detect if phone screen is on/off in iOS

Question

I have requirement in my application to detect if phone screen is on/off when the application is in the background? I found that this can be possible using private framework Spring board. Can we do so with public APIs?

Thank.

Answer 1

try this:

in AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{
    //Other code
    [self registerforDeviceLockNotif];
}

//Register Notification
-(void)registerforDeviceLockNotif
{
    //Screen screenDisplayStatus notifications
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), NULL, screenDisplayStatus, CFSTR("com.apple.iokit.hid.displayStatus"), NULL, CFNotificationSuspensionBehaviorDeliverImmediately);

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

//RemoveNotification if you don't need any more.
-(void)removeforDeviceLockNotif{
    CFNotificationCenterRemoveObserver(CFNotificationCenterGetDarwinNotifyCenter(), NULL, CFSTR("com.apple.iokit.hid.displayStatus"), NULL);
    CFNotificationCenterRemoveObserver(CFNotificationCenterGetDarwinNotifyCenter(), NULL, CFSTR("com.apple.springboard.lockstate"), NULL);
}

//Call back Methods
static void screenDisplayStatus(CFNotificationCenterRef center, void* observer, CFStringRef name, const void* object, CFDictionaryRef userInfo) {
    uint64_t state;
    int token;
    notify_register_check("com.apple.iokit.hid.displayStatus", &token);
    notify_get_state(token, &state);
    notify_cancel(token);
    if (state) {
        screenIsBlack = NO;
    }else{
        screenIsBlack = YES;
    }
}

static void screenLockStatus(CFNotificationCenterRef center, void* observer, CFStringRef name, const void* object, CFDictionaryRef userInfo)
{
    uint64_t state;
    int token;
    notify_register_check("com.apple.springboard.lockstate", &token);
    notify_get_state(token, &state);
    notify_cancel(token);
    if (state) {
        screenIsLocked = YES;
    }
    else
    {
        screenIsLocked = NO;
    }
}

Do you task when screen is black screen:

if (appIsBackground && (screenIsBlack || screenIsLocked) {
    //do Task.
}

Note that, here I have made the screen lock status as screen is black, if you need not, just remove the lock status judgement.

Answer 2

Also consider that an app in a background mode will only run / do tasks for a certain period of time before it is suspended. Then all your code stops executing and the app is "paused".

If your app offers features like GPS tracking, Audio playback - that sort of thing, then you can request permission from Apple to keep it alive in the background. If it doesn't offer the above or something similar - then your app will only live a very, undetermined, short time in the background thus, detecting the screen state may be a fruitless exercise.