如何在用户关闭Nativescript应用后重启，使其持续接收FCM消息？

Great question—this is such a common frustration when dealing with critical push notifications, especially when users force-close apps via the recent list. Let’s break this down for both Android and iOS since NativeScript targets both platforms, and cover how to keep FCM messages flowing even in these scenarios:

The approach varies drastically between Android and iOS due to platform-specific restrictions:

Android: Possible with Proper Configuration #

Android allows background services to wake your app, but you need to work within system constraints (especially for Android 10+):

• Use FCM Data Messages: Avoid sending standard notification messages (these are handled by the system when the app is closed). Instead, send data-only messages—these trigger your app's onMessageReceived callback even if the app is killed.
• Launch the Main Activity from the Callback: When a data message arrives, check if the app is closed, then launch your main activity. Here’s a NativeScript TypeScript example using the @nativescript/firebase-messaging plugin:

  import { firebase } from "@nativescript/firebase-core";
  import { Application } from "@nativescript/core";
  
  firebase().messaging().onMessageReceived((message) => {
    // Check if the app is not in the foreground
    const foregroundActivity = Application.android.foregroundActivity;
    if (!foregroundActivity) {
      // Create an intent to launch the main NativeScript activity
      const intent = new android.content.Intent(
        Application.android.context,
        com.tns.NativeScriptActivity.class
      );
      intent.addFlags(android.content.Intent.FLAG_ACTIVITY_NEW_TASK);
      Application.android.context.startActivity(intent);
    }
    // Process your critical message data here
  });
  

• Bypass Battery Optimization: Android 10+ restricts background activity launches unless your app is exempt from battery optimization. You’ll need to request the REQUEST_IGNORE_BATTERY_OPTIMIZATIONS permission and guide users to enable it for your app.
• Handle OEM Restrictions: Brands like Xiaomi, Huawei, and OPPO have their own background management tools. You’ll need to add in-app prompts to guide users to enable "Auto-Start" or "Protected App" permissions for your app—otherwise, your service may still be killed.

iOS: System Restrictions Prevent Auto-Restart #

Apple’s platform strictly prohibits auto-restarting apps that users have force-closed from the recent list. Here’s what you can do instead:

• Notifications Are Cached: When users force-close the app, FCM notifications are held by the system until the user manually opens the app again.
• Guide Users: Clearly communicate in your app and notification copy that force-closing the app will prevent critical alerts. Encourage users to keep the app running in the background instead.
• Use Silent Notifications (Limited): Silent notifications (content-available: 1) can trigger background updates when the app is in the background, but they won’t wake a force-closed app.

Beyond restarting, focus on making sure your app can receive FCM messages even when it’s not active:

Android Best Practices #

• Implement a Foreground Service: For Android 8+, long-running background services need to be foreground services (with a persistent notification) to avoid being killed. You can extend the Firebase Messaging Service to run as a foreground service:

  // Custom FirebaseMessagingService class (add to your Android native code)
  @Override
  public void onCreate() {
      super.onCreate();
      // Create a low-priority notification channel for the foreground service
      NotificationChannel channel = new NotificationChannel(
          "FOREGROUND_SERVICE_CHANNEL",
          "Background Service",
          NotificationManager.IMPORTANCE_LOW
      );
      NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
      manager.createNotificationChannel(channel);
  
      // Start the foreground service with a minimal notification
      Notification notification = new NotificationCompat.Builder(this, "FOREGROUND_SERVICE_CHANNEL")
          .setContentTitle("App monitoring for critical alerts")
          .setSmallIcon(R.drawable.ic_notification)
          .build();
      startForeground(1, notification);
  }
  

• Prioritize Messages: Mark critical FCM messages with priority: high (Android) to ensure they’re delivered promptly, even if the device is in doze mode.

iOS Best Practices #

• Enable Remote Notifications Background Mode: In Xcode, go to your app’s Capabilities and enable "Remote Notifications"—this allows the app to receive notifications while in the background.
• Use Alert Notifications: Even if the app is closed, alert notifications will prompt users to open the app, ensuring they see critical updates.

• Only auto-restart the app for urgent, time-sensitive events (like emergency alerts). Auto-restarting for non-critical messages will annoy users.
• Be transparent: Let users know why you need background permissions and how it helps them receive important alerts.
• Test across devices: Android OEMs have varying background restrictions, so test your app on popular brands to ensure reliability.

内容的提问来源于stack exchange，提问作者zarax