Why do we need a ViewModel factory?

Why do we need a ViewModel factory?

You want a ViewModel to hold the score to be displayed by the ScoreFragment . You’ll pass in the score value during the ViewModel initialization using the factory method pattern. The factory method pattern is a creational design pattern that uses factory methods to create objects.

How do I create a ViewModelProvider factory?

Android ViewModelProvider Factory Passing Parameter to ViewModel In Kotlin

1. Gradle. Add ViewModel Architecture Component dependency to gradle .
2. API Helper Class. Create a class APIHelper , this is class reference we pass as argument to ViewModel .
3. ViewModel.
4. ViewModelProvider Factory.
5. XML.
6. MainActivity.

How do I create a ViewModel?

1. Step 1: Create a ViewModel class. Note: To create a ViewModel, you’ll first need to add the correct lifecycle dependency.
2. Step 2: Associate the UI Controller and ViewModel. Your UI controller (aka Activity or Fragment) needs to know about your ViewModel.
3. Step 3: Use the ViewModel in your UI Controller.

How does a ViewModel work internally?

ViewModel works with Room and LiveData to replace the loader. The ViewModel ensures that the data survives a device configuration change. Room informs your LiveData when the database changes, and the LiveData, in turn, updates your UI with the revised data.

How to create a ViewModel with a factory?

And it is because you cannot call ViewModel constructor in Activity or Fragment when you initializing ViewModel and you want to set ViewModel constructor’s argument value so that’s why you need to pass argument value to ViewModelProvider.Factory and it will create your ViewModel. ViewModelProvider.Factory is an interface which have create method.

Why is viewmodelprovider.factory failed to initialize?

So when you add argument in the constructor, the inner implementation of ViewModelProvider.Factory failed to initialize your ViewModel because ViewModelProvider.Factory call the primary constructor for creating the ViewModel’s instance. Image below is the default implementation of ViewModelFactory.

What does viewmodelfactory do in Kotlin 5.1?

The ViewModel class allows data to survive device-configuration changes such as screen rotations and changes to keyboard availability. You use the ViewModelFactory class to instantiate and return the ViewModel object that survives configuration changes. What you should already know How to create basic Android apps in Kotlin.

How to create an instance of a ViewModel?

The ViewModelProviders internally manage for us and call our primary constructor of ViewModel and create the instance of ViewModel and give the instance back. Now let see what happens when we pass argument to the constructor of MyViewModel. Now create instance of MyViewModel in activity.