#鸿蒙通关秘籍#如何使用ApplicationContext订阅系统环境变量变化？

在鸿蒙开发中，通过ApplicationContext订阅系统环境变量的变化，首先需要获取ApplicationContext实例。使用applicationContext.on(type: 'environment', callback: EnvironmentCallback)方法注册回调函数以处理系统环境变量的变化。可以在页面中监测系统语言的变化。在不再需要时，调用ApplicationContext.off(type: 'environment', callbackId: number)注销订阅。

bash import { common, EnvironmentCallback, Configuration } from '@kit.AbilityKit'; import { hilog } from '@kit.PerformanceAnalysisKit'; import { BusinessError } from '@kit.BasicServicesKit';

const TAG: string = '[CollaborateAbility]'; const DOMAIN_NUMBER: number = 0xFF00;

@Entry @Component struct Index { private context = getContext(this) as common.UIAbilityContext; private callbackId: number = 0;

subscribeConfigurationUpdate(): void { let systemLanguage: string | undefined = this.context.config.language; let applicationContext = this.context.getApplicationContext();

let environmentCallback: EnvironmentCallback = {
  onConfigurationUpdated(newConfig: Configuration) {
    hilog.info(DOMAIN_NUMBER, TAG, `onConfigurationUpdated systemLanguage is ${systemLanguage}, newConfig: ${JSON.stringify(newConfig)}`);
    if (systemLanguage !== newConfig.language) {
      hilog.info(DOMAIN_NUMBER, TAG, `systemLanguage from ${systemLanguage} changed to ${newConfig.language}`);
      systemLanguage = newConfig.language;
    }
  },
  onMemoryLevel(level) {
    hilog.info(DOMAIN_NUMBER, TAG, `onMemoryLevel level: ${level}`);
  }
}

try {
  this.callbackId = applicationContext.on('environment', environmentCallback);
} catch (err) {
  let code = (err as BusinessError).code;
  let message = (err as BusinessError).message;
  hilog.error(DOMAIN_NUMBER, TAG, `Failed to register applicationContext. Code is ${code}, message is ${message}`);
};

}

build() { // 页面构建逻辑 } }