Archived:Handling Camera resource on Symbian
This how-to describes how to reserve and release the camera resource when the application is activated (either brought to the foreground or started) or inactivated (either sent to the background or exited).
In order to handle the camera resource correctly when the focus is gained or lost, the application must be able to react to foreground events. This code snippet uses MCoeForegroundObserver to implement this functionality, but you may want to see Getting notifications of focus change and launch of other apps using Symbian C++ for another possibility.
This snippet can be self-signed.
To use this code snippet, the application needs to provide implementation for using the camera (for example, S60 Platform: Camera Example with Autofocus).
The following capabilities and libraries are required:
CAPABILITY UserEnvironment LIBRARY ecam.lib
Inherit your class from MCoeForegroundObserver and override the HandleGainingForeground and HandleLosingForeground functions to be able to react to foreground events and handle the camera resource.
#include <ECam.h> // link against ecam.lib
#include <ccamautofocus.h> // only needed if autofocus extension is meant to be
// used; link against CamAutoFocus.lib
* From MCoeForegroundObserver
virtual void HandleGainingForeground();
virtual void HandleLosingForeground();
CCamAutoFocus* iAutoFocus; // optional
To listen for the foreground events, make the class observe changes in them:
iEikonEnv->AddForegroundObserverL( *this );
Reserving the camera resource
// Gets called when the application is brought to the foreground
iCamera->Reserve(); // Asynchronous. Calls MCameraObserver::ReserveComplete
// when the request completes.
Releasing the camera resource
// Gets called when the application is sent to the background
// Bring the AF subsystem to idle state, in case it is used
TRAPD( err, iAutoFocus->ResetToIdleL() );
if ( !err )
// Release the camera