DragEventArgs DragEventArgs DragEventArgs DragEventArgs Class

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
DragEventArgsDragEventArgsDragEventArgsDragEventArgs
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DoDragDrop操作开始时调用方法。The example calls the DoDragDrop method when the drag action starts. 如果在SystemInformation.DragSize MouseDown事件过程中鼠标移动了多个鼠标位置, 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. 方法用于确定MouseDown事件期间要拖动的项的索引。 IndexFromPointThe 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3dwarro.cur3dwno.cur个光标文件, 分别用于自定义的拖放游标和非删除光标。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. UseCustomCursorsCheck 如果CheckBox选中, 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DragOver ListBox的事件处理程序中进行计算, 以根据 SHIFT、ctrl、ALT 或 ctrl + ALT 键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. ListBox 事件DragOver期间也会确定放置过程中的位置。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String是, DragEventArgs.Effect则将设置为DragDropEffects.NoneIf the data to drop is not a String, then the DragEventArgs.Effect is set to DragDropEffects.None. 最后, 放置的状态显示在中DropLocationLabelLabelFinally, the status of the drop is displayed in the DropLocationLabelLabel.

ListBox放置给权限的数据DragDrop在事件处理程序中确定, 并String将值添加到中ListBox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DragEventArgs使用类。This code excerpt demonstrates using the DragEventArgs class. 有关完整的代码示例, 请参阅方法。DoDragDropSee 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DragEventArgs在拖放操作的源和目标之间传递。The 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, 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ListBox已使用有效文件名的列表填充了控件。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RichTextBox到控件上时, 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 事件中启动该操作。The operation is initiated in the ListBox control's MouseDown event. 在事件处理程序中, 该示例GetDataPresent使用方法来验证数据是否为RichTextBox控件可以显示的格式, 然后设置DragDropEffects属性以指定应从源控件复制数据DragEnter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GetData使用方法来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

DragDrop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来完成拖放操作时发生该事件。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. DragEnter用户将鼠标指针移到控件上并使用鼠标拖动对象时, 会发生该事件。The DragEnter event occurs when the user moves the mouse pointer onto the control while dragging an object with the mouse. DragOver用户将鼠标指针移到控件上并使用鼠标拖动对象时, 会发生该事件。The DragOver event occurs when the user moves the mouse pointer over the control while dragging an object with the mouse.

DragEventArgs对象指定与此事件相关联的任何数据、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。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) DragEventArgs(IDataObject, Int32, Int32, Int32, DragDropEffects, DragDropEffects) DragEventArgs(IDataObject, Int32, Int32, Int32, DragDropEffects, DragDropEffects) 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 AllowedEffect AllowedEffect 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 Data Data 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 Effect Effect 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 KeyState KeyState 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 X X 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 Y Y 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) Equals(Object) Equals(Object) 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.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

作为默认哈希函数。Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

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

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

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

(Inherited from Object)
ToString() ToString() ToString() ToString()

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

适用于

另请参阅