当应用程序处于后台时，来自 iOS 推送通知操作的 Http 请求

Question

我的 iOS 应用程序可以通过操作按钮接收推送通知：

点击按钮通过 UrlSession 和数据任务发送 post http 请求。当应用程序暂停或未运行时，它可以很好地工作。但当应用程序处于后台时，例如当用户刚刚从底部向上滑动（或按下主页按钮）时，它不起作用。推送操作会处理，但 http 请求不会发送。

从我的 iPhone 的控制台 os_logs 中，我看到 UrlSession 无法从后台建立连接并抛出错误 Code=-1005“网络连接丢失。”。我一杀掉应用程序就可以了。我尝试了不同的 url 会话配置、后台 url 会话、后台任务，但没有任何效果。我发现的唯一解决方法是使用exit(0)fromapplicationDidEnterBackground方法，但强烈不建议以编程方式终止应用程序。

问题：当应用程序处于后台时，如何通过推送通知操作建立 http 连接？

我的代码：

class NotificationService: NSObject, UNUserNotificationCenterDelegate {
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        // notification processing if app is in foreground
        ...
    }
    
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        let requestId = String(describing: response.notification.request.content.userInfo["requestId"] ?? "")
        switch response.actionIdentifier {
        case "CONFIRM_ACTION":
            confirmAuthenticationRequest(requestId: requestId, isConfirmed: true)
        case "REJECT_ACTION":
            confirmAuthenticationRequest(requestId: requestId, isConfirmed: false)
        default:
            // on notification tap
            ...
        }
        completionHandler()
    }

private func confirmAuthenticationRequest(requestId: String, isConfirmed: Bool) {
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        let json: [String: Any] = [
            "requestId": requestId,
            "deny": !isConfirmed
        ]
        request.httpBody = try? JSONSerialization.data(withJSONObject: json)
        request.addValue("application/json", forHTTPHeaderField: "content-type")
        
        let dataTask = urlSession.dataTask(with: request)
        dataTask.resume()
    }
}

Answer 1

最后我找到了答案。推送通知操作工作不稳定的原因是completionHandler从userNotificationCenterDidReceiveResponse方法调用的方式错误。当执行像http请求这样的异步操作时，您必须completionHandler 在操作完成后（而不是在操作调用之后）立即从主线程调用。这是工作示例：

class NotificationService: NSObject, UNUserNotificationCenterDelegate {
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        let requestId = String(describing: response.notification.request.content.userInfo["requestId"] ?? "")
        switch response.actionIdentifier {
        case "CONFIRM_ACTION":
            confirmAuthenticationRequest(requestId: requestId, isConfirmed: true, completion: completionHandler)
        case "REJECT_ACTION":
            confirmAuthenticationRequest(requestId: requestId, isConfirmed: false, completion: completionHandler)
        default:
            // on notification tap
            ...
            completionHandler()
        }
    }

private func confirmAuthenticationRequest(requestId: String, isConfirmed: Bool, completion: @escaping () -> Void) {
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        let json: [String: Any] = [
            "requestId": requestId,
            "deny": !isConfirmed
        ]
        request.httpBody = try? JSONSerialization.data(withJSONObject: json)
        request.addValue("application/json", forHTTPHeaderField: "content-type")
        
        let dataTask = urlSession.dataTask(with: request) { _, _, _ in
            DispatchQueue.main.async {
                completion()
            }
        }
        dataTask.resume()
    }
}