Alpha 4.1 - Back button exits the App

[Vinayak]

Hello

Clicking on the Back button exits the App from any screen. I want this to function like any Native Android Application.

Is there something I am missing in my settings ?

[paulus]

No this is a known issue. See also https://groups.google.com/forum/?fromgroups=#!searchin/android-qt/back$20button$20bogdan/android-qt/Dj6niGTOajk/J2Yx2MiyYO8J

[Vinayak]

Yes, I went through the links here and it was mentioned that it would be fixed in Alpha4. Hence the question.

[BogDan]

Hi,

Back button exits the App by default, this is the right behavior!

Of course because I question everything and also because I trust no 1,
I'll check if BogDan is crazy or not :)
- First I'll check what is the default behavior for any Android
Activity, then soon I'll discover that BogDan is not crazy
http://developer.android.com/reference/android/app/Activity.html#onBackPressed()
!
- Then I'll ask myself if Android is the only O.S. which has this
behavior? No it is not! Because if I press Alt+F4 on my Linux, or
Windows my application exists, so, Android is not the only O.S. with
this behavior.
- Then I'll ask myself, how can I prevent my application to close on
Linux? The easiest way is to search on net, I just search for "How can
I catch Alt+F4 in my Qt application" and I choose the first link:
http://qt-project.org/faq/answer/how_can_i_catch_altf4_in_my_qt_application
. I'll try the same thing on Android and I'll be extremely surprised
to see that it works !
- But hey, I want more ! I want to catch the back button event, then
I'll start to search if I can handle it, because there are not too
many information on this topic, I'll check if someone else reported
this problem on a bug tracker, then after a while I'll discover that
somebody reported it and BogDan closed it http://sourceforge.net/p/necessitas/tickets/76/
. Because the issue lacks basic information (I must confess that this
is indeed BogDan's fault) I'll try to check the patch
https://projects.kde.org/projects/playground/mobile/necessitas/android-qt/repository/revisions/6dc070ff2715fd75e0e8576aa6f4c524b824ad42
, for sure the patch should have enough info on this topic after
checking a few files from that patch I'll end up to this one
https://projects.kde.org/projects/playground/mobile/necessitas/android-qt/repository/diff/src/gui/kernel/qapplication_qpa.cpp?rev=6dc070ff2715fd75e0e8576aa6f4c524b824ad42&type=sbs
, at line 878 it seems that BogDan changed Qt to send a QKeyEvent with
(e->keyType == QEvent::KeyRelease && e->key == Qt::Key_Close) (check
line 859), then I'll try to overwrite keyReleaseEvent (http://doc-
snapshot.qt-project.org/4.8/qwidget.html#keyReleaseEvent) and if the
"event->key()==Qt::Key_Close" then it means that I need to accept that
event. So I'll end up with something like this:

void MainWindow::keyReleaseEvent(QKeyEvent *event)
{
static bool accepted=true;
if (event->key()==Qt::Key_Close)
{
// do something useful here
event->setAccepted(accepted); // dont't close my Top Level
Widget !
accepted=false;// close the app next time when the user press
back button
}
}

After I'll check that everything works as I expected, then, of course
because I'm a good guy I'll share my findings with everybody on
android-qt mailing list ;-)

Cheers,
BogDan.

[Vinayakam Murugan]

Thank you for the reply, Bogdan

Back button exits the App by default, this is the right behavior!

Of course because I question everything and also because I trust no 1,
I'll check if BogDan is crazy or not :)
 - First I'll check what is the default behavior for any Android
Activity, then soon I'll discover that BogDan is not crazy
http://developer.android.com/reference/android/app/Activity.html#onBackPressed()
!

Typically I define multiple screens in the main.qml and set them to visible true or false as the user navigates them. Whichever screen I am in , pressing back exits the app. I understand that in native Android applications, each screen is an activity and is closed on exit. Should i be treating the screens in qml in any different manner so that each screen is an activity?

I did check the issue and posted a note there as well :)

I am not the proficient in QT. I am not sure where does this above patch need to be applied on.

[Pritpal Bedi]

Hello Vinayak

Typically I define multiple screens in the main.qml and set them to visible true or false as the user navigates them. Whichever screen I am in , pressing back exits the app. I understand that in native Android applications, each screen is an activity and is closed on exit. Should i be treating the screens in qml in any different manner so that each screen is an activity?

I solved this like ( but on QWidget* implementation, yet to play with QML, but you can adopt the idea ) :

MainWindow::MainWindow( ... )

{

}

bool MainWindow::event( QEvent * event )

{

    if( event->type() == QEvent::Close )

    {

        if( ui->stackMain->currentIndex() > 0 )

        {

            event->ignore();

            ui->stackMain->setCurrentIndex( 0 );

            return true;

        }

        else if( ui->stackInfo->currentIndex() > 0 )

        {

            event->ignore();

            ui->stackInfo->setCurrentIndex( 0 );

            return true;

        }

    }

    return QMainWindow::event( event );

}

Application is comprised of mainwindow:stackedWidget:pages:stackedWidgetOnAPage.

"BACK" button sends QEvent::Close to the mainwindow. Depending upon where application 

stays at present I take the decision. Make sure it must quit from application entrance screen.

Hope it helps.

Pritpal Bedi

a student of software analysis & concepts

[mprag]

I sent a patch for this upstream 4 month ago.

https://git.reviewboard.kde.org/r/108332/

Applying that patch makes it much simpler to implement back button handling in QML. Unfortunately there seems to be no interest from BogDan. At least some comments would be nice... 

[Victor David Flores Enriquez]

Hooo! is a shame. that

2013/5/30 mprag <micke...@telldus.se>

--
You received this message because you are subscribed to a topic in the Google Groups "android-qt" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/android-qt/pb7un1Ye92M/unsubscribe?hl=en.
To unsubscribe from this group and all its topics, send an email to android-qt+...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.
 
 

--

[larivcl]

Hello Vinayak,

Can you read this post :

https://groups.google.com/forum/#!topicsearchin/android-qt/authorname$3Alarivcl/android-qt/V7u0SjS5JE4