Hey there! Let's tackle this problem—since iOS has strict background execution rules to preserve battery life, we can't just set a simple hourly timer. But there are ways to work within Apple's constraints to get close to your goal.

首先得明白iOS的后台限制 #

Apple doesn't allow apps to run arbitrary background tasks on a strict schedule. Any background activity has to fit into one of the system-approved background modes, and even then, the system reserves the right to delay or cancel tasks based on factors like battery level, network availability, and app usage frequency.

推荐方案：使用BGTaskScheduler（iOS 13+） #

This is the official Apple framework for scheduling deferrable background tasks. While it doesn't guarantee exact hourly execution, it's the best option for your use case without relying on push notifications.

步骤1：配置后台权限 #

1. Open your app's Info.plist and add the BGTaskSchedulerPermittedIdentifiers array. Add your task identifier (e.g., com.yourapp.refresh-badge) as an item in this array.
2. Go to your app's target settings → Capabilities → Enable Background Tasks.

步骤2：注册和处理任务 #

Here's a Swift implementation you can adapt:

import BackgroundTasks
import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Register the background task
        BGTaskScheduler.shared.register(forTaskWithIdentifier: "com.yourapp.refresh-badge", using: nil) { task in
            self.handleBadgeRefresh(task: task as! BGAppRefreshTask)
        }
        
        // Schedule the first refresh
        scheduleNextBadgeRefresh()
        return true
    }

    /// Handle the background refresh task
    private func handleBadgeRefresh(task: BGAppRefreshTask) {
        // Set up an expiration handler to clean up if the task gets cut short
        task.expirationHandler = {
            task.setTaskCompleted(success: false)
            print("Task expired before completion")
        }

        // Call your web API to get the latest badge count
        let apiURL = URL(string: "https://your-api-endpoint.com/badge-count")!
        URLSession.shared.dataTask(with: apiURL) { [weak self] data, _, error in
            defer {
                // Mark the task as completed once we're done
                task.setTaskCompleted(success: error == nil)
            }

            guard let data = data, error == nil else {
                print("API call failed: \(error?.localizedDescription ?? "Unknown error")")
                return
            }

            // Parse the response (adjust based on your API's format)
            if let badgeCount = try? JSONDecoder().decode(Int.self, from: data) {
                DispatchQueue.main.async {
                    UIApplication.shared.applicationIconBadgeNumber = badgeCount
                    print("Badge updated to \(badgeCount)")
                }
            }

            // Schedule the next refresh attempt (1 hour from now)
            self?.scheduleNextBadgeRefresh()
        }.resume()
    }

    /// Schedule the next background refresh task
    private func scheduleNextBadgeRefresh() {
        let taskRequest = BGAppRefreshTaskRequest(identifier: "com.yourapp.refresh-badge")
        // Request to run the task no earlier than 1 hour from now
        taskRequest.earliestBeginDate = Date(timeIntervalSinceNow: 3600)

        do {
            try BGTaskScheduler.shared.submit(taskRequest)
            print("Next refresh scheduled for \(taskRequest.earliestBeginDate!)")
        } catch {
            print("Failed to schedule refresh task: \(error.localizedDescription)")
        }
    }
}

关键注意事项 #

• No exact timing: The system will prioritize tasks based on device health. If the device is low on battery or in Low Power Mode, your task might be delayed or skipped entirely.
• App usage matters: If users haven't opened your app in a while, the system is less likely to schedule background tasks for it. This works best for apps that users interact with regularly.
• Testing: To test background tasks in the simulator, use Xcode's Debug → Simulate Background Task menu, or run this terminal command:

  xcrun simctl spawn booted bgtaskschedule -identifier com.yourapp.refresh-badge
  

其他可选方案（谨慎使用） #

• Location-based wakeups: If your app already uses location services, you can use significant location changes to wake the app. But if your app doesn't have a legitimate location use case, Apple will reject your app during review.
• Silent push notifications: You mentioned you don't want to use this, but it's worth noting that silent pushes are Apple's recommended way to trigger background updates. They're more reliable than BGTaskScheduler, but require a server to send pushes.

内容的提问来源于stack exchange，提问作者Passionate.C