Kotlin使用协程等待异步

Question

我想在实例化phoneViewModel和ScanViewModel时打开一个新的活动。它们是通过调用异步函数InitialRead()实例化的。我正在记录每个步骤，他们以done3 => done2 => done1的身份登录

我希望它们按以下顺序排列: done1 => done2 => done3

我有以下代码：

class MainBusinessActivity : AppCompatActivity() {

private lateinit var scanViewModel: ScanViewModel
private lateinit var phoneViewModel: PhoneViewModel

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main_business)
}

private fun startEntitySetListActivity() = GlobalScope.async {
    val sapServiceManager = (application as SAPWizardApplication).sapServiceManager
    sapServiceManager?.openODataStore {
        phoneViewModel =  ViewModelProvider(this@MainBusinessActivity).get(PhoneViewModel::class.java).also {it.initialRead{Log.e("done", "done1")}}
        scanViewModel = ViewModelProvider(this@MainBusinessActivity).get(ScanViewModel::class.java).also {it.initialRead{Log.e("done", "done2")}}
    }
}

override fun onResume() {
    super.onResume()
    //startEntitySetListActivity()
    runBlocking {
        startEntitySetListActivity().await()
        val intent = Intent(this@MainBusinessActivity, HomeActivity::class.java)
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK)
        Log.e("done", "done3")
        startActivity(intent)
    }
}

}

我做错了什么？有人能纠正我的代码吗？

Answer 1

永远不要在安卓应用程序中使用runBlocking。runBlocking完全违背了使用协程的目的，并且可能导致ANR。您也可能永远不应该使用GlobalScope，这会导致UI泄漏。您可能需要将它用于某种长期运行的任务，这些任务放在服务中没有意义，但又不依赖于任何UI组件，但我想不出任何示例

你也不应该在后台实例化ViewModels。这应该在onCreate()中完成。

将此函数设置为挂起函数，它可以在返回前在后台同时分解两个任务。

从lifecycleScope开始你的协程。

假设sapServiceManager?.openODataStore是一个接受回调的异步任务，您需要将它包装在suspendCoroutine中。

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main_business)
    phoneViewModel = ViewModelProvider(this@MainBusinessActivity).get(PhoneViewModel::class.java)
    scanViewModel = ViewModelProvider(this@MainBusinessActivity).get(ScanViewModel::class.java)
}

private suspend fun startEntitySetListActivity() = coroutineScope {
    val sapServiceManager = (application as SAPWizardApplication).sapServiceManager
    sapServiceManager ?: return
    suspendCoroutine<Unit> { continuation ->
        sapServiceManager.openODataStore { continuation.resume(Unit) }
    }
    listOf(
        launch {
            phoneViewModel.initialRead{Log.e("done", "done1")}
        },
        launch {
            scanViewModel.initialRead{Log.e("done", "done2")}
        }
    ).joinAll()
}

override fun onResume() {
    super.onResume()
    lifecycleScope.launch {
        startEntitySetListActivity()
        val intent = Intent(this@MainBusinessActivity, HomeActivity::class.java)
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK)
        Log.e("done", "done3")
        startActivity(intent)
    }
}