GH-476: Put in checks to see if location services are enabled. (#488)

* Put in checks to see if location services are enabled.

* iOS check to see if location services are enabled.

Xamarin.Essentials/Geolocation/Geolocation.android.cs

@@ -15,6 +15,7 @@ namespace Xamarin.Essentials
     public static partial class Geolocation
     {
         const long twoMinutes = 120000;
+        static readonly string[] ignoredProviders = new string[] { LocationManager.PassiveProvider, "local_database" };
 
         static async Task<Location> PlatformLastKnownLocationAsync()
         {
@@ -40,6 +41,12 @@ static async Task<Location> PlatformLocationAsync(GeolocationRequest request, Ca
 
             var locationManager = Platform.LocationManager;
 
+            var enabledProviders = locationManager.GetProviders(true);
+            var hasProviders = enabledProviders.Any(p => !ignoredProviders.Contains(p));
+
+            if (!hasProviders)
+                throw new FeatureNotEnabledException("Location services are not enabled on device.");
+
             // get the best possible provider for the requested accuracy
             var providerInfo = GetBestProvider(locationManager, request.DesiredAccuracy);
 

Xamarin.Essentials/Geolocation/Geolocation.ios.cs

@@ -9,11 +9,11 @@ namespace Xamarin.Essentials
 {
     public static partial class Geolocation
     {
-        internal static bool IsSupported
-            => CLLocationManager.LocationServicesEnabled;
-
         static async Task<Location> PlatformLastKnownLocationAsync()
         {
+            if (!CLLocationManager.LocationServicesEnabled)
+                throw new FeatureNotEnabledException("Location services are not enabled on device.");
+
             await Permissions.RequireAsync(PermissionType.LocationWhenInUse);
 
             var manager = new CLLocationManager();
@@ -24,6 +24,9 @@ static async Task<Location> PlatformLastKnownLocationAsync()
 
         static async Task<Location> PlatformLocationAsync(GeolocationRequest request, CancellationToken cancellationToken)
         {
+            if (!CLLocationManager.LocationServicesEnabled)
+                throw new FeatureNotEnabledException("Location services are not enabled on device.");
+
             await Permissions.RequireAsync(PermissionType.LocationWhenInUse);
 
             // the location manager requires an active run loop

Xamarin.Essentials/Geolocation/Geolocation.uwp.cs

@@ -32,11 +32,23 @@ static async Task<Location> PlatformLocationAsync(GeolocationRequest request, Ca
                 DesiredAccuracyInMeters = request.PlatformDesiredAccuracy
             };
 
+            CheckStatus(geolocator.LocationStatus);
+
             cancellationToken = Utils.TimeoutToken(cancellationToken, request.Timeout);
 
             var location = await geolocator.GetGeopositionAsync().AsTask(cancellationToken);
 
             return location?.Coordinate?.ToLocation();
+
+            void CheckStatus(PositionStatus status)
+            {
+                switch (status)
+                {
+                    case PositionStatus.Disabled:
+                    case PositionStatus.NotAvailable:
+                        throw new FeatureNotEnabledException("Location services are not enabled on device.");
+                }
+            }
         }
     }
 }

Xamarin.Essentials/Types/Shared/Exceptions.shared.cs

@@ -34,4 +34,21 @@ public FeatureNotSupportedException(string message, Exception innerException)
         {
         }
     }
+
+    public class FeatureNotEnabledException : InvalidOperationException
+    {
+        public FeatureNotEnabledException()
+        {
+        }
+
+        public FeatureNotEnabledException(string message)
+            : base(message)
+        {
+        }
+
+        public FeatureNotEnabledException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
 }