在协程中的侦听器中等待数据 [英] Wait For Data Inside a Listener in a Coroutine

问题描述

我有一个协程，我想在启动页面期间在android启动时启动.我想等待数据返回，然后再开始下一个活动.做这个的最好方式是什么?目前，我们的android系统正在使用实验性协程0.26.0 ...目前尚无法更改.

I have a coroutine I'd like to fire up at android startup during the splash page. I'd like to wait for the data to come back before I start the next activity. What is the best way to do this? Currently our android is using experimental coroutines 0.26.0...can't change this just yet.

更新:我们现在正在使用最新的协程，而不再是实验性的

UPDATED: We are now using the latest coroutines and no longer experimental

onResume() {
    loadData()
}

fun loadData() = GlobalScope.launch {
    val job = GlobalScope.async {
        startLibraryCall()
    }
    // TODO await on success
    job.await()
    startActivity(startnewIntent)
}

fun startLibraryCall() {
    val thirdPartyLib() = ThirdPartyLibrary()
    thirdPartyLib.setOnDataListener() { 
        ///psuedocode for success/ fail listeners
        onSuccess -> ///TODO return data
        onFail -> /// TODO return other data
    }
}

推荐答案

第一点是，我会将您的loadData函数更改为挂起函数，而不是使用launch.最好可以在呼叫站点定义要如何执行执行的选项.例如，在执行测试时，您可能希望在runBlocking中调用协程.您还应该正确实现结构并发，而不要依赖GlobalScope.

The first point is that I would change your loadData function into a suspending function instead of using launch. It's better to have the option to define at call site how you want to proceed with the execution. For example when implementing a test you may want to call your coroutine inside a runBlocking. You should also implement structured concurrency properly instead of relying on GlobalScope.

在问题的另一方面，我将在ThirdPartyLibrary上实现扩展功能，将其异步调用转换为挂起函数.这样，您可以确保调用协程实际上等待Library调用具有一定的价值.

On the other side of the problem I would implement an extension function on the ThirdPartyLibrary that turns its async calls into a suspending function. This way you will ensure that the calling coroutine actually waits for the Library call to have some value in it.

由于我们将loadData设置为挂起函数，因此我们现在可以确保仅在ThirdPartyLibrary调用完成时才开始新的活动.

Since we made loadData a suspending function we can now ensure that it will only start the new activity when the ThirdPartyLibrary call finishes.

import kotlinx.coroutines.*
import kotlin.coroutines.*

class InitialActivity : AppCompatActivity(), CoroutineScope {
    private lateinit var masterJob: Job
    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + masterJob

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        masterJob = Job()
    }

    override fun onDestroy() {
        super.onDestroy()
        masterJob.cancel()
    }

    override fun onResume() {
        this.launch {
            val data = ThirdPartyLibrary().suspendLoadData()
            // TODO: act on data!
            startActivity(startNewIntent)
        }
    }
}

suspend fun ThirdPartyLibrary.suspendLoadData(): Data = suspendCoroutine { cont ->
    setOnDataListener(
            onSuccess = { cont.resume(it) },
            onFail = { cont.resumeWithException(it) }
    )
    startLoadingData()
}

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