类型“ UIApplication”没有成员“ didBecomeActiveNotification”

Question

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

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

但是Xcode表示Type 'UIApplication' has no member 'didBecomeActiveNotification'尽管已正式将其记录为UIApplication类常量。我做错了什么？

Answer 1

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

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：

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