ios - 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' 尽管它是 officially documented作为 UIApplication 类常量。我做错了什么？

Answer 1

当你使用 Xcode 10 时，在 Build Settings 中，如果你将 Swift Language Version 设置为 Swift 4，你应该这样写:

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

如果它设置为 Swift 4.2，请改用它:

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