我的目标是能够使用Java中的Kotlin的Coroutine系统.我希望能够在给定的时间内暂停执行中期,然后在给定的时间过后在该位置进行备份.从Java开始,我希望能够执行允许暂停执行中的任务,而不是以异步方式执行,例如：

//example 1
someLogic();
pause(3000L); //3 seconds
someMoreLogic();

//example 2
while(true) {
    someContinuedLogic();
    pause(10000L); //10 seconds
}

我的问题是什么？

正如预期的那样,我能够完全从Kotlin执行协同程序,但是当谈到Java时,它变得棘手,因为代码的Java部分立即执行整个块而没有任何暂停,而Kotlin块正确地暂停1,并且然后4秒.

我的问题是什么？

甚至可以使用Kotlin作为Java协程的主干吗？如果是这样,我做错了什么？下面你可以找到源代码,展示我如何尝试在Java中使用Kotlin的协同程序.

KtScript类

abstract class KtScript {

    abstract fun execute()

    fun <T> async(block: suspend () -> T): CompletableFuture<T> {
        val future = CompletableFuture<T>()
        block.startCoroutine(completion = object : Continuation<T> {
            override fun resume(value: T) {
                future.complete(value)
            }
            override fun resumeWithException(exception: Throwable) {
                future.completeExceptionally(exception)
            }
        })
        return future
    }

    suspend fun <T> await(f: CompletableFuture<T>): T =
            suspendCoroutine { c: Continuation<T> ->
                f.whenComplete { result,exception ->
                    if (exception == null)
                        c.resume(result)
                    else
                        c.resumeWithException(exception)
                }
            }

    fun pause(ms: Long): CompletableFuture<*> {
        //todo - a better pausing system (this is just temporary!)
        return CompletableFuture.runAsync {
            val currentMs = System.currentTimeMillis()
            while (System.currentTimeMillis() - currentMs < ms) {
                /* do nothing */
            }
        }
    }

}

Kotlin执行代码

fun main(args: Array<String>) {
    ScriptTestKotlin().execute()
}

class ScriptTestKotlin : KtScript() {
    override fun execute() {
        println("Executing Kotlin script from Kotlin...")
        val future = async {
            await(pause(1000L))
            println("   1 second passed...")
            await(pause(4000L))
            println("   5 seconds passed...")
        }
        future.get() //wait for asynchronous task to finish
        println("Finished!")
    }
}

Kotlin执行结果

Executing Kotlin script from Kotlin...
   1 second passed...
   5 seconds passed...
Finished!

Java执行代码

public class ScriptTestJava extends KtScript {

    public static void main(String[] args) {
        new ScriptTestJava().execute();
    }

    @Override
    public void execute() {
        System.out.println("Executing Kotlin script from Java...");
        CompletableFuture<?> future = async(continuation -> {
            await(pause(1000L),continuation);
            System.out.println("    1 second passed...");
            await(pause(4000L),continuation);
            System.out.println("    5 seconds passed...");
            return continuation;
        });
        try {
            future.get(); //wait for asynchronous task to finish
        } catch(Exception e) {
            e.printStackTrace();
        }
        System.out.println("Finished!");
    }
}

Java执行结果

Executing Kotlin script from Java...
    1 second passed...
    5 seconds passed...
Finished!

^^^不幸的是,在Java中跳过了暂停. ^^^