登录  
 加关注
查看详情
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

pcwanli的博客

nx

 
 
 

日志

 
 

深入浅出Win32多线程设计之MFC的多线程  

2007-11-06 16:04:34|  分类: 开发杂项 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |
 
2006-01-19 14:08 作者: 宋宝华 出处: 天极开发 责任编辑:方舟
  1、创建和终止线程

  在MFC程序中创建一个线程,宜调用AfxBeginThread函数。该函数因参数不同而具有两种重载版本,分别对应工作者线程和用户接口(UI)线程。

  工作者线程

CWinThread *AfxBeginThread(
 AFX_THREADPROC pfnThreadProc, //控制函数
 LPVOID pParam, //传递给控制函数的参数
 int nPriority = THREAD_PRIORITY_NORMAL, //线程的优先级
 UINT nStackSize = 0, //线程的堆栈大小
 DWORD dwCreateFlags = 0, //线程的创建标志
 LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL //线程的安全属性
);

  工作者线程编程较为简单,只需编写线程控制函数和启动线程即可。下面的代码给出了定义一个控制函数和启动它的过程:

//线程控制函数
UINT MfcThreadProc(LPVOID lpParam)
{
 CExampleClass *lpObject = (CExampleClass*)lpParam;
 if (lpObject == NULL || !lpObject->IsKindof(RUNTIME_CLASS(CExampleClass)))
  return - 1; //输入参数非法
 //线程成功启动
 while (1)
 {
  ...//
 }
 return 0;
}

//在MFC程序中启动线程
AfxBeginThread(MfcThreadProc, lpObject);

  UI线程

  创建用户界面线程时,必须首先从CWinThread 派生类,并使用 DECLARE_DYNCREATE 和 IMPLEMENT_DYNCREATE 宏声明此类。

  下面给出了CWinThread类的原型(添加了关于其重要函数功能和是否需要被继承类重载的注释):

class CWinThread : public CCmdTarget
{
 DECLARE_DYNAMIC(CWinThread)

 public:
  // Constructors
  CWinThread();
  BOOL CreateThread(DWORD dwCreateFlags = 0, UINT nStackSize = 0,
LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL);

  // Attributes
  CWnd* m_pMainWnd; // main window (usually same AfxGetApp()->m_pMainWnd)
  CWnd* m_pActiveWnd; // active main window (may not be m_pMainWnd)
  BOOL m_bAutoDelete; // enables 'delete this' after thread termination

  // only valid while running
  HANDLE m_hThread; // this thread's HANDLE
  operator HANDLE() const;
  DWORD m_nThreadID; // this thread's ID

  int GetThreadPriority();
  BOOL SetThreadPriority(int nPriority);

  // Operations
  DWORD SuspendThread();
  DWORD ResumeThread();
  BOOL PostThreadMessage(UINT message, WPARAM wParam, LPARAM lParam);

  // Overridables
  //执行线程实例初始化,必须重写
  virtual BOOL InitInstance();

  // running and idle processing
  //控制线程的函数,包含消息泵,一般不重写
  virtual int Run();

  //消息调度到TranslateMessage和DispatchMessage之前对其进行筛选,
  //通常不重写
  virtual BOOL PreTranslateMessage(MSG* pMsg);

  virtual BOOL PumpMessage(); // low level message pump

  //执行线程特定的闲置时间处理,通常不重写
  virtual BOOL OnIdle(LONG lCount); // return TRUE if more idle processing
  virtual BOOL IsIdleMessage(MSG* pMsg); // checks for special messages

  //线程终止时执行清除,通常需要重写
  virtual int ExitInstance(); // default will 'delete this'

  //截获由线程的消息和命令处理程序引发的未处理异常,通常不重写
  virtual LRESULT ProcessWndProcException(CException* e, const MSG* pMsg);

  // Advanced: handling messages sent to message filter hook
  virtual BOOL ProcessMessageFilter(int code, LPMSG lpMsg);

  // Advanced: virtual access to m_pMainWnd
  virtual CWnd* GetMainWnd();

