DragEventHandler Delegado

Definición

Representa el método que controlará el evento DragDrop, DragEnter o DragOver de Control.Represents the method that will handle the DragDrop, DragEnter, or DragOver event of a Control.

public delegate void DragEventHandler(System::Object ^ sender, DragEventArgs ^ e);
public delegate void DragEventHandler(object sender, DragEventArgs e);
type DragEventHandler = delegate of obj * DragEventArgs -> unit
Public Delegate Sub DragEventHandler(sender As Object, e As DragEventArgs)

Parámetros

sender
Object

Origen del evento.The source of the event.

e
DragEventArgs

Objeto DragEventArgs que contiene los datos del evento.A DragEventArgs that contains the event data.

Herencia
DragEventHandler

Ejemplos

En el ejemplo siguiente se muestra una operación de arrastrar y colocar entre ListBox dos controles.The following example demonstrates a drag-and-drop operation between two ListBox controls. En el ejemplo se DoDragDrop llama al método cuando se inicia la acción de arrastrar.The example calls the DoDragDrop method when the drag action starts. La acción de arrastrar comienza si el mouse ha pasado más SystemInformation.DragSize de la ubicación del mouse durante MouseDown el evento.The drag action starts if the mouse has moved more than SystemInformation.DragSize from the mouse location during the MouseDown event. El IndexFromPoint método se utiliza para determinar el índice del elemento que se va a arrastrar MouseDown durante el evento.The IndexFromPoint method is used to determine the index of the item to drag during the MouseDown event.

En el ejemplo también se muestra el uso de cursores personalizados para la operación de arrastrar y colocar.The example also demonstrates using custom cursors for the drag-and-drop operation. En el ejemplo se da por supuesto que 3dwarro.cur dos 3dwno.curarchivos de cursor, y, existen en el directorio de la aplicación para los cursores de arrastrar y no colocar personalizados, respectivamente.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. Se usarán los cursores personalizados si UseCustomCursorsCheck CheckBox está activado.The custom cursors will be used if the UseCustomCursorsCheckCheckBox is checked. Los cursores personalizados se establecen en el GiveFeedback controlador de eventos.The custom cursors are set in the GiveFeedback event handler.

El estado del teclado se evalúa en DragOver el controlador de eventos de ListBoxla derecha, para determinar qué operación de arrastre se basará en el estado de las teclas Mayús, Ctrl, Alt o Ctrl + Alt.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. La ubicación en ListBox donde se produciría la colocación también se determina durante el DragOver evento.The location in the ListBox where the drop would occur is also determined during the DragOver event. Si los datos que se van a quitar Stringno son, DragEventArgs.Effect el se establece DragDropEffects.Noneen.If the data to drop is not a String, then the DragEventArgs.Effect is set to DragDropEffects.None. Por último, el estado de la eliminación se muestra en DropLocationLabel. LabelFinally, the status of the drop is displayed in the DropLocationLabelLabel.

Los datos que se van a quitar ListBox para el derecho se DragDrop determinan en String el controlador de eventos y el valor ListBoxse agrega en el lugar adecuado en.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. Si la operación de arrastre se mueve fuera de los límites del formulario, la operación de arrastrar y colocar se cancela en el QueryContinueDrag controlador de eventos.If the drag operation moves outside the bounds of the form, then the drag-and-drop operation is canceled in the QueryContinueDrag event handler.

En este fragmento de código se DragEventHandler muestra cómo usar DragOver el delegado con el evento.This code excerpt demonstrates using the DragEventHandler delegate with the DragOver event. Vea el DoDragDrop método para obtener el ejemplo de código completo.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

Comentarios

Cuando se crea un delegado DragEventHandler, se identifica el método que controlará el evento.When you create a DragEventHandler delegate, you identify the method that will handle the event. Para asociar el evento al controlador, se debe agregar una instancia del delegado al evento.To associate the event with your event handler, add an instance of the delegate to the event. Siempre que se produce el evento, se llama a su controlador, a menos que se quite el delegado.The event handler is called whenever the event occurs, unless you remove the delegate. Para obtener más información sobre el control de eventos con delegados, vea controlar y provocar eventos.For more information about handling events with delegates, see Handling and Raising Events.

Métodos de extensión

GetMethodInfo(Delegate)

Obtiene un objeto que representa el método representado por el delegado especificado.Gets an object that represents the method represented by the specified delegate.

Se aplica a

Consulte también: