DragEventArgs 类

定义

DragDropDragEnterDragOver 事件提供数据。Provides data for the DragDrop, DragEnter, or DragOver event.

public ref class DragEventArgs : EventArgs
[System.Runtime.InteropServices.ComVisible(true)]
public class DragEventArgs : EventArgs
type DragEventArgs = class
    inherit EventArgs
Public Class DragEventArgs
Inherits EventArgs
继承
DragEventArgs
派生
属性

示例

下面的示例演示两个 ListBox 控件之间的拖放操作。The following example demonstrates a drag-and-drop operation between two ListBox controls. 该示例在拖动操作开始时调用 DoDragDrop 方法。The example calls the DoDragDrop method when the drag action starts. 如果鼠标在 MouseDown 事件期间从鼠标位置移动了超出 SystemInformation.DragSize,则拖动操作将启动。The drag action starts if the mouse has moved more than SystemInformation.DragSize from the mouse location during the MouseDown event. IndexFromPoint 方法用于确定 MouseDown 事件期间要拖动的项的索引。The IndexFromPoint method is used to determine the index of the item to drag during the MouseDown event.

该示例还演示了如何对拖放操作使用自定义光标。The example also demonstrates using custom cursors for the drag-and-drop operation. 该示例假定应用程序目录中有两个 cursor 文件(3dwarro.cur3dwno.cur,分别用于自定义的拖放和无删除光标。The example assumes that two cursor files, 3dwarro.cur and 3dwno.cur, exist in the application directory, for the custom drag and no-drop cursors, respectively. 如果选中 UseCustomCursorsCheckCheckBox,则将使用自定义光标。The custom cursors will be used if the UseCustomCursorsCheckCheckBox is checked. 自定义游标是在 GiveFeedback 事件处理程序中设置的。The custom cursors are set in the GiveFeedback event handler.

键盘状态在右侧 ListBoxDragOver 事件处理程序中进行计算,以根据 SHIFT、CTRL、ALT 或 CTRL + ALT 键的状态确定拖动操作的状态。The keyboard state is evaluated in the DragOver event handler for the right ListBox, to determine what the drag operation will be based upon state of the SHIFT, CTRL, ALT, or CTRL+ALT keys. DragOver 事件期间,也确定了放置的 ListBox 位置。The location in the ListBox where the drop would occur is also determined during the DragOver event. 如果要删除的数据不是 String,则将 DragEventArgs.Effect 设置为 "DragDropEffects.None"。If the data to drop is not a String, then the DragEventArgs.Effect is set to DragDropEffects.None. 最后,drop 的状态显示在 DropLocationLabelLabel中。Finally, the status of the drop is displayed in the DropLocationLabelLabel.

向右 ListBox 放置的数据是在 DragDrop 事件处理程序中确定的,String 值将添加到 ListBox中的适当位置。The data to drop for the right ListBox is determined in the DragDrop event handler and the String value is added at the appropriate place in the ListBox. 如果拖动操作移到窗体的边界之外,则会在 QueryContinueDrag 事件处理程序中取消拖放操作。If the drag operation moves outside the bounds of the form, then the drag-and-drop operation is canceled in the QueryContinueDrag event handler.

此代码摘录演示了如何使用 DragEventArgs 类。This code excerpt demonstrates using the DragEventArgs class. 有关完整的代码示例,请参阅 DoDragDrop 方法。See the DoDragDrop method for the complete code example.

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 = CTL + 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) )
   {
      // CTL 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, 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(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 = CTL + 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) {

        // CTL 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 = CTL + 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

        ' CTL 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

下面的示例演示如何在拖放操作的源和目标之间传递 DragEventArgsThe following example illustrates how DragEventArgs are passed between the source and target of a drag-and-drop operation. 在此示例中,ListBox 控件是数据源,而 RichTextBox 控件是目标。In this example, a ListBox control is the source of the data, and the RichTextBox control is the target. 该示例假设已使用有效文件名的列表填充了 ListBox 控件。The example assumes that the ListBox control has been populated with a list of valid filenames. 当用户将其中一个显示的文件名从 ListBox 控件拖动到 RichTextBox 控件上时,将打开文件名中引用的文件。When the user drags one of the displayed filenames from the ListBox control onto the RichTextBox control, the file referenced in the filename is opened.

ListBox 控件的 MouseDown 事件中启动操作。The operation is initiated in the ListBox control's MouseDown event. DragEnter 事件处理程序中,该示例使用 GetDataPresent 方法来验证数据是否采用 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控件复制到目标控件。In the DragEnter event handler, the example uses the GetDataPresent method to verify that the data is in a format that the RichTextBox control can display and then sets the DragDropEffects property to specify that data should be copied from the source control to the target control. 最后,RichTextBox 控件的 System.windows.dragdrop.drop> 事件处理程序使用 GetData 方法检索要打开的文件名。Finally, the RichTextBox control's DragDrop event handler uses the GetData method to retrieve the filename to open.

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到控件上并通过释放鼠标按钮将其放到控件上完成拖放操作时,将发生 DragDrop 事件。The DragDrop event occurs when the user completes a drag-and-drop operation by dragging an object over the control and then dropping it onto the control by releasing the mouse button. 当用户将鼠标指针移到控件上并使用鼠标拖动对象时,将发生 DragEnter 事件。The DragEnter event occurs when the user moves the mouse pointer onto the control while dragging an object with the mouse. 当用户将鼠标指针移到控件上并使用鼠标拖动对象时,会发生 DragOver 事件。The DragOver event occurs when the user moves the mouse pointer over the control while dragging an object with the mouse.

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;拖动事件的源和目标所允许的拖放效果。A DragEventArgs object specifies any data associated with this event; the current state of the SHIFT, CTRL, and ALT keys; the location of the mouse pointer; and the drag-and-drop effects allowed by the source and target of the drag event.

有关事件模型的信息,请参阅处理和引发事件For information about the event model, see Handling and Raising Events.

构造函数

DragEventArgs(IDataObject, Int32, Int32, Int32, DragDropEffects, DragDropEffects)

初始化 DragEventArgs 类的新实例。Initializes a new instance of the DragEventArgs class.

属性

AllowedEffect

获取拖动事件的发起方(或源)所允许的拖放操作。Gets which drag-and-drop operations are allowed by the originator (or source) of the drag event.

Data

获取 IDataObject,它包含与此事件关联的数据。Gets the IDataObject that contains the data associated with this event.

Effect

获取或设置拖放操作中目标放置效果。Gets or sets the target drop effect in a drag-and-drop operation.

KeyState

获取 Shift、Ctrl 和 Alt 键的当前状态以及鼠标按钮的状态。Gets the current state of the SHIFT, CTRL, and ALT keys, as well as the state of the mouse buttons.

X

获取鼠标指针在屏幕坐标系中的 x 坐标。Gets the x-coordinate of the mouse pointer, in screen coordinates.

Y

获取鼠标指针在屏幕坐标系中的 y 坐标。Gets the y-coordinate of the mouse pointer, in screen coordinates.

方法

Equals(Object)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

(继承自 Object)
GetHashCode()

用作默认哈希函数。Serves as the default hash function.

(继承自 Object)
GetType()

获取当前实例的 TypeGets the Type of the current instance.

(继承自 Object)
MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(继承自 Object)
ToString()

返回一个表示当前对象的 string。Returns a string that represents the current object.

(继承自 Object)

适用于

另请参阅