Firebase Cloud Messaging数据消息是否需要调用requestPermission？

Great question—this is a common point of confusion because FCM behaves differently on iOS and Android, especially when it comes to data-only messages. Let’s break it down clearly:

iOS: Permission Rules Tie to APNs #

Since FCM relies on Apple’s APNs for iOS delivery, even data-only messages are subject to Apple’s push permission rules:

• You can technically retrieve an FCM token without calling firebase.messaging().requestPermission() or getting user consent. But here’s the catch: that token won’t let FCM deliver data messages reliably across all app states.
• If the user denies push permissions, APNs will block all message delivery (including data messages) when your app is in the background or terminated. The only time data messages might reach your app is when it’s actively in the foreground—hardly ideal for most use cases.
• Calling requestPermission() triggers the iOS system push prompt, and getting user consent is the only way to ensure data messages are delivered reliably no matter the app’s state. So while it’s not strictly required to get a token, it’s essential for functional data message delivery on iOS.

Android: No Permission Required #

Android’s approach is far more straightforward:

• You do not need to call firebase.messaging().requestPermission() for data-only messages.
• FCM tokens are generated automatically when the SDK initializes, no user consent needed.
• Data messages are delivered directly to your app’s FirebaseMessagingService whether the app is in the foreground, background, or terminated—as long as the device has an internet connection and the token is valid. Android doesn’t have a system-level prompt for FCM-related permissions here; they’re granted by default when the SDK is installed.

Quick Recap #

• iOS: Get user permission (via requestPermission()) if you want reliable data message delivery across all app states. You can get a token without permission, but it’s not useful for most delivery scenarios.
• Android: No permissions needed for data messages or token retrieval—everything works out of the box.

内容的提问来源于stack exchange，提问作者MonkeyBonkey