Android ViewModel and startActivity

android viewmodel android-architecture-components android-viewmodel
Augusto Carmo picture Augusto Carmo · Feb 21, 2019 · Viewed 9k times · Source

I am learning ViewModel and LiveData and, in the process, a doubt arose.

What should I do if I need to start an Activity?

Is it ok to pass the context as a parameter to the ViewModel (the context will not be stored inside the ViewModel)?

ActivityAViewModel : ViewModel() {
    // ...

    fun openActivityB(context: Context) {
        context.startActivity(...)
    }

    // ...
}

ActivityA {
    // ...

    fun onSomethingHappened() {
        viewModel.openActivityB(this)
    }

    // ...
}

If not, what is the most correct thing to do in that case?

Answer

Alexandr Bahach picture Alexandr Bahach · Feb 21, 2019

You should call startActivity from activity, not from viewmodel. If you want to open it from viewmodel, you need to create livedata in viewmodel with some navigation parameter and observe on livedata inside the activity.

Related questions

AndroidViewModel vs ViewModel

With the introduction of the Android Architecture Components library, several new classes were introduced, including AndroidViewModel and ViewModel. However, I'm having trouble figuring out the difference between these two classes. The documentation succinctly describes AndroidViewModel as follows: Application context aware …

Read More
How to update LiveData of a ViewModel from background service and Update UI

Recently I am exploring Android Architecture, that has been introduced recently by google. From the Documentation I have found this: public class MyViewModel extends ViewModel { private MutableLiveData<List<User>> users; public LiveData<List<User&…

Read More
Cannot resolve symbol ViewModelProviders on AppCompatActivity

Hey I'm trying to get my ViewModel working, but no luck so far. Android Studio shows error Cannot resolve symbol 'ViewModelProviders'. Every other question I found on this topic was correcting extends Activity to extends AppCompatActivity, but I am extending …

Read More