How to get an Instance of ViewModel in activity in 2020/21?

Question

I am new to the mvvm pattern. I created a ViewModel for the main activity. Now I want to get an instance of the ViewModel in the main activity.

Most Tutorials and answe

Answer 1

For now, the only thing working for me was to use: MainActivityViewModel = new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory()).get(MainActivityViewModel.class);

However, I am still thankful for any advice, how this can be done different using new ViewModelProvider(this).get(MainActivityViewModel.class);

Answer 2

You should update your gradle file to:

implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'

And due to this change you can pass Activity to the constructor you mentioned:

mainActivityViewModel = new ViewModelProvider(this).get(MainActivityViewModel.class);

Answer 3

Using Fragment-ktx libr in your app you can get viewModel as below

First Update Gradle File as app -> build.gradle

implementation 'androidx.fragment:fragment-ktx:1.1.0'

// get ViewModel in Activity or Fragment as

private val viewModel: MainActivityViewModel by viewModels()

// If you want to get same instance of ViewModel in ChildFragment as

 private val viewModel: MainActivityViewModel by viewModels(
    ownerProducer = { requireParentFragment() }
)