Xamarin.Forms远程通知：RegisteredForRemoteNotifications未触发如何获取设备令牌

Hey there, let's work through this issue together—your RegisteredForRemoteNotifications method not firing is a common gotcha when setting up push notifications with Urban Airship in Xamarin.iOS, so let's break down the fixes step by step.

The RegisteredForRemoteNotifications callback won't trigger unless you first request user permission and register for remote notifications in your FinishedLaunching method. This is the foundational step most people miss.

Update your AppDelegate.cs FinishedLaunching method with this critical code:

public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
    // Initialize Urban Airship first (double-check your UA config is correct here)
    Airship.Instance.Initialize(options);

    // Request push notification permissions from the user
    var notificationSettings = UIUserNotificationSettings.GetSettingsForTypes(
        UIUserNotificationType.Alert | UIUserNotificationType.Badge | UIUserNotificationType.Sound,
        new NSSet());

    UIApplication.SharedApplication.RegisterUserNotificationSettings(notificationSettings);
    // Register for remote notifications to trigger the system callback
    UIApplication.SharedApplication.RegisterForRemoteNotifications();

    // Rest of your existing code...
    return true;
}

Note: For iOS 10+, you can use the newer UNUserNotificationCenter API, but Xamarin's abstraction should handle backward compatibility—just make sure you're requesting all necessary notification types.

Urban Airship wraps the system's push registration flow, so using their native delegate is often more reliable than relying solely on the system's RegisteredForRemoteNotifications method. Here's how to set it up:

// Inside FinishedLaunching, after initializing UA
UAPush.Shared.PushRegistrationDelegate = new PushRegistrationHandler();

// Custom delegate class to handle UA's push events
public class PushRegistrationHandler : UAPushRegistrationDelegate
{
    public override void RegisteredForRemoteNotifications(UAPush push, string deviceToken)
    {
        // This is where you'll get the cleaned-up device token from UA
        Console.WriteLine($"Urban Airship Device Token: {deviceToken}");
        // Use this token for your backend or UA setup as needed
    }

    public override void FailedToRegisterForRemoteNotifications(UAPush push, NSError error)
    {
        Console.WriteLine($"Push registration failed: {error.LocalizedDescription}");
        // Use this to debug why registration isn't working
    }
}

UA automatically handles the system's registration callbacks and passes the token to you in a ready-to-use format, so this avoids common formatting issues with raw device tokens.

If you still don't get a token, check these common culprits:

• APNs Certificate Mismatch: Make sure your iOS project uses the correct APNs certificate (development vs production) and that you've uploaded the matching certificate to the Urban Airship dashboard. Mismatched certificates will silently fail registration.
• Simulator Limitations: iOS simulators often don't support remote notifications reliably. Test on a physical iOS device to rule out simulator-specific issues.
• User Permission Denied: If the user rejected push permissions, RegisteredForRemoteNotifications won't fire. Check your app's settings on the device to confirm push permissions are enabled.
• SDK Compatibility: Ensure your Xamarin.iOS version and Urban Airship SDK version are compatible with the iOS version you're testing on. Outdated SDKs can break registration on newer iOS releases.

Don't forget to implement the system's failure callback to get actionable error messages:

public override void FailedToRegisterForRemoteNotifications(UIApplication application, NSError error)
{
    Console.WriteLine($"System-level registration failed: {error.LocalizedDescription}");
}

This will tell you exactly why registration isn't working (e.g., invalid certificate, permission issues).

内容的提问来源于stack exchange，提问作者Hardik