HarmonyOS 自定义刷新空间问题

请参考示例如下：

@Entry
@Component
struct PageHiddenTittle {
  @State transparent: number = 255
  @State color: string = `20c8b8`
  scroller: Scroller = new Scroller()
  @State isRefreshing: boolean = false
  private arr: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

  @Builder
  customRefreshComponent() {
    Stack() {
      Row() {
        LoadingProgress().height(32)
        Text("Refreshing...").fontSize(16).margin({ left: 20 })
      }
      .alignItems(VerticalAlign.Center)
    }
    .width("100%").align(Alignment.Center)
    .constraintSize({ minHeight: 32 }) // 设置最小高度约束保证自定义组件高度随刷新区域高度变化时自定义组件高度不会低于minHeight
  }

  build() {
    Refresh({ refreshing: $$this.isRefreshing, builder: this.customRefreshComponent() }) {
      Stack({ alignContent: Alignment.TopStart }) {
        List({ scroller: this.scroller }) {
          ForEach(this.arr, (item: number) => {
            ListItem() {
              Text(item.toString())
                .width('90%')
                .height(150)
                .backgroundColor("#ff4d6654")
                .borderRadius(15)
                .fontSize(16)
                .textAlign(TextAlign.Center)
            }
          }, (item: string) => item)
        }
        .alignListItem(ListItemAlign.Center)
        .width('100%')
        .margin({ top: 100 })
        .zIndex(0)
        .onDidScroll((scrollOffset, scrollState) => {
          let y = this.scroller.getItemRect(0).y
          y = Math.abs(y)
          if (scrollOffset > 10) {
            this.transparent -= 10
          }
          // this.transparent -= 10
          console.log(this.transparent.toString())
        })

        Text("").height(100).width("100%").backgroundColor('#ffffff');
        Text("我是标题栏")
          .height(100)
          .width("100%")
          .backgroundColor(`#${this.transparent.toString(16)}${this.color}`)
          .zIndex(1)
      }

    }
    .backgroundColor('#ff914949')
    .onRefreshing(() => {
      setTimeout(() => {
        this.isRefreshing = false
      }, 2000)
      console.log('onRefreshing test')
    })
  }
}