  // Implementation
 public:
  virtual ~CWinThread();
  #ifdef _DEBUG
   virtual void AssertValid() const;
   virtual void Dump(CDumpContext& dc) const;
   int m_nDisablePumpCount; // Diagnostic trap to detect illegal re-entrancy
  #endif
  void CommonConstruct();
  virtual void Delete();
  // 'delete this' only if m_bAutoDelete == TRUE

  // message pump for Run
  MSG m_msgCur; // current message

 public:
  // constructor used by implementation of AfxBeginThread
  CWinThread(AFX_THREADPROC pfnThreadProc, LPVOID pParam);

  // valid after construction
  LPVOID m_pThreadParams; // generic parameters passed to starting function
  AFX_THREADPROC m_pfnThreadProc;

  // set after OLE is initialized
  void (AFXAPI* m_lpfnOleTermOrFreeLib)(BOOL, BOOL);
  COleMessageFilter* m_pMessageFilter;

 protected:
  CPoint m_ptCursorLast; // last mouse position
  UINT m_nMsgLast; // last mouse message
  BOOL DispatchThreadMessageEx(MSG* msg); // helper
  void DispatchThreadMessage(MSG* msg); // obsolete
};

  启动UI线程的AfxBeginThread函数的原型为:

CWinThread *AfxBeginThread(
 //从CWinThread派生的类的 RUNTIME_CLASS
 CRuntimeClass *pThreadClass,
 int nPriority = THREAD_PRIORITY_NORMAL,
 UINT nStackSize = 0,
 DWORD dwCreateFlags = 0,
 LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL
);

  我们可以方便地使用VC++ 6.0类向导定义一个继承自CWinThread的用户线程类。下面给出产生我们自定义的CWinThread子类CMyUIThread的方法。

  打开VC++ 6.0类向导,在如下窗口中选择Base Class类为CWinThread,输入子类名为CMyUIThread,点击"OK"按钮后就产生了类CMyUIThread。

深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客

  其源代码框架为:

/////////////////////////////////////////////////////////////////////////////
// CMyUIThread thread

class CMyUIThread : public CWinThread
{
 DECLARE_DYNCREATE(CMyUIThread)
 protected:
  CMyUIThread(); // protected constructor used by dynamic creation

  // Attributes
 public:

  // Operations
 public:

  // Overrides
  // ClassWizard generated virtual function overrides
  //{{AFX_VIRTUAL(CMyUIThread)
  public:
   virtual BOOL InitInstance();
   virtual int ExitInstance();
  //}}AFX_VIRTUAL

  // Implementation
 protected:
  virtual ~CMyUIThread();

  // Generated message map functions
  //{{AFX_MSG(CMyUIThread)
   // NOTE - the ClassWizard will add and remove member functions here.
  //}}AFX_MSG

 DECLARE_MESSAGE_MAP()
};

/////////////////////////////////////////////////////////////////////////////
// CMyUIThread

IMPLEMENT_DYNCREATE(CMyUIThread, CWinThread)

CMyUIThread::CMyUIThread()
{}

CMyUIThread::~CMyUIThread()
{}

BOOL CMyUIThread::InitInstance()
{
 // TODO: perform and per-thread initialization here
 return TRUE;
}

int CMyUIThread::ExitInstance()
{
 // TODO: perform any per-thread cleanup here
 return CWinThread::ExitInstance();
}

BEGIN_MESSAGE_MAP(CMyUIThread, CWinThread)
//{{AFX_MSG_MAP(CMyUIThread)
// NOTE - the ClassWizard will add and remove mapping macros here.
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

  使用下列代码就可以启动这个UI线程:

CMyUIThread *pThread;
pThread = (CMyUIThread*)
AfxBeginThread( RUNTIME_CLASS(CMyUIThread) );

  另外,我们也可以不用AfxBeginThread 创建线程,而是分如下两步完成:

  (1)调用线程类的构造函数创建一个线程对象;

  (2)调用CWinThread::CreateThread函数来启动该线程。

  在线程自身内调用AfxEndThread函数可以终止该线程:

void AfxEndThread(
 UINT nExitCode //the exit code of the thread
);

  对于UI线程而言,如果消息队列中放入了WM_QUIT消息,将结束线程。

  关于UI线程和工作者线程的分配,最好的做法是:将所有与UI相关的操作放入主线程,其它的纯粹的运算工作交给独立的数个工作者线程。

  候捷先生早些时间喜欢为MDI程序的每个窗口创建一个线程,他后来澄清了这个错误。因为如果为MDI程序的每个窗口都单独创建一个线程,在窗口进行切换的时候,将进行线程的上下文切换!

