DragAction DragAction DragAction DragAction Enum

定义

指定拖放操作应如何继续以及是否应继续。Specifies how and if a drag-and-drop operation should continue.

public enum class DragAction
[System.Runtime.InteropServices.ComVisible(true)]
public enum DragAction
type DragAction = 
Public Enum DragAction
继承
属性

字段

Cancel Cancel Cancel Cancel 2

操作被取消,没有放置消息。The operation is canceled with no drop message.

Continue Continue Continue Continue 0

该操作将继续。The operation will continue.

Drop Drop Drop Drop 1

该操作以放置而告终。The operation will stop with a drop.

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DragAction使用枚举。This code excerpt demonstrates using the DragAction enumeration. 有关完整的代码示例, 请参阅方法。DoDragDropSee the DoDragDrop method for the complete code example.

void ListDragSource_QueryContinueDrag( Object^ sender, System::Windows::Forms::QueryContinueDragEventArgs^ e )
{
   // Cancel the drag if the mouse moves off the form.
   ListBox^ lb = dynamic_cast<ListBox^>(sender);
   if ( lb != nullptr )
   {
      Form^ f = lb->FindForm();

      // Cancel the drag if the mouse moves off the form. The screenOffset
      // takes into account any desktop bands that may be at the top or left
      // side of the screen.
      if ( ((Control::MousePosition.X - screenOffset.X) < f->DesktopBounds.Left) || ((Control::MousePosition.X - screenOffset.X) > f->DesktopBounds.Right) || ((Control::MousePosition.Y - screenOffset.Y) < f->DesktopBounds.Top) || ((Control::MousePosition.Y - screenOffset.Y) > f->DesktopBounds.Bottom) )
      {
         e->Action = DragAction::Cancel;
      }
   }
}
private void ListDragSource_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e) {
    // Cancel the drag if the mouse moves off the form.
    ListBox lb = sender as ListBox;

    if (lb != null) {

        Form f = lb.FindForm();

        // Cancel the drag if the mouse moves off the form. The screenOffset
        // takes into account any desktop bands that may be at the top or left
        // side of the screen.
        if (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) ||
            ((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) ||
            ((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) ||
            ((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) {

            e.Action = DragAction.Cancel;
        }
    }
}
Private Sub ListDragSource_QueryContinueDrag(ByVal sender As Object, ByVal e As QueryContinueDragEventArgs) Handles ListDragSource.QueryContinueDrag
    ' Cancel the drag if the mouse moves off the form.
    Dim lb as ListBox = CType(sender, System.Windows.Forms.ListBox)

    If (lb isNot nothing) Then

        Dim f as Form = lb.FindForm()

        ' Cancel the drag if the mouse moves off the form. The screenOffset
        ' takes into account any desktop bands that may be at the top or left
        ' side of the screen.
        If (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) Or _
            ((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) Or _
            ((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) Or _
            ((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) Then

            e.Action = DragAction.Cancel
        End If
    End if
End Sub

注解

此枚举由使用QueryContinueDragEventArgsThis enumeration is used by QueryContinueDragEventArgs.

适用于