类型“ UIApplication”没有成员“ didBecomeActiveNotification”

Question

我正在尝试使用以下代码为UIApplication.didBecomeActiveNotification添加观察者：

NotificationCenter.default.addObserver(forName: UIApplication.didBecomeActiveNotification, object: nil, queue: nil) { _ in /* some code */ }

但是Xcode说Type 'UIApplication' has no member 'didBecomeActiveNotification'是UIApplication类常量，尽管它是officially documented。我在做什么错了？

Answer 1

使用Xcode 10时，在 Build Settings 中，如果将 Swift Language Version 设置为Swift 4，则应输入：

NotificationCenter.default.addObserver(forName: .UIApplicationDidBecomeActive, object: nil, queue: nil) { _ in /* some code */ }

如果将其设置为Swift 4.2，请改用它：

NotificationCenter.default.addObserver(forName: UIApplication.didBecomeActiveNotification, object: nil, queue: nil) { _ in /* some code */ }

Answer 2

您应将通知名称更改为.UIApplicationDidBecomeActive，如下所示：

NotificationCenter.default.addObserver(forName: .UIApplicationDidBecomeActive, object: nil, queue: nil) { _ in /* some code */ }

显然，didBecomeActiveNotification仅适用于iOS 12 SDK。