[英]Update UI async call with coroutines
我必須通過對房間數據庫的異步調用來更新UI,但是當我這樣做時,我遇到了這個錯誤:android.view.ViewRootImpl $ CalledFromWrongThreadException:只有創建視圖層次結構的原始線程才能觸及其視圖。
// FavoritesPresenter.kt
GlobalScope.launch {
favoritesView.showFavorites(ProductProvider.getAllProducts() as ArrayList<Product>)
}
// ProductProvider.kt
fun getAllProducts() : MutableList<Product> {
return dao.getAllProducts()
}
// ProductDao.kt
@Query("SELECT * FROM product")
fun getAllProducts(): MutableList<Product>
我需要的是通過我的ProductProvider更新我的UI,因為我將用於所有我需要可靠解決方案的實體。
2.1室 (目前處於alpha版)增加了對Kotlin協程的支持。 您可以執行以下操作:
將ProductDao
和ProductProvider
函數標記為暫停 :
// ProductDao.kt @Query("SELECT * FROM product") suspend fun getAllProducts(): List<Product> // ProductProvider.kt suspend fun getAllProducts(): List<Product> = dao.getAllProducts()
在FavoritesPresenter
為協程創建本地范圍:
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>) } }
在Activity
或Fragment
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導入:
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1'
您應該使用IO協程從Room中取出,並切換到Main(UI)協程以更新視圖。
嘗試:
GlobalScope.launch(Dispatchers.IO) {
val products = ProductProvider.getAllProducts() as ArrayList<Product>
withContext(Dispatchers.Main) {
favoritesView.showFavorites(products)
}
}
確保安裝了Android Coroutine庫,以便Main Dispatcher正確識別Android主線程。
api "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1"
最好不要使用GlobalScope,而是使用自己的CoroutineContext,例如:
class YourActivity : CoroutineScope {
private lateinit var job: Job
// context for io thread
override val coroutineContext: CoroutineContext
get() = Dispatchers.IO + job
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
job = Job()
}
fun toDoSmth() {
launch {
// task, do smth in io thread
withContext(Dispatchers.Main) {
// do smth in main thread after task is finished
}
}
}
override fun onDestroy() {
job.cancel()
super.onDestroy()
}
}
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