即使用户强制退出iOS objective C中的应用程序，如何在后台继续下载新图像？

我想下载大约300张图片，并在UI中显示

我有两个问题：

 - (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier
  completionHandler:(void (^)())completionHandler {
   self.backgroundSessionCompletionHandler = completionHandler;

   //add notification
   [self presentNotification];
}

-(void)presentNotification{
    UILocalNotification* localNotification = [[UILocalNotification alloc] init];
    localNotification.alertBody = @"Download Complete!";
    localNotification.alertAction = @"Background Transfer Download!";

    //On sound
    localNotification.soundName = UILocalNotificationDefaultSoundName;

    //increase the badge number of application plus 1
    localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber] + 1;

    [[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}

如果应用程序位于前台，并且假设用户将其发送到后台模式（通过单击主页按钮），那么如何确保下载继续

如果用户强制退出应用程序（双击home按钮并从app switcher中滑动应用程序），那么如何确保应用程序下载图像

我一直在读很多背景资料。很少有人会这样说。案例下载无法继续

以下是我提到的链接：

 - (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier
  completionHandler:(void (^)())completionHandler {
   self.backgroundSessionCompletionHandler = completionHandler;

   //add notification
   [self presentNotification];
}

-(void)presentNotification{
    UILocalNotification* localNotification = [[UILocalNotification alloc] init];
    localNotification.alertBody = @"Download Complete!";
    localNotification.alertAction = @"Background Transfer Download!";

    //On sound
    localNotification.soundName = UILocalNotificationDefaultSoundName;

    //increase the badge number of application plus 1
    localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber] + 1;

    [[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}

我没有得到正确的方法来下载前景、背景/挂起的图像，用户强制退出应用程序。我正在使用AFNetworking进行Web服务呼叫

下面是我的代码：

 - (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier
  completionHandler:(void (^)())completionHandler {
   self.backgroundSessionCompletionHandler = completionHandler;

   //add notification
   [self presentNotification];
}

-(void)presentNotification{
    UILocalNotification* localNotification = [[UILocalNotification alloc] init];
    localNotification.alertBody = @"Download Complete!";
    localNotification.alertAction = @"Background Transfer Download!";

    //On sound
    localNotification.soundName = UILocalNotificationDefaultSoundName;

    //increase the badge number of application plus 1
    localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber] + 1;

    [[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}

我已经将.json文件中的URL等图像详细信息上传到amazon。要下载我需要的文件

[NSData dataWithContentsOfURL:[NSURL URLWithString:@"https://someurl/imageFile.json"]];

---

从这个文件中，我读取了图像的URL，并将其与图像详细信息一起下载。这是一个大过程。我怎么处理？请帮忙

您的1个问题的解决方案如下：

 - (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier
  completionHandler:(void (^)())completionHandler {
   self.backgroundSessionCompletionHandler = completionHandler;

   //add notification
   [self presentNotification];
}

-(void)presentNotification{
    UILocalNotification* localNotification = [[UILocalNotification alloc] init];
    localNotification.alertBody = @"Download Complete!";
    localNotification.alertAction = @"Background Transfer Download!";

    //On sound
    localNotification.soundName = UILocalNotificationDefaultSoundName;

    //increase the badge number of application plus 1
    localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber] + 1;

    [[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}

后台会话允许您在应用程序未运行时在后台执行内容的上载和下载。您可以通过调用NSURLSessionConfiguration类上的backgroundSessionConfiguration:方法来创建后台会话配置

在AppDelegate中添加以下代码：

 - (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier
  completionHandler:(void (^)())completionHandler {
   self.backgroundSessionCompletionHandler = completionHandler;

   //add notification
   [self presentNotification];
}

-(void)presentNotification{
    UILocalNotification* localNotification = [[UILocalNotification alloc] init];
    localNotification.alertBody = @"Download Complete!";
    localNotification.alertAction = @"Background Transfer Download!";

    //On sound
    localNotification.soundName = UILocalNotificationDefaultSoundName;

    //increase the badge number of application plus 1
    localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber] + 1;

    [[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}

适用于您的2个解决方案

如果系统关闭你的应用程序，并且你的后台会话有活动下载，你的下载将继续，下载完成后系统将启动你的应用程序。但是，如果用户强制退出你的应用程序，所有任务都将被取消

---

谢谢。。我要试试这个。。但是第二个案例呢？在iOS中，即使用户从app switcher退出应用程序，我也可以下载内容吗？是的。。我在《苹果医生》上读到了这篇文章。。但即使用户退出应用程序，安卓系统中的下载也会发生。我不知道为什么IOS中没有此功能那么在发送远程通知时我应该下载内容吗？因为如果用户退出应用程序，将始终调用此代理。。这是正确的做法吗？@Medha如果你设置了后台NSURLSession任务，下载由操作系统处理，而不是你的应用程序。你的应用程序可以终止/崩溃，但下载不会停止。我尝试了代码并浏览了其他有关NSURLSession的网站。它正在工作。但我还有一个问题。如果应用程序处于后台，请说2天。。如果我想在一天后下载一些东西，我应该怎么做？我是说如何再次触发NSURLSession恢复代码？