How Can My Flutter iOS App Process FCM Push Notifications in the Background Without User Interaction?

When using FCM on iOS, you need to be aware that handling background messages is different from Android. On iOS the system only wakes your app for “silent” pushes and not when a full notification payload is delivered by APNs unless the user taps on it. Here are a few key points and steps to address the issue:

1. Use Silent Notifications

To ensure your background handler is invoked automatically, the message payload must be configured as a silent notification. This means:

• The notification payload should be sent as a data-only message or include the key content-available: 1 in the APNs payload.
• Avoid including a notification key in the payload. If you include one, iOS will have the system display the notification, and the background handler won’t be triggered unless the user interacts with it.

Example payload for a silent notification:

JSONCopied
{
  "aps": {
    "content-available": 1
  },
  "data": {
    "customKey": "customValue"
  }
}

2. Ensure App Capabilities Are Correctly Configured

Make sure that you have enabled both “Remote notifications” in Background Modes and “Push Notifications” in your Xcode project. Without these settings, iOS may not wake your app in the background regardless of your payload.

3. Avoid Disabling Method Swizzling

The FCM Flutter plugin relies on method swizzling for key functions (like token handling). Make sure you have not disabled it, as this may affect background processing on iOS.

4. Understand iOS Limitations for Background Tasks

Due to iOS limitations, even with a silent notification, background execution is constrained:

• The background message handler is executed in a separate context. You cannot perform UI updates. Perform only lightweight tasks (such as making network calls or updating local storage) as the OS might kill the process if it takes too long.
• Delivery of silent pushes is not guaranteed in all scenarios because iOS manages power and performance restrictions strictly.

Summary

To auto-process incoming push notifications in the background on iOS:

• Configure your FCM messages to use content-available: 1 and send a data-only payload.
• Verify that your Xcode project settings have both “Push Notifications” and “Remote notifications” enabled.
• Do not disable method swizzling.
• Keep in mind that iOS limits what you can do in the background, so ensure that your background tasks are lightweight.

With these adjustments in your payload and configurations, your background message handler should be invoked automatically on iOS even when the app is inactive, without requiring the user to tap the notification.