Kotlin协程-从暂停函数优雅地处理错误 [英] Kotlin coroutines - gracefully handling errors from suspend functions

问题描述

尝试使用从异步方法调用的暂停函数实现对错误的优雅处理，如何捕获由暂停方法引发的错误。

Trying to implement graceful handling of the errors with suspend functions that are called from async methods, How to catch the error thrown by a suspend method.

suspend fun findById(id: Long): User? {
    throw Exception("my exception") // intentionally throwing to simulate error situation.
    return userModel.findById(id) // IO, may throw an error
}

Caller件，使用IO线程启动

Caller piece, launching with IO thread

GlobalScope.launch(Dispatchers.IO) {
    try {

        var userAsync: Deferred<User?>? = null
        arguments?.getLong("id")?.let {
            userAsync = async { viewModel?.findById(it) } // async for efficiency as i've other async methods too.
        }

        val data = userAsync?.await()

        withContext(Dispatchers.Main) {
            user = data // data binding, populating UI fields of user
        }
    } catch (exception: Exception) {
        withContext(Dispatchers.Main) { fault(exception) }
    }
}

故障方法

private fun fault(exception: Exception) {
    Log.d("User", "fault: ${exception.localizedMessage}") // expecting output
}

当前运行时崩溃，想要实现错误的优雅处理。

Currently runtime is crashing, want to implement graceful handling of errors.

尝试2

尝试将尝试捕获放入异步块中，但它不喜欢它。

Tried placing try catch within the async block but it didn't like it.

var userAsync: Deferred<UserVO?>? = null
arguments?.getLong("id")?.let {
    userAsync = async {
        try {
            delegate?.findById(it)
        } catch (e: Exception) {
            print(e)
        }
    }
}

推荐答案

我将使用 CoroutineExceptionHandler 使协程正常失败：

I would use a CoroutineExceptionHandler to make your coroutines fail gracefully:

1）定义处理程序：

val exceptionHandler = CoroutineExceptionHandler { context, error ->
    // Do what you want with the error
    Log.d(TAG, error)
}

2）重构您的findById函数，使其在IO上下文中执行，并使您的ui代码成为主要安全对象：

suspend fun findById(id : Int) : User? = withContext(Dispatchers.IO){
    when(id){
        0 -> throw Exception("not valid")
        else -> return@withContext User(id)
    }
}

1. 在 MainScope 中启动您的工作（并因此更新ui），并传递exceptionHandler以启动协程生成器以捕获异常：

1. Launch your job within MainScope (and so update the ui), passing exceptionHandler to launch coroutine builder in order to catch the exception:

val exceptionHandler = CoroutineExceptionHandler { _, error ->
     // Do what you want with the error
    Log.d(TAG, error)
}

MainScope().launch(exceptionHandler) {
     val user = delegate?.findById(userId)
        user?.let {
            Timber.v(it.toString())
        }
}

这篇关于Kotlin协程-从暂停函数优雅地处理错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！