@ohos.app.ability.EnvironmentCallback (System Environment Change Listener)

import { EnvironmentCallback } from '@kit.AbilityKit';

import { UIAbility, EnvironmentCallback } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let callbackId: number;

export default class MyAbility extends UIAbility {
  onCreate() {
    console.info('MyAbility onCreate');
    let environmentCallback: EnvironmentCallback  =  {
      onConfigurationUpdated(config){
        console.info(`onConfigurationUpdated config: ${JSON.stringify(config)}`);
      },

      onMemoryLevel(level){
        console.info(`onMemoryLevel level: ${JSON.stringify(level)}`);
      }
    };
    // 1. Obtain an applicationContext object.
    let applicationContext = this.context.getApplicationContext();
    try {
      // 2. Register a listener for the environment changes through the applicationContext object.
      callbackId = applicationContext.on('environment', environmentCallback);
    } catch (paramError) {
      console.error(`error: ${(paramError as BusinessError).code}, ${(paramError as BusinessError).message}`);
    }
    console.info(`registerEnvironmentCallback number: ${JSON.stringify(callbackId)}`);
  }

  onDestroy() {
    let applicationContext = this.context.getApplicationContext();
    try {
      applicationContext.off('environment', callbackId, (error, data) => {
        if (error && error.code !== 0) {
          console.error(`unregisterEnvironmentCallback fail, error: ${JSON.stringify(error)}`);
        } else {
          console.info(`unregisterEnvironmentCallback success, data: ${JSON.stringify(data)}`);
        }
      });
    } catch (paramError) {
      console.error(`error: ${(paramError as BusinessError).code}, ${(paramError as BusinessError).message}`);
    }
  }
}