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引发的异常，但此代码在 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;
        } 

我已遵循与@jamesmontemagno/Xamarin.Plugins/Geolocator/ 相关的各个网站中提到的所有说明，但没有运气。我已确保我的 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> 

我想要实现的只是通过 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。感谢您提供任何类型的帮助。

Answer 1

与官方样例对比后发现问题是你设置的timeout参数太短，无法完成任务，所以每次都取消。

解决办法：

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