使用协程更新UI异步调用

本文介绍了使用协程更新UI异步调用的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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:

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 ：

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'