求VS 2022中Xamarin.Forms集成Firebase Cloud Messaging的可用示例

前置准备 #

• 前往Firebase控制台创建项目，分别为Android、iOS平台配置应用，下载对应的google-services.json（Android）和GoogleService-Info.plist（iOS）文件
• 确保Xamarin.Forms项目使用最新稳定版，安装对应平台的Firebase NuGet包

共享项目（Xamarin.Forms） #

创建统一的推送服务接口，用于跨平台调用：

public interface IPushNotificationService
{
    void Initialize();
    Task<string> GetTokenAsync();
    void SubscribeToTopic(string topic);
}

在App.xaml.cs中初始化服务：

protected override void OnStart()
{
    DependencyService.Get<IPushNotificationService>().Initialize();
}

Android 平台实现 #

1. 将google-services.json放在Android项目根目录，设置生成操作为GoogleServicesJson
2. 安装NuGet包：Xamarin.Firebase.Messaging、Xamarin.GooglePlayServices.Base
3. 创建FCM消息处理服务类：

[Service]
[IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
public class MyFirebaseMessagingService : FirebaseMessagingService
{
    public override void OnMessageReceived(RemoteMessage message)
    {
        base.OnMessageReceived(message);
        var title = message.GetNotification().Title;
        var body = message.GetNotification().Body;
        ShowNotification(title, body);
    }

    public override void OnNewToken(string token)
    {
        base.OnNewToken(token);
        Preferences.Set("FCM_Token", token);
        // 可将token上传至自有服务器
    }

    private void ShowNotification(string title, string body)
    {
        var intent = new Intent(this, typeof(MainActivity));
        intent.AddFlags(ActivityFlags.ClearTop);
        var pendingIntent = PendingIntent.GetActivity(this, 0, intent, PendingIntentFlags.OneShot);

        var notificationBuilder = new NotificationCompat.Builder(this, "default_channel")
            .SetContentTitle(title)
            .SetContentText(body)
            .SetSmallIcon(Resource.Drawable.ic_notification)
            .SetAutoCancel(true)
            .SetContentIntent(pendingIntent);

        var notificationManager = NotificationManager.FromContext(this);
        
        // Android 8.0+ 需创建通知渠道
        if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
        {
            var channel = new NotificationChannel("default_channel", "默认通知渠道", NotificationImportance.Default);
            notificationManager.CreateNotificationChannel(channel);
        }

        notificationManager.Notify(0, notificationBuilder.Build());
    }
}

4. 在MainActivity.cs中完成初始化：

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    Xamarin.Essentials.Platform.Init(this, savedInstanceState);
    global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
    
    FirebaseApp.InitializeApp(this);
    LoadApplication(new App());
}

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
    Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
    base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}

5. 实现共享项目的接口：

public class PushNotificationService : IPushNotificationService
{
    public void Initialize()
    {
        // 初始化已在MainActivity完成
    }

    public async Task<string> GetTokenAsync()
    {
        var token = await FirebaseMessaging.Instance.GetTokenAsync();
        Preferences.Set("FCM_Token", token);
        return token;
    }

    public void SubscribeToTopic(string topic)
    {
        FirebaseMessaging.Instance.SubscribeToTopic(topic);
    }
}

iOS 平台实现 #

1. 将GoogleService-Info.plist放在iOS项目根目录，设置生成操作为BundleResource
2. 安装NuGet包：Xamarin.Firebase.iOS.Messaging、Xamarin.Firebase.iOS.Core
3. 在AppDelegate.cs中配置推送：

using Firebase.Core;
using Firebase.Messaging;
using UserNotifications;

namespace YourApp.iOS
{
    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate, IUNUserNotificationCenterDelegate, IMessagingDelegate
    {
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init();
            FirebaseApp.Configure();
            RegisterForPushNotifications();
            LoadApplication(new App());
            return base.FinishedLaunching(app, options);
        }

        void RegisterForPushNotifications()
        {
            UNUserNotificationCenter.Current.Delegate = this;
            var authOptions = UNAuthorizationOptions.Alert | UNAuthorizationOptions.Badge | UNAuthorizationOptions.Sound;
            UNUserNotificationCenter.Current.RequestAuthorization(authOptions, (granted, error) =>
            {
                if (granted)
                {
                    InvokeOnMainThread(() => UIApplication.SharedApplication.RegisterForRemoteNotifications());
                }
            });
            Messaging.SharedInstance.Delegate = this;
        }

        public override void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
        {
            Messaging.SharedInstance.ApnsToken = deviceToken;
            var token = Messaging.SharedInstance.FcmToken;
            Preferences.Set("FCM_Token", token);
        }

        public override void FailedToRegisterForRemoteNotifications(UIApplication application, NSError error)
        {
            // 处理注册失败逻辑
        }

        [Export("userNotificationCenter:willPresentNotification:withCompletionHandler:")]
        public void WillPresentNotification(UNUserNotificationCenter center, UNNotification notification, Action<UNNotificationPresentationOptions> completionHandler)
        {
            completionHandler(UNNotificationPresentationOptions.Alert | UNNotificationPresentationOptions.Sound);
        }

        [Export("messaging:didReceiveRemoteMessage:")]
        public void DidReceiveRemoteMessage(Messaging messaging, RemoteMessage remoteMessage)
        {
            var title = remoteMessage.AppData["title"]?.ToString();
            var body = remoteMessage.AppData["body"]?.ToString();
            // 自定义消息处理逻辑
        }
    }
}

4. 实现共享项目的接口：

public class PushNotificationService : IPushNotificationService
{
    public void Initialize()
    {
        // 初始化已在AppDelegate完成
    }

    public Task<string> GetTokenAsync()
    {
        var token = Messaging.SharedInstance.FcmToken;
        Preferences.Set("FCM_Token", token);
        return Task.FromResult(token);
    }

    public void SubscribeToTopic(string topic)
    {
        Messaging.SharedInstance.SubscribeToTopic(topic);
    }
}

测试推送 #

可使用Firebase控制台的Cloud Messaging模块发送测试消息，或用curl命令：

curl -X POST -H "Authorization: key=YOUR_SERVER_KEY" -H "Content-Type: application/json" -d '{
  "to": "YOUR_FCM_TOKEN",
  "notification": {
    "title": "测试通知",
    "body": "这是一条来自FCM的测试消息"
  }
}' https://fcm.googleapis.com/fcm/send

替换YOUR_SERVER_KEY（Firebase控制台项目设置-云消息服务中获取）和YOUR_FCM_TOKEN（应用中获取的设备token）

内容的提问来源于stack exchange，提问作者MVKozyrev