Configuration Change based Android interview questions and Answers

1) How to prevent the data from reloading and resetting when the screen is rotated?

  • The most basic approach would be to use a combination of ViewModels and onSaveInstanceState() . So how we do we that?
  • Basics of ViewModel: A ViewModel is LifeCycle-Aware. In other words, a ViewModel will not be destroyed if its owner is destroyed for a configuration change (e.g. rotation). The new instance of the owner will just re-connected to the existing ViewModel. So if you rotate an Activity three times, you have just created three different Activity instances, but you only have one ViewModel.
  • So the common practice is to store data in the ViewModel class (since it persists data during configuration changes) and use OnSaveInstanceState to store small amounts of UI data.
  • For instance, let’s say we have a search screen and the user has entered a query in the Edittext. This results in a list of items being displayed in the RecyclerView. Now if the screen is rotated, the ideal way to prevent resetting of data would be to store the list of search items in the ViewModel and the query text user has entered in the OnSaveInstanceState method of the activity.

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