catch Android back button from navigation bar

shokarta

Hello,

I am trying to manage the back button action in QML, so I have tried:

Window {
    id: root
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
	
	Rectangle {
		id: main
		focus: true // important - otherwise we'll get no key events
		Component.onCompleted: main. forceActiveFocus()

		Keys.onReleased: {
			console.log("event key:", event.key);
			if (event.key == Qt.Key_Back) {
				console.log("Back button captured!");
				event.accepted = true;
			}
		}
	}
}

but it does not do anything, the back button kills the application, does not even console.log "event key".
so as far as I assume the back button in navigation bar is just hardware keyboard, then this shall work?
also, on the other hand i have made lots of manual modificaitons on my android emulator, so its possible i did disable this :D
can anyone try on real device please? or tell me if my approach is actually good?

Thank you

shokarta

Solution found...
in android manifest, in <application> i must deactivate enableOnBackInvokedCallback, so correct is:

android:enableOnBackInvokedCallback="false"

from this point, all works as expected
seems as new thing from android 13 according to google search

ankou29666

Hi

are you sure that the onReleased event is the one you need ?
have you tried other events like key pressed to see what happens ?

J.Hilk

@shokarta

release and pressed are all different signals, its possible that the uncaptured pressed key event is enough for the application to close

The way I do it in my applications is by intercepting the close event instead:

onClosing: {
    //Management for Android Back-Button
    if(Qt.platform.os === "android"){
        close.accepted = false
        if(PageManager.pageIndex > 0)
            PageManager.pageIndex = 0
    }
}

but thats based on really old legacy code, so the key event route may be the more correct way to do it :D

ankou29666

@J-Hilk According to 6.7.3's Window documentation, your way is still the appropriate one to handle such case.

shokarta

hmm very weird, i tried:

Window {
	id: root

	// Management for Android Back-Button
	onClosing: {
		console.log("debug1");
		if (Qt.platform.os === "android" || Qt.platform.os === "ios") {
			console.log("debug2");
			close.accepted = false;
			console.log("debug3");
		}
		else { console.log("debug4"); close.accepted = true; }
	}
}

and I got:

W WindowOnBackDispatcher: sendCancelIfRunning: isInProgress=falsecallback=android.app.Activity$$ExternalSyntheticLambda0@cd8e98f    // thsi is OK behaviour for back button on Android, so all good
D qml     : : debug1
D qml     : : debug2
W qt.qml.context: : qrc:/Main.qml:23:2 Parameter "close" is not declared. Injection of parameters into signal handlers is deprecated. Use JavaScript functions with formal parameters instead.   // this is line with "onClosing: {"
D qml     : : debug3 // should this also be printed to console? its after close event

what do i do wrong?

shokarta

and according to:
https://stackoverflow.com/questions/47175409/qml-asking-confirmation-before-closing-application (last post)
and https://www.direktembedded.com/qt5-to-qt6-qml-pyside-porting/

the following still does NOT work :(

onClosing: function(close) {
		console.log("debug1");
		if (Qt.platform.os === "android" || Qt.platform.os === "ios") {
			console.log("debug2");
			close.accepted = false;
			console.log("debug3");
		}
		else { console.log("debug4"); close.accepted = true; }
	}

W WindowOnBackDispatcher: sendCancelIfRunning: isInProgress=falsecallback=android.app.Activity$$ExternalSyntheticLambda0@cd303a8
D qml     : : debug1
D qml     : : debug2
D qml     : : debug3

and closes anyway

shokarta

hmm, even the official docu:

is kinda weird...

i found out that the app is realy not killed, the debugger stays active, but the app gets minimized, and when i try to bring it up, it freezes... i guess this I will report as bug

shokarta

This post is deleted!

ankou29666

writing

    onClosing: (close) => // or function (close), they're equivalent
    {
        console.log ("closing window") ;
        close.accepted = false ;
    }

works fine, and I have to forcefully close the app. I've only tested on windows, not on android.

However Qt Creator pisses me of with an "Invalid property name 'onClosing'" error

Writing

    onClosing:
    {
        console.log ("closing window") ;
        close.accepted = false ;
    }

works the same, I still have to forcefully quit, but produces me the same deprecation warning than you posted earlier.

At the origins of QtQuick, there had been criticism again the fact that slots didn't make their parameters explicit, making the parameters look like coming out of nowhere. Thus the newer syntax on your screenshot.

shokarta

works fine on Windows,
but not on Android... at least emulator... is there any chance you could try yourself? emulator, real device, anything?

shokarta

Solution found...
in android manifest, in <application> i must deactivate enableOnBackInvokedCallback, so correct is:

android:enableOnBackInvokedCallback="false"

from this point, all works as expected
seems as new thing from android 13 according to google search