Question

不幸的是，我发现UIView.animateWithDuration一旦你将应用程序最小化到主屏幕就会停止，并且一旦你把它带回到前台就不会恢复。

我花了最后一小时试图弄清楚如何解决这个问题（通过检测背景/前景切换）并导致添加一个观察者。我做到了，并在控制台中通过调试消息成功检测到它;但是，我确定如何在我的视图中恢复动画。当应用程序加载回前台时，暂停/恢复甚至重新启动动画的正确方法是什么？

ViewController.swift

class ViewController: UIViewController {
    func cameBackFromSleep(sender : AnyObject) {
        // Restart animation here or resume?
        print ("If you can see this, congrats... observer works :-)")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Observer to detect return from background
        NSNotificationCenter.defaultCenter().addObserver(    self,    selector: #selector(ViewController0.cameBackFromSleep(_:)),    name: UIApplicationDidBecomeActiveNotification,    object: nil    )

        // Add a label
        let label = UILabel(frame: CGRectMake(0, 600 , 200, 200 ))
        label.text = "test message"
        label.font = UIFont.boldSystemFontOfSize(12)
        label.sizeToFit()
        self.view.addSubview(label)

        // Animation to move label
        func animateText() {
            UIView.animateWithDuration(2.0, delay: 0.0, options: [ .Autoreverse, .Repeat, .CurveEaseInOut, .BeginFromCurrentState], animations: {
                label.alpha = 0.3
                label.frame.origin.x = ((global.maxwidth/2) * -1) 
                }, completion: { finished in
                    if finished {
                        label.frame.origin.x = 0.0
                    }
            })
        }

        // This guy here stops once you minimize the app to background
        animateText()
    }
}

Answer 1

将animateText()放入comeBackFromSleep(_:)。我相信恢复动画有点难，所以只需重新启动它。

这种行为在某种程度上是有道理的（你可以自己看看AppDelegate的方法）：

func applicationDidBecomeActive(application: UIApplication) {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

它声明您应该刷新UI（包括动画）。因此，将应用程序置于后台后动画停止是正常的行为。

返回前台后恢复animateWithDuration .Repeat

1 个答案: