DBHiltApp

Building a basic App using MVVM, DataBinding, Hilt and Retrofit

Hilt

Add the next dependencies before to start

gradle.properties (project)

classpath 'com.google.dagger:hilt-android-gradle-plugin:2.28-alpha'

gradle.properties (app)

apply plugin: 'kotlin-kapt'
apply plugin: 'dagger.hilt.android.plugin'

dependencies {
  ...
  implementation "com.google.dagger:hilt-android:2.28-alpha"
  kapt "com.google.dagger:hilt-android-compiler:2.28-alpha"
  implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha01'
  kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha01'
}

Time to create Hilt classes

Annotate your Application class

@HiltAndroidApp
class DBHiltApplication : Application() {
...
}

Create Retrofit part: DataSource + Repository

interface ApiDataSource {

    @GET("api")
    suspend fun pixabayImages(
        @Query("key") key: String?,
        @Query("q") q: String?,
        @Query("image_type") imageType: String?,
        @Query("pretty") pretty: Boolean?
    ): Response<PixabayImagesOut>

}

@Singleton
class ApiRepository @Inject constructor(private val dataSource: ApiDataSource) {

    suspend fun launchPixabayImages(pixabayIn: PixabayImagesIn): Response<PixabayImagesOut> = this.dataSource.pixabayImages(
        pixabayIn.key,
        pixabayIn.q,
        pixabayIn.imageType,
        pixabayIn.pretty
    )

}

Create the Module class

This type of Hilt class allows you to create and have the instance of any class in any point of the project. In our case, Retrofit DataSource and Repository are defined to use them to get basic data from the Pixabay server.

@Module
@InstallIn(ApplicationComponent::class)
class ApiModule {

    @Provides
    fun provideBaseUrl() = BuildConfig.BASE_URL

    @Provides
    @Singleton
    fun provideOkHttpClient() = if (BuildConfig.DEBUG) {
        val loggingInterceptor = HttpLoggingInterceptor()
        loggingInterceptor.level = HttpLoggingInterceptor.Level.BODY

        OkHttpClient.Builder().addInterceptor(loggingInterceptor).build()
    } else {
        OkHttpClient.Builder().build()
    }

    @Provides
    @Singleton
    fun provideRetrofit(okHttpClient: OkHttpClient, BASE_URL: String): Retrofit =
        Retrofit.Builder()
            .addConverterFactory(MoshiConverterFactory.create())
            .baseUrl(BASE_URL)
            .client(okHttpClient)
            .build()

    @Provides
    @Singleton
    fun provideApiDataSource(retrofit: Retrofit) = retrofit.create(ApiDataSource::class.java)

    @Provides
    @Singleton
    fun provideApiRepository(dataSource: ApiDataSource) = ApiRepository(dataSource)
}

Annotate your ViewModel

To get the Repository instance into your ViewModel, the @ViewModelInject annotation is required.

class MainViewModel @ViewModelInject constructor(private val repository: ApiRepository) : ViewModel() {
...
}

Annotate your View (Activity/Fragment)

Finally, to get and execute the ViewModel annotated from your View, it is essential to use _@AndroidEntryPoint annotation.

@AndroidEntryPoint
class MainFragment : Fragment() {

  private lateinit var viewModel: MainViewModel

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    this.viewModel = ViewModelProvider(this, defaultViewModelProviderFactory).get(MainViewModel::class.java)
    ...
  }

}

DataBinding

Add the next dependencies before to start

gradle.properties (app)

android {
  ...
  buildFeatures {
    dataBinding true
  }
}

dependencies {
  ...
  kapt 'com.android.databinding:compiler:3.1.4'
}

Modify your xml where you want to use DataBinding using layout and data tags

In this case, listVisible variable is defined to manage the visibility of a list and an empty information label.

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <import type="android.view.View" />

        <variable
            name="listVisible"
            type="java.lang.Boolean" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".feature.main.view.MainFragment">
        
        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:visibility="@{listVisible ? View.VISIBLE : View.GONE, default=gone}" />

        <TextView
            android:id="@+id/emptyView"
            style="@style/PrimaryText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/generic_empty_label"
            android:visibility="@{listVisible ? View.GONE : View.VISIBLE, default=gone}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
            
    </androidx.constraintlayout.widget.ConstraintLayout>
    
</layout>

Manage the behaviour from the View

Finally, after adding layout and data tags into your xml, DataBinding library generates a class (your xml name + Binding) to get the instances of your views.

private lateinit var binding: MainFragmentBinding

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
  super.onViewCreated(view, savedInstanceState)

  this.binding = MainFragmentBinding.bind(view)
  ...
}

private fun showList() {
  this.binding.listVisible = true
}

private fun showEmptyView() {
  this.binding.listVisible = false
}