Android MutableLiveData keeps emitting when I re-enter fragment

Question

I'm using a shared ViewModel in Navigation component rather than creating a ViewModel for every fragment (mostly because it's easier) but now I have a problem when I re-enter a fragment and subscribe to the ViewModel live data of that fragment, I get the last state also too.

here is the ViewModel Code:

  val apiLessonData: MutableLiveData<String>> = MutableLiveData()
  fun getLessonsUserCreated() =
        apiCall(MyMaybeObserver(apiLessonData))

in MyMaybeObserver, I have somthing like this:

override fun onSuccess(t: T) {
    apiDataObserver.postValue(t)
}

and this is how I observe it in my fragment:

private val apiAddGoalData = Observer<String> { response ->
    showSnack(response)
}

override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        .
        .
        viewModel.apiAddGoalData.observe(viewLifecycleOwner, apiAddGoalData)
        .
        .
    }

now when I enter the first time it works fine but I open it the second time, it shows the snack from the previous time, how to stop this without creating new ViewModel?

Answer 1

In the simple way You could set null for your MutableLiveData after getting data in onchange method of the observer. For more information you can read this article:livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case . also you can see this question maybe help you: How to clear LiveData stored value?