1. 導(dǎo)入頭文件

#import <notify.h>

2. 給 CFNotificationCenter 添加觀察者

- (void)addLockStatusObserver {
    CFNotificationCenterAddObserver(
                                    CFNotificationCenterGetDarwinNotifyCenter(),
                                    NULL,
                                    onLockStatusChange,
                                    LockStatusChangeNotiName,
                                    NULL,
                                    CFNotificationSuspensionBehaviorDeliverImmediately);
    CFNotificationCenterAddObserver(
                                    CFNotificationCenterGetDarwinNotifyCenter(),
                                    NULL,
                                    onLockStatusChange,
                                    LockStatusLockedNotiName,
                                    NULL,
                                    CFNotificationSuspensionBehaviorDeliverImmediately);
}

通知觸發(fā)的回調(diào) CFNotificationCallback :

void onLockStatusChange(
                        CFNotificationCenterRef center,
                        void *observer,
                        CFStringRef name,
                        const void *object,
                        CFDictionaryRef userInfo) {
    NSString *notiName = (__bridge NSString *)(name);
    if ([notiName isEqualToString:@"com.apple.springboard.lockstate"]) {
        // 無論鎖定還是解鎖，都會觸發(fā)士败。鎖定時鲤屡，在 `lockcomplete` 之前觸發(fā)
        NSLog(@"屏幕鎖狀態(tài)改變");
    } else if ([notiName isEqualToString:@"com.apple.springboard.lockcomplete"]) {
        // 鎖定時觸發(fā)
        NSLog(@"屏幕鎖定");
    }
}

3. 別忘記移除觀察者了

- (void)removeLockStatusOberser {
    CFNotificationCenterRemoveObserver(
                                       CFNotificationCenterGetDarwinNotifyCenter(),
                                       NULL,
                                       LockStatusChangeNotiName,
                                       NULL);
    CFNotificationCenterRemoveObserver(
                                       CFNotificationCenterGetDarwinNotifyCenter(),
                                       NULL,
                                       LockStatusLockedNotiName,
                                       NULL);
}

進一步了解：

官方文檔 CFNotificationCenter