Cannot create an instance of my AndroidViewModel

Question

this is one of my first times using android and mvvm.

I get this error:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.ClementF.logged, PID: 11719
    java.lang.RuntimeException: Cannot create an instance of class com.ClementF.logged.ActivityViewModel
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:275)
        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
        at com.ClementF.logged.ActivitySelectorFragment.onCreate(ActivitySelectorFragment.java:34)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:2684)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:270)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1173)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:442)
        at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2167)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1990)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1945)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1816)
        at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:297)
        at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:341)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:276)
        at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:67)
        at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7556)
        at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:860)
        at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8601)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8559)
        at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8547)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1641)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at androidx.viewpager2.widget.ViewPager2.onLayout(ViewPager2.java:527)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at com.google.android.material.appbar.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:148)
        at com.google.android.material.appbar.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:43)
        at com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1996)
        at androidx.coordinatorlayout.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:918)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
E/AndroidRuntime:     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:784)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3470)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2938)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:731)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:267)
            ... 79 more
     Caused by: java.lang.RuntimeException: cannot find implementation for com.ClementF.logged.ActivityDatabase. ActivityDatabase_Impl does not exist
        at androidx.room.Room.getGeneratedImplementation(Room.java:94)
        at androidx.room.RoomDatabase$Builder.build(RoomDatabase.java:952)
        at com.ClementF.logged.ActivityDatabase.getInstance(ActivityDatabase.java:24)
        at com.ClementF.logged.ActivityRepository.<init>(ActivityRepository.java:19)
        at com.ClementF.logged.ActivityViewModel.<init>(ActivityViewModel.java:18)
            ... 82 more

This is my AndroidViewModel:

package com.ClementF.logged;

import android.app.Application;
import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;

import java.util.List;

public class ActivityViewModel extends AndroidViewModel {

    private ActivityRepository activityRepository;
    private LiveData<List<ActivityEntity>> activities;


    public ActivityViewModel(@NonNull Application application) {
        super(application);
        activityRepository = new ActivityRepository(application);
        activities = activityRepository.getAllActivities();
    }

    public void insert(ActivityEntity activity) {
        activityRepository.insert(activity);
    }

    public void update(ActivityEntity activity) {
        activityRepository.update(activity);
    }

    public void delete(ActivityEntity activity) {
        activityRepository.delete(activity);
    }

    public LiveData<List<ActivityEntity>> getAllActivities() {
        return activityRepository.getAllActivities();
    }
}

And this is the fragment trying to access the ViewModel

package com.ClementF.logged;

import android.app.Application;
import android.os.Bundle;

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

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.List;

public class ActivitySelectorFragment extends Fragment {

    private ActivityViewModel activityViewModel;

    public ActivitySelectorFragment() {
        // Required empty public constructor
    }

    public static ActivitySelectorFragment newInstance() {
        return new ActivitySelectorFragment();
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // setup view model
        activityViewModel = new ViewModelProvider(this).get(ActivityViewModel.class);
        activityViewModel.getAllActivities().observe(this, new Observer<List<ActivityEntity>>() {
            @Override
            public void onChanged(List<ActivityEntity> activityEntities) {
                // TODO: update recycler view
            }
        });
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_activity_selector, container, false);
    }
}

I have tried passing a ViewModelProvider.AndroidViewModelFactory inside of the ViewModelProvider constructor however I get the same error.

Any ideas as to what I'm doing wrong? Thank you so much!

If you need to know this is a fragment inside a ViewPager2 from my main_activity, I'm using a tab layout.

Git repo: https://github.com/Teariest/Logged

So far your code looks clean but please provide some code about how you instantiated the fragement in viewpager. :) — P Sekhar
just cloned your git repo ,give me a moment to check and answer it. — P Sekhar

P Sekhar P Sekhar · Accepted Answer · 2020-08-20T11:02:48

Found out that there are no errors with ViewModel actually.

Add these two lines to your gradle so that Room library can compile the SQL codes,to handle the annotations and for compilation too.

annotationProcessor "androidx.room:room-compiler:$room_version"
androidTestImplementation "androidx.room:room-testing:$room_version"

room_version is what the latest version is available from Google

Then Sync Gradle

Add ColumnInfo to table in ActivityEntity so that it can store your data under a column and name it anything you like i just named it as activity

@ColumnInfo(name="activity")

:)

Cannot create an instance of my AndroidViewModel

1 Answers