 
2.线程间通信

  MFC中定义了继承自CSyncObject类的CCriticalSection 、CCEvent、CMutex、CSemaphore类封装和简化了WIN32 API所提供的临界区、事件、互斥和信号量。使用这些同步机制,必须包含"Afxmt.h"头文件。下图给出了类的继承关系:

深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客

  作为CSyncObject类的继承类,我们仅仅使用基类CSyncObject的接口函数就可以方便、统一的操作CCriticalSection 、CCEvent、CMutex、CSemaphore类,下面是CSyncObject类的原型:

class CSyncObject : public CObject
{
 DECLARE_DYNAMIC(CSyncObject)

 // Constructor
 public:
  CSyncObject(LPCTSTR pstrName);

  // Attributes
 public:
  operator HANDLE() const;
  HANDLE m_hObject;

  // Operations
  virtual BOOL Lock(DWORD dwTimeout = INFINITE);
  virtual BOOL Unlock() = 0;
  virtual BOOL Unlock(LONG /* lCount */, LPLONG /* lpPrevCount=NULL */)
  { return TRUE; }

  // Implementation
 public:
  virtual ~CSyncObject();
  #ifdef _DEBUG
   CString m_strName;
   virtual void AssertValid() const;
   virtual void Dump(CDumpContext& dc) const;
  #endif
  friend class CSingleLock;
  friend class CMultiLock;
};

  CSyncObject类最主要的两个函数是Lock和Unlock,若我们直接使用CSyncObject类及其派生类,我们需要非常小心地在Lock之后调用Unlock。

  MFC提供的另两个类CSingleLock(等待一个对象)和CMultiLock(等待多个对象)为我们编写应用程序提供了更灵活的机制,下面以实际来阐述CSingleLock的用法:

class CThreadSafeWnd
{
 public:
  CThreadSafeWnd(){}
  ~CThreadSafeWnd(){}
  void SetWindow(CWnd *pwnd)
  {
   m_pCWnd = pwnd;
  }
  void PaintBall(COLORREF color, CRect &rc);
 private:
  CWnd *m_pCWnd;
  CCriticalSection m_CSect;
};

void CThreadSafeWnd::PaintBall(COLORREF color, CRect &rc)
{
 CSingleLock csl(&m_CSect);
 //缺省的Timeout是INFINITE,只有m_Csect被激活,csl.Lock()才能返回
 //true,这里一直等待
 if (csl.Lock())
;
 {
  // not necessary
  //AFX_MANAGE_STATE(AfxGetStaticModuleState( ));
  CDC *pdc = m_pCWnd->GetDC();
  CBrush brush(color);
  CBrush *oldbrush = pdc->SelectObject(&brush);
  pdc->Ellipse(rc);
  pdc->SelectObject(oldbrush);
  GdiFlush(); // don't wait to update the display
 }
}

  上述实例讲述了用CSingleLock对Windows GDI相关对象进行保护的方法,下面再给出一个其他方面的例子:

int array1[10], array2[10];
CMutexSection section; //创建一个CMutex类的对象

//赋值线程控制函数
UINT EvaluateThread(LPVOID param)
{
 CSingleLock singlelock;
 singlelock(&section);

 //互斥区域
 singlelock.Lock();
 for (int i = 0; i < 10; i++)
  array1[i] = i;
 singlelock.Unlock();
}
//拷贝线程控制函数
UINT CopyThread(LPVOID param)
{
 CSingleLock singlelock;
 singlelock(&section);

