How can I detect screen lock/unlock events on the iPhone?

Question

How can I detect screen lock/unlock events on the iPhone? When the user unlocks it, I want to show a notification alert from my iPhone app. (For Just like Broadcast Receiver for screen unlock in Android.)

Answer 1

Check this out, I wanted to detect the lock/unlock events, I solved it by Darwin notifications. You can detect the event when the device is locked by "com.apple.springboard.lockcomplete".

//call back
static void displayStatusChanged(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo)
{
    // the "com.apple.springboard.lockcomplete" notification will always come after the "com.apple.springboard.lockstate" notification

    NSString *lockState = (NSString*)name;
    NSLog(@"Darwin notification NAME = %@",name);

    if([lockState isEqualToString:@"com.apple.springboard.lockcomplete"])
    {
        NSLog(@"DEVICE LOCKED");
    }
    else
    {
        NSLog(@"LOCK STATUS CHANGED");
    }   
}


-(void)registerforDeviceLockNotif
{
    //Screen lock notifications
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), //center
                                    NULL, // observer
                                    displayStatusChanged, // callback
                                    CFSTR("com.apple.springboard.lockcomplete"), // event name
                                    NULL, // object
                                    CFNotificationSuspensionBehaviorDeliverImmediately);

    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), //center
                                    NULL, // observer
                                    displayStatusChanged, // callback
                                    CFSTR("com.apple.springboard.lockstate"), // event name
                                    NULL, // object
                                    CFNotificationSuspensionBehaviorDeliverImmediately);  
}   

Answer 2

To detect lock/unlock inside app in swift 5 only this worked for me:

override func viewDidLoad() {
    super.viewDidLoad()

     NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.willEnterForegroundNotification, object: nil)
     NotificationCenter.default.addObserver(self, selector: #selector(applicationDidEnterBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
}

@objc func applicationDidBecomeActive(notification: NSNotification) {
    print("ACTIVE")
}
@objc func applicationDidEnterBackground(notification: NSNotification) {
    print("BACKGROUND")
}