Kotlin_version ='1.2.41'
我对Kotlin很陌生。我想知道async
和launch
有什么区别。特别是在以下代码中
import kotlinx.coroutines.experimental.async
import kotlinx.coroutines.experimental.awaitAll
import kotlinx.coroutines.experimental.delay
import kotlinx.coroutines.experimental.launch
import kotlinx.coroutines.experimental.runBlocking
fun main(args: Array<String>) {
runBlocking {
(20..30).forEach {
launch{
println("main before" + it)
val outer = it
delay(1000L)
val lists = (1..10)
.map { async{anotherMethod(outer, it)}}
println("main after------------------Awaiting" + it)
lists.awaitAll()
println("Done awaiting -main after-----------------" + it)
}
}
println("Hello,") // main thread continues here immediately
}
}
。
suspend fun anotherMethod (outer: Int,index: Int){
println("inner-b4----" + outer + "--" + index)
delay(3000L)
println("inner-After----" + outer + "--" + index)
}
Vs
fun main(args: Array<String>) {
runBlocking {
(20..30).forEach {
async{
println("main before" + it)
val outer = it
delay(1000L)
val lists = (1..10)
.map { async{anotherMethod(outer, it)}}
println("main after------------------Awaiting" + it)
lists.awaitAll()
println("Done awaiting -main after-----------------" + it)
}
}
println("Hello,") // main thread continues here immediately
}
}
suspend fun anotherMethod (outer: Int,index: Int){
println("inner-b4----" + outer + "--" + index)
delay(3000L)
println("inner-After----" + outer + "--" + index)
}
答案 0 :(得分:5)
async
确实返回了Deferred<>
,而launch
只返回了Job
,两者都启动了一个新的协程。因此,这取决于您是否需要返回值。
在您的第一个示例中,launch
不返回值-最后一个println
仅产生一个Unit
。如果在第二个示例中使用async
,则总体结果将相同,但是创建了一些无用的Deferred<Unit>
对象。