@Component

struct Child {

  @State private text: string = '初始值'

  private controller: ChildController = new ChildController();

  aboutToAppear() {

    if(this.controller) {

      this.controller.changeText = this.changeText

    }

    console.log('aaa')

  }

  private changeText = (value: string) =>{

    this.text = value

    console.log('bbb')

  }

  build() {

    Column() {

      Text(this.text)

    }

  }

}

class ChildController {

  changeText = (value: string) => {

    console.log('11111')

  }

}

export let ChildRef = new ChildController()

@Entry

@Component

struct Parent {

  // ChildRef = new ChildController()

  @State noShow: boolean = false

  build() {

    Column() {

      Text('获取Child的exposeMethods!').fontSize('18vp').fontColor(Color.Gray)

      Divider()

      Child({ controller: ChildRef })

      Child()

      Button('Parent调用childer的changeText').onClick(() => {

        ChildRef.changeText('Parent调用childer的changeText')

      })

    }

  }

}

第二种:eventHub  也可以  类似安卓的事件总线