/*

* Copyright (c) 2007 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*

*/

#ifndef SYSTEMOBSERVER_H

#define SYSTEMOBSERVER_H

// INCLUDES

#include <e32base.h>

#include <npscript.h>

// FORWARD DECLARATIONS

// CONSTANTS

// State enum and member variable

// CLASS DECLARATIONS

/**

 * MSystemInfoObserverClient is an interface to whatever data is being

 * observed (RProperty, int, string, etc).

 * @lib npSystemInfoPlugin.lib

 * @since S60 v3.2

 */

class MSystemInfoObserverClient

    {

public:

    virtual void SubscribeL( TInt aId, TRequestStatus& aStatus ) = 0;

    virtual void UpdateL( TInt aId ) = 0;

    virtual void Cancel( TInt aId ) = 0;

    virtual void Close( TInt aId ) = 0;

/*

 * Outline of use for a publish and subscribe variable

 * #include <e32property.h>

 * #include <hwrmpowerstatesdkpskeys.h>

 * RProperty iProperty;

 * iProperty.Attach( KPSUidHWRMPowerState, KHWRMBatteryLevel );

 * SubscribeL => iProperty.Subscribe( status );

 * UpdateL => iProperty.Get( value );

 * Cancel => iProperty.Cancel();

 * Close => iProperty.Close();

 * The ID parameter is there so that a class can contain

 * multiple observers and differentiate them in these methods by ID.

 * You can also use it for state in a state machine.

 */

    };

/**

*  CSystemInfoObserver.

*  Active class for monitoring variables.

*  @lib npSystemInfoPlugin.lib

*  @since S60 v3.2

*/

NONSHARABLE_CLASS(CSystemInfoObserver) : public CActive

    {

public:

    /**

     * Two-phased constructor.

     */

    static CSystemInfoObserver* NewL( MSystemInfoObserverClient* aClient, TInt aId );

    /**

     * Destructor.

     */

    virtual ~CSystemInfoObserver();

private:

    /**

     * C++ default constructor.

     */

    CSystemInfoObserver( MSystemInfoObserverClient* aClient, TInt aId );

    /**

     * By default Symbian 2nd phase constructor is private.

     * @param none

     * @return void

     */

    void ConstructL();

public:

    /**

     * Request observed status change notification

     * @since 3.2

     * @param none

     * @return void

     */

    void RequestNotificationL();

protected:    // CActive

    /**

     * Implements cancellation of an outstanding request.

     * @param none

     * @return void

     */

    void DoCancel();

    /**

     * Handles an active object’s request completion event.

     * @param none

     * @return void

     */

    void RunL();

    /**

     * Handles an active object’s error

     * @param error

     * @return void

     */

    TInt RunError(TInt aError);

private:

    MSystemInfoObserverClient* iClient;

    TInt iId;

    };

#endif      // SYSTEMOBSERVER_H

// End of File