Detecting focus lost & gained events in Qt for Symbian

Comments

AlterX - signal not possible in QApplication?!

Hi, i'm using that schema and i replaced qDebug with two my own signal...when i compile the application, the error:

In function `MyBackgroundApp::symbianEventFilter(QSymbianEvent const*)':

  C:/Sviluppo/QkSolitaire/mybackgroundapp.cpp:14: undefined reference to `MyBackgroundApp::appGoingInForeground()'

MyBackgroundApp is a subclass of QApplication and appGoingInForeground is a signal defined in MyBackgroundApp.

Moreover if i try to connect the signal from within QML file (after i've used setContextProperty), it shows me that is undefined!

AlterX 16:16, 19 August 2011 (EEST)

Hamishwillee - Tried the forums

Best to post question on the discussion boards, unless specifically about the article.

The problem is mos likely that your application is not a QObject based class, or you've omitted the Q_OBJECT macro in its declaration.

hamishwillee 05:15, 22 August 2011 (EEST)

Ic000001 - How to do this in a Qt Quick application?

Hi there,

Apologies - I'm really rusty on C++ and don't know much raw Qt.

I have a Qt Quick Application "using template from Qt Creator" ... how can I implement this? (i.e. suspending Audio when my Qt Quick app is suspended)

My main.cpp:

1. include <QtGui/QApplication>
2. include "qmlapplicationviewer.h"

int main(int argc, char *argv[]) {

   QApplication app(argc, argv);

   QmlApplicationViewer viewer;
   viewer.setMainQmlFile(QLatin1String("qml/QtQuickApplication/main.qml"));
   viewer.showExpanded();

   return app.exec();

}

The project also has the qmlapplicationviewer.cpp and .h files.

Your help would be much appreciated!

ic000001 10:01, 22 October 2011 (EEST)

A1291762 - Re: QML Application

Ic000001, You can replace QApplication with the MyApplication class described. You just need to find a way tp have it poke into your QML (assuming you want to handle the event from within QML). Something like this:

class MyApplicatoin
{
...
QmlApplicationViewer *viewer;
bool symbianEventFilter()
{
...
case EEventFocusGained:
viewer->rootObject()->setProperty("appFocused", true);
break;
case EEventFocusLost:
viewer->rootObject()->setProperty("appFocused", false);
break;
...
 
MyApplication app()
QmlAppViewer viewer;
app.viewer = &viewer;

Then in the element you define in main.qml, define the appFocussed property and an onAppFocussedChanged: signal handler (that will fire when the app gains and loses focus).

a1291762 16:21, 26 October 2011 (EEST)

Hamishwillee - No, for QML you'd use the "Symbian" component, foreground property

http://doc.qt.nokia.com/qt-components-symbian/qml-symbian.html#foreground-prop

This changes when the app gains and loses focus.

hamishwillee 07:32, 1 December 2011 (EET)

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Article Metadata

---

Tested with

Devices(s): Symbian

---

Compatibility

Platform(s): S60 3rd Edition, FP1
S60 3rd Edition, FP2
S60 5th Edition
Qt 4.6.2

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Article

Keywords: symbianEventFilter, focus

Created: User:Kbwiki (26 Apr 2013)

Last edited: hamishwillee (11 Oct 2012)

Overview

This article explains how to detect focus change events in Qt applications on Symbian.

Description

Qt applications need to reimplement QApplication::symbianEventFilter() in order to get notification of foreground application changes, ie. focus lost & gained events. This is needed because focusInEvent(), focusOutEvent(), or hideEvent() from the QWidget class are not called on the Symbian platform when the foreground application changes.

Solution

Define an application class that inherits QApplication and reimplement symbianEventFilter():

  #include <QDebug>
 
  #ifdef Q_OS_SYMBIAN
  #include <QSymbianEvent>
  #include <w32std.h>
  #endif
 
 
  class MyApplication : public QApplication
  {
  public:
    MyApplication( int argc, char** argv ) : QApplication( argc, argv ) {}
 
  #ifdef Q_OS_SYMBIAN
  protected:
    bool symbianEventFilter( const QSymbianEvent* symbianEvent ) {
      const TWsEvent *event = symbianEvent->windowServerEvent();
 
      if( !event ) {
        return false;
      }
 
      switch( event->Type() ) {
        case EEventFocusGained: {
          qDebug() << "Focus gained";
          break;
        }
        case EEventFocusLost: {
          qDebug() << "Focus lost";
          break;
        }
        default:
          break;
      }
 
      // Always return false so we don't stop
      // the event from being processed
      return false;
    }
  #endif // Q_OS_SYMBIAN
  };