Cannot create an instance of class ViewModel

Question

I am trying to write a sample app using Android architecture components and but even after trying for days I could not get it to work. It gives me the above exception.

Answer 1

I had this problem following google's roomdb CodeLab. Solution was changing the following.

Edited

Add the following Build dependencies to Gradle file (as of 2/22/2020)

implementation 'androidx.fragment:fragment:1.2.2'
implementation 'androidx.lifecycle:lifecycle-process:2.2.0'
implementation 'androidx.lifecycle:lifecycle-service:2.2.0'
implementation 'androidx.lifecycle:lifecycle-viewmodel-savedstate:2.2.0'
annotationProcessor 'androidx.lifecycle:lifecycle-compiler:2.2.0'

Imports within the fragment

import androidx.lifecycle.ViewModelProvider;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;

Creating the viewModel. Add one of the following methods.

Note: I'v seen this done many ways. I believe the correct way is using getDefaultViewModelProviderFactory(). But I have been using requireActivity().

 new ViewModelProvider(requireActivity(),getDefaultViewModelProviderFactory()).get(YourViewModel.class);

|

 new ViewModelProvider(requireActivity()).get(YourViewModel.class);

          

ViewModelProvider Docs

Deprecated

implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0-rc01'
annotationProcessor 'androidx.lifecycle:lifecycle-compiler:2.2.0-rc01'

Answer 2

If you are using Hilt then don't forget to add these four dependencies.

    implementation "com.google.dagger:hilt-android:2.28-alpha"
    kapt "com.google.dagger:hilt-android-compiler:2.28-alpha"
    implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha01'
    kapt "androidx.hilt:hilt-compiler:1.0.0-alpha01"

Note:- If any of these dependencies are missing you will get Cannot create an instance of class ViewModel error

Answer 3

I'm a proficient Android developer and I have used ViewModel 100s of times with no issue. Today I came across this issue. Spent hours and scrolled through various SO posts. Didn't get solved.

Then I saw that the package name in which I have the ViewModel contains new. Like this:

com.myapp.myfeature.new.feature

I changed new to neww for testing like this: com.myapp.myfeature.neww.feature

and it worked! I hope someone find it useful.

Answer 4

Please add below code. It worked for me

val binding = FragmentLayoutBinding.inflate(inflater, container, false)

val viewModel = ViewModelProvider(
            requireActivity(),
            defaultViewModelProviderFactory
            ).get(MainViewModel::class.java)

Answer 5

Make ViewModal class and constructure public

Answer 6

Make your constructor public.