Possible to access AndroidViewModel of Activity via Fragment?

So I checked the docs and as I understood right I should now use

ViewModelProvider.AndroidViewModelFactory.getInstance(
     this.getApplication()).create(CanteensViewModel.class);

Please share a link to this "docs" you mentioned, because this is NOT the first time I see this code, and yet it was equally wrong in both cases.

The code you actually should be using is

new ViewModelProvider(this).get(CanteensViewModel.class);

Is there a way I can access the Activity's ViewModel from inside the fragments? Or would it be better to recreate the ViewModel in each fragment by

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

Consider also receiving a SavedStateHandle as an argument in your AndroidViewModel, and not only Application.

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If you ask me, apparently the removal of ViewModelProviders.of() was an API mistake, but this is what we have now.

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EDIT: With the help of the provided stack trace, I can finally somewhat figure out what's going on.

    at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:219)

We are using NewInstanceFactory as the default. What does default NewInstanceFactory do? It just calls no-arg constructor if available.

Wait, what? Isn't it supposed to fill in the Application for an AndroidViewModel?

Theoretically yes, as long as you got the original default ViewModelProvider.Factory, but this is not the one!

Why is it not the one that can fill in AndroidViewModel?

See this commit

Add default ViewModel Factory interface

Use a marker interface to allow instances of
ViewModelStoreOwner, such as ComponentActivity
and Fragment, to provide a default
ViewModelProvider.Factory that can be used with
a new, concise ViewModelProvider constructor.

This updates ComponentActivity and Fragment to
use that new API to provide an
AndroidViewModelFactory by default. It updates
the 'by viewModels' Kotlin extensions to use
this default Factory if one isn't explicitly
provided.

Also

ComponentActivity:

+    @NonNull
+    @Override
+    public ViewModelProvider.Factory getDefaultViewModelProviderFactory() {
+        if (getApplication() == null) {
+            throw new IllegalStateException("Your activity is not yet attached to the "
+                    + "Application instance. You can't request ViewModel before onCreate call.");
+        }
+        return ViewModelProvider.AndroidViewModelFactory.getInstance(getApplication());
+    }
+

And most importantly

public ViewModelProvider(@NonNull ViewModelStoreOwner owner) {
    this(owner.getViewModelStore(), owner instanceof HasDefaultViewModelProviderFactory
            ? ((HasDefaultViewModelProviderFactory) owner).getDefaultViewModelProviderFactory()
            : NewInstanceFactory.getInstance());
}

This means that you get the default view model provider factory that can properly set up AndroidViewModel if the ViewModelStoreOwner implements HasDefaultViewModelProviderFactory.

Theoretically, ComponentActivity is indeed a HasDefaultViewModelProviderFactory; and AppCompatActivity extends from ComponentActivity.

In your case however, that doesn't seem to be the case. For some reason, your AppCompatActivity is not HasDefaultViewModelProviderFactory.

I think the solution to your problem is to update Lifecycle to 2.2.0, and ALSO update implementation 'androidx.core:core-ktx to at least 1.2.0. (specifically at least AndroidX-Activity 1.1.0, and AndroidX-Fragment 1.2.0).