Question

我有一个完美的下载功能，点击我的按钮，文件正在正确下载。

我想要实现的目标，如果我将应用程序置于后台或在下载文件时更改屏幕，我希望继续下载。目前，如果应用程序处于后台，则下载停止并且用户需要从零重新启动它。

这怎么可能？下面是我的下载功能，我试图添加后台下载但没有成功。

<!DOCTYPE html>
<html>
<head>
  <button onclick="generate();">Generate password</button>
</head>
<body>
  <p id="pw">
    <!-- password should go here -->
  </p>
</body>
</html>

和

 func createDownloadTask() {
        let downloadRequest = URLRequest(url: URL(string: "\(posts[selectedIndexPath].link)")!)
        let session = Foundation.URLSession(configuration: URLSessionConfiguration.default, delegate: self, delegateQueue: OperationQueue.main)

        downloadTask = session.downloadTask(with: downloadRequest)
        downloadTask!.resume()


    }

Answer 1

您需要使用UIBackgroundTaskIdentifier。您可以使用beginBackgroundTask在后台启动一些任务，请参阅： https://developer.apple.com/reference/uikit/uiapplication/1623031-beginbackgroundtask。系统会给你一些时间，你可以完成你的任务。如果时间到期，您将收到处理程序。请参阅我用于上传图像的示例

  static var backgroundUpload:UIBackgroundTaskIdentifier?
static func praiseCollegue(praiseCollegueId:Int,image:UIImageView,praisedBy:Int,praiseText:String,praiseCategory:Int,successBlock: (()->())?,errorBlock: (()->())?){
    backgroundUpload = UIApplication.shared.beginBackgroundTask(expirationHandler: {
        if let task = self.backgroundUpload{
            UIApplication.shared.endBackgroundTask(task)
        }

    })

    let url = NSURL(string: "someUrl")

    let request = NSMutableURLRequest(url: url! as URL)
    request.httpMethod = "POST"
    request.setValue(InfoManager.sharedInstance.tokenInfo?.accessToken, forHTTPHeaderField: "AccessToken")


    let session = URLSession.shared
    let task = session.dataTask(with: request as URLRequest) {
        (
        data, response, error) in
        if let responseData = data{
            do {
                if let dict = try JSONSerialization.jsonObject(with: responseData, options: []) as? [String: AnyObject]{
                    if let errorCode = dict["errorCode"] as? Int{
                        if(errorCode == 1){
                            successBlock?()
                            if let task = self.backgroundUpload{
                                UIApplication.shared.endBackgroundTask(task)
                            }
                        }
                        else{
                            errorBlock?()
                            if let task = self.backgroundUpload{
                                UIApplication.shared.endBackgroundTask(task)
                            }
                        }
                    }
                }
            }
        }
    }

    task.resume()

}

继续在我的ios应用程序的背景/其他屏幕上下载

1 个答案: