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androidandroid-architecture-componentsandroid-livedataandroid-viewmodel

Observing LiveData from ViewModel

I have a separate class in which I handle data fetching (specifically Firebase) and I usually return LiveData objects from it and update them asynchronously. Now I want to have the returned data stored in a ViewModel, but the problem is that in order to get said value, I need to observe the LiveData object returned from my data fetching class. The observe method required a LifecycleOwner object as the first parameter, but I obviously don't have that inside of my ViewModel and I know I am not supposed to keep a reference to the Activity/Fragment inside of the ViewModel. What should I do?

Solution

  • In this blog post by Google developer Jose Alcérreca it is recommended to use a transformation in this case (see the "LiveData in repositories" paragraph) because ViewModel shouldn't hold any reference related to View (Activity, Context etc) because it made it hard to test.