如何在AppDelegate外发起Firebase Cloud Messaging（FCM）通知授权请求？

当咱们要在iOS应用里集成FCM推送功能时，第一步必须要向用户请求通知权限。根据Firebase官方文档的建议，咱们应该把权限请求的代码放在AppDelegate的didFinishLaunchingWithOptions方法里，下面是完整的实现示例：

import UIKit
import Firebase
import UserNotifications // iOS 10+ 需要导入该框架

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 初始化Firebase服务
        FirebaseApp.configure()
        
        // 分版本处理通知权限请求
        if #available(iOS 10.0, *) {
            // iOS 10及以上版本的权限请求逻辑
            let notificationCenter = UNUserNotificationCenter.current()
            notificationCenter.delegate = self
            // 请求弹窗、声音、角标三种通知权限
            notificationCenter.requestAuthorization(options: [.alert, .sound, .badge]) { granted, error in
                if let error = error {
                    print("请求通知权限出错：\(error.localizedDescription)")
                    return
                }
                if granted {
                    print("用户已授权通知权限")
                    // 注册远程通知，获取设备令牌
                    application.registerForRemoteNotifications()
                } else {
                    print("用户拒绝了通知权限")
                }
            }
        } else {
            // iOS 9及以下版本的权限请求逻辑
            let notificationSettings = UIUserNotificationSettings(types: [.alert, .sound, .badge], categories: nil)
            application.registerUserNotificationSettings(notificationSettings)
            application.registerForRemoteNotifications()
        }
        
        return true
    }
    
    // iOS 9及以下版本，监听权限请求结果
    func application(_ application: UIApplication, didRegisterUserNotificationSettings settings: UIUserNotificationSettings) {
        if settings.types != .none {
            application.registerForRemoteNotifications()
        }
    }
    
    // 成功获取设备令牌的回调，需将令牌同步给Firebase
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let tokenString = deviceToken.map { String(format: "%02.2hhx", $0) }.joined()
        print("FCM设备令牌：\(tokenString)")
        Messaging.messaging().apnsToken = deviceToken
    }
    
    // 注册远程通知失败的回调
    func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("注册远程通知失败：\(error.localizedDescription)")
    }
    
    // iOS 10+ 前台收到通知时的处理逻辑
    @available(iOS 10.0, *)
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        // 自定义前台通知的展示方式，这里保留弹窗、声音、角标
        completionHandler([.alert, .sound, .badge])
    }
}

关键细节说明： #

• Firebase初始化：FirebaseApp.configure()必须放在权限请求之前，确保Firebase服务正常启动
• 权限类型调整：你可以根据业务需求，修改权限选项（比如只请求.sound权限）
• 设备令牌作用：获取到的设备令牌是FCM定向推送消息的核心标识，一定要同步给Firebase
• 版本兼容：代码做了iOS版本判断，同时覆盖高、低版本系统的权限请求逻辑

内容的提问来源于stack exchange，提问作者Agung