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NativeWindow.ReleaseHandle Metode

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Definisi

Ruang nama:
System.Windows.Forms
Rakitan:
System.Windows.Forms.dll

Melepaskan handel yang terkait dengan jendela ini.

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

Contoh

Contoh kode berikut menunjukkan penyadapan pesan jendela sistem operasi dalam prosedur jendela. Contoh membuat kelas yang mewarisi NativeWindow untuk mencapai hal ini.

Kelas MyNativeWindowListener mengaitkan ke prosedur jendela formulir yang diteruskan ke konstruktor, dan mengambil WndProc alih metode untuk mencegat WM_ACTIVATEAPP pesan jendela. Kelas menunjukkan penggunaan AssignHandle metode dan ReleaseHandle untuk mengidentifikasi handel jendela yang NativeWindow akan digunakan. Handel ditetapkan berdasarkan Control.HandleCreated peristiwa dan Control.HandleDestroyed . WM_ACTIVATEAPP Ketika pesan jendela diterima, kelas memanggil form1.ApplicationActivated metode .

Kode ini adalah kutipan dari contoh yang ditunjukkan dalam NativeWindow gambaran umum kelas. Beberapa kode tidak ditampilkan untuk tujuan keringkasan. Lihat NativeWindow untuk seluruh daftar kode.

// 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

Keterangan

Metode ini tidak menghancurkan handel jendela. Sebaliknya, ini mengatur prosedur jendela handel ke prosedur jendela default. Ini mengatur properti ke Handle 0 dan panggilan OnHandleChange untuk mencerminkan perubahan.

Jendela secara otomatis memanggil metode ini jika menerima pesan WM_NCDESTROY Win32 asli, yang menunjukkan bahwa Windows telah menghancurkan handel.

Berlaku untuk

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