CrossFirebasePushNotification.Current.OnTokenRefresh启动时约1/3概率不触发求助

使用Windows版Visual Studio开发Xamarin.Forms应用时，CrossFirebasePushNotification.Current.OnTokenRefresh事件在应用启动时约有1/3的概率不会触发，该问题在调试模式及设备离线运行场景下均存在。

相关代码如下：

App.xaml.cs #

public partial class App : Application
{
    public App()
    {
        InitializeComponent();

        CrossFirebasePushNotification.Current.OnTokenRefresh += Current_OnTokenRefresh;
    }

    private void Current_OnTokenRefresh(object source, FirebasePushNotificationTokenEventArgs e)
    {
        System.Diagnostics.Debug.WriteLine($"Token: {e.Token}");
    }
}

MainActivity.cs #

namespace MyApp.Droid
{
    [Activity(Label = "MyApp", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize )]
    public partial class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        partial void OnPreCreate(Bundle savedInstanceState);

        protected override void OnCreate(Bundle savedInstanceState)
        {
            this.OnPreCreate(savedInstanceState);

            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(savedInstanceState);

            FirebasePushNotificationManager.ProcessIntent(this, Intent);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);

            LoadApplication(new App());

            this.OnPostCreate(savedInstanceState);
        }

        protected override void OnNewIntent(Intent intent)
        {
            base.OnNewIntent(intent);

            FirebasePushNotificationManager.ProcessIntent(this, intent);
        }
    }
}

Android项目Application.cs #

namespace MyApp.Droid
{
    [Application]
    public class MainApplication : Application
    {
        public override void OnCreate()
        {
            base.OnCreate();

            //Set the default notification channel for your app when running Android Oreo
            if (Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O)
            {
                //Change for your default notification channel id here
                FirebasePushNotificationManager.DefaultNotificationChannelId = "FirebasePushNotificationChannel";

                //Change for your default notification channel name here
                FirebasePushNotificationManager.DefaultNotificationChannelName = "General";

                FirebasePushNotificationManager.DefaultNotificationChannelImportance = NotificationImportance.High;
            }

            //If debug you should reset the token each time.
#if DEBUG
            FirebasePushNotificationManager.Initialize(this, true);
#else
            FirebasePushNotificationManager.Initialize(this, false);
#endif

            //Handle notification when app is closed here
            CrossFirebasePushNotification.Current.OnNotificationReceived += (s, p) =>
            {
            };
        }
    }
}

• 调整事件绑定时机：将OnTokenRefresh事件的绑定从App构造函数移至App的OnStart方法中，确保Firebase初始化完成后再绑定事件，避免因初始化未完成导致事件丢失：

  protected override void OnStart()
  {
      base.OnStart();
      CrossFirebasePushNotification.Current.OnTokenRefresh += Current_OnTokenRefresh;
      // 主动触发Token获取
      _ = CrossFirebasePushNotification.Current.GetTokenAsync();
  }
  

• 主动获取Token：在绑定事件后主动调用GetTokenAsync()方法，即使OnTokenRefresh未自动触发，也能主动获取Token，部分情况下该方法会在Token存在时触发OnTokenRefresh事件。
• 检查初始化日志：在MainApplication的OnCreate方法末尾、App的事件绑定后添加日志输出，确认Firebase初始化状态与事件绑定状态，便于定位问题：

  // MainApplication中Initialize后添加
  System.Diagnostics.Debug.WriteLine("Firebase Push Notification初始化完成");
  // App的OnStart中绑定事件后添加
  System.Diagnostics.Debug.WriteLine("OnTokenRefresh事件已绑定");
  

• 处理Token缓存逻辑：Release模式下Initialize的第二个参数为false（不重置Token），若本地已有缓存Token，OnTokenRefresh不会触发。可在启动时主动检查Token是否为空，为空时再调用GetTokenAsync()：

  var existingToken = CrossFirebasePushNotification.Current.Token;
  if(string.IsNullOrEmpty(existingToken))
  {
      _ = CrossFirebasePushNotification.Current.GetTokenAsync();
  }
  else
  {
      // 直接使用已有Token，或手动触发事件处理逻辑
      Current_OnTokenRefresh(null, new FirebasePushNotificationTokenEventArgs(existingToken));
  }
  

• 确认权限配置：检查Android项目的AndroidManifest.xml是否正确配置了Firebase所需权限，确保网络权限（INTERNET）及通知权限已添加，避免因权限问题导致Token获取失败。

内容的提问来源于stack exchange，提问作者Y U