Android 的任务队列 - Kotlin

Question

I want to add Tasks (or Runnable) in queue that I want to execute in series. New task comes in at run time, depending on conditions. I also want to add a delay after each task before it starts the next one.

For example: I am downloading a file, and user taps another file to download. Now I dont want it to start in parallel. I want it to start only after first file is downloaded.

What would be the best way to do it in Kotlin for Android?

Answer 1

The following does what you are asking for:

fun main() {
    val delay = { millis:Long ->  Runnable { println("delay..."); Thread.sleep(millis) } }
    val r1 = Runnable { println("r1") }
    val r2 = Runnable { println("r2") }
    val r3 = Runnable { println("r3") }

    val queue: List<Runnable> = listOf(r1, delay(1_000), r2, delay(2_000), r3)
    
    thread {
        queue.forEach { it.run() }
    }

    // alternatively, if you have an ExecutorService:
    // 
    // executorService.execute { queue.forEach { it.run() } }
}

prints:

r1
delay...
r2
delay...
r3