HarmonyOS ts中BaseAbility extends UIAbility：Cannot find name 'Context'.

export default abstract class BaseAbility extends UIAbility { 
 
  static appContext:common.ApplicationContext; 
 
  onWindowStageCreate(windowStage: window.WindowStage): void { 
    BaseAbility.appContext = this.context.getApplicationContext() 
    Logger.info('testTag', '%{public}s', 'BaseAbility onWindowStageCreate'); 
    super.onWindowStageCreate(windowStage) 
  } 
 
  static getContext(): common.ApplicationContext { 
    return BaseAbility.appContext; 
  } 
}