harmony 鸿蒙@ohos.app.ability.EnvironmentCallback (EnvironmentCallback)

2025-06-12
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@ohos.app.ability.EnvironmentCallback (EnvironmentCallback)

The EnvironmentCallback module provides APIs for the application context to listen for system environment changes.

NOTE

The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.

The APIs of this module can be used only in the stage model.

Modules to Import

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

EnvironmentCallback.onConfigurationUpdated

onConfigurationUpdated(config: Configuration): void

Called when the system environment changes.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Ability.AbilityRuntime.AbilityCore

Parameters

Name	Type	Mandatory	Description
config	Configuration	Yes	Configuration object after the change.

Example

See Usage of EnvironmentCallback.

EnvironmentCallback.onMemoryLevel

onMemoryLevel(level: AbilityConstant.MemoryLevel): void

Called when the system memory level changes.

Atomic service API: This API can be used in atomic services since API version 11.

System capability: SystemCapability.Ability.AbilityRuntime.AbilityCore

Parameters

Name	Type	Mandatory	Description
level	AbilityConstant.MemoryLevel	Yes	Memory level that indicates the memory usage status. When the specified memory level is reached, a callback will be invoked and the system will start adjustment.

Example

See Usage of EnvironmentCallback.

Usage of EnvironmentCallback

Example

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

let callbackId: number;

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

      onMemoryLevel(level){
        console.log(`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.log(`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.log(`unregisterEnvironmentCallback success, data: ${JSON.stringify(data)}`);
        }
      });
    } catch (paramError) {
      console.error(`error: ${(paramError as BusinessError).code}, ${(paramError as BusinessError).message}`);
    }
  }
}