ViewModelProviders is deprecated in 1.1.0

Question

Looking at the Google docs for ViewModel, they show the below sample code on how to get a ViewModel:

val model = ViewModelProviders         


        

Answer 1

Early in 2020, Google have deprecated the ViewModelProviders class, in version 2.2.0 of the androidx lifecycle library.

It's no longer necessary to use ViewModelProviders to create an instance of a ViewModel, you can pass your Fragment or Activity instance to the ViewModelProvider constructor instead.

If you use the code like:

val viewModel = ViewModelProviders.of(this).get(CalculatorViewModel::class.java)

you'll get a warning that ViewModelProviders has been deprecated.

To avoid using deprecated libraries, make the following changes:

1. In the build.gradle (Module: app) file, use version 2.2.0 of the lifecycle components:

   implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
   implementation "androidx.activity:activity-ktx:1.1.0"
   

   If you want to use the ViewModel from a Fragment instead, use

   implementation "androidx.fragment:fragment-ktx:1.2.2"
   

   fragment-ktx automatically includes activity-ktx, so you don't need to specify both in the dependencies.

2. You need to specify Java 8 in the android section :

   android {
       compileSdkVersion 28
       defaultConfig {
           applicationId "com.kgandroid.calculator"
           minSdkVersion 17
           targetSdkVersion 28
           versionCode 1
           versionName "1.0"
           testInstrumentationRunner 
       "androidx.test.runner.AndroidJUnitRunner"
       }
       buildTypes {
           release {
               minifyEnabled false
               proguardFiles getDefaultProguardFile('proguard-android.txt'), 
              'proguard-rules.pro'
           }
       }
   
       kotlinOptions { jvmTarget = "1.8" }
   }
   

3. In your Fragment or Activity, change the import to:

   import androidx.activity.viewModels

4. The code to create a ViewModel then becomes:

   val viewModel: CalculatorViewModel by viewModels()
   

   instead of

   val viewModel = ViewModelProviders.of(this).get(CalculatorViewModel::class.java)
   

   Use the viewModel object as :

   val viewModel: CalculatorViewModel by viewModels()
   
   viewModel.newNumber.observe(this, Observer { 
       stringResult -> newNumber.setText(stringResult) 
   })
   

   where newNumer is a LiveData object

   In a Fragment that you want to share the Activity's ViewModel, you'd use

   val viewModel: CalculatorViewModel by activityViewModels()
   

That's the equivalent of passing the Activity instance in the (deprecated) ViewModelProviders.of() function.