HarmonyOS 父组件如何响应子组件内的事件方法 ，子组件如何响应父组件内的事件方法？

@Component  
struct Child  {  
  @State private text: string = '初始值'  
  private controller: ChildController = new ChildController();  
  aboutToAppear() {  
    if(this.controller) {  
//给controller对应的方法赋值  
      this.controller.changeText = this.changeText  
    }  
  }  
//封装的能力  
  private changeText = (value: string) =>{  
    this.text = value  
  }  
  
  build() {  
    Column() {  
      Text(this.text)  
    }  
  }  
}  
//定义controller对象  
class ChildController {  
  changeText = (value: string) => {}  
}  
@Entry  
@Component  
struct Parent {  
  private  ChildRef = new ChildController()  
  build() {  
    Column() {  
      Text('调用Child的changeText').fontSize('18vp').fontColor(Color.Gray)  
      Divider()  
      Child({ controller:this. ChildRef })  
      Button('Parent调用childer的changeText').onClick(() => {  
        this.ChildRef.changeText('Parent调用childer的changeText')  
      })  
    }  
    .justifyContent(FlexAlign.Center)  
    .width("100%")  
    .height("100%")  
  }  
}