How to Check If the iOS Device Is Locked/Unlocked

Is there a way to check if the iOS device is locked/unlocked?

I solved it like this:

//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
    CFStringRef nameCFString = (CFStringRef)name;
    NSString *lockState = (NSString*)nameCFString;
    NSLog(@"Darwin notification NAME = %@",name);
    
    if([lockState isEqualToString:@"com.apple.springboard.lockcomplete"])
    {
        NSLog(@"DEVICE LOCKED");
        //Logic to disable the GPS
    }
    else
    {
        NSLog(@"LOCK STATUS CHANGED");
        //Logic to enable the GPS
    }
}

-(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);
}

Note: the "com.apple.springboard.lockcomplete" notification will always come after the "com.apple.springboard.lockstate" notification

Update

The order of the two notifications can no longer be relied upon, as of recent versions of iOS

how to tell when the device screen is locked or unlocked in swift

As the device is being locked, if your app was frontmost, then you'll get applicationWillResignActive(_:) in the app delegate, and the corresponding notification if you register for it.

As the device is being unlocked, if your app was frontmost, then it will be active and frontmost again and you'll get applicationDidBecomeActive in the app delegate, and the corresponding notification if you register for it.

(If your app was not frontmost, you have no way to detect that anything is happening, but that's okay because there is no "you" — the app is not running.)

That is sufficient to let you write a timer that "keeps counting" in the background by looking at the different between the time it started (or the time we deactivated) and the time when we are activated. So the timer effectively "runs" in the background.

Xcode Device Locked When iPhone is unlocked

Did you by chance not "trust" the device? This will prevent it from communicating with xcode even if the device is unlocked.

Update here's a support doc from Apple: http://support.apple.com/en-us/HT5868

Checking for iOS device first unlock to determine if items stored with kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly are available

I've come across the same situation in my app and here's how I'm checking if the keychain is available (objective-c code):

+ (BOOL)isKeychainAvailable {
    NSString *testVal = @"testVal";
    NSString *testKey = @"testKey";
    [JNKeychain saveValue:testVal forKey:testKey];
    NSString *validatedValue = [JNKeychain loadValueForKey:testKey];
    [JNKeychain deleteValueForKey:testKey];
    return (validatedValue == testVal);
}

I basically save a value in the keychain and try to read it again. If it's not the same as I've just written it means the keychain is unavailable, which also means the phone hasn't been through the first unlock since the keychain should be available after the first unlock thanks to the option kSecAttrAccessibleAfterFirstUnlock.

What I ended up doing in this situation is terminating the app if it was started in the background and the keychain is unavailable:

- (void) methodStartedInBackgroundThatNeedsKeychain {
    if (!JNKeychain.isKeychainAvailable && [UIApplication sharedApplication].applicationState != UIApplicationStateActive) {
        exit(0);
    }
}

ATTENTION! please be aware that Apple strongly discourages the usage of exit(0) when the app is in foreground mode, thats why I'm making sure to only call it in background with [UIApplication sharedApplication].applicationState != UIApplicationStateActive. Here's Apple's QA discussion on the subject: https://developer.apple.com/library/archive/qa/qa1561/_index.html

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