FontDialog.HookProc(IntPtr, Int32, IntPtr, IntPtr) Metodo

protected:
 override IntPtr HookProc(IntPtr hWnd, int msg, IntPtr wparam, IntPtr lparam);

protected override IntPtr HookProc(IntPtr hWnd, int msg, IntPtr wparam, IntPtr lparam);

override this.HookProc : nativeint * int * nativeint * nativeint -> nativeint

Protected Overrides Function HookProc (hWnd As IntPtr, msg As Integer, wparam As IntPtr, lparam As IntPtr) As IntPtr

Parametri

Valori restituiti

Valore zero se la routine della finestra di dialogo predefinita elabora il messaggio; un valore diverso da zero se la routine della finestra di dialogo predefinita ignora il messaggio.

Esempio

Nell'esempio di codice seguente viene illustrato come eseguire l'override del HookProc metodo . L'esempio è costituito da una classe che eredita la FontDialog classe . Nell'override dell' della classe, l'esempio valuta il parametro /> del metodo è uguale alla costante specificata, nell'esempio viene scritto l'output di traccia che identifica il messaggio Windows passato al metodo /> HookProc metodo sia dichiarato eredita la FontDialog classe .

private:
   // Defines the constants for Windows messages.
   literal int WM_SETFOCUS = 0x0007;
   literal int WM_INITDIALOG = 0x0110;
   literal int WM_LBUTTONDOWN = 0x0201;
   literal int WM_RBUTTONDOWN = 0x0204;
   literal int WM_MOVE = 0x0003;

protected:
   // Overrides the base class hook procedure...
   [SecurityPermission(SecurityAction::Demand, Flags=SecurityPermissionFlag::UnmanagedCode)] 
   virtual IntPtr HookProc( IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam ) override
   {
      // Evaluates the message parameter to determine the user action.
      #if defined(TRACE)
      switch ( msg )
      {
         case WM_INITDIALOG:
            System::Diagnostics::Trace::Write( "The WM_INITDIALOG message was received." );
            break;
         case WM_SETFOCUS:
            System::Diagnostics::Trace::Write( "The WM_SETFOCUS message was received." );
            break;
         case WM_LBUTTONDOWN:
            System::Diagnostics::Trace::Write( "The WM_LBUTTONDOWN message was received." );
            break;
         case WM_RBUTTONDOWN:
            System::Diagnostics::Trace::Write( "The WM_RBUTTONDOWN message was received." );
            break;
         case WM_MOVE:
            System::Diagnostics::Trace::Write( "The WM_MOVE message was received." );
            break;
      }
      #endif
     
      // Always call the base class hook procedure.
      return FontDialog::HookProc( hWnd, msg, wParam, lParam );
   }

// Defines the constants for Windows messages.

const int WM_SETFOCUS = 0x0007;
const int WM_INITDIALOG = 0x0110;
const int WM_LBUTTONDOWN = 0x0201;
const int WM_RBUTTONDOWN = 0x0204;
const int WM_MOVE = 0x0003;

// Overrides the base class hook procedure...
protected override IntPtr HookProc(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam)
{
    // Evaluates the message parameter to determine the user action.

    switch(msg)
    {

        case WM_INITDIALOG:
            System.Diagnostics.Trace.Write("The WM_INITDIALOG message was received.");
            break;
        case WM_SETFOCUS:
            System.Diagnostics.Trace.Write("The WM_SETFOCUS message was received.");
            break;
        case WM_LBUTTONDOWN:
            System.Diagnostics.Trace.Write("The WM_LBUTTONDOWN message was received.");
            break;
        case WM_RBUTTONDOWN:
            System.Diagnostics.Trace.Write("The WM_RBUTTONDOWN message was received.");
            break;
        case WM_MOVE:
            System.Diagnostics.Trace.Write("The WM_MOVE message was received.");
            break;
    }

    // Always call the base class hook procedure.

    return base.HookProc(hWnd, msg, wParam, lParam);
}

    ' Defines the constants for Windows messages.

    Const WM_SETFOCUS = &H7
    Const WM_INITDIALOG = &H110
    Const WM_LBUTTONDOWN = &H201
    Const WM_RBUTTONDOWN = &H204
    Const WM_MOVE = &H3
<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
    Protected Overrides Function HookProc(ByVal hWnd As IntPtr, ByVal msg As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr


        ' Evaluates the message parameter to determine the user action.

        Select Case msg

            Case WM_INITDIALOG
                System.Diagnostics.Trace.Write("The WM_INITDIALOG message was received.")
            Case WM_SETFOCUS
                System.Diagnostics.Trace.Write("The WM_SETFOCUS message was received.")
            Case WM_LBUTTONDOWN
                System.Diagnostics.Trace.Write("The WM_LBUTTONDOWN message was received.")
            Case WM_RBUTTONDOWN
                System.Diagnostics.Trace.Write("The WM_RBUTTONDOWN message was received.")
            Case WM_MOVE
                System.Diagnostics.Trace.Write("The WM_MOVE message was received.")

        End Select

        ' Always call the base class hook procedure.

        Return MyBase.HookProc(hWnd, msg, wParam, lParam)

    End Function

Commenti

Una routine hook è un meccanismo tramite il quale una funzione può intercettare gli eventi prima di raggiungere un'applicazione. Quando si esegue l'override del CommonDialog.HookProc metodo per una CommonDialog classe, il sistema operativo richiama l'override della funzione per pubblicare i messaggi del sistema operativo nella finestra.

Note per gli eredi

Quando si esegue l'override HookProc(IntPtr, Int32, IntPtr, IntPtr) in una classe derivata, assicurarsi di chiamare il metodo della classe di HookProc(IntPtr, Int32, IntPtr, IntPtr) base.

Vedi anche

• CommonDialog