c# - CLGeocoder.ReverseGecode 在 50 个请求后挂起

Question

首先是我的代码:

private CLGeocoder _coder = new CLGeocoder();

private void TestWithTpl()
{
    Console.WriteLine("Test started");
    var testLocation = new CLLocation(52.268157,-1.4209);
    Task.Factory.StartNew(async () => 
    {
        for (var i=0; i < 100; i++)
        {
            Console.WriteLine("Starting iteration {0}", i);
            var res = await _coder.ReverseGeocodeLocationAsync(testLocation);
            Console.WriteLine(res[0].AdministrativeArea);
            Console.WriteLine("Finished iteration {0}", i);
        }
    });
    Console.WriteLine("Finished");
}

private void TestDefault()
{
    Console.WriteLine("Test started");
    var testLocation = new CLLocation(52.268157,-1.4209);
    Task.Factory.StartNew(() => 
    {
        for (var i=0; i < 100; i++)
        {
            Console.WriteLine("Starting iteration {0}", i);
            var res = _coder.ReverseGeocodeLocationAsync(testLocation).Result;
            Console.WriteLine(res[0].AdministrativeArea);
            Console.WriteLine("Finished iteration {0}", i);
        }
    });
    Console.WriteLine("Finished");
}

如您所见，TestWithTpl 将使用异步和等待，而 TestDefault 仅使用 ReverseGeocodeLocationAsync 的结果。

无论我使用两者中的哪一种方法:输出都会是这样的:

2013-10-11 12:05:54.882 AddressResolveTest[5290:a0b] Test started
Thread started: <Thread Pool> #3
Thread started: <Thread Pool> #4
2013-10-11 12:05:54.892 AddressResolveTest[5290:a0b] Finished
2013-10-11 12:05:54.897 AddressResolveTest[5290:6303] Starting iteration 0
2013-10-11 12:05:55.125 AddressResolveTest[5290:6303] England
2013-10-11 12:05:55.126 AddressResolveTest[5290:6303] Finished iteration 0
2013-10-11 12:05:55.127 AddressResolveTest[5290:6303] Starting iteration 1
...
2013-10-11 12:05:57.302 AddressResolveTest[5290:6303] Finished iteration 49
2013-10-11 12:05:57.302 AddressResolveTest[5290:6303] Starting iteration 50

在最后一行之后没有任何反应。

我不知道，为什么:

1. “完成”是在代码准备好之前写的。
2. 代码总是在请求号停止。 50.

Answer 1

1. “完成”应该在开始时打印，至少对于 TPL 版本，因为 StartNew() 在后台启动任务，然后继续执行。 “默认”版本不应该是这种情况。你能查一下吗？

2. 问题是 StartNew() 吞下了异常。如果您这样更改代码:

Console.WriteLine("Test started");
var testLocation = new CLLocation(52.268157,-1.4209);
Task.Factory.StartNew(async () => 
    {
        try{
            for (var i=0; i < 100; i++)
            {
                Console.WriteLine("Starting iteration {0}", i);
                var res = await _coder.ReverseGeocodeLocationAsync(testLocation);
                Console.WriteLine(res[0].AdministrativeArea);
                Console.WriteLine("Finished iteration {0}", i);
            }
        }catch(Exception e){
            Console.WriteLine (e);
        }
    });
Console.WriteLine("Finished");

您将能够获得带有消息的Exception:操作无法完成。 (kCLErrorDomain 错误 2。)

在谷歌上搜索这条消息会让你在 stackoverflow 上获得很多点击率，例如1和 2 . This answer甚至宣布与您相同的“50”限制。

最后，我会说 Apple 限制了您每分钟可以执行的请求量，甚至 recommend you not to overuse the API :

Applications should be conscious of how they use geocoding. Here aresome rules of thumb for using this class effectively:

Send at most one geocoding request for any one user action.

希望对您有所帮助。