What is the wear os app lifecycle? Like when does an app go into start/resume/pause/stop ? If it's o...

# compose-wear

[Arjun Achatz]

What is the wear os app lifecycle? Like when does an app go into start/resume/pause/stop ? If it's only OS driven, is there a way to trigger this manually ?

[Ataul Munim]

What are you trying to do?

[Arjun Achatz]

I'm trying to test a scenario out. Apparently I have stateflow causing me an NPE.

class VM(val x: X) {
init {
viewmodelScope.launch {
x.getStateFlow().collect { y.update {} }
}
}

val y = MutableStateFlow(0)
}

[Arjun Achatz]

Apparently the solution is to move the declaration of y to be above the init block

[Arjun Achatz]

So I wanted to repro this, and it seems to be happening during onPause onStop and onSavedInstanceState

[Ataul Munim]

You can press the "home" button to background the app which should trigger onPause/onStop. On the emulator either button 1 or 2 will work (one is home the other is recent apps but I don't recall which)

[Ataul Munim]

Similarly the palm button should turn the screen off and it should go through onPause/onStop

[Arjun Achatz]

Okay ! I'll try those

[Arjun Achatz]

Is there a way to force the app to go through an app kill and to trigger onSavedInstanceState ?

[Arjun Achatz]

I've been using adb shell am start -S -n ...

[Ataul Munim]

Developer settings might include "don't keep activities" like it does on phones but I'm not sure. In that case, I think pressing home will kill the activity/app

[Arjun Achatz]

I didn't see it in the wear settings :(

[Gustavo Pagani]

follow these steps:

1. launch your app
2. push the button 1 from the emulator to put your app in background - this step is important
3. kill your app via adb: adb shell am kill <your app package>
4. from the recents menu, open your app

[Gustavo Pagani]

just tested with the sample app from horologist, added this log to onCreate in`MainActivity`:

Log.d("REMOVEME", "savedInstanceState null? ${savedInstanceState == null}")

followed the steps above and could can see in logcat:

---------------------------- PROCESS STARTED (8852) for package com.google.android.horologist.sample.debug ----------------------------
2022-11-24 19:35:16.345  8852-8852  REMOVEME                com...droid.horologist.sample.debug  D  savedInstanceState null? true
---------------------------- PROCESS ENDED (8852) for package com.google.android.horologist.sample.debug ----------------------------
---------------------------- PROCESS STARTED (8913) for package com.google.android.horologist.sample.debug ----------------------------
2022-11-24 19:35:29.926  8913-8913  REMOVEME                com...droid.horologist.sample.debug  D  savedInstanceState null? false

[florent]

press on the secondary button to display the recent app and do a long press on the one you want to kill

[Gustavo Pagani]

that doesn't simulate the process death, just tried and savedInstanceState is null after launching it

[Arjun Achatz]

Thanks @Gustavo Pagani this works and helped debug !