//回调
static void displayStatusChanged(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo)
{
    // "com.apple.springboard.lockcomplete" 通知总是接在 "com.apple.springboard.lockstate" 通知后面
    CFStringRef nameCFString = (CFStringRef)name;
    NSString *lockState = (NSString*)nameCFString;
    NSLog(@"Darwin notification NAME = %@",name);

    if([lockState isEqualToString:@"com.apple.springboard.lockcomplete"])
    {
        NSLog(@"锁屏");
        //应用逻辑
    }
    else
    {
        NSLog(@"锁屏状态改变");
        //应用逻辑
    }
}

-(void)registerforDeviceLockNotif
{
    //锁屏通知
    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);
}

注意：“com.apple.springboard.lockcomplete” 通知总是会接在 “com.apple.springboard.lockstate” 后面