如何在指定时间段后每2秒触发重复本地通知？

现有代码的问题 #

现有代码通过循环创建多个一次性通知模拟间隔触发，存在以下不足：

• 逻辑冗余，需手动计算每个通知的触发时间
• APP重启或通知被清除后，后续通知会失效
• 无法灵活启停重复通知

解决方案 #

iOS系统限制UNTimeIntervalNotificationTrigger设置repeats: true时，时间间隔必须≥60秒，无法直接实现2秒间隔的系统重复通知。根据APP运行状态，分两种场景处理：

场景1：APP前台运行时 #

使用Timer实现精准的2秒重复触发，先延迟指定时间后启动Timer：

import UIKit
import UserNotifications

class ViewController: UIViewController, UNUserNotificationCenterDelegate {
    let notificationCenter = UNUserNotificationCenter.current()
    var repeatTimer: Timer?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        notificationCenter.requestAuthorization(options: [.alert, .sound, .badge]) { [weak self] granted, error in
            guard granted, error == nil else {
                print("通知权限未获取")
                return
            }
            // 自定义初始延迟时间（示例为1分钟）
            let initialDelay: TimeInterval = 60
            // 延迟后启动重复通知
            DispatchQueue.main.asyncAfter(deadline: .now() + initialDelay) {
                self?.startRepeatingNotifications()
            }
        }
        notificationCenter.delegate = self
    }
    
    /// 启动每2秒重复的通知
    func startRepeatingNotifications() {
        repeatTimer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] _ in
            self?.sendSingleNotification()
        }
    }
    
    /// 发送单条通知
    func sendSingleNotification() {
        let content = UNMutableNotificationContent()
        content.title = "Alarm present"
        content.body = "Alarm triggered at \(Date())"
        content.sound = .default
        
        // 立即触发通知
        let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 1, repeats: false)
        let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
        
        notificationCenter.add(request) { error in
            if let error = error {
                print("添加通知失败：\(error.localizedDescription)")
            }
            // 可选：清除已送达的通知，避免通知中心堆积
            self?.notificationCenter.removeAllDeliveredNotifications()
        }
    }
    
    /// 停止重复通知
    func stopRepeatingNotifications() {
        repeatTimer?.invalidate()
        repeatTimer = nil
    }
    
    // 前台接收通知时，允许弹窗和播放声音
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.alert, .sound])
    }
}

场景2：APP后台/锁屏时 #

后台无法使用Timer，只能通过批量创建一次性通知模拟间隔触发：

import UIKit
import UserNotifications

class ViewController: UIViewController, UNUserNotificationCenterDelegate {
    let notificationCenter = UNUserNotificationCenter.current()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        notificationCenter.requestAuthorization(options: [.alert, .sound, .badge]) { [weak self] granted, error in
            guard granted, error == nil else {
                print("通知权限未获取")
                return
            }
            // 自定义初始延迟时间（示例为1分钟）
            let initialDelay: TimeInterval = 60
            // 自定义重复次数（示例重复30次，总时长60秒）
            let repeatCount = 30
            self?.scheduleBatchNotifications(initialDelay: initialDelay, repeatCount: repeatCount)
        }
        notificationCenter.delegate = self
    }
    
    /// 批量创建延迟通知
    func scheduleBatchNotifications(initialDelay: TimeInterval, repeatCount: Int) {
        for index in 0...repeatCount {
            let triggerTime = initialDelay + TimeInterval(index * 2)
            let content = UNMutableNotificationContent()
            content.title = "Alarm present"
            content.body = "Alarm \(Int(triggerTime))"
            content.sound = .default
            
            let trigger = UNTimeIntervalNotificationTrigger(timeInterval: triggerTime, repeats: false)
            let request = UNNotificationRequest(identifier: "Alarm_\(index)", content: content, trigger: trigger)
            
            notificationCenter.add(request) { error in
                if let error = error {
                    print("添加通知失败：\(error.localizedDescription)")
                }
            }
        }
        // 可选：清除已送达的通知
        notificationCenter.removeAllDeliveredNotifications()
    }
}

重要提示 #

• 系统限制：iOS原生重复通知的最小间隔为60秒，2秒间隔的需求只能通过上述两种方式模拟
• 前台Timer限制：APP进入后台后Timer会暂停，若需后台持续触发，需申请后台任务权限，但后台任务有时间限制
• 权限处理：必须先获取用户的通知授权，否则无法发送任何通知

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