Listening for Symbian Window Server events in Qt

Comments

Note that in Qt 4.7, the s60eventFilter method was replaced with the symbianEventFilter(const QSymbianEvent* event): bool method.

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Article Metadata

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Tested with

Devices(s): Nokia 5800 XpressMusic

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Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

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Article

Keywords: QApplication, TWsEvent, RWsSession, TApaTaskList, TApaTask

Created: tepaa (26 Mar 2009)

Last edited: hamishwillee (30 May 2013)

Overview

This code snippets shows how a Qt application listens for native Symbian TWsEvent window server events.

Preconditions

• Install Qt SDK

Send a message

A native Symbian application sends a message to the Qt application.

#include <apgtask.h> // Symbian header
 
TApaTaskList tasklist(iCoeEnv->WsSession());
 
// A task is a running application
TUid id = TUid::Uid(0x12345678); //Qt app UID
TApaTask task(tasklist.FindApp(id));
 
TUid messageid = TUid::Uid(0x000001); //Custom message uid
 
TBuf8<20> param;
param.Append(_L("hello world"));
task.SendMessage(messageid, param));

TApaTask::SendMessage() does not need SwEvent capability.

Listen for the message

The Qt application listens for TWsEvent window server events. Derive QApplication and implement the base class s60EventFilter() method to listen for window server events. In this case we listen for EEventMessageReady type of events with the custom message UID.

#include <QApplication>
#include <apgtask.h> // Symbian header
 
class S60QApplication: public QApplication
    {
    Q_OBJECT
public:
    S60QApplication(int &argc, char **argv, int = QT_VERSION);
    S60QApplication(int &argc, char **argv, bool GUIenabled, int = QT_VERSION);
    S60QApplication(int &argc, char **argv, Type, int = QT_VERSION);
    bool s60EventFilter(TWsEvent *);
    };

S60QApplication::S60QApplication(int &argc, char **argv, int version)
: QApplication(argc,argv,version)
    {
    }
 
S60QApplication::S60QApplication(int &argc, char **argv, bool GUIenabled, int version)
:QApplication(argc, argv, GUIenabled, version)
    {
    }
 
S60QApplication::S60QApplication(int &argc, char **argv, Type type, int version)
:QApplication(argc, argv, type, version)
    {
    }
 
bool S60QApplication::s60EventFilter(TWsEvent *aEvent)
    {
    bool handled = false;
    const TInt KCustomMessageId=0x000001; // Custom message uid
 
    switch(aEvent->Type())
        {       
        case EEventMessageReady:    
              {
              RWsSession iWsSession;
              TInt err = iWsSession.Connect();
 
              TUid messageUid;
              TPtr8 messageParameters(NULL, 0, 0);
              // Fetch message
              User::LeaveIfError(iWsSession.FetchMessage(messageUid,
              messageParameters, *aEvent));
              // Was it our custom message?
              switch(messageUid.iUid)
                {
                case KCustomMessageId:
                    {
                    HBufC *p = HBufC::NewL(messageParameters.Length());
                    p->Des().Copy(messageParameters);
 
                    // Converting message from HBufC to QString
                    QString message((QChar*)p->Des().Ptr(),p->Length());
 
                    handled = true;
                    delete p;
                    break;
                    }
                default:
                    {
                    break;
                    }
                }
              iWsSession.Close();
              break;
              }
        default:
            break;
        };
 
    return handled;
    }

Postconditions

The events have been sent and received.