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Example of Task based LocationService implementation using Mvx Location Plugin
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| public interface ILocationService | |
| { | |
| Coordinates GetLastSeenLocation(); | |
| Task<Coordinates> GetCurrentLocation (); | |
| } | |
| public class LocationService : ILocationService | |
| { | |
| private const string Tag = "LocationService"; | |
| private readonly object _lock = new object(); | |
| private static readonly TimeSpan timeOut = TimeSpan.FromSeconds (10); | |
| private TaskCompletionSource<Coordinates> taskSource; | |
| private readonly IMvxLocationWatcher locationWatcher; | |
| private readonly IMvxMainThreadDispatcher dispatcher; | |
| public LocationService (IMvxLocationWatcher locationWatcher, IMvxMainThreadDispatcher dispatcher) | |
| { | |
| this.locationWatcher = locationWatcher; | |
| this.dispatcher = dispatcher; | |
| this.locationWatcher.OnPermissionChanged += PermissionChanged; | |
| } | |
| public Coordinates GetLastSeenLocation() | |
| { | |
| var location = locationWatcher.LastSeenLocation; | |
| if (location == null) | |
| { | |
| return Coordinates.Empty; | |
| } | |
| return new Coordinates(location.Coordinates.Latitude, location.Coordinates.Longitude); | |
| } | |
| public Task<Coordinates> GetCurrentLocation() | |
| { | |
| Task<Coordinates> task; | |
| bool startWatcher = false; | |
| lock (_lock) | |
| { | |
| if (taskSource == null) | |
| { | |
| taskSource = new TaskCompletionSource<Coordinates>(); | |
| startWatcher = true; | |
| } | |
| task = taskSource.Task; | |
| } | |
| if (startWatcher) | |
| { | |
| StartWatcher(); | |
| } | |
| return task; | |
| } | |
| private void StartWatcher () | |
| { | |
| Trace.Debug (Tag, "StartWatcher"); | |
| dispatcher.RequestMainThreadAction(() => | |
| { | |
| if (locationWatcher.Started) { | |
| Trace.Warn (Tag, "Watcher already started!"); | |
| return; | |
| } | |
| locationWatcher.Start(new MvxLocationOptions() { Accuracy = MvxLocationAccuracy.Coarse }, | |
| location => | |
| { | |
| locationWatcher.Stop(); | |
| OnSuccess (new Coordinates(location.Coordinates.Latitude, location.Coordinates.Longitude)); | |
| }, | |
| error => | |
| { | |
| locationWatcher.Stop(); | |
| OnError (new LocationException(error.Code)); | |
| }); | |
| Task.Delay (timeOut).ContinueWith (_ => OnTimeout ()); | |
| }); | |
| } | |
| private void OnTimeout () | |
| { | |
| Trace.Debug(Tag, "Timeout"); | |
| TaskCompletionSource<Coordinates> source; | |
| lock (_lock) | |
| { | |
| source = taskSource; | |
| taskSource = null; | |
| } | |
| source?.SetException (new LocationException (MvxLocationErrorCode.Timeout)); | |
| if (locationWatcher.Started) { | |
| locationWatcher.Stop(); | |
| } | |
| } | |
| private void OnSuccess (Coordinates coordinates) | |
| { | |
| Trace.Debug(Tag, "Updated: " + coordinates); | |
| TaskCompletionSource<Coordinates> source; | |
| lock (_lock) | |
| { | |
| source = taskSource; | |
| taskSource = null; | |
| } | |
| source?.SetResult(coordinates); | |
| } | |
| private void OnError (LocationException error) | |
| { | |
| Trace.Warn(Tag, "Error: " + error.Code.ToString()); | |
| TaskCompletionSource<Coordinates> source; | |
| lock (_lock) | |
| { | |
| source = taskSource; | |
| taskSource = null; | |
| } | |
| source?.SetException(error); | |
| } | |
| private void PermissionChanged (object sender, MvxValueEventArgs<MvxLocationPermission> e) | |
| { | |
| Trace.Warn(Tag, "Permission changed: " + e.Value.ToString ()); | |
| if (e.Value != MvxLocationPermission.Denied) | |
| { | |
| return; | |
| } | |
| // Process only if denied | |
| TaskCompletionSource<Coordinates> source; | |
| lock (_lock) | |
| { | |
| source = taskSource; | |
| taskSource = null; | |
| } | |
| source?.SetException(new LocationException (MvxLocationErrorCode.PermissionDenied)); | |
| } | |
| } |
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