kotlin Channel的用法

channel相当于管道，协程间通信用。测试下：

private fun tsetChannel() {
        lifecycleScope.launch {
            val channel = Channel<Int>()
            launch {
                for (i in 1..5) {
                    Log.d("zxzx", "开始发送数据：$i")
                    channel.send(i)
                }
                channel.close()
            }
            for (i in channel) {
                Log.d("zxzx", "接收到数据：$i")
            }
//           Log.d("zxzx", "receive: ${channel.receive()}") // 抛异常： Channel was closed
        }
        Log.d("zxzx", "东风不与周郎便，铜雀春深锁二乔。")
    }

运行，打印：

ok. 一个协程在发数据，另一个协程接受到数据。

再测试下：

fun testProduceAndConsume() {
        GlobalScope.launch {
            val channel = Channel<Int>()

            val producer = GlobalScope.launch(Dispatchers.IO) {
                var i = 0
                while (true) {
                    if (channel.isClosedForReceive) {
                        Log.d("zxzx", "channel已关闭")
                        break
                    }
                    Log.d("zxzx", "生产者生产了：$i")
                    channel.send(i++)
                    delay(1000)
                }
            }

            val consumer = GlobalScope.launch {
                while (true) {
                    val element = channel.receive() // 没数据时会挂起等待数据
                    Log.d("zxzx", "消费者消费了: $element")
                    if (element == 10) {
                        channel.close()
                        break
                    }
                }
            }

            producer.join()
            consumer.join()
            Log.d("zxzx", "所有任务完成")
        }
    }

打印：

ok .