DragEventHandler Delegar

Definição

Representa o método que manipulará o evento DragDrop, DragEnter ou DragOver de um 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)

Parâmetros

sender
Object

A fonte do evento.The source of the event.

e
DragEventArgs

Um DragEventArgs que contém os dados do evento.A DragEventArgs that contains the event data.

Herança
DragEventHandler

Exemplos

O exemplo a seguir demonstra uma operação de arrastar e soltar entre dois ListBox controles.The following example demonstrates a drag-and-drop operation between two ListBox controls. O exemplo chama o DoDragDrop método quando a ação de arrastar é iniciada.The example calls the DoDragDrop method when the drag action starts. A ação de arrastar será iniciada se o mouse tiver mudado mais do que SystemInformation.DragSize o local do mouse durante o MouseDown evento.The drag action starts if the mouse has moved more than SystemInformation.DragSize from the mouse location during the MouseDown event. O IndexFromPoint método é usado para determinar o índice do item a ser arrastado durante MouseDown o evento.The IndexFromPoint method is used to determine the index of the item to drag during the MouseDown event.

O exemplo também demonstra o uso de cursores personalizados para a operação de arrastar e soltar.The example also demonstrates using custom cursors for the drag-and-drop operation. O exemplo supõe que dois arquivos de cursor 3dwarro.cur e 3dwno.cur existam no diretório do aplicativo, para os cursores arrastar e não soltar 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. Os cursores personalizados serão usados se o UseCustomCursorsCheck CheckBox estiver marcado.The custom cursors will be used if the UseCustomCursorsCheckCheckBox is checked. Os cursores personalizados são definidos no GiveFeedback manipulador de eventos.The custom cursors are set in the GiveFeedback event handler.

O estado do teclado é avaliado no DragOver manipulador de eventos à direita ListBox , para determinar qual será a operação de arrastar com base no estado das teclas Shift, CTRL, ALT ou 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. O local no ListBox qual a queda ocorre também é determinado durante o DragOver evento.The location in the ListBox where the drop would occur is also determined during the DragOver event. Se os dados a serem descartados não forem um String , o DragEventArgs.Effect será definido como DragDropEffects.None .If the data to drop is not a String, then the DragEventArgs.Effect is set to DragDropEffects.None. Por fim, o status da remoção é exibido no DropLocationLabel Label .Finally, the status of the drop is displayed in the DropLocationLabelLabel.

Os dados a serem descartados para a direita ListBox são determinados no DragDrop manipulador de eventos e o String valor é adicionado no local apropriado no ListBox .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. Se a operação de arrastar se mover para fora dos limites do formulário, a operação de arrastar e soltar será cancelada no QueryContinueDrag manipulador 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.

Este trecho de código demonstra o uso do DragEventHandler delegado com o DragOver evento.This code excerpt demonstrates using the DragEventHandler delegate with the DragOver event. Consulte o DoDragDrop método para obter o exemplo 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

Comentários

Ao criar um DragEventHandler delegado, você identifica o método que manipulará o evento.When you create a DragEventHandler delegate, you identify the method that will handle the event. Para associar o evento ao manipulador de eventos, adicione uma instância do delegado ao evento.To associate the event with your event handler, add an instance of the delegate to the event. O manipulador de eventos é chamado sempre que o evento ocorre, a menos que você remova o representante.The event handler is called whenever the event occurs, unless you remove the delegate. Para obter mais informações sobre como manipular eventos com delegados, consulte manipulando e gerando eventos.For more information about handling events with delegates, see Handling and Raising Events.

Métodos de Extensão

GetMethodInfo(Delegate)

Obtém um objeto que representa o método representado pelo delegado especificado.Gets an object that represents the method represented by the specified delegate.

Aplica-se a

Veja também