This document discusses key concepts for Android app development including: - The repository layer for managing app data from both local databases and remote sources. - Using the Room library as an ORM for local SQLite databases. - Making network requests using Retrofit and Moshi to fetch and parse JSON API responses. - Scheduling background tasks with WorkManager. - Following Material Design principles and testing apps thoroughly. Code samples and demos are provided to illustrate implementing these concepts.

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Android Study Jams
Prior Programming Experience Track: Session 4

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Prior Programming Experience Track: Session 4
Android Study Jams

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Learning Objectives
० Learn about Repository Layer to manage Data
० Using WorkManager for scheduled tasks
० Design your app using Material Design
० Test your app

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A little about me

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Concept Overview
What is the Repository Layer?

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Repository Modules handle data operations.

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Repository Components
● Model (Database)
● Remote Data (Network)
● Provides API for accessing both

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Why Repository
● Separation of Concerns
● Activity/Fragment are glue
● UI driven by data
● Testable and Consistent

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Repository cont...
● DI vs Service Lookup
● View Models and Streams
● ORMs

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Databases
● Caches
● Room Library - ORM
● Database Refresh Strategy
● Observables

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Room
● @Entity @ColumnInfo
● @Dao
● @Insert, @Delete, and @Update
● @Query

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Don’t forget to test!

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@Dao
interface VideoDao {
@Query("select * from databasevideo")
fun getVideos(): LiveData<List<DatabaseVideo>>
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insertAll( videos: List<DatabaseVideo>)
}
@Database(entities = [DatabaseVideo::class], version = 1)
abstract class VideosDatabase: RoomDatabase() {
abstract val videoDao: VideoDao
}
private lateinit var INSTANCE: VideosDatabase
fun getDatabase(context: Context): VideosDatabase {
synchronized(VideosDatabase::class.java) {
if (!::INSTANCE.isInitialized) {
INSTANCE = Room.databaseBuilder(context.applicationContext,
VideosDatabase::class.java,
"videos").build()
}
}
return INSTANCE
}
Room.kt

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@Entity
data class DatabaseVideo constructor(
@PrimaryKey
val url: String,
val updated: String,
val title: String,
val description: String,
val thumbnail: String)
/**
* Map DatabaseVideos to domain entities
*/
fun List<DatabaseVideo>.asDomainModel(): List<DevByteVideo> {
return map {
DevByteVideo(
url = it.url,
title = it.title,
description = it.description,
updated = it.updated,
thumbnail = it.thumbnail)
}
}
DatabaseEntities.kt

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Network
● REST Services
● Retrofit Library - for API Calls
● Moshi - for JSON to Model
● Observables

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interface DevbyteService {
@GET("devbytes")
suspend fun getPlaylist(): NetworkVideoContainer
}
object DevByteNetwork {
// Configure retrofit to parse JSON and use coroutines
private val retrofit = Retrofit.Builder()
.baseUrl("https://android-kotlin-fun-mars-server.appspot.com/")
.addConverterFactory(MoshiConverterFactory.create())
.build()
val devbytes = retrofit.create(DevbyteService::class.java)
}
Service.kt

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@JsonClass(generateAdapter = true)
data class NetworkVideoContainer(val videos: List<NetworkVideo>)
@JsonClass(generateAdapter = true)
data class NetworkVideo(
val title: String,
val description: String,
val url: String,
val updated: String,
val thumbnail: String,
val closedCaptions: String?)
fun NetworkVideoContainer.asDomainModel(): List<DevByteVideo> {}
fun NetworkVideoContainer.asDatabaseModel(): List<DatabaseVideo> {}
DTO.kt

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Work Manager

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Work Manager
● For scheduling repeating tasks
● Define constraints
● Retry
● Chaining
● Threading

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Material Design

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Testing

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Testing

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Demos

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Learn More

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Want to learn more?
● Official Android Developers Site: https://developer.android.com/
● Android Samples on GitHub
● Official Android Developers Blog (for announcements)
● Android Developers Medium Blog (for more technical articles)
● Android Developers YouTube channel
● Follow @AndroidDev on Twitter
● Subscribe to the Android Developer Newsletter
● Kotlin Vocabulary series
● Official Kotlin language site
Version 1.0