Movies App Android

This repository contains a detailed sample project that implements MVVM architecture using Jetpack's ViewModel and LiveData. It also uses Dagger2 and RxJava.

Package Structure

• activity: Contains all activities of the app.
• data: Contains all network and local data repository.
• di: Dependency providing classes using Dagger2.
• viewmodel: View-Model classes which extends Jetpack's ViewModel.
• network: Web service calling classes and interface.
• model: Contains POJO classes.
• utils: Utility classes.

MVVM Structure

Below is the description of how movie list feature is built with MVVM architecture-

• View- MovieListActivity is the view for showing movie list. It contains recycler view. It observes movie data.
• Model- MovieRepository is the data model for movies.
• View-Model- MovieViewModel extends Jetpack's ViewModel which manipulates data, coming from movie repository and post the value which view observes.

Dependency Injection

Component

MoviesApplication initializes AppComponent as follows:

AppComponent appComponent = DaggerAppComponent.builder().
                appModule(new AppModule(this))
                .networkModule(new NetworkModule())
                .movieModule(new MovieModule()).build();

Modules

AppComponent builds modules i.e. NetworkModule which provides web service objects, MovieModule provides movie repository and view-model factory, and AppModule provides app context.

ViewModel Factory

By default, ViewModel requires zero argument constructor. ViewModel factory is used to provide a correct parameterized constructor of ViewModel. It is used as follows:

@Inject
ViewModelFactory viewModelFactory;
    
// some code

MoviesViewModel moviesViewModel = ViewModelProviders.of(this, viewModelFactory).get(MoviesViewModel.class);
moviesViewModel.observeMoviesResponse().observe(this, this::consumeResponse);

Unit Test

In order to test LiveData, it’s values need to be directly updated on the calling thread.

@Test
public void testFetchAllMovies_testError() {
     MutableLiveData<ApiResponse> responseMutableLiveData = new MutableLiveData<>();
     Exception exception = new Exception();
     ApiResponse apiResponse = ApiResponse.error(exception);
     responseMutableLiveData.postValue(apiResponse);
     Assert.assertEquals(Status.ERROR, responseMutableLiveData.getValue().status);
     Assert.assertNull(responseMutableLiveData.getValue().data);
     Assert.assertNotNull(responseMutableLiveData.getValue().error);
}