Platform.TryGetCurrentLocationAsync

src/PostIt/PostIt.Android/Application.cs

@@ -1,4 +1,5 @@
 using Android.App;
+using Android;
 using Android.Runtime;
 using Avalonia;
 using Avalonia.Android;
@@ -9,6 +10,9 @@ using Avalonia.Controls;
 using Avalonia.Styling;
 using Yavsc.Api.Client;
 
+[assembly: UsesPermission(Manifest.Permission.AccessFineLocation)]
+[assembly: UsesPermission(Manifest.Permission.AccessCoarseLocation)]
+
 namespace PostIt.Android
 {
     [Application]

src/PostIt/PostIt.Android/MainActivity.cs

@@ -57,6 +57,17 @@ public class MainActivity : AvaloniaMainActivity
 
     }
 
+    public override void OnRequestPermissionsResult(int requestCode, string[]? permissions, Permission[]? grantResults)
+    {
+        if (PostIt.Android.Services.AndroidCurrentLocationProvider
+            .HandlePermissionResult(requestCode, grantResults))
+        {
+            return;
+        }
+
+        base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
+    }
+
     internal static class AndroidOidcCallbackSink
     {
         private static System.Threading.Tasks.TaskCompletionSource<string>? _pending;

src/PostIt/PostIt.Android/PlatformBootstrap.cs

@@ -14,11 +14,12 @@ internal static class PlatformBootstrap
 {
     internal static void InitPlatform()
     {
-
         Platform.CreateBrowser = () =>
         {
             var activity = MainActivity.Current;
             return activity is null ? null : new AndroidSystemBrowser(activity);
         };
+
+        Platform.TryGetCurrentLocationAsync = AndroidCurrentLocationProvider.TryGetCurrentLocationAsync;
     }
 }

src/PostIt/PostIt.Android/Services/AndroidCurrentLocationProvider.cs

@@ -0,0 +1,130 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Android;
+using Android.App;
+using Android.Content.PM;
+using Android.Locations;
+using AndroidX.Core.App;
+using AndroidX.Core.Content;
+using PostIt.Services;
+
+namespace PostIt.Android.Services;
+
+internal static class AndroidCurrentLocationProvider
+{
+    public static async Task<CurrentLocationResult> TryGetCurrentLocationAsync(CancellationToken cancellationToken)
+    {
+        var activity = MainActivity.Current;
+        if (activity is null)
+        {
+            return CurrentLocationResult.Unavailable("L'activité Android n'est pas encore prête.");
+        }
+
+        var permissionGranted = await LocationPermissionBroker.EnsureGrantedAsync(activity, cancellationToken).ConfigureAwait(false);
+        if (!permissionGranted)
+        {
+            return CurrentLocationResult.PermissionDenied();
+        }
+
+        var locationManager = activity.GetSystemService(global::Android.Content.Context.LocationService) as LocationManager;
+        if (locationManager is null)
+        {
+            return CurrentLocationResult.Unavailable("Le service de localisation Android est indisponible.");
+        }
+
+        var location = locationManager.GetProviders(enabledOnly: true)?
+            .Select(provider => locationManager.GetLastKnownLocation(provider))
+            .Where(candidate => candidate is not null)
+            .OrderByDescending(candidate => candidate!.Time)
+            .ThenBy(candidate => candidate!.Accuracy)
+            .FirstOrDefault();
+
+        if (location is null)
+        {
+            return CurrentLocationResult.Unavailable("Aucune position n'est disponible. Activez la localisation du système puis réessayez.");
+        }
+
+        return CurrentLocationResult.Success(location.Latitude, location.Longitude);
+    }
+
+    public static bool HandlePermissionResult(int requestCode, Permission[]? grantResults)
+        => LocationPermissionBroker.HandleResult(requestCode, grantResults);
+
+    private static class LocationPermissionBroker
+    {
+        private const int RequestCode = 4042;
+        private static readonly string[] RequestedPermissions =
+        {
+            Manifest.Permission.AccessFineLocation,
+            Manifest.Permission.AccessCoarseLocation,
+        };
+
+        private static readonly object SyncRoot = new();
+        private static TaskCompletionSource<bool>? _pendingRequest;
+
+        public static Task<bool> EnsureGrantedAsync(Activity activity, CancellationToken cancellationToken)
+        {
+            if (HasLocationPermission(activity))
+            {
+                return Task.FromResult(true);
+            }
+
+            lock (SyncRoot)
+            {
+                if (_pendingRequest is null)
+                {
+                    _pendingRequest = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+                    ActivityCompat.RequestPermissions(activity, RequestedPermissions, RequestCode);
+                }
+
+                if (!cancellationToken.CanBeCanceled)
+                {
+                    return _pendingRequest.Task;
+                }
+
+                return WaitAsync(_pendingRequest.Task, cancellationToken);
+            }
+        }
+
+        public static bool HandleResult(int requestCode, Permission[]? grantResults)
+        {
+            if (requestCode != RequestCode)
+            {
+                return false;
+            }
+
+            var granted = grantResults is { Length: > 0 } && grantResults.All(result => result == Permission.Granted);
+            TaskCompletionSource<bool>? pendingRequest;
+            lock (SyncRoot)
+            {
+                pendingRequest = _pendingRequest;
+                _pendingRequest = null;
+            }
+
+            pendingRequest?.TrySetResult(granted);
+            return true;
+        }
+
+        private static bool HasLocationPermission(Activity activity)
+        {
+            return ContextCompat.CheckSelfPermission(activity, Manifest.Permission.AccessFineLocation) == Permission.Granted
+                || ContextCompat.CheckSelfPermission(activity, Manifest.Permission.AccessCoarseLocation) == Permission.Granted;
+        }
+
+        private static async Task<bool> WaitAsync(Task<bool> task, CancellationToken cancellationToken)
+        {
+            using var registration = cancellationToken.Register(() =>
+            {
+                lock (SyncRoot)
+                {
+                    _pendingRequest?.TrySetCanceled(cancellationToken);
+                    _pendingRequest = null;
+                }
+            });
+
+            return await task.ConfigureAwait(false);
+        }
+    }
+}