Stop a timer when Fragment onStop is called

Question

I've got a problem when I try to stop my timer. This timer is created in a FragmentViewModel. If I navigate away from the app, the timer keeps running. Im looking for a way to stop him, but I cant access him from the Fragments onStop() function, since hes created in the ViewModel, which only gets referenced in the Fragments onCreate() function. Anyone got an idea how to solve this problem?

This is how I create the ViewModel (with the timer inside):

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    val binding: GameFragmentBinding = DataBindingUtil.inflate(
        inflater, R.layout.game_fragment, container, false)


    val application = requireNotNull(this.activity).application

    val dataSource = TranslationDB.getInstance(application).translationDBDao

    val viewModelFactory = GameFragmentViewModelFactory(dataSource, application)

    val gameFragmentViewModel =
        ViewModelProviders.of(
            this, viewModelFactory).get(GameFragmentViewModel::class.java)


    binding.gameFragmentViewModel = gameFragmentViewModel

Thanks in advance!

score 0 · Answer 1 · answered Nov 26 '19 at 16:59

0

You can use the ViewModels onCleared() callback.

To get an understanding of when this is called (so you can decide if it's appropriate) please see this question and the answers When is the viewmodel onCleared called

answered Nov 26 '19 at 16:59

Ivan Wooll

4,145
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I saw that post before and tried it again and I think it isn't called here. When the user just navigates away from the app, it shouldn't be called if I understand it correctly, right? What I need is something exactly for that case cause the timer should just be stopped an be able to resume. – Phil T. Nov 26 '19 at 17:04

score 0 · Accepted Answer · answered Nov 26 '19 at 17:12

0

If you want to execute some action in your viewmodel based on a lifecycle event, make your viewmodel implement the LifecycleObserver interface, then in your viewmodel you do

@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
fun stop() {
    // stop timer
}

and in your fragment, in onCreateView you do

lifecycle.addObserver(viewmodel)

answered Nov 26 '19 at 17:12

Francesc

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10
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That definetly seems like I want. The first time I heard of this handling. Can you tell me how I can implement the LifecycleObserver interface in my viewmodel? Already big thanks! – Phil T. Nov 26 '19 at 17:31

Stop a timer when Fragment onStop is called

2 Answers2