How to renew a request from the active scheduler

It is possible to maintain an outstanding request from the active scheduler, by overriding the CActiveScheduler::WaitForAnyRequest() function.

In this case, it is useful for the active scheduler to have a data member which points to the active object for which it will maintain an outstanding request. Implement the active scheduler as follows:

class CExampleScheduler : public CActiveScheduler
    {
public:
    void Error (TInt aError) const;
    void WaitForAnyRequest();
    void SetActiveObject(CActiveConsole* aActiveConsole);
private:
    CActiveConsole* iActiveConsole;
    };

void CExampleScheduler::SetActiveObject(CActiveConsole* aActiveConsole)
    {
    iActiveConsole = aActiveConsole;
    }

where iActiveConsole is a pointer to an active object, initialised by call to SetActiveObject() during the construction of the controlling active object:

void CMessageKeyProcessor::ConstructL()
    {
    CActiveScheduler::Add(this);
    (CExampleScheduler*)(CActiveScheduler::Current())->SetActiveObject(this);
    }

Now override CActiveScheduler::WaitForAnyRequest():

void CExampleScheduler::WaitForAnyRequest()
    {
    if (!(iActiveConsole->IsActive()))
        {
        iActiveConsole->RequestCharacter();
        }
    CActiveScheduler::WaitForAnyRequest();
    }

• The state of the active request flag is examined and a request is not issued if it is active. This check is important because the function may be called as a result of other active objects completing (for example, a timed messenger) and in these cases it would be inappropriate to renew the keyboard service request.

• It is no longer necessary to call RequestCharacter() either before starting the active scheduler, or as part of key processing.

• The static function CActiveScheduler::Current() is used to fetch a pointer to the currently installed active scheduler (in this example, an object of type CExampleScheduler). This is necessary in order to access the SetActiveObject() member function of CExampleScheduler.