使用协同程序执行Android Kotlin任务

问题描述

作为示例，我使用FusedLocationProviderClient访问当前位置，它返回一个任务，回调将最终返回该位置.该方法如下所示:

As an example, I'm using FusedLocationProviderClient to access the current location, which returns a task which callback will eventually return the location. The method looks something like follows:

fun getLocation(callback: MyCallback){
    val flpc = LocationServices.getFusedLocationProviderClient(it)
    flpc.lastLocation.addOnSuccessListener {
        callback.onLocation(it)
    }
}

是否可以对此进行转换，以便可以使用例程来挂起此函数并等待flpc.lastLocation返回的任务，以便可以在此方法中将其返回，从而摆脱该回调?例如这样的东西:

Is it possible to transform this so that I can use corroutines to suspend this function and wait for the task returned by flpc.lastLocation so I can return it in this method and this way get rid of that callback? For example something like this:

suspend fun getLocation(): Location? =
    withContext(Dispachers.IO){
        val flpc = LocationServices.getFusedLocationProviderClient(it)
        return@withContext flpc.lastLocation.result()
    }

我的问题是，协程周围是否有东西可以返回Task的结果(在本例中为Task<Location>)

My question is if there is something around coroutines where I can return the result of a Task (in this example, a Task<Location>)

提前谢谢！

推荐答案

kotlinx-coroutines-play-services 库具有 Task<T>.await(): T 助手.

import kotlinx.coroutines.tasks.await

suspend fun getLocation(): Location? =
    LocationServices.getFusedLocationProviderClient(context).lastLocation.await()

或者查看阻止任务

它将以另一种方式使用:

It would be used the next way:

suspend fun getLocation(): Location? =
    withContext(Dispachers.IO){
        val flpc = LocationServices.getFusedLocationProviderClient(context)
        try{
            return@withContext Tasks.await(flpc.lastLocation)
        catch(ex: Exception){
            ex.printStackTrace()
        }
        return@withContext null
    }

仅出于示例目的而添加到此示例中，将以以下方式完成对getLocation()的调用:

Just to add to this example, for completion purposes, the call to getLocation() would be done the next way:

coroutineScope.launch(Dispatchers.Main) {
    val location = LocationReceiver.getLocation(context)
    ...
}

但是，这通过不利用可用的回调并阻塞IO调度程序上的线程而否定了协程的好处，如果有替代方法，则不应使用.

However this negates the benefits of coroutines by not leveraging the available callback and blocking a thread on the IO dispatcher and should not be used if the alternative is available.

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