鸿蒙代码回调``` @Entry @Component struct Parent { @State cnt: numb

@Entry
@Component
struct Parent {
  @State cnt: number = 0

  submit: () => void = () => { this.cnt++; }

  build() {
    Column() {
      Text(`${this.cnt}`) 
      Son({ submitArrow: this.submit }) 
    }
  }
}

@Component
struct Son {
  submitArrow?: () => void

  build() {
    Row() {
      Button('add')
        .width(80)
        .onClick(() => {
          if (this.submitArrow) {
            this.submitArrow()
          }
        })
    }
    .justifyContent(FlexAlign.SpaceBetween)
    .height(56)
  }
}