 //互斥区域
 singlelock.Lock();
 for (int i = 0; i < 10; i++)
  array2[i] = array1[i];
 singlelock.Unlock();
}
}

AfxBeginThread(EvaluateThread, NULL); //启动赋值线程
AfxBeginThread(CopyThread, NULL); //启动拷贝线程

  上面的例子中启动了两个线程EvaluateThread和CopyThread,线程EvaluateThread把10个数赋值给数组array1[],线程CopyThread将数组array1[]拷贝给数组array2[]。由于数组的拷贝和赋值都是整体行为,如果不以互斥形式执行代码段:

for (int i = 0; i < 10; i++)
array1[i] = i;

  和

for (int i = 0; i < 10; i++)
array2[i] = array1[i];

  其结果是很难预料的!

  除了可使用CCriticalSection、CEvent、CMutex、CSemaphore作为线程间同步通信的方式以外,我们还可以利用PostThreadMessage函数在线程间发送消息:

BOOL PostThreadMessage(DWORD idThread, // thread identifier
UINT Msg, // message to post
WPARAM wParam, // first message parameter
LPARAM lParam // second message parameter
);
 3.线程与消息队列

  在WIN32中,每一个线程都对应着一个消息队列。由于一个线程可以产生数个窗口,所以并不是每个窗口都对应着一个消息队列。下列几句话应该作为"定理"被记住:

  "定理" 一

  所有产生给某个窗口的消息,都先由创建这个窗口的线程处理;

  "定理" 二

  Windows屏幕上的每一个控件都是一个窗口,有对应的窗口函数。

  消息的发送通常有两种方式,一是SendMessage,一是PostMessage,其原型分别为:

LRESULT SendMessage(HWND hWnd, // handle of destination window
 UINT Msg, // message to send
 WPARAM wParam, // first message parameter
 LPARAM lParam // second message parameter
);
BOOL PostMessage(HWND hWnd, // handle of destination window
 UINT Msg, // message to post
 WPARAM wParam, // first message parameter
 LPARAM lParam // second message parameter
);

  两个函数原型中的四个参数的意义相同,但是SendMessage和PostMessage的行为有差异。SendMessage必须等待消息被处理后才返回,而PostMessage仅仅将消息放入消息队列。SendMessage的目标窗口如果属于另一个线程,则会发生线程上下文切换,等待另一线程处理完成消息。为了防止另一线程当掉,导致SendMessage永远不能返回,我们可以调用SendMessageTimeout函数:

LRESULT SendMessageTimeout(
 HWND hWnd, // handle of destination window
 UINT Msg, // message to send
 WPARAM wParam, // first message parameter
 LPARAM lParam, // second message parameter
 UINT fuFlags, // how to send the message
 UINT uTimeout, // time-out duration
 LPDWORD lpdwResult // return value for synchronous call
);

  4. MFC线程、消息队列与MFC程序的"生死因果"

  分析MFC程序的主线程启动及消息队列处理的过程将有助于我们进一步理解UI线程与消息队列的关系,为此我们需要简单地叙述一下MFC程序的"生死因果"(侯捷:《深入浅出MFC》)。

  使用VC++ 6.0的向导完成一个最简单的单文档架构MFC应用程序MFCThread:

  (1) 输入MFC EXE工程名MFCThread;

  (2) 选择单文档架构,不支持Document/View结构;

  (3) ActiveX、3D container等其他选项都选择无。

  我们来分析这个工程。下面是产生的核心源代码:

  MFCThread.h 文件

class CMFCThreadApp : public CWinApp
{
 public:
  CMFCThreadApp();

  // Overrides
  // ClassWizard generated virtual function overrides
  //{{AFX_VIRTUAL(CMFCThreadApp)
   public:
    virtual BOOL InitInstance();
  //}}AFX_VIRTUAL

  // Implementation

 public:
  //{{AFX_MSG(CMFCThreadApp)
   afx_msg void OnAppAbout();
   // NOTE - the ClassWizard will add and remove member functions here.
   // DO NOT EDIT what you see in these blocks of generated code !
  //}}AFX_MSG
 DECLARE_MESSAGE_MAP()
};

