Kotlin 协程在 Android 中的正确方式 [英] Kotlin Coroutines the right way in Android

问题描述

我正在尝试使用异步更新适配器内的列表，我可以看到样板太多.

I'm trying to update a list inside the adapter using async, I can see there is too much boilerplate.

这是使用 Kotlin 协程的正确方法吗?

Is it the right way to use Kotlin Coroutines?

可以进一步优化吗?

fun loadListOfMediaInAsync() = async(CommonPool) {
        try {
            //Long running task 
            adapter.listOfMediaItems.addAll(resources.getAllTracks())
            runOnUiThread {
                adapter.notifyDataSetChanged()
                progress.dismiss()
            }
        } catch (e: Exception) {
            e.printStackTrace()
            runOnUiThread {progress.dismiss()}
        } catch (o: OutOfMemoryError) {
            o.printStackTrace()
            runOnUiThread {progress.dismiss()}
        }
    }

推荐答案

在这个问题上挣扎了好几天后，我认为使用 Kotlin 的 Android Activity 最简单明了的 async-await 模式是:

After struggling with this question for days, I think the most simple and clear async-await pattern for Android activities using Kotlin is:

override fun onCreate(savedInstanceState: Bundle?) {
    //...
    loadDataAsync(); //"Fire-and-forget"
}

fun loadDataAsync() = async(UI) {
    try {
        //Turn on busy indicator.
        val job = async(CommonPool) {
           //We're on a background thread here.
           //Execute blocking calls, such as retrofit call.execute().body() + caching.
        }
        job.await();
        //We're back on the main thread here.
        //Update UI controls such as RecyclerView adapter data.
    } 
    catch (e: Exception) {
    }
    finally {
        //Turn off busy indicator.
    }
}

协程的唯一 Gradle 依赖项是:kotlin-stdlib-jre7、kotlinx-coroutines-android.

The only Gradle dependencies for coroutines are: kotlin-stdlib-jre7, kotlinx-coroutines-android.

注意:使用 job.await() 而不是 job.join() 因为 await()重新抛出异常，但 join() 不会.如果您使用 join()，您将需要在作业完成后检查 job.isCompletedExceptionally.

Note: Use job.await() instead of job.join() because await() rethrows exceptions, but join() does not. If you use join() you will need to check job.isCompletedExceptionally after the job completes.

要开始并发改造调用，您可以这样做:

To start concurrent retrofit calls, you can do this:

val jobA = async(CommonPool) { /* Blocking call A */ };
val jobB = async(CommonPool) { /* Blocking call B */ };
jobA.await();
jobB.await();

或者:

val jobs = arrayListOf<Deferred<Unit>>();
jobs += async(CommonPool) { /* Blocking call A */ };
jobs += async(CommonPool) { /* Blocking call B */ };
jobs.forEach { it.await(); };

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