CommonDialog.HookProc(IntPtr, Int32, IntPtr, IntPtr) Metode

Definisi

Ruang nama:

System.Windows.Forms

Rakitan:

System.Windows.Forms.dll

Sumber:

CommonDialog.cs

Menentukan prosedur kait kotak dialog umum yang ditimpa untuk menambahkan fungsionalitas tertentu ke kotak dialog umum.

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

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

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

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

Parameter

hWnd

IntPtr

nativeint

Gagang ke jendela kotak dialog.

msg

Int32

Pesan yang diterima.

wparam

IntPtr

nativeint

Informasi tambahan tentang pesan.

lparam

IntPtr

nativeint

Informasi tambahan tentang pesan.

Mengembalikan

IntPtr

nativeint

Nilai nol jika prosedur kotak dialog default memproses pesan; nilai bukan nol jika prosedur kotak dialog default mengabaikan pesan.

Contoh

Contoh kode berikut menunjukkan cara mengambil alih HookProc metode . Contohnya terdiri dari kelas yang mewarisi CommonDialog kelas. Dalam HookProc kelas mengambil alih, contoh mengevaluasi parameter msg metode terhadap nilai konstan untuk pesan Windows tertentu. Jika parameter msg sama dengan konstanta yang ditentukan, contoh menulis output jejak yang mengidentifikasi pesan Windows yang diteruskan ke metode HookProc. Contoh ini mengasumsikan bahwa kelas tempat HookProc metode dinyatakan mewarisi CommonDialog kelas.

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

Keterangan

Prosedur kait adalah mekanisme di mana fungsi dapat mencegat peristiwa sebelum mencapai aplikasi. Saat Anda mengambil HookProc alih metode untuk CommonDialog kelas, sistem operasi memanggil penimpaan fungsi Anda untuk memposting pesan sistem operasi ke jendela.

Secara default, prosedur kait mempusatkan kotak dialog di layar sebagai respons terhadap pesan WM_INITDIALOG .

Catatan Bagi Inheritor

Mewarisi kelas dapat mengambil alih metode ini untuk menambahkan fungsionalitas tertentu ke kotak dialog umum. Saat mengambil alih kelas turunan HookProc(IntPtr, Int32, IntPtr, IntPtr) , pastikan untuk memanggil metode kelas HookProc(IntPtr, Int32, IntPtr, IntPtr) dasar.