  MFCThread.cpp文件

CMFCThreadApp theApp;

/////////////////////////////////////////////////////////////////////////////
// CMFCThreadApp initialization

BOOL CMFCThreadApp::InitInstance()
{
 …
 CMainFrame* pFrame = new CMainFrame;
 m_pMainWnd = pFrame;

 // create and load the frame with its resources
 pFrame->LoadFrame(IDR_MAINFRAME,WS_OVERLAPPEDWINDOW | FWS_ADDTOTITLE, NULL,NULL);
 // The one and only window has been initialized, so show and update it.
 pFrame->ShowWindow(SW_SHOW);
 pFrame->UpdateWindow();

 return TRUE;
}

  MainFrm.h文件

#include "ChildView.h"

class CMainFrame : public CFrameWnd
{
 public:
  CMainFrame();
 protected:
  DECLARE_DYNAMIC(CMainFrame)

  // Attributes
 public:

  // Operations
 public:
  // Overrides
  // ClassWizard generated virtual function overrides
  //{{AFX_VIRTUAL(CMainFrame)
   virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
   virtual BOOL OnCmdMsg(UINT nID, int nCode, void* pExtra, AFX_CMDHANDLERINFO* pHandlerInfo);
  //}}AFX_VIRTUAL

  // Implementation
 public:
  virtual ~CMainFrame();
  #ifdef _DEBUG
   virtual void AssertValid() const;
   virtual void Dump(CDumpContext& dc) const;
  #endif
  CChildView m_wndView;

  // Generated message map functions
 protected:
 //{{AFX_MSG(CMainFrame)
  afx_msg void OnSetFocus(CWnd *pOldWnd);
  // NOTE - the ClassWizard will add and remove member functions here.
  // DO NOT EDIT what you see in these blocks of generated code!
 //}}AFX_MSG
 DECLARE_MESSAGE_MAP()
};

  MainFrm.cpp文件

IMPLEMENT_DYNAMIC(CMainFrame, CFrameWnd)

BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
 //{{AFX_MSG_MAP(CMainFrame)
  // NOTE - the ClassWizard will add and remove mapping macros here.
  // DO NOT EDIT what you see in these blocks of generated code !
  ON_WM_SETFOCUS()
 //}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CMainFrame construction/destruction

CMainFrame::CMainFrame()
{
 // TODO: add member initialization code here
}

CMainFrame::~CMainFrame()
{}

BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
 if( !CFrameWnd::PreCreateWindow(cs) )
  return FALSE;
  // TODO: Modify the Window class or styles here by modifying
  // the CREATESTRUCT cs

 cs.dwExStyle &= ~WS_EX_CLIENTEDGE;
 cs.lpszClass = AfxRegisterWndClass(0);
 return TRUE;
}

  ChildView.h文件

// CChildView window

class CChildView : public CWnd
{
 // Construction
 public:
  CChildView();

  // Attributes
 public:
  // Operations
 public:
  // Overrides
  // ClassWizard generated virtual function overrides
  //{{AFX_VIRTUAL(CChildView)
   protected:
    virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
  //}}AFX_VIRTUAL

  // Implementation
 public:
  virtual ~CChildView();

  // Generated message map functions
 protected:
  //{{AFX_MSG(CChildView)
   afx_msg void OnPaint();
  //}}AFX_MSG
 DECLARE_MESSAGE_MAP()
};

ChildView.cpp文件
// CChildView

CChildView::CChildView()
{}

CChildView::~CChildView()
{}

BEGIN_MESSAGE_MAP(CChildView,CWnd )
//{{AFX_MSG_MAP(CChildView)
ON_WM_PAINT()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CChildView message handlers

