Question

我想经常在App中保留手机的位置，因此我正在使用GetPositionAsync方法，并继续调用它。我已经写了一些代码，当我将其附加到一个简单的OnAppearing方法中时，一切工作正常。如果我在方法或while循环中编写它，那么当它到达GetPositionAsync或其他一些本地数据库时，我认为只有可以等待的方法，它才退出循环/方法。我正在使用异步。有什么想法吗？

var locator = CrossGeolocator.Current;
locator.DesiredAccuracy = 20;

var position = await locator.GetPositionAsync(TimeSpan.FromSeconds(10));

location.Latitude = position.Latitude;
location.Longitude = position.Longitude;

await App.LocationDatabase.SaveLocationAsync(location);
await Task.Delay(TimeSpan.FromSeconds(10));

Answer 1

您不共享任何循环代码，因此很难重现您的问题。

无论如何，您不应循环调用GetPositionAsync，而应使用StartListeningAsync方法并连接到PositionChange事件。

async Task StartListeningAsync()
{
    if(CrossGeolocator.Current.IsListening)
        return;

    await CrossGeolocator.Current.StartListeningAsync(TimeSpan.FromSeconds(5), 10, true);

    CrossGeolocator.Current.PositionChanged += PositionChanged;
    CrossGeolocator.Current.PositionError += PositionError;
}

private void PositionChanged(object sender, PositionEventArgs e)
{
    //If updating the UI, ensure you invoke on main thread
    var position = e.Position;
    var output = "Full: Lat: " + position.Latitude + " Long: " + position.Longitude;
    output += "\n" + $"Time: {position.Timestamp}";
    output += "\n" + $"Heading: {position.Heading}";
    output += "\n" + $"Speed: {position.Speed}";
    output += "\n" + $"Accuracy: {position.Accuracy}";
    output += "\n" + $"Altitude: {position.Altitude}";
    output += "\n" + $"Altitude Accuracy: {position.AltitudeAccuracy}";
    Debug.WriteLine(output);
} 

private void PositionError(object sender, PositionErrorEventArgs e)
{
    Debug.WriteLine(e.Error);
    //Handle event here for errors
} 

async Task StopListeningAsync()
{
    if(!CrossGeolocator.Current.IsListening)
        return;

    await CrossGeolocator.Current.StopListeningAsync();

    CrossGeolocator.Current.PositionChanged -= PositionChanged;
    CrossGeolocator.Current.PositionError -= PositionError;
}

https://jamesmontemagno.github.io/GeolocatorPlugin/LocationChanges.html

CrossGeolocator GetPositionAsync退出循环/方法

1 个答案: