Using CActiveSchedulerWait

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ID  CS000982  Creation date  May 28, 2008
Platform  S60 3rd Edition, MR  Tested on devices  Nokia N95
Category  Symbian C++  Subcategory  Code Examples

Keywords (APIs, classes, methods, functions): CActiveSchedulerWait, CActiveScheduler, RThread
Overview

CActiveSchedulerWait controls a single scheduling loop in the current global CActiveScheduler active scheduler. CActiveSchedulerWait provides better control of nested wait loops in the active scheduler.

Note that a CActiveSchedulerWait object can be used as a data member inside other CBase-derived classes.

See also the code example about threads CS000867 - RThread.

Source: creating and starting CActiveSchedulerWait

Execute RThread:

TInt CSomeThread::ExecuteThread(TAny *aPtr)
    {
    // Create cleanupstack 
    CTrapCleanup* cleanupStack = CTrapCleanup::New();
 
    // Create active sheduler and start thread
    TRAPD( error, CThreadAOEngine::CreateActiveSchedulerL( sharedMediator ) )
 
    delete cleanupStack;
    return 0;
    }

Start the active scheduler and the asynchronous operation:

void CSomeThread::CreateActiveSchedulerL()
    {
    // 1. Create a new active scheduler.
    CActiveScheduler* activeScheduler = new (ELeave) CActiveScheduler;
    CleanupStack::PushL(activeScheduler);
 
    // 2. Use the static function Install to install the previously created scheduler.
    CActiveScheduler::Install(activeScheduler);
 
    // 3. Created a nested loop inside CActiveScheduler.
    CActiveSchedulerWait* wait = new (ELeave) CActiveSchedulerWait;
    CleanupStack::PushL(wait);
 
    // 4. Create a class that must be handled asynchronously.
    CSomeAsyncClassTimer* timer = CSomeAsyncClassTimer::NewL(wait);
    CleanupStack::PushL(timer);
 
    // 5. Add an active object in CActiveScheduler.
    CActiveScheduler::Add(timer);
 
    // 6. Active scheduler must have one outstanding request before it can
    //    be started.
    timer->StartL();
 
    // 7. Start the nested scheduler loop.
    wait->Start(); 
 
 
    // 8. The process continues here after calling CActiveSchedulerWait::AsyncStop()
    //    that is called in CSomeAsyncClassTimer::StopWaitLoop()
 
 
    // Remove and delete the scheduler and the rest.
    CleanupStack::PopAndDestroy(3);
    }

Source: stopping CActiveSchedulerWait

void CSomeAsyncClassTimer::StartL()
    {
    // TODO: An asynchronous operation starts in
    // this CActive object
    }
 
void CSomeAsyncClassTimer::RunL()
    {
    // Asynchronous operation stops
 
    // We desided to stop our own CActiveSchedulerWait
    StopWaitLoop();
    // NOTE: This does not stop the global CActiveScheduler but it continues
    // running.
    }
 
void CSomeAsyncClassTimer::StopWaitLoop()
    {
    Cancel();
    // Stops our own nested scheduler loop
    iActiveSchedulerWait->AsyncStop();
    }

Postconditions

CActiveSchedulerWait, a nested wait loop, has been created in global CActiveScheduler. CActiveSchedulerWait stopped after running the asynchronoys operation. CActiveSchedulerWait does not stop the global CActiveScheduler but it continues running.