Qt Android application. Backround swipe closure handling

[deleted510]

Hi guys,

I need help with clean exit when user shuts down application from background (swipe quit/kill).

I want to call method from class that is written in C++, in onDestroy() method.
Problem is that one is .java and other .cpp

Is there a way, and how, to handle that swipe from .cpp file or it must be done in .java?

[deleted510]

For Linux, Windows and MACOSX (desktop app) i have done this way and it is working without problems

I tried to add Android but its not working. I tried also to call closeEvent in destructor ~MainWindow() but still no effect.

[deleted510]

I have found what is the problem, but still cannot find the solution.

When i press BACK BUTTON, this is the order of events:
1. closeEvent() ---> most important thing for my app, cleanup done there
2. onPause
3. onStop
4. onDestroy

But when i press HOME BUTTON, this is the order of events:
2. onPause
3. onStop
4. onDestroy

I tried adding finish(), but even that is not working(closeEvent() is ALWAYS missing )

Can anyone tell me am i doing something wrong or how can mimic BACK BUTTON by pressing HOME BUTTON?

[J.Hilk]

@Stasa-Sekulic
well, on mobile, when your app gets pushed into the back ground, the application state is changed to suspended

https://doc.qt.io/qt-5/qguiapplication.html#applicationStateChanged

you could listen for that signal and react accordingly ?

[deleted510]

@J-Hilk

Thanks for the hint!

Problem is that my class is derived from QWidget.

Or can i emit close signal from one class to another?

[J.Hilk]

@Stasa-Sekulic
if you add #include <QGuiApplication> to your class, than you have access to the qApp global pointer of your QGuiApplication instance. You can use that to connect to the signal

[deleted510]

@J-Hilk

Thanks! I have implemented everything that you said and IT WORKS!

I summary i have done next:

I have connected my QCoreApplication with my widget like this
connect(QCoreApplication::instance(), SIGNAL(applicationStateChanged(Qt::ApplicationState)), this, SLOT(state_changed_event(Qt::ApplicationState)));

and inside my state_changed_event slot i am handling state when application is suspended.

Main idea was to handle force closure of application from background, i suppose this is not the correct solution, but this workaround is handling that ok for now.