Question

我试图了解哪种方法是在Kotlin中按计划的速率启动异步作业的最佳方法，而应用程序通常正在运行它的正常任务。假设我有一个简单的应用程序，该应用程序每秒仅打印“ ...”，但是每5秒我要另一个作业/线程/协程（最适合）打印“您有消息！”。对于异步作业，我有一个NotificationProducer类，它看起来像这样。

class NotificationProducer {

    fun produce() {
        println("You have a message!")
    }
}

然后，我的主要方法如下。

    while (true) {
        println("...")
        sleep(1000)
    }

我应该使用GlobalScope.async，Timer().schedule(...)还是某些Quartz作业来实现我想要的？任何建议都将受到高度赞赏。关键是通知必须来自另一个类（例如NotificationProducer）

Answer 1

如果我正确理解了这个问题，可以使用Kotlin Coroutines如下实现它：

class Presenter : CoroutineScope { // implement CoroutineScope to create local scope
    private var job: Job = Job()
    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Default + job 

    // this method will help to stop execution of a coroutine. 
    // Call it to cancel coroutine and to break the while loop defined in the coroutine below    
    fun cancel() {
        job.cancel()
    }

    fun schedule() = launch { // launching the coroutine
        var seconds = 1
        val producer = NotificationProducer()
        while (true) {
            println("...")
            delay(1000)

            if (seconds++ == 5) {
                producer.produce()
                seconds = 1
            }
        }
    }
}

然后，您可以使用Presenter类的实例启动协程并停止协程：

val presenter = Presenter()
presenter.schedule() // calling `schedule()` function launches the coroutine

//...

presenter.cancel() // cancel the coroutine when you need

Answer 2

对于简单的调度要求，我会使用协程实现它，因为它很有趣：

class NotificationProducerScheduler(val service: NotificationProducer, val interval: Long, val initialDelay: Long?) :
    CoroutineScope {
    private val job = Job()

    private val singleThreadExecutor = Executors.newSingleThreadExecutor()

    override val coroutineContext: CoroutineContext
        get() = job + singleThreadExecutor.asCoroutineDispatcher()


    fun stop() {
        job.cancel()
        singleThreadExecutor.shutdown()
    }

    fun start() = launch {
        initialDelay?.let {
            delay(it)
        }
        while (isActive) {
            service.produce()
            delay(interval)
        }
        println("coroutine done")
    }
}

否则，Java并发API也非常可靠：

class NotificationProducerSchedulerJavaScheduler(
    val service: NotificationProducer,
    val interval: Long,
    val initialDelay: Long = 0
) {

    private val scheduler = Executors.newScheduledThreadPool(1)
    private val task = Runnable { service.produce() }

    fun stop() {
        scheduler.shutdown()
    }

    fun start() {
        scheduler.scheduleWithFixedDelay(task, initialDelay, interval, TimeUnit.MILLISECONDS)
    }
}

Kotlin中的异步预定作业

2 个答案: