我在我的項目中使用MVVM,Retrofit,LiveData但我在看到這些鏈接之前得到了這個錯誤

> Cannot create an instance of custom ViewModel

> Cannot create an instance of class ViewModel

錯誤

java.lang.RuntimeException:

Unable to start activity ComponentInfo{ir.orangehat.movieinfo/ir.orangehat.movieinfo.application.home.HomeActivity}: java.lang.RuntimeException:

Cannot create an instance of class ir.orangehat.movieinfo.application.home.HomeViewModel

這是我的ViewModel,我認為問題出在我的構造函數中

public class HomeViewModel extends AndroidViewModel {

private MovieRepository movieRepository;

public HomeViewModel(@NonNull Application application, Context context, LifecycleOwner lifecycleOwner) {

super(application);

movieRepository = new MovieRepository(lifecycleOwner, context);

}

LiveData> getMovies() {

return movieRepository.getMovies();

}}

知識庫

public class MovieRepository extends BaseRepository {

private LifecycleOwner lifecycleOwner;

private MovieApi movieApi;

private MovieDatabaseHelper movieDatabaseHelper;

public MovieRepository(LifecycleOwner lifecycleOwner, Context context) {

this.lifecycleOwner = lifecycleOwner;

movieApi = getRetrofitHelper().getService(MovieApi.class);

movieDatabaseHelper = new MovieDatabaseHelper(context);

}

public LiveData> getMovies() {

LiveData> moviesLiveData = movieApi.getMovieList();

moviesLiveData.observe(lifecycleOwner, new Observer>() {

@Override

public void onChanged(@Nullable List movieArrayList) {

movieDatabaseHelper.Save(movieArrayList);

}

});

return movieDatabaseHelper.getAll();

} }

活動類

public class HomeActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

// the error is here

HomeViewModel homeViewModel = ViewModelProviders.of(this).get(HomeViewModel.class);

homeViewModel.getMovies().observe(HomeActivity.this, new Observer>() {

@Override

public void onChanged(@Nullable List movieArrayList) {

String str = null;

if (movieArrayList != null) {

str = Arrays.toString(movieArrayList.toArray());

}

Log.e("movies", str);

}

});

}

}

我應該在我的項目和定制工廠中使用Dagger嗎？

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