Android Arch Components ViewModel and LiveData trigger after screen rotation

Question

I have a problem when using ViewModel and LiveData I am new using ViewModel and LiveData arch components and have the problem when using frag

Answer 1

It's how LiveData and ViewModel works. You are getting same ViewModel with same LiveData and LiveData has previous object, User for instance, with previous credentials when you call ViewModelProviders.of(this).get(MainViewModel::class.java). You can reset User of LiveData onPause()or onStop() to reset it to initial state.

I don't know how you call toast, if you can share your ViewModel and MainActivity i can be more specific.

Answer 2

Ok Finally found the problem and how to solve. LiveData is not designed for single events. For that reason there is a couple of ways to fix it or handle it, this two links were useful for me:

Jose Alcérreca's post dealing with this problem

Jose Alcérreca's EventObserver

Jose Alcérreca's SingleLiveEvent class

Basically:

In ViewModel:

var eventLiveData: MutableLiveData<Event<ErrorResponse>> = MutableLiveData()

and In Activity or Fragment:

viewModel.eventLiveData.observe(this, EventObserver {
     it?.let {
          shortToast(it.message)
     }
})