Android Architecture Sample

Sample Android App to access Discogs API.

This app performs basic REST call to obtain a public list of records from Discogs API, with the idea to test and showcase some Android architecture and coding patterns.

Code Features

• Kotlin.
• Coroutines.
• Dependency injection with Koin.
• Retrofit + Moshi.
• Architecture Components.
• Modularization.
• Unit Testing.
• Instrumentation Testing with Espresso.

App Modules

- app                  (App and MainActivity; Android)
- api                  (Retrofit Service; Kotlin)
- common-domain        (Kotlin)
- collection           
  | - collection-ui    (Fragment and ViewModel; Android)
  | - collection-data  (Use case; Kotlin)

Cool Examples

Dependency Injection with Koin

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/app/src/main/java/work/beltran/discogsbrowser/App.kt#L11

startKoin(this, listOf(
    collectionKoinModule
))

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-ui/src/main/java/work/beltran/discogsbrowser/collection/CollectionFragment.kt#L20

private val viewModel: CollectionViewModel by viewModel()

Retrofit with Coroutines

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/api/src/main/java/work/beltran/discogsbrowser/api/DiscogsService.kt#L22

@GET("users/{username}/collection/folders/{folder_id}/releases")
fun getCollectionItemsByFolder(
    @Path("username") username: String,
    @Path("folder_id") folderId: String,
    @Query("page") page: Int,
    @Query("per_page") perPage: Int
) : Deferred<Response<CollectionItemsByFolderResponse>>

Use Case Implementation with Coroutines and Arrow

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-data/src/main/java/work/beltran/discogsbrowser/collection/data/GetCollectionUseCase.kt#L17

private suspend fun requestItems(
    folder: String,
    page: Int
): Response<CollectionItemsByFolderResponse> {
    return discogsService.getCollectionItemsByFolder(
        username = "mike513",
        folderId = folder,
        page = page,
        perPage = PAGE_SIZE
    ).await()
}

Use Case Unit Test using Mockk and Coroutines

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-data/src/test/kotlin/work/beltran/discogsbrowser/collection/data/GetCollectionUseCaseImplTest.kt

every {
    service.getCollectionItemsByFolder(
        username = "mike513",
        folderId = "0",
        page = 1,
        perPage = 20
    )
} returns CompletableDeferred(
    Response.success(
        collectionItemsByFolderResponse
    )
)

ViewModel and LiveData with Coroutines (Kotlin 1.3)

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-ui/src/main/java/work/beltran/discogsbrowser/collection/CollectionViewModel.kt

loadingJob = launch(dispatcher) {
    val result = collectionUseCase.getCollectionPage("0", page)
    when (result) {
        is Either.Left -> Log.e("CollectionViewModel", result.a)
        is Either.Right -> {
            pages[page] = result.b.data
            nextPage = result.b.nextPage
        }
    }
    updateCollectionScreenState()
}

ViewModel Unit Test

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-ui/src/test/java/work/beltran/discogsbrowser/collection/CollectionViewModelTest.kt

val viewModel = CollectionViewModel(
    collectionUseCase = useCase,
    dispatcher = Dispatchers.Unconfined
)

val data = viewModel.liveData.value!!
assertEquals(1, data.size)

val item = data[0] as CollectionItem.AlbumItem
assertEquals(album, item.album)

Fragment Instrumentation Test with Espresso

https://github.com/miquelbeltran/android-discogsbrowser/blob/master/collection/collection-ui/src/androidTest/java/work/beltran/discogsbrowser/collection/CollectionFragmentTest.kt

@Test
fun load_single_item_page() {

    // Mock the use case to return a single item
    val collectionUseCase = mockUseCaseForSingleItem()

    // Configure dependency injection to provide ViewModel with Use Case
    configureKoin(collectionUseCase)

    // Launch Fragment in a Test Activity
    launchFragment()

    // Assert Album title is displayed in the list
    onView(withText("title")).check(matches(isDisplayed()))
}

License

Android Architecute Sample  Copyright (C) 2018  Miguel Beltran Febrer
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions.