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我编写了以下（测试）函数来通过 volley 和协程与 google maps api 对话。遗憾的是，当使用 suspendCoroutine 调用它时，它永远不会完成。如果我使用相同的函数，删除协程内容并实现“正常”回调，一切正常。我有点不知所措，这里有什么问题。有人能帮忙吗？

代码执行到 Log.d(LOGTAG, "AFTERAFTER")，但永远不会到达 Log.d("findNaturalLocations", "Response: " + response)

suspend fun testNaturalLocations(tag: Tag, lastKnownUserLocation: 
Location): ArrayList<CLDistanceRequest> = suspendCoroutine { 
continuation ->

    Log.d("findNaturalLocations", "getDistanceAndTimeBetweenLocations")

    var distanceRequests = ArrayList<CLDistanceRequest>()

    val mapsBaseUrl = "https://maps.googleapis.com/maps/api/place/nearbysearch/"
    val mapsOutputFormat = "json"

    val location = "location=" + lastKnownUserLocation.latitude.toString() + "," + lastKnownUserLocation.longitude.toString()
    val radius = "radius=5000"
    val keyword = "keyword=Supermarket"
    val name = "name=Supermarket"
    val sensor = "sensor=true"
    val apiKey = "key=API_KEY"

    val finishedUrl = mapsBaseUrl + mapsOutputFormat + "?" + location + "&" + radius + "&" + keyword + "&" + name + "&" + sensor + "&" + apiKey

    Log.d(LOGTAG, finishedUrl)

    val jsObjectRequest = JsonObjectRequest(Request.Method.GET, finishedUrl, null,
            Response.Listener<JSONObject> { response ->
                Log.d("findNaturalLocations", "Response: " + response)

                var results = response.getJSONArray("results")

                // parse distanceRequests, ommitted for brevity

                continuation.resume(distanceRequests)
            },
            Response.ErrorListener { error ->
                Log.e("Error", error.localizedMessage, error)

                continuation.resumeWithException(error)
            }
    )

    Log.d(LOGTAG, "AFTER");

    jsObjectRequest.setShouldCache(false)
    CLGlobal.getRequestQueue().add(jsObjectRequest)

    Log.d(LOGTAG, "AFTERAFTER");
}

用一个简单的回调做同样的事情是完美的。

var i = 0;
    runBlocking {
        val query = async(CommonPool) {
            i = this@CLTaskList.test2()
        }

        query.await()
    }

suspend fun test2():Int = suspendCoroutine<Int> { continuation ->
    Log.d("TESTTEST", "TEST2 CALLED")
    test {
        Log.d("TESTTEST", "CONTINUATION")
        continuation.resume(it)
    }
}

fun test(completionHandler: (Int) -> Unit) {
    Log.d("TESTTEST", "TEST CALLED")
    completionHandler(1)
}
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1 回答 1

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正如您在评论中所揭示的，这就是您运行查询的方式：

val query = async(CommonPool) { 
    this@CLTaskList.testNaturalLocations(tags[0], 
         CLGlobal.getInstance().mLastKnownLocation!!) 
} 
runBlocking<Unit> { query.await() }

您已经接近正确了，但是这段代码都是倒退的：

  1. 您让可挂起函数在线程池中运行，从而减轻一些工作线程的阻塞责任，直到您得到答案（它不会关心它是否被阻塞）；
  2. 你用runBlocking.

在正确的解决方案中，您不需要async，CommonPool或者runBlocking，您需要的只是：

launch(UI) {
    val result = testNaturalLocations(tags[0], 
       CLGlobal.getInstance().mLastKnownLocation!!)
    // deal with the result right here
}

由于testNaturalLocations是一个可挂起的函数，它不会阻塞你的 UI 线程，当你写的回调恢复它时，你的代码会简单地进入下一行，并result赋值。

于 2018-02-23T18:47:16.090 回答