前台服务中的位置更新

Question

我正在尝试实现一个用于在后台导航用户的应用程序。我正在运行前台服务。但是对于RequestLocationUpdates，我有两个选择：

1. 使用PendingIntent（通常这个用作背景）
2. 使用LocationCallback

哪一个应该用于前台的位置更新？我想LocationCallback，但不确定。

提前致谢。

Answer 1

在前台服务中使用RequestLocationUpdates更新位置时，请实现Android.Locations.ILocationListener接口，实现OnLocationChanged方法。

这是一些相关的代码

 [Service]
    public class LocationService : Service, ILocationListener
    {
        const int SERVICE_RUNNING_NOTIFICATION_ID = 123;
        const string NOTIFICATION_CHANNEL_ID = "com.company.app.channel";

        readonly string logTag = "LocationService";
        IBinder binder;

        // Set our location manager as the system location service
        protected LocationManager LocMgr = Application.Context.GetSystemService("location") as LocationManager;

        // ILocationListener is a way for the Service to subscribe for updates
        // from the System location Service

        public void OnLocationChanged(Android.Locations.Location location)
        {
            LocationChanged(this, new LocationChangedEventArgs(location));

            // This should be updating every time we request new location updates
            // both when teh app is in the background, and in the foreground
            Log.Debug(logTag, $"Latitude is {location.Latitude}");
            Log.Debug(logTag, $"Longitude is {location.Longitude}");
            Log.Debug(logTag, $"Altitude is {location.Altitude}");
            Log.Debug(logTag, $"Speed is {location.Speed}");
            Log.Debug(logTag, $"Accuracy is {location.Accuracy}");
            Log.Debug(logTag, $"Bearing is {location.Bearing}");
        }

        public void OnProviderDisabled(string provider)
        {
            ProviderDisabled(this, new ProviderDisabledEventArgs(provider));
        }

        public void OnProviderEnabled(string provider)
        {
            ProviderEnabled(this, new ProviderEnabledEventArgs(provider));
        }

        public void OnStatusChanged(string provider, Availability status, Bundle extras)
        {
            StatusChanged(this, new StatusChangedEventArgs(provider, status, extras));
        }

        public event EventHandler<LocationChangedEventArgs> LocationChanged = delegate { };
        public event EventHandler<ProviderDisabledEventArgs> ProviderDisabled = delegate { };
        public event EventHandler<ProviderEnabledEventArgs> ProviderEnabled = delegate { };
        public event EventHandler<StatusChangedEventArgs> StatusChanged = delegate { };

        public override void OnCreate()
        {
            base.OnCreate();
            Log.Debug(logTag, "OnCreate called in the Location Service");
        }

        // This gets called when StartService is called in our App class
        [Obsolete("deprecated in base class")]
        public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
        {
            Log.Debug(logTag, "LocationService started");

            // Check if device is running Android 8.0 or higher and call StartForeground() if so
            if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
            {
                var notification = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
                                   .SetContentTitle(Resources.GetString(Resource.String.app_name))
                                   .SetContentText(Resources.GetString(Resource.String.notification_text))
                                   .SetSmallIcon(Resource.Drawable.notification_icon_background)
                                   .SetOngoing(true)
                                   .Build();

                var notificationManager =
                    GetSystemService(NotificationService) as NotificationManager;

                var chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "On-going Notification", NotificationImportance.Min);

                notificationManager.CreateNotificationChannel(chan);

                StartForeground(SERVICE_RUNNING_NOTIFICATION_ID, notification);
            }

            return StartCommandResult.Sticky;
        }

        // This gets called once, the first time any client bind to the Service
        // and returns an instance of the LocationServiceBinder. All future clients will
        // reuse the same instance of the binder
        public override IBinder OnBind(Intent intent)
        {
            Log.Debug(logTag, "Client now bound to service");

            binder = new LocationServiceBinder(this);
            return binder;
        }

        // Handle location updates from the location manager
        public void StartLocationUpdates()
        {
            //we can set different location criteria based on requirements for our app -
            //for example, we might want to preserve power, or get extreme accuracy
            var locationCriteria = new Criteria();

            locationCriteria.Accuracy = Accuracy.NoRequirement;
            locationCriteria.PowerRequirement = Power.NoRequirement;

            // get provider: GPS, Network, etc.
            var locationProvider = LocMgr.GetBestProvider(locationCriteria, true);
            Log.Debug(logTag, string.Format("You are about to get location updates via {0}", locationProvider));

            // Get an initial fix on location
            LocMgr.RequestLocationUpdates(locationProvider, 2000, 0, this);

            Log.Debug(logTag, "Now sending location updates");
        }

        public override void OnDestroy()
        {
            base.OnDestroy();
            Log.Debug(logTag, "Service has been terminated");

            // Stop getting updates from the location manager:
            LocMgr.RemoveUpdates(this);
        }
    }
}

这是我的demo，大家可以参考一下。

https://github.com/851265601/XAndroidLocation