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商店的重新开业：使用协程将数据加载到Android中

我提请您注意Mike Nakhimovich 的原始文章翻译


曾几何时，我在《纽约时报》工作，并创建了一个名为的库Store，该库是“用于轻松，响应式地加载数据的Java库”。我们使用RxJava从Guava的Cache实现中获取的模板创建了Store 。当今的应用程序用户期望在用户界面中进行数据更新，而无需执行如需刷新的操作刷新数据或在屏幕之间来回移动。响应式前端使我想到了如何使用简单的API来创建声明性数据仓库，该API可以抽象化复杂的功能，如多任务调节和磁盘缓存，这是现代移动应用程序所必需的。在运营的三年中，Store拥有45位贡献者和超过3500个GitHub star。从现在开始，我很高兴地宣布，Dropbox将积极参与Store的开发，并将在Kotlin上全面发布并支持Coroutinesand Flow。现在Store 4，这是一个通过重新思考API和Android生态系统当前需求来利用我们所学知识的机会。



Android . . , , Google. , Android. Android Jetpack:



, Android Jetpack :



https://developer.android.com/jetpack/docs/guide


  • :  , AndroidX , Lifecycle Scopes . , view- .
  • View Model Live Data:  , , ( , !).
  • Room:  SQLite, ORM RxJava .
  • Remote Data Source:  Jetpack, Retrofit Okhttp Square .

, , , ( , , Jetpack ;-) ). , . , Dropbox Store, , .


, Store, . ,


«… , , .  , , , ».

. , , , . , .


Store?


, , Store, Android- . — , . , UX. , , . , . Store, .


, , . …



Store :



Store


, , Store, , , .


4 – Android . , . , Room SQLDelight, , . -, push-, Firebase, «» . Store , , , , , . , Store: http://github.com/dropbox/Store.


Store 4 . RxJava , Flow.


, , , , RxJava? . , , . , . , , , , .


— . RxJava - . API RxJava :


// Observable.java
@CheckReturnValue
public final Disposable subscribe(Consumer onNext) {}

, , RxJava Observable Disposable . dispose(), . . RxJava2 @CheckReturnValue— , flowable.subscribe , . , , . , RxJava, .


RxJava , dispose(). . RxJava, , , Kotlin Flow , . , Flow . Flow , .


suspend fun Flow.collect(...)

Collect RxJava, , Flow. RxJava, collect() "suspend". , ( async/await), . Flow.collect , , .


, Android ( ) , , . , Kotlin, , viewModelScope Jetpack, , . , Android: , .


public fun CoroutineScope.launch(...)
 
viewModelScope.launch {
  flow.collect{ handle(it) }
}

, Flow. Android. , AndroidX . , ViewModel, , Room Flow. , (Paging). Store , Android , .


, Store , Android, , , , Kotlin multi-platform, . RxJava Kotlin native/js 6000 .


Store?


Store . Store, Fetcher, , , . , Store . Store Flow, — ! Store // , , .


Store


, Store. , :


StoreBuilder.fromNonFlow { api.fetchSubreddit(it, "10")}
            .persister(
              reader = db.postDao()::loadPosts,
              writer = db.postDao()::insertPosts,
              delete = db.postDao()::clearFeed)
            .cachePolicy(MemoryPolicy)
            .build()

:


  • ,
  • API , , .

Store  . persister() Store. , Observable, Jetpack Room, SQLDelight Realm.


:


Store



 Store  . , Flow, , ReturnType.


val store = StoreBuilder.from {
                articleId -> api.getArticle(articleId) //Flow<Article>
            }
            .build()

Store , , toString(), equals() hashCode(). Fetcher . . , equals() hashcode() data- Kotlin.


: Stream



API, Store, :


fun stream(request: StoreRequest<Key>):Flow<StoreResponse>Output>>

StoreRequest, , . StoreResponse. StoreResponse — Kotlin, Loading, Data Error. StoreResponse ResponseOrigin, , .



  • Loading ResponseOrigin. .
  • Data , , Store.
  • Error , , ResponseOrigin.

Store , StoreResponse.Error, Flow , , . - , render/updateUI . . :


lifecycleScope.launchWhenStarted {
  store.stream(StoreRequest.cached(key = key, refresh=true)).collect { response ->
    when(response) {
        is StoreResponse.Loading -> showLoadingSpinner()
        is StoreResponse.Data -> {
            if (response.origin == ResponseOrigin.Fetcher) hideLoadingSpinner()
            updateUI(response.value)
        }
        is StoreResponse.Error -> {
            if (response.origin == ResponseOrigin.Fetcher) hideLoadingSpinner()
            showError(response.error)
        }
    }
  }
}

: Store.get(key), Store.stream(key)  Store.fresh(key).


  • suspend fun Store.get(key: Key): Value
 — . , .
  • suspend fun Store.fresh(key: Key): Value
 — , .
  • suspend fun Store.stream(key: Key): Flow
 — (Flow) .

get():


lifecycleScope.launchWhenStarted {
  val article = store.get(key)
  updateUI(article)
}

store.get(key), ( ), . store.get(key) , . ( ) , . , , , Store. Store . Store , , .






 store.fresh(key)  ( ). ,  fresh()  ,  store.get()/stream()  .  fresh()  pull-to-refresh .
 fresh()  get()  .


Stream



, store.stream(key), , , / . stream() , .


lifecycleScope.launchWhenStarted { 
  store.stream(StoreRequest.cached(3, refresh = false)) 
.collect{ }
 
 
store.stream(StoreRequest.get(3)) // ,   
    .collect{  }







, Store . , , , . , . Store.get() 12 . , . .




 Store ,  persister()  . , , Store , , .




 persister(),  Flow  Store  . , ,  Store,   Store.


, Observable (Jetpack Room, SQLDelight Realm), , , UX.


StoreBuilder.fromNonFlow {api.fetchSubreddit(it, "10")}
            .persister(
              reader = db.postDao()::loadPosts,
              writer = db.postDao()::insertPosts,
              delete = db.postDao()::clearFeed)
            .cachePolicy(MemoryPolicy)
            .build()

Store , . , Store (Realm, SQLite, Firebase ..). SQLite Room, Jetpack.


API Store — , . :


  • , Room
  • (StoreRequest)
  • (stream)
  • API, Kotlin.


, Store. , , Android, . , -, - . , , .


KotlinConf:




Store : github.com/dropbox/Store



, , Android Open Source Project, , Creative Commons 2.5 Attribution License

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