BOOL CChildView::PreCreateWindow(CREATESTRUCT& cs)
{
 if (!CWnd::PreCreateWindow(cs))
  return FALSE;

 cs.dwExStyle |= WS_EX_CLIENTEDGE;
 cs.style &= ~WS_BORDER;
 cs.lpszClass = AfxRegisterWndClass(CS_HREDRAW|CS_VREDRAW|CS_DBLCLKS,::LoadCursor(NULL, IDC_ARROW),
HBRUSH(COLOR_WINDOW+1),NULL);

 return TRUE;
}

void CChildView::OnPaint()
{
 CPaintDC dc(this); // device context for painting

 // TODO: Add your message handler code here
 // Do not call CWnd::OnPaint() for painting messages
}

  文件MFCThread.h和MFCThread.cpp定义和实现的类CMFCThreadApp继承自CWinApp类,而CWinApp类又继承自CWinThread类(CWinThread类又继承自CCmdTarget类),所以CMFCThread本质上是一个MFC线程类,下图给出了相关的类层次结构:

深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客
我们提取CWinApp类原型的一部分:

class CWinApp : public CWinThread
{
 DECLARE_DYNAMIC(CWinApp)
 public:
  // Constructor
  CWinApp(LPCTSTR lpszAppName = NULL);// default app name
  // Attributes
  // Startup args (do not change)
  HINSTANCE m_hInstance;
  HINSTANCE m_hPrevInstance;
  LPTSTR m_lpCmdLine;
  int m_nCmdShow;
  // Running args (can be changed in InitInstance)
  LPCTSTR m_pszAppName; // human readable name
  LPCTSTR m_pszExeName; // executable name (no spaces)
  LPCTSTR m_pszHelpFilePath; // default based on module path
  LPCTSTR m_pszProfileName; // default based on app name

  // Overridables
  virtual BOOL InitApplication();
  virtual BOOL InitInstance();
  virtual int ExitInstance(); // return app exit code
  virtual int Run();
  virtual BOOL OnIdle(LONG lCount); // return TRUE if more idle processing
  virtual LRESULT ProcessWndProcException(CException* e,const MSG* pMsg);

 public:
  virtual ~CWinApp();
 protected:
  DECLARE_MESSAGE_MAP()
};

  SDK程序的WinMain 所完成的工作现在由CWinApp 的三个函数完成:

virtual BOOL InitApplication();
virtual BOOL InitInstance();
virtual int Run();

  "CMFCThreadApp theApp;"语句定义的全局变量theApp是整个程式的application object,每一个MFC 应用程序都有一个。当我们执行MFCThread程序的时候,这个全局变量被构造。theApp 配置完成后,WinMain开始执行。但是程序中并没有WinMain的代码,它在哪里呢?原来MFC早已准备好并由Linker直接加到应用程序代码中的,其原型为(存在于VC++6.0安装目录下提供的APPMODUL.CPP文件中):

extern "C" int WINAPI
_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPTSTR lpCmdLine, int nCmdShow)
{
 // call shared/exported WinMain
 return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}

  其中调用的AfxWinMain如下(存在于VC++6.0安装目录下提供的WINMAIN.CPP文件中):

int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPTSTR lpCmdLine, int nCmdShow)
{
 ASSERT(hPrevInstance == NULL);

 int nReturnCode = -1;
 CWinThread* pThread = AfxGetThread();
 CWinApp* pApp = AfxGetApp();

 // AFX internal initialization
 if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))
  goto InitFailure;

 // App global initializations (rare)
 if (pApp != NULL && !pApp->InitApplication())
  goto InitFailure;

 // Perform specific initializations
 if (!pThread->InitInstance())
 {
  if (pThread->m_pMainWnd != NULL)
  {
   TRACE0("Warning: Destroying non-NULL m_pMainWnd\n");
   pThread->m_pMainWnd->DestroyWindow();
  }
  nReturnCode = pThread->ExitInstance();
  goto InitFailure;
 }
 nReturnCode = pThread->Run();

 InitFailure:
 #ifdef _DEBUG
  // Check for missing AfxLockTempMap calls
  if (AfxGetModuleThreadState()->m_nTempMapLock != 0)
  {
   TRACE1("Warning: Temp map lock count non-zero (%ld).\n",
AfxGetModuleThreadState()->m_nTempMapLock);
  }
  AfxLockTempMaps();
  AfxUnlockTempMaps(-1);
 #endif

