【Koltin Flow（一）】五种创建flow的方式

前言

1. flow 是序列的异步版本，这是一种收集类型，其中的值是逐个生成的。与序列一样，只有需要某个值时，flow 才会根据需要生成该值，而且 flow 可以包含无限数量的值。
2. 简单来说就是流式处理，用过Rx的会比较容易理解。
3. flow通过api和协程支持，处理响应式编程更方便。

创建方式

创建方式1 flow{}

代码如下

		flow {
    
              repeat(10){
    
                    delay(10)
                    emit(it)
                }
            }.collect {
    
                Log.d(TAG.TAG,"method 1 it is $it")
            }

日志如下：

2022-07-28 17:05:01.070 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 0
2022-07-28 17:05:01.080 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 1
2022-07-28 17:05:01.091 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 2
2022-07-28 17:05:01.106 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 3
2022-07-28 17:05:01.130 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 4
2022-07-28 17:05:01.140 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 5
2022-07-28 17:05:01.153 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 6
2022-07-28 17:05:01.163 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 7
2022-07-28 17:05:01.174 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 8
2022-07-28 17:05:01.186 3699-3724/edu.test.demo D/Test-TAG: method 1 it is 9

创建方式2 flowof

代码如下

            flowOf(1,2,3,4,5).collect {
    
                Log.d(TAG.TAG,"method 2 it is $it")
            }

日志如下：

2022-07-28 17:05:01.187 3699-3724/edu.test.demo D/Test-TAG: method 2 it is 1
2022-07-28 17:05:01.187 3699-3724/edu.test.demo D/Test-TAG: method 2 it is 2
2022-07-28 17:05:01.187 3699-3724/edu.test.demo D/Test-TAG: method 2 it is 3
2022-07-28 17:05:01.187 3699-3724/edu.test.demo D/Test-TAG: method 2 it is 4
2022-07-28 17:05:01.187 3699-3724/edu.test.demo D/Test-TAG: method 2 it is 5

创建方式3 asFlow

代码如下

    listOf(6,7,8,9,10).asFlow().collect {
    
                Log.d(TAG.TAG,"method 3 it is $it")
            }

日志如下：

2022-07-28 17:05:01.204 3699-3724/edu.test.demo D/Test-TAG: method 3 it is 6
2022-07-28 17:05:01.204 3699-3724/edu.test.demo D/Test-TAG: method 3 it is 7
2022-07-28 17:05:01.204 3699-3724/edu.test.demo D/Test-TAG: method 3 it is 8
2022-07-28 17:05:01.204 3699-3724/edu.test.demo D/Test-TAG: method 3 it is 9
2022-07-28 17:05:01.204 3699-3724/edu.test.demo D/Test-TAG: method 3 it is 10

创建方式4 channelFlow{}

代码如下

	channelFlow {
    
                repeat(10){
    
                    delay(10)
                    send(it)
                }
            }.collect {
    
                Log.d(TAG.TAG,"method 4 it is $it")
            }

日志如下：

2022-07-28 17:05:01.227 3699-3724/edu.test.demo D/Test-TAG: method 4 it is 0
2022-07-28 17:05:01.238 3699-3724/edu.test.demo D/Test-TAG: method 4 it is 1
2022-07-28 17:05:01.250 3699-3724/edu.test.demo D/Test-TAG: method 4 it is 2
2022-07-28 17:05:01.260 3699-3724/edu.test.demo D/Test-TAG: method 4 it is 3
2022-07-28 17:05:01.272 3699-3725/edu.test.demo D/Test-TAG: method 4 it is 4
2022-07-28 17:05:01.284 3699-3725/edu.test.demo D/Test-TAG: method 4 it is 5
2022-07-28 17:05:01.295 3699-3725/edu.test.demo D/Test-TAG: method 4 it is 6
2022-07-28 17:05:01.306 3699-3725/edu.test.demo D/Test-TAG: method 4 it is 7
2022-07-28 17:05:01.317 3699-3725/edu.test.demo D/Test-TAG: method 4 it is 8
2022-07-28 17:05:01.329 3699-3724/edu.test.demo D/Test-TAG: method 4 it is 9

创建方式5 callbackFlow{}

代码如下

 callbackFlow<String> {
    
                delay(100)
                trySendBlocking("123456")
                awaitClose {
      }
            }.collect {
    
                Log.d(TAG.TAG,"method 5 it is $it")
            }

日志如下：

2022-07-28 17:05:01.438 3699-3724/edu.test.demo D/Test-TAG: method 5 it is 123456

总结

本篇主要介绍flow的基础创建部分，介绍了五种方式，因为内容比较简单，介绍比较少，直接上代码也比较好理解。