Detecting focus lost & gained events in Qt for Symbian

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Article Metadata

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Tested with

Devices(s): S60

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Compatibility

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

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Article

Keywords: symbianEventFilter

Created: (26 Apr 2013)

Last edited: Forum Nokia KB (26 Apr 2010)

Description

In Qt for Symbian, detecting foreground application changes, ie. focus lost & gained events, requires reimplementing the QApplication::symbianEventFilter() function.

This is required 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
  };