New viewmodel for every instance of same fragment

[Bodo1981]

Describe the bug
I have a fragment which has a personId to show details of a person

class PersonDetailsFragment : Fragment {
   val personId: Int by lazy { intent.extras.getInt("personId") }
   val viewModel: PersonViewModel by viewModel()

   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel.personDetailsLiveData.observe(this, Observer<List<Cryptocurrency>> {
           // show person
        })
    }
}

To Reproduce
Steps to reproduce the behavior:

1. Open a person (PersonFragment)
2. Click on a friend of this person
3. It opens a new instance of PersonFragment but gets the viewmodel of the previous PersonFragment
4. The app crashes with the following exception

java.lang.IllegalArgumentException: Cannot add the same observer with different lifecycles

Expected behavior
If i open a new instance of the same fragment it should also create a new viewmodel.

Koin project used and used version (please complete the following information):
koin-android-architecture v0.9.3

[arnaudgiuliani]

Hello,

you are injecting with by inject().

You have to use by viewModel() to inject and bind your viewModel to the lifecycle owner: val viewModel: PersonViewModel by viewModel()

[Bodo1981]

I am sorry.
In my project i am using by viewModel(). I corrected it in this issue.

This one is working (it is using the android standard implementation:

class HomeFragment : Fragment() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        ViewModelProviders.of(this).get(HomeViewModel::class.java).liveData.observe(this,
             Observer<List<Items>> {
              })
}

And this one is not working (using di with koin)

class HomeFragment : Fragment() {
    private val homeViewModel: HomeViewModel by viewModel()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        homeViewModel.liveData.observe(this,
             Observer<List<Items>> {
              })
}

Steps to reproduce:

1. App starts with HomeFragment
2. Navigate to another Fragment
3. Navigate again to HomeFragment (not going back, but put another HomeFragment on the stack)
4. Error throws with koin implementation

java.lang.IllegalArgumentException: Cannot add the same observer with different lifecycles

[arnaudgiuliani]

Ok, what project did you use? koin-android-architecture v0.9.3 ?

[Bodo1981]

Yes i am using koin-android-architecture v0.9.3
Thanks for your investigation

[arnaudgiuliani]

If you can make a very small project that reproduces your case (just a public GitHub project), I would be very nice and help us save time 👍

[Bodo1981]

Of course... :-)
Here it is: https://github.com/Bodo1981/KoinViewModelCrash

You have to use Android Studio 3.2 Canary 18

When you checkout the repo it is working like intended.

1. Click "Go Details"
2. on next fragment click "Go back"
3. another HomeFragment is created and pushed on the stack -> "Go Details" Button is visible

If you change HomeFragment to this the app crashes after clicking back on second fragment:

1. Click "Go Details"
2. on next fragment click "Go back"
3. another HomeFragment is created and pushed on the stack -> App crashes!

class HomeFragment : Fragment() {

    // not working
    private val homeViewModel: HomeViewModel2 by viewModel()

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_home, container, false)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // working
        //val homeViewModel = ViewModelProviders.of(this).get(HomeViewModel2::class.java)

        homeViewModel.cryptocurrencyLiveData.observe(this,
                                                 Observer<List<Cryptocurrency>> {

                                                 })
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        detailsButton.setOnClickListener {
            view.findNavController().navigate(R.id.navToDetails)
        }
    }
}

[arnaudgiuliani]

Thanks!

[arnaudgiuliani]

You have to declare a ViewModel class with viewModel dsl keyword:

val homeModule: Module = applicationContext{
    context("home") {
    bean { CryptocurrencyRepository(get(), get()) }
    viewModel { HomeViewModel(get()) }
    viewModel { HomeViewModel2() }
    }
}

I've added a protection to not allow injection of definition that are not ViewModel 👍 (koin-android-viewmodel version 1.0.0-alpha-23)

[arnaudgiuliani]

I'll push you a PR to fix your sample.

[Bodo1981]

Shame on me... I looked everywhere if i use it the correct way but did not see it...

SORRY!

[arnaudgiuliani]

No problem :)

This was also the moment to reinforce viewmodel injection check ;)

[joelfernandes19]

@arnaudgiuliani I'm using version 2.0.0-beta-1, and I'm facing the exact same issue as described above. I have declared my ViewModel classes with viewModel dsl keyword.

I'm also using Navigation Component to navigate between fragments. When I navigate from fragment A to B, and then navigate back to A, a new ViewModel is created and the observer is called multiple times.

Is there something that I'm doing wrong?

[dawnchen]

@arnaudgiuliani I'm using version 2.0.0-beta-1, and I'm facing the exact same issue as described above. I have declared my ViewModel classes with viewModel dsl keyword.

I'm also using Navigation Component to navigate between fragments. When I navigate from fragment A to B, and then navigate back to A, a new ViewModel is created and the observer is called multiple times.

Is there something that I'm doing wrong?

Please double check your ViewModel injection in activity or fragment, should be "by viewModel()" or "by sharedViewModel()"， not "by inject()".

[e4basil]

@arnaudgiuliani same problem here also I'm using version 2.0.1

[arnaudgiuliani]

Please reopen a new ticket

[mrizyver]

@joelfernandes19, I had the same issue. When i rotate screen, my activity in onCreate method created a new instance of fragment. When we create a new instance of fragment, it takes a new instance of ViewModel. I just do like that