kotlin协程flow任务意外结束未emit数据retryWhen onEmpty（5）

向右看齐 2023-09-25 23:52 31阅读 0赞

import kotlinx.coroutines.delay
    import kotlinx.coroutines.flow.*
    import kotlinx.coroutines.runBlocking
    import kotlinx.coroutines.withTimeoutOrNull
    
    fun main(args: Array<String>) {
        val MSG = "fly_error"
    
        runBlocking {
            load().onStart {
                println("---")
                println("onStart")
            }.onEach {
                if (it == null) {
                    throw Exception(MSG)
                } else {
                    println("获取数据 $it")
                }
            }.retryWhen { cause, attempt ->
                println("${cause.message}")
                println("retry ${attempt}")
                delay(100) //延时重试
    
                attempt < 3  //重试3次
            }.catch {
                it.printStackTrace() //如果重试3次仍失败，此次将抛出异常打印错误栈
            }.onCompletion {
                println("onCompletion")
            }.onEmpty {
                // flow完成但没有发射任何元素。
                // 可用onEmpty发射一些默认的空态值。
                println("onEmpty")
    
                emit("empty")
            }.collect {
                println("collect $it")
            }
        }
    }
    
    fun load() = flow {
        var time = 1000L
    
        withTimeoutOrNull(time) {
            //生成一个概率布尔，模拟加载概率性成功/失败
            var b = Boolean.let {
                var p: Int = (Math.random() * 100).toInt() % 2
                when (p) {
                    0 -> true
                    1 -> false
                    else -> false
                }
            }
    
            var s: String? = null
            if (b) {
                println("加载成功")
                s = "fly"
            } else {
                println("加载失败")
            }
    
            delay(time + 1) //模拟超时
    
            emit(s)
        }
    }

> \---  
> onStart  
> 加载失败  
> onCompletion  
> onEmpty  
> collect empty

[kotlin协程flow retry功能函数返回失败后重试（4）\_zhangphil的博客-CSDN博客一、flow ,emit,onCompletion,collect。kotlin协程flow retryWhen当功能函数加载失败后重试（3）\_zhangphil的博客-CSDN博客。kotlin协程flow retryWhen当功能函数加载失败后重试（3）加载一次失败，重试1次成功。kotlin协程flow retry retryWhen（2）\_zhangphil的博客-CSDN博客。kotlin协程flow retry retryWhen（2）二、retryWhen。初次加载失败，重试两次成功。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130093111][kotlin_flow retry_4_zhangphil_-CSDN_flow _emit_onCompletion_collect_kotlin_flow retryWhen_3_zhangphil_-CSDN_kotlin_flow retryWhen_3_1_kotlin_flow retry retryWhen_2_zhangphil_-CSDN_kotlin_flow retry retryWhen_2_retryWhen_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130093111][kotlin协程flow retryWhen当功能函数加载失败后重试（3）\_zhangphil的博客-CSDN博客kotlin协程flow retryWhen当功能函数加载失败后重试（3）加载一次失败，重试1次成功。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130092299][kotlin_flow retryWhen_3_zhangphil_-CSDN_kotlin_flow retryWhen_3_1_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130092299]

[kotlin协程flow retry retryWhen（2）\_zhangphil的博客-CSDN博客kotlin协程flow retry retryWhen（2）二、retryWhen。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130086523][kotlin_flow retry retryWhen_2_zhangphil_-CSDN_kotlin_flow retry retryWhen_2_retryWhen_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130086523]

[kotlin协程flow filter map flowOn zip combine（1）\_zhangphil的博客-CSDN博客一、flow ,emit,onCompletion,collect。四、map，重组改写数据。八、conflate 合并。九、debounce去重。二、函数作为flow。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130084723][kotlin_flow filter map flowOn zip combine_1_zhangphil_-CSDN_flow _emit_onCompletion_collect_map_conflate _debounce_flow_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130084723]

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