iOS 应用程序在后台执行任务 [英] iOS application executing tasks in background

问题描述

我想知道是否可以在我的应用程序在后台时发送一些网络服务调用.Skype 是如何做到的?即使我按下主页按钮，我的电话也会保持连接.

I was wondering if I could send some webservice calls while my application is in the background. How does skype do it? Even if I press the home button my call stays connected.

推荐答案

根据 rckoenes 所述，允许应用程序注册要在用户点击主页按钮后完成的后台任务.完成这些任务有 10 或 15 分钟的时间限制.同样，您可以在用户回家后立即注册要完成的任务，这不允许您在他们退出应用后一小时执行代码.

Building on what rckoenes stated, applications are allowed to register background tasks to be completed after the user hits the home button. There is a time limit of 10 or 15 minutes for these tasks to complete. Again, you can register a task to complete immediately after the user hits home, this does NOT allow you to execute code say an hour after they exit the app.

UIApplication*    app = [UIApplication sharedApplication];
task = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:task];
        task = UIBackgroundTaskInvalid;
    }];
// Start the long-running task and return immediately.
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // Do the work associated with the task.
        NSLog(@"Started background task timeremaining = %f", [app backgroundTimeRemaining]);
        if (connectedToNetwork) {
            // do work son...
        }

        [app endBackgroundTask:task];
        task = UIBackgroundTaskInvalid;
    });

更新:如果您的应用支持 iOs 4 之前的 iOS 版本，您还应该检查以确保在注册后台任务之前支持多任务处理.使用以下内容:

UPDATE: if your app supports versions of iOS previous to iOs 4, you should also check to ensure that multitasking is supported before registering a background task. Use something along the lines of:

UIDevice* device = [UIDevice currentDevice];

BOOL backgroundSupported = NO;

if ([device respondsToSelector:@selector(isMultitaskingSupported)])

   backgroundSupported = device.multitaskingSupported;

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