 AfxWinTerm();
 return nReturnCode;
}

  我们提取主干,实际上,这个函数做的事情主要是:

CWinThread* pThread = AfxGetThread();
CWinApp* pApp = AfxGetApp();
AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow)
pApp->InitApplication()
pThread->InitInstance()
pThread->Run();

  其中,InitApplication 是注册窗口类别的场所;InitInstance是产生窗口并显示窗口的场所;Run是提取并分派消息的场所。这样,MFC就同WIN32 SDK程序对应起来了。CWinThread::Run是程序生命的"活水源头"(侯捷:《深入浅出MFC》,函数存在于VC++ 6.0安装目录下提供的THRDCORE.CPP文件中):

// main running routine until thread exits
int CWinThread::Run()
{
 ASSERT_VALID(this);

 // for tracking the idle time state
 BOOL bIdle = TRUE;
 LONG lIdleCount = 0;

 // acquire and dispatch messages until a WM_QUIT message is received.
 for (;;)
 {
  // phase1: check to see if we can do idle work
  while (bIdle && !::PeekMessage(&m_msgCur, NULL, NULL, NULL, PM_NOREMOVE))
  {
   // call OnIdle while in bIdle state
   if (!OnIdle(lIdleCount++))
    bIdle = FALSE; // assume "no idle" state
  }

  // phase2: pump messages while available
  do
  {
   // pump message, but quit on WM_QUIT
   if (!PumpMessage())
    return ExitInstance();

   // reset "no idle" state after pumping "normal" message
   if (IsIdleMessage(&m_msgCur))
   {
    bIdle = TRUE;
    lIdleCount = 0;
   }

  } while (::PeekMessage(&m_msgCur, NULL, NULL, NULL, PM_NOREMOVE));
 }
 ASSERT(FALSE); // not reachable
}

  其中的PumpMessage函数又对应于:

/////////////////////////////////////////////////////////////////////////////
// CWinThread implementation helpers

BOOL CWinThread::PumpMessage()
{
 ASSERT_VALID(this);

 if (!::GetMessage(&m_msgCur, NULL, NULL, NULL))
 {
  return FALSE;
 }

 // process this message
 if(m_msgCur.message != WM_KICKIDLE && !PreTranslateMessage(&m_msgCur))
 {
  ::TranslateMessage(&m_msgCur);
  ::DispatchMessage(&m_msgCur);
 }
 return TRUE;
}

  因此,忽略IDLE状态,整个RUN的执行提取主干就是:

do {
 ::GetMessage(&msg,...);
 PreTranslateMessage{&msg);
 ::TranslateMessage(&msg);
 ::DispatchMessage(&msg);
 ...
} while (::PeekMessage(...));

  由此,我们建立了MFC消息获取和派生机制与WIN32 SDK程序之间的对应关系。下面继续分析MFC消息的"绕行"过程。

  在MFC中,只要是CWnd 衍生类别,就可以拦下任何Windows消息。与窗口无关的MFC类别(例如CDocument 和CWinApp)如果也想处理消息,必须衍生自CCmdTarget,并且只可能收到WM_COMMAND消息。所有能进行MESSAGE_MAP的类都继承自CCmdTarget,如:

深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客深入浅出Win32多线程设计之MFC的多线程 - pcwanli - pcwanli的博客

  MFC中MESSAGE_MAP的定义依赖于以下三个宏:

DECLARE_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(
 theClass, //Specifies the name of the class whose message map this is
 baseClass //Specifies the name of the base class of theClass
)

END_MESSAGE_MAP()

