kotlin协程flow retry功能函数返回失败后重试（4）

阳光穿透心脏的1/2处 2023-09-25 23:29 16阅读 0赞

## kotlin协程flow retry功能函数返回失败后重试（4） ##

import kotlinx.coroutines.delay
    import kotlinx.coroutines.flow.*
    import kotlinx.coroutines.runBlocking
    
    fun main(args: Array<String>) {
        var count = 0 //重试计数
    
        runBlocking {
            load().onEach {
                if (it == null) {
                    throw NullPointerException()
                } else {
                    println("获取数据 $it")
                }
            }.retry(3) { //重试3次
                println("retry ${count++}")
    
                delay(1000) //延时重试
    
                if (it is NullPointerException)
                //为空时重试
                    true
                else
                    false
            }.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") }
                .collect { println("collect $it") }
        }
    }
    
    fun load() = flow {
        //生成一个概率布尔，模拟加载概率性成功与失败
        var b = Boolean.let {
            var p: Int = (Math.random() * 10).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")
        }
    
        emit(s)
    }

初次加载失败，重试一次成功：

> 加载失败  
> retry 0  
> 加载成功  
> 获取数据 fly  
> collect fly  
> onCompletion

初次加载即成功：

> 加载成功  
> 获取数据 fly  
> collect fly  
> onCompletion

初次加载失败，重试两次成功

> 加载失败  
> retry 0  
> 加载失败  
> retry 1  
> 加载成功  
> 获取数据 fly  
> collect fly  
> onCompletion

[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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