Android 协程 异常捕获 异常的传播特性

    @Test
    fun `test exception propagation`() = runBlocking<Unit> {
        val job = GlobalScope.launch {
            try {
                throw IndexOutOfBoundsException()
            } catch (e: Exception) {
                println("Caught: ${e}}")
            }
        }
        job.join()
        val deferred = GlobalScope.async {
            throw ArithmeticException()
        }
        try {
            deferred.await()
        } catch (e: Exception) {
            println("Caught: ${e}}")
        }
 
        delay(1000)
 
    }

launch的异常是再方法体里面 无论是否执行 

 job.join()

都会报错/

而async的异常则是需要在await的时候才会抛出来

不执行则不会抛出来异常

  @Test
    fun `test exception propagation2`() = runBlocking<Unit> {
        val scope = CoroutineScope(Job())
        val job = scope.launch {
            //非根协程的异常 launch就会立即抛出异常
            async {
                throw IllegalArgumentException()
            }
        }
        job.join()
 
    }

 异常的传播特性

当一个协程由于一个异常而运行失败时，它会传播这个异常并传递给他的父级。接下来，

父级会

1、取消它自己的子级

2、取消它自己

3、将异常传播并传递给它的父级

很对情况下这不是我们想要的 可以是用

SupervisorJob

   @Test
    fun `test SupervisorJob`() = runBlocking<Unit> {
        val supervisor = CoroutineScope(SupervisorJob())
        val job1 = supervisor.launch {
            delay(1000)
            println("child 1")
            throw IllegalArgumentException()
        }
 
        val job2 = supervisor.launch {
            try {
                delay(Long.MAX_VALUE)
            } finally {
                println("child 2 finished")
            }
        }
        joinAll(job1, job2)
 
 
    }

 这是一个进行中的状态。程序依然在执行

这说明他不会影响它的child协程的执行

换成Job后

  val supervisor = CoroutineScope(Job())

 程序会执行结束。 和我们上面说的生命周期一样。

也可以是用

supervisorScope 效果是和SupervisorJob 一样的

    @Test
    fun `test SupervisorScope`() = runBlocking<Unit> {
        supervisorScope {
            launch {
                delay(1000)
                println("child 1")
                throw IllegalArgumentException()
            }
 
            launch {
                try {
                    delay(Long.MAX_VALUE)
                } finally {
                    println("child 2 finished")
                }
            }
 
 
        }
 
 
    }

但是如果父协程的抛出了异常。子协程也会跟着退出

 @Test
    fun `test SupervisorScope2`() = runBlocking<Unit> {
        supervisorScope {
            try {
                val child = launch {
                    println("The child is sleeping")
                    delay(Long.MAX_VALUE)
                }
            } finally {
                println("The child is over")
 
            }
            yield()
            println("Throwing an exception from the scope")
            throw AssertionError()
 
 
        }
 
 
    }

 捕获的异常的时机与位置

 

 @Test
    fun `test CoroutineExceptionHandler`() = runBlocking<Unit> {
        val coroutineExceptionHandler = CoroutineExceptionHandler { _, exception ->
            println("Caught $exception")
        }
        val job1 = GlobalScope.launch(coroutineExceptionHandler) {
            throw AssertionError()
        }
        val job2 = GlobalScope.async(coroutineExceptionHandler) {
            throw ArithmeticException()
        }
        job1.join()
        job2.await()
 
    }

 

  @Test
    fun `test CoroutineExceptionHandler2`() = runBlocking<Unit> {
        val coroutineExceptionHandler = CoroutineExceptionHandler { _, exception ->
            println("Caught $exception")
        }
        val scope = CoroutineScope(Job())
        val job = scope.launch(coroutineExceptionHandler) {
            launch {
                throw IllegalArgumentException()
            }
        }
        job.join()
 
    }
 
    @Test
    fun `test CoroutineExceptionHandler3`() = runBlocking<Unit> {
        val coroutineExceptionHandler = CoroutineExceptionHandler { _, exception ->
            println("Caught $exception")
        }
        val scope = CoroutineScope(Job())
        val job = scope.launch() {
            launch(coroutineExceptionHandler) {
                throw IllegalArgumentException()
            }
        }
        job.join()
 
    }

test CoroutineExceptionHandler2的异常是可以捕获到的

test CoroutineExceptionHandler3的异常是捕获不到的。内部是不行的外部可以。