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ID	TSS001475	Creation date	October 30, 2009
Platform	S60 3rd Edition, 3rd Edition FP1, 3rd Edition FP2, 5th Edition	Devices	Tested on Nokia 6210 Navigator
Category	Symbian C++	Subcategory	Base/System

Keywords (APIs, classes, methods, functions): CEnvironmentChangeNotifier

Overview

This article provides a way to detect changes in the system environment, such as system time change, thread death, or system locale change.

Description

The CEnvironmentChangeNotifier class can be used for this purpose. This is an active object whose constructor takes a reference to a callback function (TCallBack) for handling environment change events.

Solution

Required headers and libraries

#include <bacntf.h> // Link against bafl.lib

// NotifyChange is a static member function declared as follows:
 // static TInt NotifyChange( TAny* aObject );
 
 TCallBack envChangeCallback( NotifyChange, this );
 iEnvNotifier = CEnvironmentChangeNotifier::NewL( CActive::EPriorityHigh, envChangeCallback );
 
 // Issues a request for change events. When a change events occurs, the 
 // callback function is called. Note that after the first call to this 
 // function, the callback function is called immediately.
 iEnvNotifier->Start();

Interpreting changes through TChanges enum

TInt CMyEnvironMentChangeNotifier::NotifyChange( TAny* aObject )
   {
   CMyEnvironMentChangeNotifier* thisPtr = static_cast<CMyEnvironMentChangeNotifier*>( aObject );
 
   // Retrieve the changes in a bit field
   const TInt changes( thisPtr->iEnvNotifier->Change() );
 
   if( changes & EChangesLocale )
     {
     // System locale changed
     }
   if( changes & EChangesMidnightCrossover )
     {
     // Midnight crossover
     }
    if( changes & EChangesThreadDeath )
     {
     // Thread death
     }
    if( changes & EChangesPowerStatus )
     {
     // Power status changed
     }
    if( changes & EChangesSystemTime )
     {
     // System time changed
     }
    if( changes & EChangesFreeMemory )
     {
     // Free memory changed
     }
    if( changes & EChangesOutOfMemory )
     {
     // Out of memory
     }
 }