在Swift中将后台任务作为循环运行

本文介绍了在Swift中将后台任务作为循环运行的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我知道我可以创建这样的后台任务：

I know that I can create a background task like this:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // do some task dispatch_async(dispatch_get_main_queue(), ^{ // update some UI }); });

（来源）

如何创建一个后台任务，每个 n执行代码块秒，如何停止此任务？

How can I create a background task which executes a code block every n seconds and how can I stop this task?

推荐答案

结合 NSTimer 和您的背景代码。这将是：

Combine NSTimer and your background code. That will be like:

- (void)someBackgroundTask:(NSTimer *)timer { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{ // do some task dispatch_async(dispatch_get_main_queue(), ^{ // update some UI }); }); }

然后通过计时器调用此方法

and then call this method through timer

NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(someBackgroundTask:) userInfo:nil repeats:YES];

停止该计时器和后台执行

to stop that timer and the background execution

[timer invalidate];

func someBackgroundTask(timer:NSTimer) { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), { () -> Void in println("do some background task") dispatch_async(dispatch_get_main_queue(), { () -> Void in println("update some UI") }) }) }

然后通过计时器调用此方法

and then call this method through timer

var timer = NSTimer(timeInterval: 1.0, target: self, selector: "someBackgroundTask:", userInfo: nil, repeats: true)

停止该计时器和后台执行

to stop that timer and the background execution

timer.invalidate()

Swift 3及更高版本

Swift 3 and later

func someBackgroundTask(timer:Timer) { DispatchQueue.global(qos: DispatchQoS.background.qosClass).async { print("do some background task") DispatchQueue.main.async { print("update some UI") } } }

并创建/调用计时器

var timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in self.someBackgroundTask(timer: timer) }

invalidate 方法相同。