CEvent 類別

表示事件，是同步物件可讓執行緒向類別上的事件發生。

class CEvent : public CSyncObject

Members

公用建構函式

公用方法

備註

指定執行緒時必須知道執行其工作時，事件會很有用處。例如，複製至資料檔案的執行緒必須告知，當新資料可用時。您可以使用告知複本的 CEvent 物件執行緒，新增資料可用，執行緒可以儘快執行其工作。

CEvent 具有兩種類型:手動和自動。

將自動 CEvent 物件自動復原為未收到信號的 (無法使用) 狀態，在釋放之後至少一個執行緒。根據預設，在中，除非您在建構時，您可以 bManualReset 參數的 TRUECEvent 物件會自動進行。

方針 CEvent 物件在 SetEvent 或 ResetEvent 設定的狀態會暫停，直到另一個函式呼叫。若要建立手動 CEvent 物件，請在建構期間傳遞 bManualReset 參數的 TRUE 。

如果需要時，要使用 CEvent 物件，請 CEvent 建構物件。指定要等候事件的名稱，並指定您的應用程式應初始擁有它。當建構函式傳回時，您可以存取事件。呼叫 SetEvent 信號 (可提供事件) 物件，然後呼叫 解除鎖定 在進行存取控制資源時。

替代方法是使用 CEvent 要加入物件的型別 CEvent 的變數時，您要將控制項的類別的資料成員。控制在建構物件時，請呼叫 CEvent 資料成員的建構函式並指定事件是否一開始就會收到信號，因此的事件物件的 specifythe 型別時，事件的名稱 (如果它跨越處理序界限是使用) 和所有需要的安全性屬性。

若要存取 CEvent 物件做控制項的資源，請先建立型別 CSingleLock 的變數或輸入於資源存取方法的 CMultiLock 。然後呼叫鎖定物件 (例如， CMultiLock::Lock) 的 Lock 方法。此時，您的執行緒存取資源的存取權，會等候資源釋放並存取或等候資源釋放，時間和錯誤才能存取資源。無論如何，您的資源存取以安全執行緒方法。若要釋放資源，請呼叫 SetEvent 事件發出信號物件，然後使用鎖定物件的 Unlock 方法 (例如， CMultiLock::Unlock)，或是讓鎖定物件落在範圍外。

如需如何使用 CEvent 物件的詳細資訊，請參閱 多執行緒：如何使用同步類別。

範例

// The following demonstrates trivial usage of the CEvent class.
// A CEvent object is created and passed as a parameter to another 
// thread.  The other thread will wait for the event to be signaled
// and then exit

UINT __cdecl MyThreadProc(LPVOID lpParameter)
{
   CEvent* pEvent = (CEvent*)(lpParameter);
   VERIFY(pEvent != NULL);

   // Wait for the event to be signaled
   ::WaitForSingleObject(pEvent->m_hObject, INFINITE);

   // Terminate the thread
   ::AfxEndThread(0, FALSE); 
   return 0L;
}

void CEvent_Test()
{
   // Create the CEvent object that will be passed to the thread routine
   CEvent* pEvent = new CEvent(FALSE, FALSE);

   // Create a thread that will wait on the event
   CWinThread* pThread;
   pThread = ::AfxBeginThread(&MyThreadProc, pEvent, 0, 0, CREATE_SUSPENDED, NULL);
   pThread->m_bAutoDelete = FALSE; 
   pThread->ResumeThread();

   // Signal the thread to do the next work item
   pEvent->SetEvent();

   // Wait for the thread to consume the event and return
   ::WaitForSingleObject(pThread->m_hThread, INFINITE); 
   delete pThread;
   delete pEvent;
}

// This example builds upon the previous one.
// A second thread is created to calculate prime numbers.
// The main thread will signal the second thread to calulate the next 
// prime number in the series.  The second thread signals the first 
// after each number is calculated. Finally, after several iterations 
// the worker thread is signaled to terminate.

class CPrimeTest
{
public:
   CPrimeTest()
      : m_pCalcNext(new CEvent(FALSE, FALSE))
      , m_pCalcFinished(new CEvent(FALSE, FALSE))
      , m_pTerminateThread(new CEvent(FALSE, FALSE))
      , m_iCurrentPrime(0)
   {   
      // Create a thread that will calculate the prime numbers
      CWinThread* pThread;
      pThread = ::AfxBeginThread(&PrimeCalcProc, this, 0, 0, CREATE_SUSPENDED, NULL);
      pThread->m_bAutoDelete = FALSE; 
      pThread->ResumeThread();

      // Calcuate the first 10 prime numbers in the series on the thread
      for(UINT i = 0; i < 10; i++)
      {
         // Signal the thread to do the next work item
         m_pCalcNext->SetEvent();
         // Wait for the thread to complete the current task
         ::WaitForSingleObject(m_pCalcFinished->m_hObject, INFINITE);
         // Print the result
         TRACE(_T("The value of m_iCurrentPrime is: %d\n"), m_iCurrentPrime);
      }

      // Notify the worker thread to exit and wait for it to complete
      m_pTerminateThread->SetEvent();
      ::WaitForSingleObject(pThread->m_hThread, INFINITE); 
      delete pThread;
   }
   ~CPrimeTest()
   {
      delete m_pCalcNext;
      delete m_pCalcFinished;
      delete m_pTerminateThread;
   }

private:
   // Determines whether the given number is a prime number
   static BOOL IsPrime(INT ThisPrime)
   {
      if(ThisPrime < 2) 
         return FALSE;

      for(INT n = 2; n < ThisPrime; n++)
      {
         if(ThisPrime % n == 0)
            return FALSE;
      }
      return TRUE;
   }

   // Calculates the next prime number in the series
   static INT NextPrime(INT ThisPrime)
   {
      while(TRUE)
      {
         if(IsPrime(++ThisPrime))
         {
            return ThisPrime;
         }
      }
   }

   // Worker thread responsible for calculating the next prime
   // number in the series
   static UINT __cdecl PrimeCalcProc(LPVOID lpParameter)
   {
      CPrimeTest* pThis = static_cast<CPrimeTest*>(lpParameter);
      VERIFY(pThis != NULL);

      VERIFY(pThis->m_pCalcNext != NULL);
      VERIFY(pThis->m_pCalcFinished != NULL);
      VERIFY(pThis->m_pTerminateThread != NULL);

      // Create a CMultiLock object to wait on the various events
      // WAIT_OBJECT_0 refers to the first event in the array, WAIT_OBJECT_0+1 refers to the second
      CSyncObject* pWaitObjects[] = { pThis->m_pCalcNext, pThis->m_pTerminateThread };
      CMultiLock MultiLock(pWaitObjects, 2L);
      while(MultiLock.Lock(INFINITE, FALSE) == WAIT_OBJECT_0) 
      {         
         // Calculate next prime
         pThis->m_iCurrentPrime = NextPrime(pThis->m_iCurrentPrime);
         // Notify main thread calculation is complete
         pThis->m_pCalcFinished->SetEvent();
       } 

      // Terminate the thread
       ::AfxEndThread(0, FALSE); 
      return 0L;
   }

   CEvent* m_pCalcNext;      // notifies worker thread to calculate next prime
   CEvent* m_pCalcFinished;   // notifies main thread current calculation is complete
   CEvent* m_pTerminateThread;   // notifies worker thread to terminate

   INT m_iCurrentPrime;   // current calculated prime number
};

繼承階層架構

CObject

CSyncObject

CEvent

需求

Header: afxmt.h

請參閱

參考

CSyncObject 類別

階層架構圖