ScrollBar.OnScroll(ScrollEventArgs) ScrollBar.OnScroll(ScrollEventArgs) ScrollBar.OnScroll(ScrollEventArgs) ScrollBar.OnScroll(ScrollEventArgs) Method

Definición

Genera el evento Scroll.Raises the Scroll event.

protected:
 virtual void OnScroll(System::Windows::Forms::ScrollEventArgs ^ se);
protected virtual void OnScroll (System.Windows.Forms.ScrollEventArgs se);
abstract member OnScroll : System.Windows.Forms.ScrollEventArgs -> unit
override this.OnScroll : System.Windows.Forms.ScrollEventArgs -> unit
Protected Overridable Sub OnScroll (se As ScrollEventArgs)

Parámetros

se
ScrollEventArgs ScrollEventArgs ScrollEventArgs ScrollEventArgs

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

Ejemplos

En el ejemplo de código siguiente se usa VScrollBarla clase derivada.The following code example uses the derived class VScrollBar. Se crean los controladores de Scroll eventos ValueChanged para los eventos y.Event handlers for the Scroll and ValueChanged events are created. En este código se supone Label que Button se han creado y en un formulario y que el botón tiene un controlador de eventos Click para el evento.This code assumes that a Label and Button have been created on a form and that the button has an event handler for the Click event. Al hacer clic en el botón, la Value propiedad de la barra de desplazamiento se ajusta en el código.When the button is clicked, the Value property of the scroll bar is adjusted in code. La etiqueta mostrará el valor actual de la Value propiedad y el evento que lo ha modificado.The label will display the current value of the Value property and the event that changed it. Observará que cuando el evento del Click botón cambia el valor de desplazamiento, solo se genera el ValueChanged evento.You will notice that when the scroll value is changed by the button's Click event, only the ValueChanged event is raised. Por el contrario, cuando la barra de desplazamiento se desplaza manualmente, Scroll el evento se genera inmediatamente después ValueChanged del evento.In contrast, when the scroll bar is scrolled manually, the Scroll event is raised immediately after the ValueChanged event.

void AddMyScrollEventHandlers()
{
   // Create and initialize a VScrollBar.
   VScrollBar^ vScrollBar1 = gcnew VScrollBar;

   // Add event handlers for the OnScroll and OnValueChanged events.
   vScrollBar1->Scroll += gcnew ScrollEventHandler( this, &Form1::vScrollBar1_Scroll );
   vScrollBar1->ValueChanged += gcnew EventHandler( this, &Form1::vScrollBar1_ValueChanged );
}

// Create the ValueChanged event handler.
void vScrollBar1_ValueChanged( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   // Display the new value in the label.
   label1->Text = String::Format( "vScrollBar Value:(OnValueChanged Event) {0}", vScrollBar1->Value );
}

// Create the Scroll event handler.
void vScrollBar1_Scroll( Object^ /*sender*/, ScrollEventArgs^ e )
{
   // Display the new value in the label.
   label1->Text = String::Format( "VScrollBar Value:(OnScroll Event) {0}", e->NewValue );
}

void button1_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   // Add 40 to the Value property if it will not exceed the Maximum value.
   if ( vScrollBar1->Value + 40 < vScrollBar1->Maximum )
   {
      vScrollBar1->Value = vScrollBar1->Value + 40;
   }
}
private void AddMyScrollEventHandlers()
 {
    // Create and initialize a VScrollBar.
    VScrollBar vScrollBar1 = new VScrollBar();
 
    // Add event handlers for the OnScroll and OnValueChanged events.
    vScrollBar1.Scroll += new ScrollEventHandler(
       this.vScrollBar1_Scroll);
    vScrollBar1.ValueChanged += new EventHandler(
       this.vScrollBar1_ValueChanged); 
 }
 
 // Create the ValueChanged event handler.
 private void vScrollBar1_ValueChanged(Object sender, 
                                       EventArgs e)
 {
     // Display the new value in the label.
     label1.Text = "vScrollBar Value:(OnValueChanged Event) " + vScrollBar1.Value.ToString();
 }
 
 // Create the Scroll event handler.
 private void vScrollBar1_Scroll(Object sender, 
                                 ScrollEventArgs e)
 {
     // Display the new value in the label.
     label1.Text = "VScrollBar Value:(OnScroll Event) " + e.NewValue.ToString();
 }
 
 private void button1_Click(Object sender, 
                           EventArgs e)
 {
    // Add 40 to the Value property if it will not exceed the Maximum value.
    if (vScrollBar1.Value + 40 < vScrollBar1.Maximum)
    {
        vScrollBar1.Value = vScrollBar1.Value + 40;
    }
 }
 
Private Sub AddMyScrollEventHandlers()
    ' Create and initialize a VScrollBar.
    Dim vScrollBar1 As New VScrollBar()
    
    ' Add event handlers for the OnScroll and OnValueChanged events.
    AddHandler vScrollBar1.Scroll, AddressOf Me.vScrollBar1_Scroll
    AddHandler vScrollBar1.ValueChanged, AddressOf Me.vScrollBar1_ValueChanged
End Sub    

' Create the ValueChanged event handler.
Private Sub vScrollBar1_ValueChanged(sender As Object, e As EventArgs)
    ' Display the new value in the label.
    label1.Text = "vScrollBar Value:(OnValueChanged Event) " & _
        vScrollBar1.Value.ToString()
End Sub    

' Create the Scroll event handler.
Private Sub vScrollBar1_Scroll(sender As Object, e As ScrollEventArgs)
    ' Display the new value in the label.
    label1.Text = "VScrollBar Value:(OnScroll Event) " & _
        e.NewValue.ToString()
End Sub    

Private Sub button1_Click(sender As Object, e As EventArgs)
    ' Add 40 to the Value property if it will not exceed the Maximum value.
    If vScrollBar1.Value + 40 < vScrollBar1.Maximum Then
        vScrollBar1.Value = vScrollBar1.Value + 40
    End If
End Sub

Comentarios

Cuando se genera un evento, se invoca el controlador de eventos a través de un delegado.Raising an event invokes the event handler through a delegate. Para obtener más información, consulte controlar y provocar eventos.For more information, see Handling and Raising Events.

El método OnScroll también permite que las clases derivadas controlen el evento sin adjuntar ningún delegado.The OnScroll method also allows derived classes to handle the event without attaching a delegate. Ésta es la técnica preferida para controlar el evento en una clase derivada.This is the preferred technique for handling the event in a derived class.

Notas a los desarrolladores de herederos

Al reemplazar OnScroll(ScrollEventArgs) en una clase derivada, asegúrese de llamar al OnScroll(ScrollEventArgs) método de la clase base para que los delegados registrados reciban el evento.When overriding OnScroll(ScrollEventArgs) in a derived class, be sure to call the base class' OnScroll(ScrollEventArgs) method so that registered delegates receive the event.

Se aplica a

Consulte también: