HarmonyOS AlphabetIndexer组件问题

参考示例如下：

class Contacts {
  constructor(index: string, names: string[]) {
    this.index = index
    this.names = names
  }

  index: string
  names: string[]
}

@Entry
@Component
struct Index {
  @State contacts: Contacts[] = [
    new Contacts('A', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
    new Contacts('B', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
    new Contacts('C', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
    new Contacts('D', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
    new Contacts('E', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
    new Contacts('F', ['HarmonyOS', 'HarmonyOS', 'ArkTS', 'ArkTS', 'ETS', 'ArkUI']),
  ]
  scroller: Scroller = new Scroller
  value: string[] = ['A', 'B', 'C', 'D', 'E', 'F']
  @State flag: number = 0
  preIndex: number = 0

  build() {
    Row() {
      List({ space: 20, initialIndex: 0, scroller: this.scroller }) {
        ForEach(this.contacts, (value: Contacts) => {
          ListItem() {
            Column() {
              Text('' + value.index)
                .fontSize(30)
                .textAlign(TextAlign.Center)
                .backgroundColor('#ffffff')
                .margin(30)
              ForEach(value.names, (names: string) => {
                Column({ space: 10 }) {
                  Text('' + value.names)
                    .fontSize(20)
                    .textAlign(TextAlign.Center)
                    .backgroundColor('#ffffff')
                    .margin(10)
                }
              })
            }
          }
        })
      }
      .width('80%')
      .backgroundColor(Color.Pink)
      .listDirection(Axis.Vertical)
      .onScrollIndex((firstIndex: number, lastIndex: number) => {
        this.flag = firstIndex
      })

      AlphabetIndexer({ arrayValue: this.value, selected: this.flag })
        .width('20%')
        .font({ size: 20, weight: FontWeight.Bold })
        .selectedColor(Color.Gray)
        .usingPopup(true)
        .selectedFont({ size: 28, weight: FontWeight.Bolder })
        .itemSize(30)
        .alignStyle(IndexerAlign.Left)
        .onSelect((index: number) => {
          for (let i = 0; i < this.contacts.length; i++) {
            if (this.contacts[i].index.toString() === this.value[index]) {
              this.scroller.scrollToIndex(i)
              this.preIndex = index
              return
            }
          }
          this.flag = this.preIndex
        })
    }
  }
}