NativeWindow.ReleaseHandle Methode

  • Referenz

Definition

Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms.dll

Gibt das diesem Fenster zugeordnete Handle frei.

public:
 virtual void ReleaseHandle();
public virtual void ReleaseHandle ();
abstract member ReleaseHandle : unit -> unit
override this.ReleaseHandle : unit -> unit
Public Overridable Sub ReleaseHandle ()

Beispiele

Im folgenden Codebeispiel wird das Abfangen von Betriebssystemfenstermeldungen in einer Fensterprozedur veranschaulicht. Im Beispiel wird eine Klasse erstellt, die von NativeWindow erbt, um dies zu erreichen.

Die MyNativeWindowListener -Klasse bindet in die Fensterprozedur des Formulars ein, das an den Konstruktor übergeben wird, und überschreibt die WndProc -Methode, um die WM_ACTIVATEAPP Fensternachricht abzufangen. Die -Klasse veranschaulicht die Verwendung der AssignHandle Methoden und ReleaseHandle zum Identifizieren des Fensterhandles, das von NativeWindow verwendet wird. Das Handle wird basierend auf den Control.HandleCreated Ereignissen und Control.HandleDestroyed zugewiesen. Wenn die WM_ACTIVATEAPP Fenstermeldung empfangen wird, ruft die -Klasse die form1.ApplicationActivated -Methode auf.

Dieser Code ist ein Auszug aus dem Beispiel in der NativeWindow Klassenübersicht. Ein Teil des Codes wird aus Gründen der Kürze nicht angezeigt. Die gesamte Codeauflistung finden Sie NativeWindow unter.

// NativeWindow class to listen to operating system messages.
ref class MyNativeWindowListener: public NativeWindow
{
private:

   // Constant value was found in the S"windows.h" header file.
   literal int WM_ACTIVATEAPP = 0x001C;
   Form1^ parent;

public:
   MyNativeWindowListener( Form1^ parent )
   {
      parent->HandleCreated += gcnew EventHandler( this, &MyNativeWindowListener::OnHandleCreated );
      parent->HandleDestroyed += gcnew EventHandler( this, &MyNativeWindowListener::OnHandleDestroyed );
      this->parent = parent;
   }

internal:

   // Listen for the control's window creation and then hook into it.
   void OnHandleCreated( Object^ sender, EventArgs^ /*e*/ )
   {
      // Window is now created, assign handle to NativeWindow.
      AssignHandle( (dynamic_cast<Form1^>(sender))->Handle );
   }

   void OnHandleDestroyed( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      // Window was destroyed, release hook.
      ReleaseHandle();
   }

protected:

   virtual void WndProc( Message %m ) override
   {
      // Listen for operating system messages
      switch ( m.Msg )
      {
         case WM_ACTIVATEAPP:

            // Notify the form that this message was received.
            // Application is activated or deactivated,
            // based upon the WParam parameter.
            parent->ApplicationActived( ((int)m.WParam != 0) );
            break;
      }
      NativeWindow::WndProc( m );
   }

};

// NativeWindow class to listen to operating system messages.
internal class MyNativeWindowListener : NativeWindow
{
    // Constant value was found in the "windows.h" header file.
    private const int WM_ACTIVATEAPP = 0x001C;

    private Form1 parent;

    public MyNativeWindowListener(Form1 parent)
    {

        parent.HandleCreated += new EventHandler(this.OnHandleCreated);
        parent.HandleDestroyed += new EventHandler(this.OnHandleDestroyed);
        this.parent = parent;
    }

    // Listen for the control's window creation and then hook into it.
    internal void OnHandleCreated(object sender, EventArgs e)
    {
        // Window is now created, assign handle to NativeWindow.
        AssignHandle(((Form1)sender).Handle);
    }
    internal void OnHandleDestroyed(object sender, EventArgs e)
    {
        // Window was destroyed, release hook.
        ReleaseHandle();
    }

    protected override void WndProc(ref Message m)
    {
        // Listen for operating system messages

        switch (m.Msg)
        {
            case WM_ACTIVATEAPP:

                // Notify the form that this message was received.
                // Application is activated or deactivated, 
                // based upon the WParam parameter.
                parent.ApplicationActivated(((int)m.WParam != 0));

                break;
        }
        base.WndProc(ref m);
    }
}

' NativeWindow class to listen to operating system messages.
Friend Class MyNativeWindowListener
    Inherits NativeWindow

    ' Constant value was found in the "windows.h" header file.
    Private Const WM_ACTIVATEAPP As Integer = &H1C

    Private parent As Form1

    Public Sub New(ByVal parent As Form1)

        AddHandler parent.HandleCreated, AddressOf Me.OnHandleCreated
        AddHandler parent.HandleDestroyed, AddressOf Me.OnHandleDestroyed
        Me.parent = parent
    End Sub

    ' Listen for the control's window creation and hook into it.    
    Private Sub OnHandleCreated(ByVal sender As Object, ByVal e As EventArgs)
        ' Window is now created, assign handle to NativeWindow.
        AssignHandle(CType(sender, Form).Handle)
    End Sub

    Private Sub OnHandleDestroyed(ByVal sender As Object, ByVal e As EventArgs)
        ' Window was destroyed, release hook.
        ReleaseHandle()
    End Sub

    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
        Protected Overrides Sub WndProc(ByRef m As Message)
        ' Listen for operating system messages

        Select Case (m.Msg)
            Case WM_ACTIVATEAPP

                ' Notify the form that this message was received.
                ' Application is activated or deactivated, 
                ' based upon the WParam parameter.
                parent.ApplicationActivated(m.WParam.ToInt32() <> 0)

        End Select

        MyBase.WndProc(m)
    End Sub
End Class

Hinweise

Diese Methode zerstört nicht das Fensterhandle. Stattdessen wird die Fensterprozedur des Handles auf die Standardfensterprozedur festgelegt. Sie legt die Handle -Eigenschaft auf 0 fest und ruft auf OnHandleChange , um die Änderung widerzuspiegeln.

Ein Fenster ruft diese Methode automatisch auf, wenn es eine native Win32-WM_NCDESTROY-Meldung empfängt, die angibt, dass Windows das Handle zerstört hat.

Gilt für:

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