How do you instantiate a ViewModel?
There are four main steps in creating and using a ViewModel :
- Add dependencies in your app-level build.
- Separate out all your data from your activity by creating a class that extends the ViewModel .
- Create a ViewModel instance in your activity to use it.
- Set up communications between your ViewModel and your View layer.
What is by ViewModel?
The ViewModel class is designed to store and manage UI-related data in a lifecycle conscious way. The ViewModel class allows data to survive configuration changes such as screen rotations. The Android framework manages the lifecycles of UI controllers, such as activities and fragments.
What is a ViewModel in Android?
AndroidViewModel. Application context aware ViewModel . ViewModel is a class that is responsible for preparing and managing the data for an Activity or a Fragment . It also handles the communication of the Activity / Fragment with the rest of the application (e.g. calling the business logic classes).
What is a ViewModel provider?
android.arch.lifecycle.ViewModelProvider. An utility class that provides ViewModels for a scope. Default ViewModelProvider for an Activity or a Fragment can be obtained from ViewModelProviders class.
Should I use AndroidViewModel?
If you need to use context inside your Viewmodel you should use AndroidViewModel (AVM), because it contains the application context. To retrieve the context call getApplication() , otherwise use the regular ViewModel (VM). AndroidViewModel has application context.
How does a ViewModel survive?
ViewModel objects are automatically retained during configuration changes so that data they hold is immediately available to the next activity or fragment instance. FYI: You can use ViewModel to preserve UI state only during a configuration change, nothing else as explained perfectly in this official doc.
How do I clear ViewModel data on Android?
As stated by @Nagy Robi, you could clear the ViewModel by call viewModelStore. clear() . The problem with this is that it will clear ALL the view model scoped within this ViewModelStore . In other words, you won’t have control of which ViewModel to clear.
What is Factory in MVVM?
Factory interface are responsible to instantiate ViewModels. That means you write your own implementation for creating an instance of ViewModel.
Is ViewModel Life Cycle Aware?
Lifecycle Awareness: ViewModel objects are also lifecycle-aware. They are automatically cleared when the Lifecycle they are observing gets permanently destroyed.
How is ViewModel retained?
Handle configuration changes: ViewModel objects are automatically retained whenever activity is recreated due to configuration changes. Lifecycle Awareness: ViewModel objects are also lifecycle-aware. They are automatically cleared when the Lifecycle they are observing gets permanently destroyed.