使用协程更新UI异步调用 [英] Update UI async call with coroutines

问题描述

我必须使用对Room数据库的异步调用来更新UI，但是当我收到此错误时：android.view.ViewRootImpl $ CalledFromWrongThreadException：只有创建视图层次结构的原始线程才能触摸

I've got to update the UI with an async call to the Room Database, but when I do I've got this error : android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

//收藏夹Presenter.kt

// FavoritesPresenter.kt

GlobalScope.launch {
    favoritesView.showFavorites(ProductProvider.getAllProducts() as ArrayList<Product>)
}

// ProductProvider.kt

// ProductProvider.kt

fun getAllProducts() : MutableList<Product> {
    return dao.getAllProducts()
}

// ProductDao.kt

// ProductDao.kt

@Query("SELECT * FROM product")
fun getAllProducts(): MutableList<Product>

我需要通过ProductProvider更新UI，因为我将对所有实体使用我需要一个可靠的解决方案。

What I need is to update my UI though my ProductProvider, as I'll use for all my entities I need a reliable solution.

推荐答案

房间2.1 （当前为Alpha版）添加了对 Kotlin协程。您可以执行以下操作：

Room 2.1 (currently in alpha) adds support for Kotlin coroutines. You can do the following:

1. 在 ProductDao 和 ProductProvider 作为挂起：

// ProductDao.kt
@Query("SELECT * FROM product")
suspend fun getAllProducts(): List<Product>

// ProductProvider.kt
suspend fun getAllProducts(): List<Product> = dao.getAllProducts()

在 FavoritesPresenter ：

class FavoritesPresenter {
    private var favoritesView: FavoritesView? = null
    private val provider: ProductProvider = ...// initialize it somehow
    private var job: Job = Job()
    private val scope = CoroutineScope(job + Dispatchers.Main)

    fun getProducts() {
        scope.launch {
            favoritesView?.showFavorites(provider.getAllProducts())
        }
    }

    fun attachView(view: FavoritesView) {
        this.favoritesView = view
    }

    fun detachView() {
        job.cancel() // cancel the job when Activity or Fragment is destroyed
        favoritesView = null
    }

    interface FavoritesView {
        fun showFavorites(products: List<Product>)
    }
}

使用 FavoritesPresenter 活动或片段中的c>：

class MainActivity : AppCompatActivity(), FavoritesPresenter.FavoritesView {
    lateinit var presenter: FavoritesPresenter
    override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       // ...
       presenter = FavoritesPresenter()
       presenter.attachView(this)
       presenter.getProducts()

    }

    override fun onDestroy() {
        presenter.detachView()
        super.onDestroy()
    }

    override fun showFavorites(products: List<Product>) {
        // use products to update UI
    }
}

要使用 Dispatchers.Main 导入：

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1'

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