注册监听关机事件，该如何处理？

import Base from '@ohos.base'; 
import commonEventManager from '@ohos.commonEventManager'; 
 
let subscriber:commonEventManager.CommonEventSubscriber; //用于保存创建成功的订阅者对象，后续使用其完成订阅及退订的动作 
 
//订阅者信息 
let subscribeInfo:commonEventManager.CommonEventSubscribeInfo = { 
  events: ["usual.event.SHUTDOWN"] 
}; 
 
//订阅公共事件回调 
function SubscribeCB(err:Base.BusinessError, data:commonEventManager.CommonEventData) { 
  if (err) { 
    console.error(`subscribe failed, code is ${err.code}, message is ${err.message}`); 
  } else { 
    console.info("subscribe usual.event.SCREEN_ON"); 
  } 
} 
 
//创建订阅者回调 
function createCB(err:Base.BusinessError, commonEventSubscriber:commonEventManager.CommonEventSubscriber) { 
  if(!err) { 
    console.info("createSubscriber"); 
    subscriber = commonEventSubscriber; 
    //订阅公共事件 
    try { 
      commonEventManager.subscribe(subscriber, SubscribeCB); 
      console.info(`subscribe success`); 
    } catch (error) { 
      let err:Base.BusinessError = error as Base.BusinessError; 
      console.error(`subscribe failed, code is ${err.code}, message is ${err.message}`); 
    } 
  } else { 
    console.error(`createSubscriber failed, code is ${err.code}, message is ${err.message}`); 
  } 
} 
 
//创建订阅者 
try { 
  commonEventManager.createSubscriber(subscribeInfo, createCB); 
} catch (error) { 
  let err:Base.BusinessError = error as Base.BusinessError; 
  console.error(`createSubscriber failed, code is ${err.code}, message is ${err.message}`); 
} 
 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}