 DragOver 事件。

DragEventArgs 对象指定与此事件关联的任何数据;SHIFT、CTRL 和 Alt 键的当前状态;鼠标指针的位置;以及拖动事件的源和目标所允许的拖放效果。

有关事件模型的信息，请参阅处理和引发事件。

构造函数

DragEventArgs(IDataObject, Int32, Int32, Int32, DragDropEffects, DragDropEffects)	初始化 DragEventArgs 类的新实例。
DragEventArgs(IDataObject, Int32, Int32, Int32, DragDropEffects, DragDropEffects, DropImageType, String, String)	初始化 DragEventArgs 类的新实例。

属性

AllowedEffect	获取拖动事件的发起方（或源）允许的拖放操作。
Data	获取包含与此事件关联的数据的 IDataObject。
DropImageType	获取或设置放置说明图像类型。
Effect	获取或设置拖放操作中的目标放置效果。
KeyState	获取 Shift、Ctrl 和 Alt 键的当前状态，以及鼠标按钮的状态。
Message	获取或设置放置说明文本，例如“移动到 %1”。
MessageReplacementToken	获取或设置在 Message中指定 %1 时放置说明文本，如“文档”。
X	获取鼠标指针的 x 坐标（以屏幕坐标为单位）。
Y	获取鼠标指针的 y 坐标（以屏幕坐标为单位）。

方法

Equals(Object)	确定指定的对象是否等于当前对象。 (继承自 Object)
GetHashCode()	用作默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object的浅表副本。 (继承自 Object)
ToString()	返回一个表示当前对象的字符串。 (继承自 Object)

适用于

通过

DragEventArgs 类

定义

示例

注解

构造函数

属性

方法

适用于

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