Kotlin EventBus 触发了两次

Question

我在 kotlin 中将此代码用于 eventBus，但它触发了两次。我不知道为什么会这样

object EventBus {
    val bus: BroadcastChannel<Any> = BroadcastChannel<Any>(1)

    private val parentJob = Job()
    private val coroutineContext: CoroutineContext
        get() = parentJob + Dispatchers.Default

    private val scope = CoroutineScope(coroutineContext)
    fun send(o: Any) {
        scope.launch {
            bus.send(o)
        }
    }

    inline fun <reified T> asChannel(): ReceiveChannel<T> {
        return bus.openSubscription().filter { it is T }.map { it as T }
    }
}

并这样使用

EventBus.send(NetEvent(false))

听如下（此代码运行两次）

 var subscription = EventBus.asChannel<NetEvent>()
    var s = scope.launch {
        subscription.consumeEach { event ->

            Timber.i("NetEvent ${event.isConected}")
            currentNet = event.isConected
        }
    }

Answer 1

我更喜欢MutableSharedFlow:

class EventBus {
    private val events = MutableSharedFlow<Any>()

    suspend fun dispatch(event: Any) {
        events.emit(event)
    }

    suspend fun on(coroutineScope: CoroutineScope, handler: suspend (Any) -> Unit) =
        coroutineScope.launch(start = CoroutineStart.UNDISPATCHED) {
            events.asSharedFlow().collect { event -> handler(event) }
        }
}

class EventBusTest {
    @Test
    fun testEventBus() {
        val events = ConcurrentLinkedDeque<String>()
        runBlocking {
            val eventBus = EventBus()

            val job1 = eventBus.on(this) { events.add("1: $it") }
            eventBus.dispatch("a")

            val job2 = eventBus.on(this) { events.add("2: $it") }
            eventBus.dispatch("b")

            job1.cancelAndJoin()

            eventBus.dispatch("c")

            job2.cancelAndJoin()
        }
        assertEquals(listOf("1: a", "1: b", "2: b", "2: c"), events.toList())
    }
}

Kotlin EventBus 触发了两次

Kotlin EventBus triggered twice

android

kotlin

kotlin-coroutines