# Detecting device locking in an iOS app

Language: en
Canonical: [Detecting device locking in an iOS app](<https://allluckly.cn/en/journal/2015-07-31-detecting-device-locking-in-an-ios-app/>)
中文：[中文 HTML](<https://allluckly.cn/iOS%E5%BC%80%E5%8F%91%E4%B9%8B%E6%A3%80%E6%B5%8B%E8%AE%BE%E5%A4%87%E9%94%81%E5%B1%8F>)
English: [English HTML](<https://allluckly.cn/en/journal/2015-07-31-detecting-device-locking-in-an-ios-app/>)
Published: 2015-07-31T00:00:00+08:00
Modified: 2026-10-23T10:34:09+08:00
Author: [Bison](<https://allluckly.cn/about/>)

Records SpringBoard lock-notification handling used to investigate a failure in an embedded game when the device locked. It preserves the troubleshooting approach and callback code; the conditions under which those interfaces may be used need separate verification.

Originally credited to Bison. Content is retained as published.

English translation of the [Chinese original](<https://allluckly.cn/iOS%E5%BC%80%E5%8F%91%E4%B9%8B%E6%A3%80%E6%B5%8B%E8%AE%BE%E5%A4%87%E9%94%81%E5%B1%8F>), translated on 2026-10-23. The article body uses automated translation; app descriptions, historical reading notes and video subtitles receive separate editorial checks. Original publication dates, attribution, code and version notes are retained.

**Before you read** This technical note dates from 2015–2017. The examples have not been rerun as part of this archive update. Published in 2015. The example listens for com.apple.springboard lock-screen notifications.

> "Health is the foundation of everything. Getting more exercise is the way to go." Bison

A recent project contains an embedded game, and the app crashes as soon as the screen locks. I spent a long time looking for a solution.

The code is as follows

Core code

```css
#define NotificationLock CFSTR("com.apple.springboard.lockcomplete")

#define NotificationChange CFSTR("com.apple.springboard.lockstate")

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    
    [self lookLockScreen];

    return YES;
    
}

- (void)lookLockScreen
{
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), NULL, screenLockStateChanged, NotificationLock, NULL, CFNotificationSuspensionBehaviorDeliverImmediately);

    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), NULL, screenLockStateChanged, NotificationChange, NULL, CFNotificationSuspensionBehaviorDeliverImmediately);


}

static void screenLockStateChanged(CFNotificationCenterRef center,void* observer,CFStringRef name,const void* object,CFDictionaryRef userInfo)

{

    NSString* lockstate = (__bridge NSString*)name;

    if ([lockstate isEqualToString:(__bridge  NSString*)NotificationLock]) {

        //锁屏
        NSLog(@"locked.");

    } else {
        //锁屏状态改变
        NSLog(@"lock state changed.");

    }

}
```