Application Lost Focus / Inactive / In Background

[javed_alam786]

Hi All,

The issue i am facing is basically how do i detect my application has lost focus as a result of user doing something else maybe checking there SMS or making/receiving a call.

All i want to do is detect this focus change and 'Pause' my app from doing any heavy calculation or simply sending a message "User Inactive State" to TCP Server.

Regards,
Javed

---

Added after 25 minutes:

i have tried these two solutions but none works for me, perhaps i am doing it wrong.

Solution 1:- Does not ssems to be emitting signal when app looses focus.

ProgressWin::ProgressWin(QWidget *parent) : QDialog(parent), ui(new Ui::ProgressWin)
{
    ui->setupUi(this);
 
    #ifdef Q_OS_SYMBIAN
        this->showMaximized();
    #else
        this->show();
    #endif
 
    QWidget::setFocusPolicy(Qt::StrongFocus);
    connect(this, SIGNAL(focusChanged(QWidget*, QWidget*)), this, SLOT(OnAppFocusChanged(QWidget*, QWidget*)));
}
 
 
void ProgressWin::OnAppFocusChanged(QWidget* old, QWidget* now)
{
    if(NULL == old)
    {
        // do something or nothing
    }
    else if(NULL == now)
    {        
        Pause(); // Pause all calculation
        SendTCP_UserInActive();
    }
    else
    {     
        // do something or nothing
    }
}

ProgressWin::ProgressWin(QWidget *parent) : QDialog(parent), ui(new Ui::ProgressWin)
{
    ui->setupUi(this);

    #ifdef Q_OS_SYMBIAN
        this->showMaximized();
    #else
        this->show();
    #endif

    QWidget::setFocusPolicy(Qt::StrongFocus);
    connect(this, SIGNAL(focusChanged(QWidget*, QWidget*)), this, SLOT(OnAppFocusChanged(QWidget*, QWidget*)));
}


void ProgressWin::OnAppFocusChanged(QWidget* old, QWidget* now)
{
    if(NULL == old)
    {
        // do something or nothing
    }
    else if(NULL == now)
    {        
        Pause(); // Pause all calculation
        SendTCP_UserInActive();
    }
    else
    {     
        // do something or nothing
    }
}

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Solution 2 :- Does not work if user selects "Calendar key or Email Key" pressed on Nokia E52 Handset. Its a crappy solution anyway.

void ProgressWin::keyPressEvent(QKeyEvent *e)
{
    switch (e->key())
    {
            case Qt::Key_Calendar:
            case Qt::Key_LaunchMail:            
            case Qt::Key_Menu:
            .........
            .........
            .........
                    Pause(); // Pause all calculation
                    SendTCP_UserInActive();
                    break;
           default:
                     // do something or nothing
    }
}

void ProgressWin::keyPressEvent(QKeyEvent *e)
{
    switch (e->key())
    {
            case Qt::Key_Calendar:
            case Qt::Key_LaunchMail:            
            case Qt::Key_Menu:
            .........
            .........
            .........
                    Pause(); // Pause all calculation
                    SendTCP_UserInActive();
                    break;
           default:
                     // do something or nothing
    }
}

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[AlexSudnik]

QApplication class has a static method : QWidget * QApplication::focusWidget ().

Since it returns 0 if no widget in this application has the focus,it might be useful for what you're trying to achieve.

So your main.cpp might look like this:

QApplication app( argc,argv );
 
ProgressWin mainWindow;
 
...
 
connect( &app , SIGNAL( focusChanged( QWidget*, QWidget* ) ) , &mainWindow , SLOT( OnAppFocusChanged()  ) );
 
...

QApplication app( argc,argv );

ProgressWin mainWindow;

...

connect( &app , SIGNAL( focusChanged( QWidget*, QWidget* ) ) , &mainWindow , SLOT( OnAppFocusChanged()  ) );

...

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And then the slot itslef:

void ProgressWin :: OnAppFocusChanged()
{
 
   if( !QApplication::focusWidget() ) 
   {
 
   // pause or whatever action you'd like to perform
 
   }
 
 
}

void ProgressWin :: OnAppFocusChanged()
{

   if( !QApplication::focusWidget() ) 
   {

   // pause or whatever action you'd like to perform

   }


}

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[javed_alam786]

Hi Alex,

Thanks for the solution. I managed to get it done a different way which works fine according to my need. This solution is open to critisim.

Kind Regards,
Javed

className.h

....
bool eventFilter(QObject *object, QEvent *event);
....

....
bool eventFilter(QObject *object, QEvent *event);
....

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className.cpp

bool ClassName::eventFilter(QObject *object, QEvent *event)
{
    if (event->type() == QEvent::FocusIn)
    {    
         // pause or whatever action you'd like to perform
    }
    else if (event->type() == QEvent::FocusOut)
    {    
        // pause or whatever action you'd like to perform
    }
    else if (event->type() == QEvent::WindowDeactivate)
    {    
        // pause or whatever action you'd like to perform
    }
    else
    {    
        // pause or whatever action you'd like to perform
    }
    return false;
}

bool ClassName::eventFilter(QObject *object, QEvent *event)
{
    if (event->type() == QEvent::FocusIn)
    {    
         // pause or whatever action you'd like to perform
    }
    else if (event->type() == QEvent::FocusOut)
    {    
        // pause or whatever action you'd like to perform
    }
    else if (event->type() == QEvent::WindowDeactivate)
    {    
        // pause or whatever action you'd like to perform
    }
    else
    {    
        // pause or whatever action you'd like to perform
    }
    return false;
}

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