HarmonyOS 自定义组件，然后在组件内部需要知道外面给这个组件的宽度

@Component
struct MyChildComp {
  @Prop pWidth:string|number
  build(){
    Column(){
      Text(this.pWidth.toString())
    }
  }
}
@Entry
@Component
struct ParentChildSizePage {
  @State pWidth: string|number = 'Hello World';
  build() {
    Row() {
      Column() {
        MyChildComp({pWidth:this.pWidth}).width(200).height(100)
      }
      .width('200vp')
      .height('300vp')
      .border({width:1})
      .onAreaChange((oldV:Area,newV:Area)=>{
        this.pWidth=newV.width.toString()
      })
    }
    .height('100%')
  }
} 

参考文档：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-universal-component-area-change-event-V5#onareachange