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Kotlin try catch异常处理i详解

开发者 https://www.devze.com 2022-11-28 12:47 出处:网络 作者: 且听真言
目录一、cancel()无效1.cancel()不被响应2.结构被破坏3.未正确处理CancellationException二、try-catch不起作用三、SupervisorJob四、Coro...
目录
  • 一、cancel()无效
    • 1.cancel()不被响应
    • 2.结构被破坏
    • 3.未正确处理 CancellationException
  • 二、try-catch不起作用
    • 三、SupervisorJob
      • 四、CoroutineExceptandroidionHandler

        一、cancel()无效

        当协程任务被取消的时候,它的内部是会产生一个 CancellationException 的。而协程的结构化并发,最大的优势就在于:如果我们取消了父协程,子协程也会跟着被取消。

        1.cancel()不被响应

              val job = launch(Dispatchers.Default) {
                    var i = 0
                    while (true) {
                        Thread.sleep(500L)
                        i++
                        println("i =$i")
                    }
                }
                delay(2000L)
                job.cancel()
                job.join()
                println("END")
            }
        Log

        i =1

        i =2

        i =3

        i =4

        i =5

        i =6

        i =7

        i =8

        i =9

        i =10

        i =11

        i =12

        ......

        程序无法停止

        上面的程序无法停止,协程任务的取消,需要互相协作。协程外部取消,协程内部需要做出响应才行。当我们调用 job.cancel() 以后,协程任务已经不是活跃状态了,但代码并没有把 isActive 作为循环条件,因此协程无法真正取消。

        可以在协程体中加入状态判断:

         runblocking {
                val job = launch(Dispatchers.Default) {
                    var i = 0
                    while (isActive) {
                        Thread.sleep(500L)
                        i++
                        println("i =$i")
                    }
                }
                delay(2000L)
                job.cancel()
                job.join()
                println("END")
            }

        Log

         

        i =1

        i =2

        i =3

        i =4

        END

         

        Process finished with exit code 0

        把 while 循环的条件改成了 while (isActive),这就意味着,只有协程处于活跃状态的时候,才会继续执行循环体内部的代码。协程的取消需要内部的配合。

        2.结构被破坏

        协程是结构化的,当我们取消父协程的时候,子协程也会跟着被取消。

        但是特殊情况是嵌套创建的子协程并不会跟随父协程一起取消。

         runBlocking {
                val parentJob = launch(fixedDispatcher) {
                    launch(Job()) {
                        var i = 0
                        while (isActive) {
                            Thread.sleep(500L)
                            i++
                            println("First i:$i")
                        }
                    }
                    launch {
                        var i = 0
                        while (isActive) {
                            Thread.sleep(500L)
                            i++
                            println("Second i:$i")
                        }
                    }
                }
                delay(2000L)
                parentJob.cancel()
                parentJob.join()
                println("End")
            }

        Log

         

        Second i:1

        First i:1

        First i:2

        Second i:2

        Second i:3

        First i:3

        Second i:4

        First i:4

        End

        First i:5

        First i:6

        First i:7

        First i:8

        First i:9

        First i:10

        First i:11

        First i:12

        First i:13

        First i:14

        First i:15

        ......

        可以发现,创建子协程的时候,使用了 launch(Job()){},就打破了原有的协程结构。因为 launch(Job()){}创建的协程的父 Job 是在 launch 当中传入的 Job() 对象。所以调用 parentJob.cancel() 的时候,无法销毁该协程。

        可以按如下修改:

         runBlocking {
                val parentJob = launch(fixedDispatcher) {
                    launch {
                        var i = 0
                        while (isActive) {
                            Thread.sleep(500L)
                            i++
                            println("First i:$i")
                        }
                    }
                    launch {
                        var i = 0
                        while (isActive) {
                            Thread.sleep(500L)
                            i++
                            println("Second i:$i")
                        }
                    }
                }
                delay(2000L)
                parentJob.cancel()
                parentJob.join()
                println("End")
            }

        First i:1

        Second i:1

        First i:2

        Second i:2

        First i:3

        Second i:3

        First i:4

        Second i:4

        End

        parentJob 与它内部的子协程之间都是父子关系,因此它们两个都是会响应协程取消的事件的。不要轻易打破协程的父子结构!

        3.未正确处理 CancellationException

        对于 Kotlin 提供的挂起函数,可以自动响应协程的取消。

        例如:

            runBlocking {
                val parentJob = launch(Dispatchers.Default) {
                    launch {
                        var i = 0
                        while (true) {
                            delay(500L)
                            i++
                            println("First i = $i")
                        }
                    }
                    launch {
                        var i = 0
                        while (true) {
                            delay(500L)
                            i++
                            println("Second i = $i")
                        }
                    }
                }
                delay(2000L)
                parentJob.cancel()
                parentJob.join()
                println("End")
            }
        

        First i = 1

        Second i = 1

        First i = 2

        Second i = 2

        First i = 3

        Second i = 3

        End

         

