detect screen unlock events in IOS Swift

Question

How can i detect screen unlock events on iPhone? When the user unlocks it, I want to perform an action in my app. I searched on googled but only found code related to objective C , change it to swift but its not working.
Follow this blog: http://kidtechblogs.blogspot.com/2014/07/how-to-detect-screen-lockunlock-events.html.
Any help how can i detect it in swift. Below is the code change into swift..

func displayStatusChanged(center: CFNotificationCenter, observer: Void, name: CFString, object: Void, userInfo: CFDictionaryRef) {
        // the "com.apple.springboard.lockcomplete" notification will always come after the "com.apple.springboard.lockstate" notification
        let lockState = (name as String)
        print("Darwin notification NAME = (name)")
        if (lockState == "com.apple.springboard.lockcomplete") {
            print("DEVICE LOCKED")
        }
        else {
            print("LOCK STATUS CHANGED")
        }
    }

func registerforDeviceLockNotification() {
        //Screen lock notifications
        CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),     //center
                nil,     // observer
                displayStatusChanged,     // callback
                CFSTR("com.apple.springboard.lockcomplete"),     // event name
                nil,     // object
                .deliverImmediately)
        CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),     //center
                nil,     // observer
                displayStatusChanged,     // callback
                CFSTR("com.apple.springboard.lockstate"),     // event name
                nil,     // object
                .deliverImmediately)
    }

Answer 1

There a few errors in your code sample:

• Using CFString in swift is done by a simple cast: myString as CFString, no more CFSTR()...
• The easiest way to get the notification callback is to have add an observer using Unmanaged.passUnretained(self).toOpaque(). That will give you the possibility to catch the callback in your class

In the end, the swift version is quite different from the objective-c one, here the full code in Swift 3:

func registerforDeviceLockNotification() {
    //Screen lock notifications
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),     //center
        Unmanaged.passUnretained(self).toOpaque(),     // observer
        displayStatusChangedCallback,     // callback
        "com.apple.springboard.lockcomplete" as CFString,     // event name
        nil,     // object
        .deliverImmediately)
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),     //center
        Unmanaged.passUnretained(self).toOpaque(),     // observer
        displayStatusChangedCallback,     // callback
        "com.apple.springboard.lockstate" as CFString,    // event name
        nil,     // object
        .deliverImmediately)
}

private let displayStatusChangedCallback: CFNotificationCallback = { _, cfObserver, cfName, _, _ in
    guard let lockState = cfName?.rawValue as? String else {
        return
    }

    let catcher = Unmanaged<MyClassObserving>.fromOpaque(UnsafeRawPointer(OpaquePointer(cfObserver)!)).takeUnretainedValue()
    catcher.displayStatusChanged(lockState)
}

private func displayStatusChanged(_ lockState: String) {
    // the "com.apple.springboard.lockcomplete" notification will always come after the "com.apple.springboard.lockstate" notification
    print("Darwin notification NAME = (lockState)")
    if (lockState == "com.apple.springboard.lockcomplete") {
        print("DEVICE LOCKED")
    } else {
        print("LOCK STATUS CHANGED")
    }
}

and just in case, don't forget to remove your observer:

CFNotificationCenterRemoveObserver(CFNotificationCenterGetLocalCenter(),
                                   Unmanaged.passUnretained(self).toOpaque(),
                                   nil,
                                   nil)