iPhone Objective-c detect Screen Lock

Question

I'm new to make iPhone App with Objective-c

I want to make the App which sends a notification when iPhone screen is locked(Pressed Lock button) How can I make this app?

I'm trying to make it using "applicationWillSuspend", but

/*----------------------------------------*/
- (void)applicationWillSuspend
{
     NSLog(@"WillSuspend");
}
/*----------------------------------------*/

This code doesn't work

I'm not sure when applicationWillSuspend is called

Please, give me some knowledge

#import "AppDelegate.h"
#import <notify.h>

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    // iOS8 Notification permit
    if ([UIApplication
         instancesRespondToSelector:@selector(registerUserNotificationSettings:)]) {
        [[UIApplication sharedApplication]
         registerUserNotificationSettings:[UIUserNotificationSettings
                                           settingsForTypes:UIUserNotificationTypeAlert|UIUserNotificationTypeSound
                                           categories:nil]];
    }
    return YES;

    int notify_token;
    notify_register_dispatch("com.apple.springboard.lockstate",
                             &notify_token,
                             dispatch_get_main_queue(),
                             ^(int token)
                             {
                                 uint64_t state = UINT64_MAX;
                                 notify_get_state(token, &state);
                                 if(state == 0) {
                                     NSLog(@"unlock device");
                                 } else {
                                     NSLog(@"lock device");
                                 }
                             }
                             );

}

Answer 1

Import this in app delegate #import <notify.h>

Write this piece of code in didFinishLaunchingWithOptions

int notify_token;
    notify_register_dispatch("com.apple.springboard.lockstate",
                         &notify_token,
                         dispatch_get_main_queue(),
                         ^(int token)
                         {
                             uint64_t state = UINT64_MAX;
                             notify_get_state(token, &state);
                             if(state == 0) {
                                 NSLog(@"unlock device");
                             } else {
                                 NSLog(@"lock device");
                             }
                         }
                         );

So once your iPhone gets locked, you will get "lock device" as log. So you can write your code in that block. This will help you.