HarmonyOS Stack容器中子view自适应高度问题

@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
  @State sizeValue:string = "" 
  @State sizeValueOld:string = "" 
  @State heightValue:string = "" 
 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
        Text(this.sizeValue+"") 
          .height(100) 
          .fontSize(15) 
        Text(this.sizeValueOld+"") 
          .height(100) 
          .fontSize(15) 
        Stack({ alignContent: Alignment.Bottom }) { 
          //A组件 
          Flex({ direction:FlexDirection.Column,justifyContent:FlexAlign.SpaceBetween }){ 
            Text('First child, show in bottom') 
              .width('95%') 
              .height("50%") 
              .backgroundColor(0xd2cab3) 
              .align(Alignment.Top) 
              .onAreaChange((oldValue: Area, newValue: Area) => { 
                console.info(`Ace: on area change, oldValue is ${JSON.stringify(oldValue)} value is ${JSON.stringify(newValue)}`) 
                this.heightValue = newValue.height.toString() 
                this.sizeValue = JSON.stringify(newValue) 
                this.sizeValueOld = JSON.stringify(oldValue) 
              }) 
          } 
          //B组件 
          Flex({ direction:FlexDirection.Column,justifyContent:FlexAlign.SpaceBetween }){ 
            Text('Second child, show in top') 
              .width(200) 
                //可直接写 this.heightValue ，也可以转换成数字类型进行计算调整B组件高度 
              .height(Number(this.heightValue)-100) 
              .backgroundColor(0xc1cbac) 
              .align(Alignment.Top) 
          } 
        } 
        .width('100%') 
        .height(500) 
        .margin({ top: 5 }) 
        .alignContent(Alignment.Center) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}