ios - 返回 App 时如何读取设置包？

Question

我在设置包中创建了“updateheading”

如果用户离开应用程序，转到设置更改值，当用户返回应用程序时，locationManager 应该根据更新的值启动/停止。

但应用程序不运行 viewWillAppear。如何读取更新值？

private let locationManager : CLLocationManager = CLLocationManager()

override func viewDidLoad() {
    super.viewDidLoad()

    locationManager.requestWhenInUseAuthorization()
    locationManager.delegate = self
}
override func viewWillAppear(_ animated: Bool) {

    let userDefault = UserDefaults.standard
    let updateheading = userDefault.object(forKey: "updateheading") as! Bool
    if(updateheading){
        locationManager.startUpdatingHeading()
    }else{
        locationManager.stopUpdatingHeading()
    }
}

Answer 1

View Controller 不响应应用程序状态。这是 AppDelegate 的责任。但是您可以订阅通知。

var observer: Any?

override func viewWillAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    observer = NotificationCenter.default.addObserver(forName: NSNotification.Name.UIApplicationDidBecomeActive, object: nil, queue: .main) { (_) in
        doUpdate()
    }
    doUpdate()
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    observber = nil
}

doUpdate 是您当前的代码。

PS:“如果您覆盖 viewWillAppear，则必须在实现的某个时刻调用 super。” (c) Apple Docs