  我们程序中涉及到的有:MFCThread.h、MainFrm.h、ChildView.h文件

DECLARE_MESSAGE_MAP()
MFCThread.cpp文件
BEGIN_MESSAGE_MAP(CMFCThreadApp, CWinApp)
//{{AFX_MSG_MAP(CMFCThreadApp)
ON_COMMAND(ID_APP_ABOUT, OnAppAbout)
// NOTE - the ClassWizard will add and remove mapping macros here.
// DO NOT EDIT what you see in these blocks of generated code!
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
MainFrm.cpp文件
BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
//{{AFX_MSG_MAP(CMainFrame)
// NOTE - the ClassWizard will add and remove mapping macros here.
// DO NOT EDIT what you see in these blocks of generated code !
ON_WM_SETFOCUS()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
ChildView.cpp文件
BEGIN_MESSAGE_MAP(CChildView,CWnd )
//{{AFX_MSG_MAP(CChildView)
ON_WM_PAINT()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

  由这些宏,MFC建立了一个消息映射表(消息流动网),按照消息流动网匹配对应的消息处理函数,完成整个消息的"绕行"。

  看到这里相信你有这样的疑问:程序定义了CWinApp类的theApp全局变量,可是从来没有调用AfxBeginThread或theApp.CreateThread启动线程呀,theApp对应的线程是怎么启动的?

  答:MFC在这里用了很高明的一招。实际上,程序开始运行,第一个线程是由操作系统(OS)启动的,在CWinApp的构造函数里,MFC将theApp"对应"向了这个线程,具体的实现是这样的:

CWinApp::CWinApp(LPCTSTR lpszAppName)
{
 if (lpszAppName != NULL)
  m_pszAppName = _tcsdup(lpszAppName);
 else
  m_pszAppName = NULL;

 // initialize CWinThread state
 AFX_MODULE_STATE *pModuleState = _AFX_CMDTARGET_GETSTATE();
 AFX_MODULE_THREAD_STATE *pThreadState = pModuleState->m_thread;
 ASSERT(AfxGetThread() == NULL);
 pThreadState->m_pCurrentWinThread = this;
 ASSERT(AfxGetThread() == this);
 m_hThread = ::GetCurrentThread();
 m_nThreadID = ::GetCurrentThreadId();

 // initialize CWinApp state
 ASSERT(afxCurrentWinApp == NULL); // only one CWinApp object please
 pModuleState->m_pCurrentWinApp = this;
 ASSERT(AfxGetApp() == this);

 // in non-running state until WinMain
 m_hInstance = NULL;
 m_pszHelpFilePath = NULL;
 m_pszProfileName = NULL;
 m_pszRegistryKey = NULL;
 m_pszExeName = NULL;
 m_pRecentFileList = NULL;
 m_pDocManager = NULL;
 m_atomApp = m_atomSystemTopic = NULL; //微软懒鬼?或者他认为
 //这样连等含义更明确?
 m_lpCmdLine = NULL;
 m_pCmdInfo = NULL;

 // initialize wait cursor state
 m_nWaitCursorCount = 0;
 m_hcurWaitCursorRestore = NULL;

 // initialize current printer state
 m_hDevMode = NULL;
 m_hDevNames = NULL;
 m_nNumPreviewPages = 0; // not specified (defaults to 1)

 // initialize DAO state
 m_lpfnDaoTerm = NULL; // will be set if AfxDaoInit called

 // other initialization
 m_bHelpMode = FALSE;
 m_nSafetyPoolSize = 512; // default size
}

  很显然,theApp成员变量都被赋予OS启动的这个当前线程相关的值,如代码:

m_hThread = ::GetCurrentThread();//theApp的线程句柄等于当前线程句柄
m_nThreadID = ::GetCurrentThreadId();//theApp的线程ID等于当前线程ID

  所以CWinApp类几乎只是为MFC程序的第一个线程量身定制的,它不需要也不能被AfxBeginThread或theApp.CreateThread"再次"启动。这就是CWinApp类和theApp全局变量的内涵!如果你要再增加一个UI线程,不要继承类CWinApp,而应继承类CWinThread。而参考第1节,由于我们一般以主线程(在MFC程序里实际上就是OS启动的第一个线程)处理所有窗口的消息,所以我们几乎没有再启动UI线程的需求!
  评论这张
 
阅读(510)| 评论(0)

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2018