subscribeOn(Schedulers.io())不工作，但subscribeOn(Schedulers.trampoline())工作

Question

fun main() {
    Single.just("faefw")
        .subscribeOn(Schedulers.trampoline())
        .map {
            println("map in thread ${Thread.currentThread().name}")
        }
        .flatMap {
            return@flatMap Single.just(231).map {
                println("map in thread ${Thread.currentThread().name}")
                return@map it
            }
        }
        .subscribe({
            println(it)
        }, {
            println(it)
        })
}

打印输出：

map in thread main
map in thread main
231

但

fun main() {
    Single.just("faefw")
        .subscribeOn(Schedulers.io())
        .map {
            println("map in thread ${Thread.currentThread().name}")
        }
        .flatMap {
            return@flatMap Single.just(231).map {
                println("map in thread ${Thread.currentThread().name}")
                return@map it
            }
        }
        .subscribe({
            println(it)
        }, {
            println(it)
        })
}

不输出任何内容！

subscribeOn(Schedulers.computation())和subscribeOn(Schedulers.newThread())也不起作用

为什么？

Answer 1

程序在代码有时间执行之前就退出了。尝试在subscribe之后使用睡眠或put in语句

fun main() {
    Single.just("faefw")
        .subscribeOn(Schedulers.io())
        .map {
            println("map in thread ${Thread.currentThread().name}")
        }
        .flatMap {
            return@flatMap Single.just(231).map {
                println("map in thread ${Thread.currentThread().name}")
                return@map it
            }
        }
        .subscribe({
            println(it)
        }, {
            println(it)
        })
    println("just subscribed in last statement!")
    Thread.sleep(500)
    println("exiting main thread...")
}

使用trampoline时，输出为

map in thread main
map in thread main
231
just subscribed in last statement!
exiting main thread...

对于在不同线程中执行“工作”的其他调度器(如.io()和.computation())，输出将如下所示：

just subscribed in last statement!
map in thread RxComputationThreadPool-1
map in thread RxComputationThreadPool-1
231
exiting main thread...

PS。您可以将io()调度器视为无界线程池，将computation()视为有界线程池。