        Process finished with exit code 0

        delay() 函数可以自动检测当前的协程是否已经被取消,如果已经被取消的话,它会抛出一个 CancellationException,从而终止当前的协程。

        runBlocking {
                val parentJob = launch(Dispatchers.Default) {
                    launch {
                        var i = 0
                        while (true) {
                            try {
                                delay(500L)
                            } catch (e: CancellationException) {
                                println("Catch CancellationException")
                                throw e
                            }
                            i++
                            println("First i =$i")
                        }
                    }
                    launch {
                        var i = 0
                        while (true) {
                            delay(500L)
                            i++
                            println("Second i = $i")
                        }
                    }
                }
                delay(2000L)
                parentJob.cancel()
                parentJob.join()
                println("END")
            }

        Log:

         

        First i =1

        Second i = 1

        First i =2

        Second i = 2

        First i =3

        Second i = 3

        Catch CancellationException

        END

         

        Process finished with exit code 0

        try-catch 包裹了 delay() 以后,打印出“Catch CancellationException”,这就说明 delay() 确实可以自动响应协程的取消,并且产生 CancellationException 异常。

        注意:捕获了 CancellationException 以后没有重新抛出去,就导致子协程无法正常取消。

        runBlocking {
                val parentJob = launch(Dispatchers.Default) {
                    launch {
                        var i = 0
                        while (true) {
                            try {
                                delay(500L)
                            } catch (e: CancellationException) {
                                println("Catch CancellationException")
                                //throw e
                            }
                            i++
                            println("First i =$i")
                        }
                    }
                    launch {
                        var i = 0
                        while (true) {
                            delay(500L)
                            i++
                            println("Second i = $i")
                        }
                    }
                }
                delay(2000L)
                parentJob.cancel()
                parentJob.join()
                println("END")
            }
        

        ......

        First i =656179

        Catch CancellationException

        First i =656180

        Catch CancellationException

        First i =656181

        Catch CancellationException

        First i =656182

        Catch CancellationException

        First i =656183

        Catch CancellationException

        .....

        所以,捕获了 CancellationException 以后,要考虑是否应该重新抛出来。

        二、try-catch不起作用

        runBlocking {
                try {
                    launch {
                        delay(100L)
                        1 / 0
                    }
                } catch (e: Exception) {
                    println("catch: $e")
                }
                delay(500L)
                println("End")
            }

        Log

        Exception in thread "main" Java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch8$1$1.invokeSuspend(TestTryCatch.kt:225)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

            at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch8(TestTryCatch.kt:221)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:15)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

        Process finished with exit code 1

        可以发现:try-catch 并没有成功捕获异常,程序等待了 100 毫秒左右,最终还是崩溃了。

        使用async

        runBlocking {
                var deffered: Deferred<Any>? = null
                try {
                    deffered = async {
                        delay(100L)
                        1 / 0
                    }
                } catch (e: ArithmeticException) {
                    println("Catch:$e")
                }
                deffered?.await()
                println("End")
            }
        

        Exception in thread "main" java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch9$1$1.invokeSuspend(TestTryCatch.kt:242)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

            at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch9(TestTryCatch.kt:237)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:16)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

        Process finished with exit code 1

        当协程体当中的“1/0”执行的时候,程序已经跳出 try-catch 的作用域了,所以 try-catch失效。

        把 try-catch 挪到 launch{} 协程体内部。可以正常捕获到 ArithmeticException 这个异常了。

        runBlocking {
                var deffered: Deferred<Any>? = null
                deffered = async {
                    try {
                        delay(100L)
                        1 / 0
                    } catch (e: ArithmeticException) {
                        println("Catch:$e")
                    }
                }
                deffered.await()
                println("End")
            }

        Log

         

        Catch:java.lang.ArithmeticException: / by zero

        End

         

        Process finished with exit code 0

        注意:不要用 try-catch 直接包裹 launch、async。

        使用 try-catch 包裹“deferred.await()”。

        例:

        runBlocking {
                var deffered = async {
                    delay(100L)
                    1 / 0
                }
                try {
                    deffered.await()
                } catch (e: Exception) {
                    println("Catch:$e")
                }
                println("End")
            }

        atch:java.lang.ArithmeticException: / by zero

        End

        Exception in thread "main" java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch11$1$deffered$1.invokeSuspend(TestTryCatch.kt:275)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

            at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch11(TestTryCatch.kt:272)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:16)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

         

        Process finished with exit code 1

        await() 如果不调用的话,async 当中的异常是否编程发生?

        runBlocking {
                var deffered = async {
                    delay(100L)
                    1 / 0
                }
                delay(500L)
                println("End")
            }

        Exception in thread "main" java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch12$1$deffered$1.invokeSuspend(TestTryCatch.kt:290)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

            at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch12(TestTrphpyCatch.kt:287)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:16)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

         

        Process finished with exit code 1

        可见,async 当中产生异常,即使不调用 await() 同样是会导致程序崩溃的。

        三、SupervisorJob

        使用 try-catch 包裹“deferred.await()”,需要配合 SupervisorJob 一起使用。实现“不调用 await() 就不会产生异常而崩溃”。

        unBlocking {
                val scope = CoroutineScope(SupervisorJob())
                scope.async {
                    delay(100L)
                    1 / 0
                }
                delay(开发者_Go入门500L)
                println("End")
            }

