DrawItemEventHandler Delegado

Definición

Espacio de nombres:

System.Windows.Forms

Ensamblado:

System.Windows.Forms.dll

Representa el método que controlará el evento DrawItem de un control ComboBox, ListBox, MenuItem o TabControl.

public delegate void DrawItemEventHandler(System::Object ^ sender, DrawItemEventArgs ^ e);

public delegate void DrawItemEventHandler(object? sender, DrawItemEventArgs e);

type DrawItemEventHandler = delegate of obj * DrawItemEventArgs -> unit

Public Delegate Sub DrawItemEventHandler(sender As Object, e As DrawItemEventArgs)

Parámetros

sender

Object

Origen del evento.

e

DrawItemEventArgs

Objeto DrawItemEventArgs que contiene los datos del evento.

Ejemplos

En el ejemplo de código siguiente se muestra un menú con un elemento de menú dibujado por el propietario. En este ejemplo se usa la AddHandler instrucción y el AddressOf operador para designar un delegado para controlar el MenuItem.DrawItem evento. Para ejecutar el ejemplo, péguelo en un formulario que importe los espacios de nombres System, System.Windows.Forms y System.Drawing. Asegúrese de que todos los eventos están asociados a sus métodos de control de eventos.

internal:
   // Declare the MainMenu control.
   System::Windows::Forms::MainMenu^ MainMenu1;

   // Declare MenuItem2 as With-Events because it will be user drawn.
   System::Windows::Forms::MenuItem^ MenuItem2;

private:
   void InitializeMenu()
   {
      
      // Create MenuItem1, which will be drawn by the operating system.
      MenuItem^ MenuItem1 = gcnew MenuItem( "Regular Menu Item" );
      
      // Create MenuItem2.
      MenuItem2 = gcnew MenuItem( "Custom Menu Item" );
      
      // Set OwnerDraw property to true. This requires handling the
      // DrawItem event for this menu item.
      MenuItem2->OwnerDraw = true;
      
      //Add the event-handler delegate to handle the DrawItem event.
      MenuItem2->DrawItem += gcnew DrawItemEventHandler( this, &Form1::DrawCustomMenuItem );
      
      // Add the items to the menu.
      array<MenuItem^>^temp0 = {MenuItem1,MenuItem2};
      MainMenu1 = gcnew MainMenu( temp0 );
      
      // Add the menu to the form.
      this->Menu = this->MainMenu1;
   }

   // Draw the custom menu item.
   void DrawCustomMenuItem( Object^ sender, DrawItemEventArgs^ e )
   {
      // Cast the sender to MenuItem so you can access text property.
      MenuItem^ customItem = dynamic_cast<MenuItem^>(sender);
      
      // Create a Brush and a Font to draw the MenuItem.
      System::Drawing::Brush^ aBrush = System::Drawing::Brushes::DarkMagenta;
      System::Drawing::Font^ aFont = gcnew System::Drawing::Font( "Garamond",10,FontStyle::Italic,GraphicsUnit::Point );
      
      // Get the size of the text to use later to draw an ellipse
      // around the item.
      SizeF stringSize = e->Graphics->MeasureString( customItem->Text, aFont );
      
      // Draw the item and then draw the ellipse.
      e->Graphics->DrawString( customItem->Text, aFont, aBrush, (float)e->Bounds.X, (float)e->Bounds.Y );
      e->Graphics->DrawEllipse( gcnew Pen( System::Drawing::Color::Black,2 ), Rectangle(e->Bounds.X,e->Bounds.Y,(System::Int32)stringSize.Width,(System::Int32)stringSize.Height) );
   }

// Declare the MainMenu control.
internal System.Windows.Forms.MainMenu MainMenu1;

// Declare MenuItem2 as With-Events because it will be user drawn.
internal System.Windows.Forms.MenuItem MenuItem2;

private void InitializeMenu()
{

    // Create MenuItem1, which will be drawn by the operating system.
    MenuItem MenuItem1 = new MenuItem("Regular Menu Item");

    // Create MenuItem2.
    MenuItem2 = new MenuItem("Custom Menu Item");

    // Set OwnerDraw property to true. This requires handling the
    // DrawItem event for this menu item.
    MenuItem2.OwnerDraw = true;

