Marvel Cinematic Universe

Marvel Cinematic Universe is an app for practicing various Jetpack libraries.

Libraries

• Kotlin
  • Coroutines
  • Flow
• Android
  • AppStartup : A straightforward, performant way to initialize components at application startup.
  • DataBinding : Bind UI components in your layouts to data sources in your app using a declarative format.
  • Datastore : A data storage using Kotlin coroutines and Flow to store small and simple datasets.
  • Hilt : Jetpack's recommended DI solution for Android.
  • JankStats : Track and analyze jank performance problems in your app's UI.
  • Lifecycle : Defines an object that has an Android Lifecycle.
  • Navigation-component : Framework for navigating between destinations within an app.
  • Room : Database persistence layer designed for usability, safety, and testability.
  • Splash-screens : A new app launch animation for all apps when running on a device with Android 12 or higher.
  • ViewModel : A business logic or screen level state holder.
  • WorkManager : A library for managing deferrable and guaranteed background work.
• Glide : An image loading and caching library for Android.
• Gson : A Java serialization/deserialization library to convert Java Objects into JSON and back.
• Material-Components : Modular and customizable Material Design UI components for Android.
• Timber : A logger with a small, extensible API.

Architecture

• MVVM (Model - View - ViewModel)
• Repository Pattern
• Trying to follow Guide to app architecture.

• This application consists of two layers.
  • UI Layer : display the data on the screen.
  • Data Layer : contains the business logic.
• Unidirectional Data Flow(UDF)
  • In UDF, data flows in only one direction.
  • The events that modify the data in the opposite direction.

UI Layer

• UI Layer consists of two things.
  • View(UI elements) that renders data to the screen.
  • ViewModel that holds data, exposes data, handles logic.
• ViewModel exposes the data, and the View observes the data.
  • This interaction is simplified by Data Binding Library.

Data Layer

• Data layer contains Repositories where DAO is injected to access Database.
• Repositories get immutable data stream from Database and expose it to the ViewModel.

Room Database

• To use the Room database efficiently, refer to the 7-pro-tips.

• Pre-populate your database via RoomDatabase#Callback.

  • You can detect the moment the database is created with RoomDatabase.Callback().
  • Using WorkManager, add default data when a database is created.
  • You can build an offline-first app by adding default data.
  • That is, it can perform some or all of its business logic without access to the internet.

  Room.databaseBuilder(
      context,
      MarvelDatabase::class.java,
      "Marvel.db"
  ).addCallback(
      object : RoomDatabase.Callback() {
          override fun onCreate(db: SupportSQLiteDatabase) {
              super.onCreate(db)
              val request = OneTimeWorkRequestBuilder<MarvelDatabaseWorker>().build()
              WorkManager.getInstance(context).enqueue(request)
          }
      }
  ).build()

• Read only what you need.

  • For example, Movie data class stored in the database has 7 fields.

  @Entity
  data class Movie(
      @PrimaryKey val id: Int,
      val title: String,
      val phase: Int,
      val content: String,
      val release: String,
      @ColumnInfo(name = "running_time") val runningTime: Int,
      val image: String
  )
  
  // In DAO
  @Query("SELECT * FROM Movie")
  fun getMovies(): Flow<List<Movie>>

  • Instead of getting all field values stored in the database, read only what you need.

  data class MovieBasicInfo(
      val id: Int,
      val title: String,
      val image: String
  )
  
  // In DAO
  @Query("SELECT id, title, image FROM Movie")
  fun getMovies(): Flow<List<MovieBasicInfo>>

  • This will also improve the speed of queries by reducing the IO cost.

Contents

• All contents used in this application belongs to Marvel Official site.