继续上节，我们还是用工程文件创建一个MDI窗口。代码如下：

program MDIApp;uses  Windows,  Messages;var  TheMessage:TMsg;  FrameWindow,ClientWindow,ChildWindow:HWND;const  IDCHILDWND = 100;   //第一个MDI子窗口ID{
    $R *.RES}//回调函数function FrameWindowProc(TheFrameWindow:HWND;TheMessage,WParam,LParam:LongInt):LongInt;stdcall;var  ClientStruct:TClientCreateStruct;begin  case TheMessage of  WM_CREATE:    begin      ClientStruct.hWindowMenu:=0;      ClientStruct.idFirstChild:=IDCHILDWND;      ClientWindow  := CreateWindowEx(0,                  'MDICLIENT',                  nil,                  WS_CHILD or                  WS_CLIPCHILDREN or                  WS_VISIBLE,                  0,                  0,                  0,                  0,                  TheFrameWindow,                  0,                  HInstance,                  @ClientStruct);      if ClientWindow = 0 then        begin          MessageBox(0,'createwindow faild',nil,MB_OK);          Exit;        end;    end;  WM_DESTROY:    begin      PostQuitMessage(0);      Exit;    end;  end;  Result := DefFrameProc(TheFrameWindow,ClientWindow,TheMessage,WParam,LParam);end;//注册主窗口function RegisterFrameClass:Boolean;var  WindowClass:TWndClass;begin  WindowClass.style:=CS_HREDRAW or CS_VREDRAW;  WindowClass.lpfnWndProc:=@FrameWindowProc;  WindowClass.cbClsExtra := 0;  WindowClass.cbWndExtra := 0;  WindowClass.hInstance := HInstance;  WindowClass.hIcon := LoadIcon(0,IDI_WINLOGO);  WindowClass.hCursor:= LoadCursor(0,IDC_ARROW);  WindowClass.hbrBackground:= COLOR_WINDOW;  WindowClass.lpszMenuName:= nil;  WindowClass.lpszClassName:= 'FrameClass';  Result := windows.RegisterClass(WindowClass)<>0;end;//注册子窗口function RegisterChildClass: Boolean;var  WindowClass:TWndClass;begin   WindowClass.style := CS_HREDRAW or CS_VREDRAW;   WindowClass.lpfnWndProc:= @DefMDICHildProc;   WindowClass.cbClsExtra := 0;   WindowClass.cbWndExtra := 0;   WindowClass.hInstance := HInstance;   WindowClass.hIcon := LoadIcon(0,IDI_APPLICATION);   WindowClass.hCursor := LoadCursor(0,IDC_ARROW);   WindowClass.hbrBackground := COLOR_WINDOW;   WindowClass.lpszMenuName := nil;   WindowClass.lpszClassName := 'ChildClass';   Result := windows.RegisterClass(WindowClass)<>0;end;//开始主程序begin  if not RegisterFrameClass then  begin    MessageBox(0,'RegisterFrameClass faild',nil,MB_OK);    Exit;  end;  FrameWindow := CreateWindowEx(0,                              'FrameClass',                              'Frame Window',                              WS_OVERLAPPEDWINDOW or                              WS_CLIPCHILDREN,                              CW_USEDEFAULT,                              CW_USEDEFAULT,                              CW_USEDEFAULT,                              CW_USEDEFAULT,                              0,                              0,                              HInstance,                              nil);  if FrameWindow <> 0 then  begin    ShowWindow(FrameWindow,SW_SHOWNORMAL);    UpdateWindow(FrameWindow);  end  else  begin    MessageBox(0,'CreateFrameWindow failed',nil,MB_OK);    Exit;  end;   if not RegisterChildClass then   begin     MessageBox(0,'RegisterChildClass failed',nil,MB_OK);     Exit;   end;   ChildWindow:= CreateMDIWindow('ChildClass',                        'Child Window',                        WS_VISIBLE,                        CW_USEDEFAULT,                        CW_USEDEFAULT,                        CW_USEDEFAULT,                        CW_USEDEFAULT,                        ClientWindow,                        HInstance,                        0);   if ChildWindow <> 0 then   begin     ShowWindow(ChildWindow,SW_SHOWNORMAL);     UpdateWindow(ChildWindow);   end   else   begin     MessageBox(0,'CreateChildWindow falid',nil,MB_OK);     Exit;   end;   while GetMessage(TheMessage,0,0,0) do   begin     TranslateMessage(TheMessage);     DispatchMessage(TheMessage);   end;end.

效果如下：