HarmonyOS 怎么实现下拉分类列表？

@Entry  
@Component  
struct GridHighLight {  
  @State selectIndex_: number = 0  
  private scrollerForScroll: Scroller = new Scroller()  
  private scrollerForList: Scroller = new Scroller()  
  @State showDialog: boolean = false  
  private hoursList: Array<string> = [  
    "全城区", "城关区", "七里河区", "西固区", "安宁区", "红古区", "永登区", "皋兰区", "榆中区", "兰州新区"  
  ]  
  @State recordTitleList: string = ''  
  @State businessHours: string = ''  
  
  onPageShow() {  
    this.businessHours = this.hoursList[0];  
  }  
  
  @Builder  
  //初始下拉按钮  
  tabBuilder() {  
    Row() {  
      Row() {  
        Text(this.businessHours)  
          .fontColor(this.showDialog ? Color.Orange : Color.Black)  
          .fontSize(16)  
          .maxLines(1)  
          .textOverflow({  
            overflow: TextOverflow.Ellipsis  
          })  
          .constraintSize({ maxWidth: 70 })  
  
        Image($r('app.media.ic_public_spinner_small'))  
          .width(20)  
          .height(20)  
          .margin({ left: 8 })  
          .fillColor(this.showDialog ? Color.Orange : Color.Black)  
          .rotate({  
            x: 1,  
            y: 0,  
            z: 0,  
            centerX: '50%',  
            centerY: '50%',  
            angle: this.showDialog ? 180 : 0  
          })  
      }  
      .onClick(() => {  
        this.showDialog = true  
        this.scrollerForScroll.scrollEdge(Edge.Bottom)  
      })  
    }  
    .width('100%')  
    .padding({ left: 16 })  
    .justifyContent(FlexAlign.Start)  
    .alignItems(VerticalAlign.Center)  
  }  
  
  @Builder  
  //下拉的内容  
  tabContentData() {  
    List({ scroller: this.scrollerForList }) {  
      ListItem() {  
        Stack() {  
          // 内容区  
          Column()  
            .width('100%')  
            .height('100%')  
            .opacity(this.showDialog ? .3 : 1)  
            .backgroundColor(this.showDialog ? Color.Black : Color.White)  
  
          // 选择弹窗区域  
          if (this.showDialog) {  
            Column() {  
              Column() {  
                this.ChooseContent()  
              }  
              .width('100%')  
              .backgroundColor($r('sys.color.ohos_id_color_dialog_bg'))  
  
              Column()  
                .layoutWeight(1)  
                .width('100%')  
                .onClick(() => {  
                  this.showDialog = false  
                })  
            }  
            .height('100%')  
          }  
        }  
        .alignContent(Alignment.TopStart)  
      }  
    }  
    .height('100%')  
    .scrollBar(BarState.Off)  
    .edgeEffect(EdgeEffect.None)  
    .nestedScroll({  
      scrollForward: NestedScrollMode.PARENT_FIRST,  
      scrollBackward: NestedScrollMode.SELF_FIRST  
    })  
  }  
  
  @Builder  
  ChooseContent() {  
    Column() {  
      Grid() {  
        ForEach(this.hoursList, (item: string, index: number) => {  
          GridItem() {  
            Text(item)  
              .fontColor(this.selectIndex_ == index ? Color.White : Color.Black)  
          }  
          .backgroundColor(this.selectIndex_ == index ? '#ff5700' : '#efedee')  
          .onClick(() => {  
            this.selectIndex_ = index  
            this.businessHours = item;  
          })  
        }, (item: string): string => item)  
      }  
      .columnsGap(10)  
      .rowsGap(10)  
      .padding({ left: 16, right: 16 })  
      .width('100%')  
      .height(220)  
      .columnsTemplate('1fr 1fr 1fr')  
      .rowsTemplate('1fr 1fr 1fr 1fr')  
  
      Divider()  
        .height('1px')  
        .margin(10)  
        .color($r('sys.color.ohos_id_color_list_separator'))  
  
      Row() {  
        Button('重置')  
          .backgroundColor('#ffefeded')  
          .fontSize(20)  
          .fontColor(Color.Grey)  
          .height(48)  
          .width('50%')  
          .margin({ right: 4 })  
          .onClick(() => {  
            this.selectIndex_ = 0  
            this.businessHours = this.hoursList[0];  
          })  
  
        Button('确认')  
          .fontSize(20)  
          .backgroundColor("#ff5700")  
          .fontColor(Color.White)  
          .height(48)  
          .width('50%')  
          .margin({ right: 4 })  
          .onClick(() => {  
            this.showDialog = false  
          })  
      }  
      .padding({ left: 20, right: 20, bottom: 20 })  
      .justifyContent(FlexAlign.SpaceBetween)  
      .width('100%')  
    }  
    .onTouch((e) => {  
      e.stopPropagation()  
    })  
  }  
  build() {  
    Stack() {  
      Scroll(this.scrollerForScroll) {  
        Column() {  
          if (!this.showDialog) {  
            Row().height(100).width('100%')  
              .backgroundColor('#F1F3F5')  
          }  
          Tabs({ barPosition: BarPosition.Start }) {  
            TabContent() {  
              this.tabContentData()  
            }  
            .tabBar(this.tabBuilder())  
          }  
          .vertical(false)  
          .barWidth('100%')  
        }  
      }  
      .scrollBar(BarState.Off)  
  
      if (this.showDialog) {  
        Column()  
          .height('100%')  
          .width('100%')  
          .hitTestBehavior(HitTestMode.Transparent)  
      }  
    }  
    .alignContent(Alignment.TopStart)  
    .width('100%')  
    .height('100%')  
    .backgroundColor('#F1F3F5')  
  }  
}