MFC 中消息循环实例

时间：2011-06-09 来源：zip's

让 APP 发送和处理自定义消息

1，自定消息；由于 app 不是继承与窗口类，所以不能向窗口那样 send 或 post message；

2，可以直接在 app 中 post thread message，例如这里的 WM_APP1；也可以从窗口中 post WM_COMMAND，例如这里的 WM_APP2;

2，防止 thread message 丢失，下面这个例子中，WM_APP2在主窗口创建后被post，处理函数弹出一个dialog，这时如果不显示滴用PeekMessage，thread message就被发到了窗口线程里，就丢失了。

#define WM_APP1 (WM_APP+1)
#define WM_APP2 (WM_APP+2)

BEGIN_MESSAGE_MAP(CProgramApp, CWinApp)
    ON_THREAD_MESSAGE(WM_APP1, &CProgramApp::OnHandleApp1)
    ON_COMMAND(WM_APP2, &CProgramApp::OnHandleApp2)
    ON_COMMAND(ID_APP_ABOUT, &CProgramApp::OnAppAbout)
    // Standard file based document commands
    ON_COMMAND(ID_FILE_NEW, &CWinApp::OnFileNew)
    ON_COMMAND(ID_FILE_OPEN, &CWinApp::OnFileOpen)
END_MESSAGE_MAP()

BOOL CProgramApp::InitInstance()
{
    ...

    // Dispatch commands specified on the command line.  Will return FALSE if
    // app was launched with /RegServer, /Register, /Unregserver or /Unregister.
    if (!ProcessShellCommand(cmdInfo))
        return FALSE;
    // The main window has been initialized, so show and update it
    pMainFrame->ShowWindow(m_nCmdShow);
    pMainFrame->UpdateWindow();

    // 
    // WM_APP2 was posted after main window created, need dispatch all those msg,
    // then post the thread msg, otherwise, the thread message lost.
    //
    MSG Msg;
    while(PeekMessage(&Msg, NULL, 0, 0, PM_REMOVE))
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    this->PostThreadMessage(WM_APP1, 0, 0);

    return TRUE;
}

void CProgramApp::OnHandleApp1(WPARAM wParam, LPARAM lParam)
{
    AfxMessageBox(_T("WM_APP1 handler"));
}

void CProgramApp::OnHandleApp2()
{
    AfxMessageBox(_T("WM_APP2 handler"));
}

int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    if (CMDIFrameWnd::OnCreate(lpCreateStruct) == -1)
        return -1;

    if (!m_wndStatusBar.Create(this))
    {
        TRACE0("Failed to create status bar\n");
        return -1;      // fail to create
    }
    m_wndStatusBar.SetIndicators(indicators, sizeof(indicators)/sizeof(UINT));

    // 
    this->PostMessage(WM_COMMAND, WM_APP2, 0);

    return 0;
}