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kotlin协程并发/并行与串行互相切换，CoroutineScope与await

news 2025/6/26 10:10:06

import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")CoroutineScope(Dispatchers.Default).launch {// 并发执行this.launch {println("${LocalTime.now()} A start")delay(1000)println("${LocalTime.now()} A end")}this.launch {println("${LocalTime.now()} B start")delay(1500)println("${LocalTime.now()} B end")}}println("${LocalTime.now()} - main end")
}

输出表明main退出后，A,B均没有输出。CoroutineScope(Dispatchers.IO).launch新起的任务不阻塞主main任务执行流程。

如果换成runBlocking(Dispatchers.IO)：

import kotlinx.coroutines.*
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")runBlocking(Dispatchers.IO) {// 并发执行this.launch {println("${LocalTime.now()} A start")delay(1000)println("${LocalTime.now()} A end")}this.launch {println("${LocalTime.now()} B start")delay(1500)println("${LocalTime.now()} B end")}}println("${LocalTime.now()} - main end")
}

看一下async

import kotlinx.coroutines.*
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")CoroutineScope(Dispatchers.IO).launch() {// 并发执行this.async {println("${LocalTime.now()} A start")delay(1000)println("${LocalTime.now()} A end")}this.async {println("${LocalTime.now()} B start")delay(1500)println("${LocalTime.now()} B end")}}println("${LocalTime.now()} - main end")
}

如果main线程休息1000ms:

import kotlinx.coroutines.*
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")CoroutineScope(Dispatchers.IO).launch() {// 并发执行this.async {println("${LocalTime.now()} A start")delay(1000)println("${LocalTime.now()} A end")}this.async {println("${LocalTime.now()} B start")delay(1500)println("${LocalTime.now()} B end")}}Thread.sleep(1000)println("${LocalTime.now()} - main end")
}

import kotlinx.coroutines.*
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")runBlocking {CoroutineScope(Dispatchers.IO).launch() {val task1 = this.async {println("${LocalTime.now()} A start")delay(1000)println("${LocalTime.now()} A end")"task1 return"}val task2 = this.async {println("${LocalTime.now()} B start")delay(1500)println("${LocalTime.now()} B end")"task2 return"}val t1 = task1.await()println("${LocalTime.now()} $t1")val t2 = task2.await()println("${LocalTime.now()} $t2")}}println("${LocalTime.now()} - main end")
}

总体上CoroutineScope(Dispatchers.IO).launch()的意义在于新起一个线程，不阻塞主main线程，由于

理解await

import kotlinx.coroutines.*
import java.time.LocalTimefun main(args: Array<String>) {println("${LocalTime.now()} - main start")runBlocking {//launch() {val task1 = this.async {println("${LocalTime.now()} A start")delay(3000)println("${LocalTime.now()} A end")"task1 return"}val task2 = this.async {println("${LocalTime.now()} B start")delay(1000)println("${LocalTime.now()} B end")"task2 return"}val t1 = task1.await()println("${LocalTime.now()} $t1")val t2 = task2.await()println("${LocalTime.now()} $t2")//}}println("${LocalTime.now()} - main end")
}

虽然task2很快就完成，因为await，所以必须等待task1返回。

kotlin协程async与await_zhangphil的博客-CSDN博客runBlocking 内部启动的3个协程做耗时操作，从输出可以看到3个协程交叉并发执行，runBlocking 会等到3个协程执行结束后才退出，输出结果有明确先后顺序。一般编程的技法，比如，在Android中，假设在主线程中实现了一个函数，但该函数是耗时操作，毫无疑问，需要将这个函数的实现切入非主线程中操作，那么可以设计一种托管的函数，在托管的函数里面干脏活，处理完成后，把结果抛到主线程。结果1-a: 5 - tid:22。结果1-b: 5 - tid:24。结果2-a: 9 - tid:22。https://blog.csdn.net/zhangphil/article/details/129268399

https://zhangphil.blog.csdn.net/article/details/129265638https://zhangphil.blog.csdn.net/article/details/129265638

kotlin协程、线程切换，函数方法委托_zhangphil的博客-CSDN博客runBlocking 内部启动的3个协程做耗时操作，从输出可以看到3个协程交叉并发执行，runBlocking 会等到3个协程执行结束后才退出，输出结果有明确先后顺序。一般编程的技法，比如，在Android中，假设在主线程中实现了一个函数，但该函数是耗时操作，毫无疑问，需要将这个函数的实现切入非主线程中操作，那么可以设计一种托管的函数，在托管的函数里面干脏活，处理完成后，把结果抛到主线程。结果1-a: 5 - tid:22。结果1-b: 5 - tid:24。结果2-a: 9 - tid:22。https://blog.csdn.net/zhangphil/article/details/130161705

https://zhangphil.blog.csdn.net/article/details/129250518https://zhangphil.blog.csdn.net/article/details/129250518

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