ios - 应用程序在后台时来自 iOS 推送通知操作的 Http 请求

Question

我的 iOS 应用程序可以接收带有操作按钮的推送通知:

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，它运行良好。但是当应用程序处于后台时它不起作用，例如当用户刚刚从底部向上滑动(或按下主页按钮)时。推送操作处理但未发送 http 请求。

从我的 iPhone 的控制台 os_logs 我看到 UrlSession 无法从后台建立连接并抛出错误代码=-1005“网络连接丢失。”。它可以在我终止应用程序后立即执行。我尝试了不同的 url session 配置、后台 url session 、后台任务，但没有任何效果。我发现的唯一解决方法是使用 applicationDidEnterBackground 方法中的 exit(0)，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

终于找到答案了。推送通知操作工作不稳定的原因是从 userNotificationCenterDidReceiveResponse 方法调用 completionHandler 的方式错误。当执行像 http 请求这样的异步操作时，您必须调用 completionHandler 在操作完成之后(而不是在操作调用之后)并且从主线程。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()
    }
}