Android MVVM with Dagger 2, Retrofit, RxJava, Architecture Components

I used to work with MVP pattern until now. However, when Google released nice-to-use components like the ViewModel along with the Android Jetpack, I have tried to work with MVVM pattern. In this article, we will see how can we use the MVVM pattern with Retrofit, RxJava, and Dagger 2.

What is MVVM?

Model-View-ViewModel architecture consists of 3 parts.

• The View gets user’s actions and sends to the ViewModel, or listens live data stream from the ViewModel and provides to the users.
• The ViewModel gets user’s actions from the View or provides data to View.
• The Model abstracts the data source. View and ViewModel uses that on data stream.

Project Configuration

We implement Android Lifecycle, Retrofit, RxJava, ButterKnife and Dagger 2 libraries in addition to Support libraries.

Project Structure

We will create packages by features. It will make your code more modular and manageable.

Setting Up Retrofit Interface

We have used Github API for Json source and as you see Single<> return type in order to observe data with RxJava.

Setting Up Application Class, Base Activity, Base Fragment

We have to use DaggerApplication, DaggerAppCompatActivity and DaggerFragment classes for injecting objects with ContributesAndroidInjector annotation.

We have used abstract layoutRes() function in order to get resource layout id from Activity which extends BaseActivity.

Setting Up Dagger 2 Component & Modules

As you can see, we have wrote only AndroidSupportInjectionModule, ActivityBindingModule and ViewModelModule to the module parameter. We will write other required modules in which Activity or Fragment they needed.

If explain what we have did in that code snippet;

• provideRetrofit — Provides Retrofit adjusted with base url, adapter and converter factories. addCallAdapterFactory() function gets adapter factory for supporting service method return types, add instance of RxJava2CallAdapterFactory for RxJava support.
• provideRepoService— Provides Retrofit interface class for making requests.

Creating Custom ViewModel Factory

ViewModelFactory is a factory that extends ViewModelProvider.Factory in order to provide ViewModel instances to consumer fragment classes. We have injected that class with the ViewModelModule.

Setting Up ViewModel

In ViewModel, we will assign the data which loaded with Retrofit to the MutableLiveData. So, how we can use MutableLiveData? We assign the data to MutableLiveData with setValue or postValue methods, and observe this data in LifeCycleOwner (Activity or Fragment). When we make any changes on the MutableLiveData, this change is dynamically declared to the view. Also, It does not oblige us to check whether View is alive in every transaction.

As you can see, we didn’t use any component injecting code, because we have injected all required classes in the MainFragmentBindingModule and also we have did same thing for activities in the ActivityBindingModule.

Setting Up Fragment

As you know, fragment is our View part. We have injected ViewModelFactory and started to observe LiveData objects.

Creating RecyclerView Adapter

In recyclerView adapter, we have only observed List<Repo> LiveData and bind them to the recyclerView.

Recommended Sources

• Offline first Android App with MVVM, Dagger2, RxJava, LiveData and Room
• Clean Architecture — Kotlin, Dagger 2, RxJava, MVVM and Unit Testing
• Advanced Android — Architecture with Dagger 2 and more (Udemy)
• New Android Injector with Dagger 2 — part 1

You can find the repository here!

ibrahimsn98/android-mvvm-dagger-2-rxjava-example