    //Add the event-handler delegate to handle the DrawItem event.
    MenuItem2.DrawItem += new DrawItemEventHandler(DrawCustomMenuItem);
    
    // Add the items to the menu.
    MainMenu1 = new MainMenu(new MenuItem[]{MenuItem1, MenuItem2});																													  

    // Add the menu to the form.
    this.Menu = this.MainMenu1;
}

// Draw the custom menu item.
private void DrawCustomMenuItem(object sender, 
    DrawItemEventArgs e)
{

    // Cast the sender to MenuItem so you can access text property.
    MenuItem customItem = (MenuItem) sender;

    // Create a Brush and a Font to draw the MenuItem.
    System.Drawing.Brush aBrush = System.Drawing.Brushes.DarkMagenta;
    Font aFont = new Font("Garamond", 10, 
        FontStyle.Italic, GraphicsUnit.Point);

    // Get the size of the text to use later to draw an ellipse
    // around the item.
    SizeF stringSize = e.Graphics.MeasureString(
        customItem.Text, aFont);

    // Draw the item and then draw the ellipse.
    e.Graphics.DrawString(customItem.Text, aFont, 
        aBrush, e.Bounds.X, e.Bounds.Y);
    e.Graphics.DrawEllipse(new Pen(System.Drawing.Color.Black, 2),
        new Rectangle(e.Bounds.X, e.Bounds.Y, 
        (System.Int32)stringSize.Width,
        (System.Int32)stringSize.Height));
}

' Declare the MainMenu control.
Friend WithEvents MainMenu1 As System.Windows.Forms.MainMenu

' Declare MenuItem2 as With-Events because it will be user drawn.
Friend WithEvents MenuItem2 As System.Windows.Forms.MenuItem


Private Sub InitializeMenu()

    ' Create MenuItem1, which will be drawn by the operating system.
    Dim MenuItem1 As New MenuItem("Regular Menu Item")

    ' Create MenuItem2.
    MenuItem2 = New MenuItem("Custom Menu Item")

    ' Set OwnerDraw property to true. This requires handling the
    ' DrawItem event for this menu item.
    MenuItem2.OwnerDraw = True

    'Add the event-handler delegate to handle the DrawItem event.
    AddHandler MenuItem2.DrawItem, New DrawItemEventHandler(AddressOf DrawCustomMenuItem)

    ' Add the items to the menu.
    MainMenu1 = New MainMenu(New MenuItem() {MenuItem1, MenuItem2})

    ' Add the menu to the form.
    Me.Menu = Me.MainMenu1
End Sub

' Draw the custom menu item.
Private Sub DrawCustomMenuItem(ByVal sender As Object, ByVal e As _
        System.Windows.Forms.DrawItemEventArgs)

    ' Cast the sender to MenuItem so you can access text property.
    Dim customItem As MenuItem = CType(sender, MenuItem)

    ' Create a Brush and a Font to draw the MenuItem.
    Dim aBrush As System.Drawing.Brush = System.Drawing.Brushes.DarkMagenta
    Dim aFont As New Font("Garamond", 10, FontStyle.Italic, _
        GraphicsUnit.Point)

    ' Get the size of the text to use later to draw an ellipse
    ' around the item.
    Dim stringSize As SizeF = e.Graphics.MeasureString( _
        customItem.Text, aFont)

    ' Draw the item and then draw the ellipse.
    e.Graphics.DrawString(customItem.Text, aFont, _
        aBrush, e.Bounds.X, e.Bounds.Y)
    e.Graphics.DrawEllipse(New Pen(System.Drawing.Color.Black, 2), _
        New Rectangle(e.Bounds.X, e.Bounds.Y, CInt(stringSize.Width), _
        CInt(stringSize.Height)))
End Sub

Comentarios

Cuando se crea un delegado DrawItemEventArgs, se identifica el método que controlará el evento. Para asociar el evento al controlador, se debe agregar una instancia del delegado al evento. Siempre que se produce el evento, se llama a su controlador, a menos que se quite el delegado. Para obtener más información sobre los delegados del controlador de eventos, vea Control y generación de eventos.

Métodos de extensión

Consulte también

• DrawItemEventArgs
• ComboBox
• ListBox
• MenuItem
• TabControl