Xamarin.Forms中是否有监听GPS开关状态变更的对应事件？

Xamarin.Forms 本身没有内置的GPS开关状态变更事件，你需要通过平台特定实现+依赖服务的方式完成需求，具体实现方式如下：

1. 共享层代码定义 #

首先在共享项目中定义监听接口和事件回调：

public interface IGpsStatusListener
{
    // 事件参数bool表示GPS是否为开启状态
    event EventHandler<bool> GpsStatusChanged;
    // 启动监听
    void StartListening();
    // 停止监听，避免内存泄漏
    void StopListening();
}

在需要使用功能的位置注册监听事件：

var gpsListener = DependencyService.Get<IGpsStatusListener>();
gpsListener.GpsStatusChanged += (sender, isGpsEnabled) =>
{
    if (isGpsEnabled)
    {
        // GPS开启时执行的自定义操作
    }
    else
    {
        // GPS关闭时执行的自定义操作
    }
};
// 启动监听
gpsListener.StartListening();

2. 安卓平台实现 #

安卓端通过系统广播监听GPS状态变更：

[assembly: Dependency(typeof(GpsStatusListener_Android))]
namespace 你的项目命名空间.Droid
{
    public class GpsStatusListener_Android : IGpsStatusListener
    {
        public event EventHandler<bool> GpsStatusChanged;
        private GpsBroadcastReceiver _receiver;

        public void StartListening()
        {
            _receiver = new GpsBroadcastReceiver(OnStatusUpdate);
            Android.App.Application.Context.RegisterReceiver(_receiver, 
                new IntentFilter(Android.Provider.Settings.ActionLocationModeChanged));
        }

        public void StopListening()
        {
            if (_receiver != null)
            {
                Android.App.Application.Context.UnregisterReceiver(_receiver);
                _receiver = null;
            }
        }

        private void OnStatusUpdate(bool isEnabled)
        {
            GpsStatusChanged?.Invoke(this, isEnabled);
        }
    }

    internal class GpsBroadcastReceiver : BroadcastReceiver
    {
        private readonly Action<bool> _statusCallback;
        public GpsBroadcastReceiver(Action<bool> callback) => _statusCallback = callback;

        public override void OnReceive(Context context, Intent intent)
        {
            if (intent.Action == Android.Provider.Settings.ActionLocationModeChanged)
            {
                var locationManager = (LocationManager)context.GetSystemService(Context.LocationService);
                bool isGpsOn = locationManager.IsProviderEnabled(LocationManager.GpsProvider);
                _statusCallback?.Invoke(isGpsOn);
            }
        }
    }
}

需要在AndroidManifest.xml中添加定位权限：

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

3. iOS平台实现 #

iOS端通过CoreLocation的授权变更事件监听GPS状态：

[assembly: Dependency(typeof(GpsStatusListener_iOS))]
namespace 你的项目命名空间.iOS
{
    public class GpsStatusListener_iOS : IGpsStatusListener
    {
        public event EventHandler<bool> GpsStatusChanged;
        private CLLocationManager _locationManager;

        public void StartListening()
        {
            _locationManager = new CLLocationManager();
            _locationManager.AuthorizationChanged += (s, e) =>
            {
                bool isGpsOn = CLLocationManager.LocationServicesEnabled 
                    && CLLocationManager.Status is CLAuthorizationStatus.AuthorizedWhenInUse or CLAuthorizationStatus.AuthorizedAlways;
                GpsStatusChanged?.Invoke(this, isGpsOn);
            };
            // 首次启动主动返回当前状态
            bool initialStatus = CLLocationManager.LocationServicesEnabled 
                && CLLocationManager.Status is CLAuthorizationStatus.AuthorizedWhenInUse or CLAuthorizationStatus.AuthorizedAlways;
            GpsStatusChanged?.Invoke(this, initialStatus);
        }

        public void StopListening()
        {
            _locationManager?.Dispose();
            _locationManager = null;
        }
    }
}

需要在Info.plist中添加定位权限描述：

<key>NSLocationWhenInUseUsageDescription</key>
<string>需要使用定位权限以检测GPS状态</string>

注意事项 #

• 页面销毁或者不需要监听时，一定要调用StopListening()方法释放资源，避免内存泄漏
• 安卓6.0+、iOS14+都需要先完成动态定位权限申请，才能正常获取GPS状态

内容的提问来源于stack exchange，提问作者Dev