Xamarin.iOS中Geolocator.Plugin定位失效问题求助

Hey there, let's break down what's going wrong with your Xamarin.iOS geolocation setup and fix it step by step!

Key Issues Causing the Crash #

Let's start with the two most critical problems in your code and configuration:

1. UI Thread Deadlock
   In your MyViewExample constructor, you're using Task.Run(() => api.GetDeviceCurrentLocation()).Result to block the UI thread while waiting for the asynchronous location call. iOS has strict rules about UI thread responsiveness, and this blocking pattern almost always leads to a deadlock (and subsequent crash) because the async operation tries to return to the already-blocked UI thread.

2. Invalid Info.plist Permission Keys
   Your Info.plist contains an incorrect key: RequestWhenInUseAuthorization — this isn't a valid iOS system permission key. Additionally, you're missing the required NSLocationWhenInUseUsageDescription (needed for foreground location access), and NSLocationAlwaysUsageDescription is deprecated on iOS 11+.

Fixes to Apply #

1. Fix the Async/Await Pattern (Eliminate Deadlock)

Move your location logic out of the page constructor and into the Appearing event, using proper async/await instead of blocking with .Result:

public partial class MyViewExample : ContentPage {
    public MyViewExample() {
        InitializeComponent();
        // Subscribe to the Appearing event to run async logic after the page loads
        Appearing += OnPageAppearing;
    }

    private async void OnPageAppearing(object sender, EventArgs e) {
        // Unsubscribe to avoid repeated calls if the page appears multiple times
        Appearing -= OnPageAppearing;
        
        Service cs = new Service();
        var myLocation = await cs.GetDeviceCurrentLocation(); // Use await to avoid blocking
        var myLatitude = myLocation.Latitude;
        var myLongitude = myLocation.Longitude;
        Debug.WriteLine($"Latitude is : {myLatitude} and Longitude is : {myLongitude}");
    }
}

2. Correct Info.plist Permissions

Update your Info.plist to use valid iOS location permission keys. Remove the invalid RequestWhenInUseAuthorization key, and add/keep the appropriate keys based on your needs:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <!-- ... your existing keys ... -->
    <key>UILaunchStoryboardName</key>
    <string>LaunchScreen</string>
    
    <!-- Required if you need background location access (iOS 11+) -->
    <key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
    <string>This app needs access to your location when open and in the background</string>
    
    <!-- Required for foreground location access (works on all supported iOS versions) -->
    <key>NSLocationWhenInUseUsageDescription</key>
    <string>This app needs access to your location while in use</string>
    
    <key>CFBundleIdentifier</key>
    <string>my.app.development</string>
</dict>
</plist>

3. Additional Checks

• Update the Geolocator Plugin: Ensure you're using the latest version of Plugin.Geolocator — older versions may have iOS-specific bugs.
• Adjust Timeout: Your 3-second timeout in GetPositionAsync might be too short, especially if the user is granting location permission for the first time. Try increasing it to 10 seconds:

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

• Verify Device Settings: Make sure location services are enabled on your test iOS device, and that your app has been granted location permissions (check Settings > [Your App] > Location).

These changes should resolve the crash by fixing the deadlock issue and ensuring iOS recognizes your location permission requests.

内容的提问来源于stack exchange，提问作者John