CEnvironmentChangeNotifier Class Reference

#include <bacntf.h>

Link against: bafl.lib

class CEnvironmentChangeNotifier : public CActive

Inherits from

  • CEnvironmentChangeNotifier

    Detailed Description

    Environment change notifier. This is an active object and can be used to handle environment change events.

    Constructor & Destructor Documentation

    ~CEnvironmentChangeNotifier ( )


    Destructor. Frees all resources owned by the object, prior to its destruction.

    In particular, it cancels any outstanding request to the Kernel side change notifier before closing the handle to it.

    Member Function Documentation

    Change ( )

    TInt Change()const [inline]

    Returns the last set of change events.

    If the last outstanding request completed normally, the function returns a bit pattern where each bit value corresponds to one of the enumerators defined by TChanges. A set bit indicates that the corresponding change event occurred.

    For example, if the bit value TChanges::EChangesMidnightCrossover is set, then the system time has passed midnight.

    See also: TChanges

    Returns: A set of bits consisting of one or more of the values defined by TChanges, or KErrCancel if the last outstanding request was cancelled.

    NewL ( TInt, const TCallBack & )

    IMPORT_C CEnvironmentChangeNotifier *NewL(TIntaPriority,
    const TCallBack &aCallBack

    Constructs a new environment change notifier object with the specified active object priority and callback function.

    The function requires a priority value for this active object and a reference to a TCallBack object encapsulating a pointer to the call back function which is to run when change events occur.

    As part of its implementation, the function:

    creates a Kernel side change notifier and opens a handle (an RChangeNotifier) to it.

    adds this active object to the current active scheduler.

    Note that construction of the environment change notifier does not issue any requests for change events.

    See also: CEnvironmentChangeNotifier::Start() CActive::TPriority

    aPriorityThe priority of this active object. Priority values determine the order in which an active scheduler handles completed active object requests.
    aCallBackA reference to a callback object which the caller must construct to encapsulate the callback function.

    Returns: A pointer to the new environment change notifier object.

    Set ( const TCallBack & )

    IMPORT_C TIntSet(const TCallBack &aCallBack)

    Sets the callback function.

    A callback is normally set when this active object is constructed through the NewL() function. This function replaces any existing callback object with the specified callback object.

    aCallBackA reference to the call back object encapsulating the call back function.

    Returns: KErrNone if successful, KErrInUse if this active object currently has an outstanding request for change events, or another of the system-wide error-codes.

    Start ( )

    IMPORT_C voidStart()

    Issues a request for change events.

    The request completes when change events occur, as signalled by the Kernel side change notifier service. The request may also complete if it is cancelled by calling the Cancel() member function of this active object.

    When change events occur, the callback function is called.

    Note that after the first call to this function, the callback function is called immediately; this is because of the way the underlying change notifier is implemented. The changes reported are all those defined by the TChanges enum.

    See also: CActive::Cancel() TChanges