以 xamarin 形式获取位置

Question

我正在尝试从我的设备获取位置。这是代码：

public class Geolocation
{        
    private readonly LocationManager _locationManager;

    public Geolocation()
    {
        _locationManager = Forms.Context.GetSystemService(Context.LocationService) as LocationManager;
    }

    public Task<double> GetLocation()
    {

        var provider = _locationManager.GetBestProvider(new Criteria() { Accuracy = Accuracy.Fine }, true);
        var location = _locationManager.GetLastKnownLocation(provider);

        if(location == null) return null;

        var result = location.Latitude;

        return result;
    }
}

我从一本关于 xamarin 的书中得到了这段代码。我不明白，为什么大部分时间我都没有得到结果？几次都有效，但我不知道为什么。对于那些想知道为什么我不使用 James Montemagno 的 Geolocator 插件的人，因为我不能。它需要一些无法在我的 VS 中更新的内容。

Answer 1

尝试通过依赖服务来协调。阅读 xamrin 文档 Get Current Device Location github中有一个示例项目get_current_device_location

您仍然希望它在 xamarin.forms 中实现，然后观看此视频link

Answer 2

_locationManager.GetBestProvider(new Criteria() { Accuracy = Accuracy.Coarse}, true);

这将使您更快地获得位置，尽管准确度当然较低。
Here 是如何检索位置的综合示例。

Answer 3

以下是如何使用 Xamarin.Forms 项目中的 GeoLocator 插件。

此代码 sn-p 取自示例 Xamarin.Forms 应用，该应用使用带有 Xamarin.Forms 和 MVVM 架构的 GeoLocator 插件：

https://github.com/brminnick/GeolocatorSample

public class Geolocation
{ 
    string _latLongText, _latLongAccuracyText, _altitudeText, _altitudeAccuracyText;

    public Geolocation()
    {
        StartListeningForGeoloactionUpdates.GetAwaiter().GetResult();
    }

    public string LatLongText
    {
        get => _latLongText;
        set => _latLongText = value;
    }

    public string LatLongAccuracyText
    {
        get => _latLongAccuracyText;
        set => _latLongAccuracyText = value;
    }

    public string AltitudeText
    {
        get => _altitudeText;
        set => _altitudeText = value;
    }

    public string AltitudeAccuracyText
    {
        get => _altitudeAccuracyText;
        set => _altitudeAccuracyText = value;
    }

    Task StartListeningForGeoloactionUpdates()
    {
        bool isGeolocationAvailable = CrossGeolocator.IsSupported
                                    && CrossGeolocator.Current.IsGeolocationAvailable
                                    && CrossGeolocator.Current.IsGeolocationEnabled;

        if (isGeolocationAvailable)
        {
            CrossGeolocator.Current.PositionChanged += HandlePositionChanged;
            return CrossGeolocator.Current.StartListeningAsync(TimeSpan.FromSeconds(1), 10);
        }

        LatLongText = "Geolocation Unavailable";
        return Task.CompletedTask;
    }

    void HandlePositionChanged(object sender, PositionEventArgs e)
    {
        AltitudeAccuracyText = $"{ConvertDoubleToString(e.Position.AltitudeAccuracy, 0)}m";
        AltitudeText = $"{ConvertDoubleToString(e.Position.Altitude, 2)}m";
        LatLongAccuracyText = $"{ConvertDoubleToString(e.Position.Accuracy, 0)}m";
        LatLongText = $"{ConvertDoubleToString(e.Position.Latitude, 2)}, {ConvertDoubleToString(e.Position.Longitude, 2)}";

        string ConvertDoubleToString(double number, int decimalPlaces) => number.ToString($"F{decimalPlaces}");
    }
}