问题描述
fun getWeather(callback: (WeatherInfo) -> Unit) {
println("Start loading")
GlobalScope.launch(Applicationdispatcher) {
while (true) {
val response = httpClient.get<String>(API_URL) {
url.parameters.apply {
set("q","Moscow")
set("units","metric")
set("appid",weatherApiKey())
}
println(url.build())
}
val result = Json {
ignoreUnkNownKeys = true
}.decodeFromString<WeatherApiResponse>(response).main
callback(result)
// because Applicationdispatcher on IOS do not support delay
withContext(dispatchers.Default) { delay(DELAY_TIME) }
}
}
}
如果我用 withContext(dispatchers.Default) { delay(DELAY_TIME) }
替换 delay(DELAY_TIME)
,执行永远不会返回到 while 循环,它将只有一次迭代。
IOS 的 Applicationdispatcher
看起来像:
internal actual val Applicationdispatcher: Coroutinedispatcher = NsQueuedispatcher(dispatch_get_main_queue())
internal class NsQueuedispatcher(
private val dispatchQueue: dispatch_queue_t
) : Coroutinedispatcher() {
override fun dispatch(context: CoroutineContext,block: Runnable) {
dispatch_async(dispatchQueue) {
block.run()
}
}
}
从 delay
源代码我可以猜到,应该返回 DefaultDelay
并且应该有类似的行为,有/没有 withContext(dispatchers.Default)
/** Returns [Delay] implementation of the given context */
internal val CoroutineContext.delay: Delay get() = get(ContinuationInterceptor) as? Delay ?: DefaultDelay
谢谢!
附言我收到了 ktor-samples 的 Applicationdispatcher
。
解决方法
可能 ApplicationDispatcher
是一些旧东西,你不需要再使用它了:
CoroutineScope(Dispatchers.Default).launch {
}
或
MainScope().launch {
}
不要忘记使用 -native-mt
版本的协程,更多信息在此 issue