What is a ViewModel Android?

The android. 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).

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. Data Sharing: Data can be easily shared between fragments in an activity using ViewModels .

How do you use a ViewModel?

There are three steps to setting up and using a ViewModel: Separate out your data from your UI controller by creating a class that extends ViewModel.

  1. Step 1: Create a ViewModel class. …
  2. Step 2: Associate the UI Controller and ViewModel. …
  3. Step 3: Use the ViewModel in your UI Controller.


What is the use of ViewModel factory in Android?

You use the ViewModel class to store and manage UI-related data in a lifecycle-conscious way. The ViewModel class allows data to survive device-configuration changes such as screen rotations and changes to keyboard availability.

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What is the difference between ViewModel and AndroidViewModel?

The difference between the ViewModel and the AndroidViewModel class is that the later one provides you with an application context, which you need to provide when you create a view model of type AndroidViewModel.

What should ViewModel contain?

ViewModel objects are designed to outlive specific instantiations of views or LifecycleOwners . This design also means you can write tests to cover a ViewModel more easily as it doesn’t know about view and Lifecycle objects. ViewModel objects can contain LifecycleObservers , such as LiveData objects.

How do I get ViewModel in activity?

Simple ViewModel

  1. Add dependencies in your app-level build. gradle .
  2. Separate out all your data from your activity by creating a class that extends the ViewModel .
  3. Create a ViewModel instance in your activity to use it.
  4. Set up communications between your ViewModel and your View layer.


What is the purpose of ViewModel?

The purpose of the ViewModel is to acquire and keep the information that is necessary for an Activity or a Fragment. The Activity or the Fragment should be able to observe changes in the ViewModel. ViewModels usually expose this information via LiveData or Android Data Binding.

Where do I put ViewModel?

3 Answers. Just create a new folder called ViewModels inside your project. So that along with the Views, Controllers and Models folders, you’ll also have ViewModels. Like you already said, you talk to your DAL using your models and you talk to your views using your view models.

How do I set ViewModel data?

Let’s go through the steps to set up Interface .

  1. Step 1: Create Interface. The First step is to create an Interface and make a function like below snippet.
  2. Step 2: Implement Interface in MyActivity. …
  3. Step 3: Set Value in Interface. …
  4. Step 4: Get Value in Detail List Fragment by Implementing Interface.
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How does a ViewModel work internally?

How does the Android Viewmodel works internally? Android’s ViewModel is designed to store and manage UI-related data in such a way that it can survive configuration changes such as screen rotations. Function calls added here will be invoked.

What is data binding in Android?

The Data Binding Library is an Android Jetpack library that allows you to bind UI components in your XML layouts to data sources in your app using a declarative format rather than programmatically, reducing boilerplate code.

How use MVVM pattern in Android?

Using any tool like RxJava for DataBinding.

  1. Data Binding:
  2. Step 1: Create a new project.
  3. Step 2: Modify String.xml file.
  4. Step 3: Creating the Model class.
  5. Step 4: Working with the activity_main.xml file.
  6. Step 5: Creating the ViewModel class.
  7. Step 6: Define functionalities of View in the MainActivity file.


Is it good to use AndroidViewModel?

AndroidViewModel provides Application context

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.

What is LiveData Android?

LiveData is an observable data holder class. Unlike a regular observable, LiveData is lifecycle-aware, meaning it respects the lifecycle of other app components, such as activities, fragments, or services. This awareness ensures LiveData only updates app component observers that are in an active lifecycle state.

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