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

There are few reason to throw the exception . I have mention some of them..

1. Make sure your view Model class is public

2. Make sure your view model class constructor is public

3. Make sure you have added the dependency in your gridle file for lifecycle also if you use room and other libries you have added ..

4. if you create object any other dependent class in your view model class constructor . Other class can throw error to create the instance of viewModel

Answer 2

Extend AndroidViewModel from your ViewModel class.

public class YourViewModel extends AndroidViewModel {

    public YourViewModel(Application application) {
        super(application);

        //Todo: ...
    }

}

Answer 3

In my case, it was gradle a dependencies problem.

If you are using Livedata,,

build.gradle(Module.app)

not

implementation 'android.arch.lifecycle:extensions:1.1.1'
kapt 'android.arch.lifecycle:common-java8:1.1.1'

use these

implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
kapt 'androidx.lifecycle:lifecycle-common-java8:2.2.0'

Answer 4

My problem was that the IDE had added a "abstract" modifier to my ViewModel class.

Answer 5

I'm using this example android-arcuitecture-component BasicSample to make a new project, facing a similar error log, found I did'n change de applicatio name

AndroidManifest.xml

and that was my error, to fix put the aplicacion name to de BasicApp, this class is implement in the example.

...
<application
    android:name=".BasicApp"
    android:allowBackup="false"

Answer 6

If you used viewmodel inside your activity check that your activity extends "DaggerAppCompatActivity" or not

For instance

public class UserComments extends AppCompatActivity 

change this to

public class UserComments extends DaggerAppCompatActivity