Differentiate between screen lock and home button

Question

I need to do something in applicationDidEnterBackground. But I need to differentiate which user action causes the "enter background": screen lock or home button press.

I was using this code, which is from this post - How to differentiate between screen lock and home button press on iOS5?:

UIApplicationState state = [application applicationState];
if (state == UIApplicationStateInactive) {
    NSLog(@"Sent to background by locking screen");
} else if (state == UIApplicationStateBackground) {
    NSLog(@"Sent to background by home button/switching to other app");
}

It works fine on iOS6. but on iOS7 (both device and simulator), I always get UIApplicationStateBackground, whether the user clicks the home or the lock button.

Does someone have an idea about what could cause this? iOS 7 updates to multi-task background handling? Or some setting of my app (my app's background mode is off)?

And is there an alternative solution?

Answer 1

It doesn't work in Swift, you need to do some modification to make it work in Swift as follow

1.create a objectiveC file named LockNotifierCallback.m as follow:

static void displayStatusChanged(CFNotificationCenterRef center,
                                 void *observer,
                                 CFStringRef name,
                                 const void *object,
                                 CFDictionaryRef userInfo) {
    if ([(__bridge NSString *)name  isEqual: @"com.apple.springboard.lockcomplete"]) {
        NSLog(@"Screen Locked");
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"kDisplayStatusLocked"];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }
}

@implementation LockNotifierCallback

+ (void(*)(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo))notifierProc {
return displayStatusChanged;
}

@end

create a head as well: #import

@interface LockNotifierCallback : NSObject


+ (void(*)(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo))notifierProc;


@end

2.bridge this file to swift

3.add function to APPdelegate.swift:

CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), nil, LockNotifierCallback.notifierProc(), "com.apple.springboard.lockcomplete", nil, CFNotificationSuspensionBehavior.DeliverImmediately)

PS:UIApplicationState doesn't work perfectly in here

Answer 2

This solution was taken from this answer and worked for me. It is a bit hacky but it makes it easier to be accepted on the appstore because it doesn't use com.apple.springboard.lockcomplete or com.apple.springboard.lockstate.

The following code goes into your AppDelegate:

func applicationDidEnterBackground(_ application: UIApplication) {
    if (DidUserPressLockButton()) {
        print("User pressed lock button")
    } else {
        print("user pressed home button")
    }
}

private func DidUserPressLockButton() -> Bool {
    let oldBrightness = UIScreen.main.brightness
    UIScreen.main.brightness = oldBrightness + (oldBrightness <= 0.01 ? (0.01) : (-0.01))
    return oldBrightness != UIScreen.main.brightness
}

The idea is to try changing the brightness of the screen after the application went to background and to check if this change was successful.

Disclaimer: it doesn't work on the simulator and you will have to test it on a real device.

Answer 3

This can help you both on iOS6 & iOS7 :).

When user press lock button you will get a com.apple.springboard.lockcomplete notification.

//new way
//put this in - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),
                                    NULL,
                                    displayStatusChanged,
                                    CFSTR("com.apple.springboard.lockcomplete"),
                                    NULL,
                                    CFNotificationSuspensionBehaviorDeliverImmediately);

//put this function in AppDelegate
static void displayStatusChanged(CFNotificationCenterRef center,
                                 void *observer,
                                 CFStringRef name,
                                 const void *object,
                                 CFDictionaryRef userInfo) {
    if (name == CFSTR("com.apple.springboard.lockcomplete")) {
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"kDisplayStatusLocked"];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }
}

//put this in onAppEnterBackground
UIApplicationState state = [[UIApplication sharedApplication] applicationState];
    if (state == UIApplicationStateInactive) {
        NSLog(@"Sent to background by locking screen");
    } else if (state == UIApplicationStateBackground) {
        if (![[NSUserDefaults standardUserDefaults] boolForKey:@"kDisplayStatusLocked"]) {
            NSLog(@"Sent to background by home button/switching to other app");
        } else {
            NSLog(@"Sent to background by locking screen");
        }
    }

//put this in - (void)applicationWillEnterForeground:(UIApplication *)application
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"kDisplayStatusLocked"];
[[NSUserDefaults standardUserDefaults] synchronize];

CGFloat screenBrightness = [[UIScreen mainScreen] brightness];

NSLog(@"Screen brightness: %f", screenBrightness);

UIApplicationState state = [[UIApplication sharedApplication] applicationState];

if (state == UIApplicationStateInactive) {

    NSLog(@"Sent to background by locking screen");

} else if (state == UIApplicationStateBackground) {
    if (screenBrightness > 0.0) {
        NSLog(@"Sent to background by home button/switching to other app");
    } else {
        NSLog(@"Sent to background by locking screen");
    }
}