        Log

         

        End

         

        Process finished with exit code 0

        使用 SupervisorJob 创建一个 scope 以后,用 scope.async{}启动协程后,只要不调用“deferred.await()”,程序就不会因为异常而崩溃。

          runBlocking {
                val coroutineScope = CoroutineScope(SupervisorJob())
                val deferred = coroutineScope.async {
                    delay(100L)
                    1 / 0
                }
                try {
                    deferred.await()
                } catch (e: Exception) {
                    println("Catch:$e")
                }
                delay(500L)
                println("End")
            }

        Log

        Catch:java.lang.ArithmeticException: / by zero

        End

         

        Process finished with exit code 0

        使用“coroutineScope.async {}”创建了协程,同时也用 try-catch 包裹“deferred.await()”,这样一来,异常就成功地被捕获了。

        public fun SupervisorJob(parent: Job? = null) : CompletableJob 
                            = SupervisorJobImpl(parent)
        public interface CompletableJob : Job {
            public fun complete(): Boolean
            public fun completeExceptionally(exception: Throwable): Boolean
        }

        SupervisorJob() 不是构造函数,它只是一个普通的顶层函数。这个方法返回的对象,是 Job 的子类。SupervisorJob 与 Job 最大的区别就在于,当它的子 Job 发生异常的时候,其他的子 Job 不会受到牵连。

        对于普通 Job, 出现异常时的应对策略是:由于 parentJob 是一个普通的 Job 对象,当 job1 发生异常之后,它会导致 parentJob 取消,进而导致 job2、job3 也受到牵连。

        如果把 parentJob 改为 SupervisorJob,job1 发生异常的的话,就不会影响到其他的 Job 了。

        注意:灵活使用 SupervisorJob,控制异常传播的范围。

        四、CoroutineExceptionHandler

        runBlocking {
                val coroutineScope = CoroutineScope(coroutineContext)
                coroutineScope.launch {
                    async {
                        delay(100L)
                    }
                    launch {
                        delay(100L)
                        1/0
                    }
                }
                delay(1000L)
                println("END")
            }

        Exception in thread "main" java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch15$1$1$2.invokeSuspend(TestTryCatch.kt:338)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

         &nbPqXsniZBjsp;  at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch15(TestTryCatch.kt:329)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:16)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

         

        Process finished with exit code 1

        使用CoroutineExceptionHandler处理上述代码中的异常。

          runBlocking {
                val coroutineExceptionHandler = CoroutineExceptionHandler { _, throwable ->
                    print编程客栈ln("Catch: $throwable")
                }
                val coroutineScope = CoroutineScope(coroutineContext + Job() + coroutineExceptionHandler)
                coroutineScope.launch {
                    async {
                        delay(100L)
                    }
                    launch {
                        delay(100L)
                        1 / 0
                    }
                }
                delay(1000L)
                println("END")
            }

        Log

        Catch: java.lang.ArithmeticException: / by zero

        END

         

        Process finished with exit code 0

        定义了一个 CoroutineExceptionHandler,然后把它传入了 scope 当中,就可以捕获其中所有的异常了。

        注意点:在特定场景,为什么 CoroutineExceptionHandler 不起作用?

        runBlocking {
                val coroutineExceptionHandler = CoroutineExceptionHandler { _, throwable ->
                    println("Catch: $throwable")
                }
                val coroutineScope = CoroutineScope(coroutineContext)
                coroutineScope.launch {
                    async {
                        delay(100L)
                    }
                    launch(coroutineExceptionHandler) {
                        delay(100L)
                        1 / 0
                    }
                }
                delay(1000L)
                println("END")
            }

        Exception in thread "main" java.lang.ArithmeticException: / by zero

            at com.example.myapplication.testcoroutinue.TestTryCatchKt$testTryCatch17$1$1$2.invokeSuspend(TestTryCatch.kt:383)

            at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)

            at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:234)

            at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)

            at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)

            at kotlinx.coroutines.CancellableContinuationImpl.resumeUndispatched(CancellableContinuationImpl.kt:518)

            at kotlinx.coroutines.EventLoopImplBase$DelayedResumeTask.run(EventLoop.common.kt:494)

            at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:279)

            at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)

            at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)

            at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)

            at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.testTryCatch17(TestTryCatch.kt:371)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt:16)

            at com.example.myapplication.testcoroutinue.TestTryCatchKt.main(TestTryCatch.kt)

         

        Process finished with exit code 1

        把自定义的 myExceptionHandler,放到出现异常的 launch 那里传了进去。myExceptionHandler 并不会起作用,异常不会被它捕获。注意:myExceptionHandler 直接定义在发生异常的位置反而不生效,而定义在最顶层却可以生效。因为只在顶层的协程当中才会起作用。也就是说,当子协程当中出现异常以后,它们都会统一上报给顶层的父协程,然后顶层的父协程才会去调用 CoroutineExceptionHandler,来处理对应的异常。所以需要记住:使用 CoroutineExceptionHandler 处理复杂结构的协程异常,它仅在顶层协程中起作用。

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