Navigation message observable lifecycle

[sdelaysam]

Kinda question which may be a bug

fun onCreate() {
 navigationMessagesDisposable = presentationModel.navigationMessages.observable
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe {
                navigationMessagesDispatcher.dispatch(it)
            }
}

fun onDestroy() {
navigationMessagesDisposable.dispose()
}

Posting navigation messages which commit fragment transactions may lead to

 Can not perform this action after onSaveInstanceState

Or I'm missing something?

[dmdevgo]

The property navigationMessages is aCommand, it buffer values while a View unbound from PresentationModel. So, despite that the subscription is alive, messages will not be delivered to the subscriber until the view is binded to the PresentationModel.
There is a test for this case:

    @Test fun commandBlocksItemsAfterUnbinded() {
        val testObserver = pm.commands.observable.test()

        pm.lifecycleConsumer.accept(CREATED)
        pm.lifecycleConsumer.accept(BINDED)
        pm.lifecycleConsumer.accept(UNBINDED)
        pm.acceptCommand(1)

        testObserver.assertEmpty()
    }

[sdelaysam]

I see and it must work as you describe..
I faced that crash on the test project I made.
Appreciate If you can point out the issue on my side if any

class TestActivity : PmSupportActivity<TestActivityPm>(), NavigationMessageHandler {

    override fun providePresentationModel() = TestActivityPm()

    override fun onBindPresentationModel(pm: TestActivityPm) {}

    override fun handleNavigationMessage(message: NavigationMessage): Boolean {
        when (message) {
            is NavigationCommand ->
                supportFragmentManager.beginTransaction()
                        .replace(R.id.container, TestFragment())
                        .commit()
        }
        return true
    }
}

class TestActivityPm : PresentationModel() {

    override fun onUnbind() {
        super.onUnbind()
        navigationMessages.consumer.accept(NavigationCommand())
    }
}

class NavigationCommand : NavigationMessage

Log gives the following

TestActivity, onCreate
TestActivityPm, onBind
TestActivity, onStart
TestActivityPm, onUnbind
TestActivity, onStop
TestActivity, handleNavigationMessage

Caused by: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

I'm on latest develop branch and PresentationModelTest all passed.

[sdelaysam]

Please check if the fix is appropriate

[dmdevgo]

You're right, the bug is reproduced.

[sdelaysam]

@dmdevgo sorry but another related issue.
Same setup, only difference

class TestActivityPm : PresentationModel() {

    override fun onBind() {
        super. onBind()
        navigationMessages.consumer.accept(NavigationCommand())
    }
}

Android studio starts the launcher activity when device is idle and log is the same.

TestActivity, onCreate
12:44:18.848 TestActivityPm, onBind
12:44:18.850 TestActivity, onStart
12:44:18.889 TestActivityPm, onUnbind
12:44:18.892 TestActivity, onStop
12:44:18.895 TestActivity, handleNavigationMessage

The "issue" seems to be here

navigationMessagesDisposable = presentationModel.navigationMessages.observable
            .observeOn(AndroidSchedulers.mainThread()) <--- 
            .subscribe {
                navigationMessagesDispatcher.dispatch(it)
            }

Associated looper decide to execute dispatch on the next frame while with Schedulers.trampoline() it works fine.

Not sure its library issue - most likely its not real-life scenario.

[dmdevgo]

@sdelaysam why the view unbind immediately after binding? Can you describe more details?

[sdelaysam]

I just noticed that issue when build and run the app on device (device was idle) via Android Studio.
onStart/onStop called almost instantly ( in less than 50ms according to the timing )

PS: I think it can be ignored because

most likely its not real-life scenario.

[dmdevgo]

First issue has been fixed. Second case is not reproduced from me. So I close issue.