ios - GetPositionAsync 适用于 android 但不适用于 IOS 11

Question

System.Threading.Tasks.TaskCanceledException: A task was canceled.

2017-11-05 14:46:31.228 Project.iOS[36807:4480015] 
Unhandled Exception:
System.Threading.Tasks.TaskCanceledException: A task was canceled.
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00020] in /Library/Frameworks/Xamarin.iOS.framework/Versions/11.2.0.11/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:179 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/11.2.0.11/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/11.2.0.11/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`

当我尝试在 ios.11 模拟器上调试时，我很难处理以下代码抛出的异常，但这段代码在 android 中运行良好。

private async Task<Plugin.Geolocator.Abstractions.Position> GetPositionAsync() {
            var locator = CrossGeolocator.Current;
            locator.DesiredAccuracy = 50;
            TimeSpan ts = new TimeSpan((Int32)10000);
            _position = await locator.GetPositionAsync(timeout: ts);
            return _position;
        } 

我已经按照与@jamesmontemagno/Xamarin.Plugins/Geolocator/相关的各种网站中提到的所有说明进行操作，但没有成功。我确保我的 info.plist 包含以下代码:

  <key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
  <string>This app needs access location when open and in the background.</string>
  <key>NSLocationAlwaysUsageDescription</key>
  <string>Need location for geolocator plugin.</string>
  <key>RequestWhenInUseAuthorization</key>
  <string>Need location for geolocator plugin.</string>
  <key>NSLocationWhenInUseUsageDescription</key>
  <string>Need location for geolocator plugin.</string> 

我想要实现的是通过 Xamarin.Froms 在所有三个平台(IOS、Android、Windows)上获取当前位置。 Android 运行良好，但 IOS 是我卡住的地方。感谢任何类型的帮助。

Answer 1

和官方的sample对比后，发现问题是你设置的timeout参数太短，无法完成任务，所以每次都cancel了。

解决方案:

await locator.GetPositionAsync(TimeSpan.FromSeconds(10));