HarmonyOS 自定义tabbar左对齐

请参考示例：

@Entry
@Component
struct Index {
  @State tabArray: Array<number> = [0, 1]
  @State focusIndex: number = 0
  @State pre: number = 0
  @State index: number = 0
  private controller: TabsController = new TabsController()
  @State test: boolean = false
  // 单独的页签
  @Builder
  Tab(tabName: string, tabItem: number, tabIndex: number) {
    Column({ space: 20 }) {
      Text(tabName).fontSize(18)
      Image($r('app.media.icon')).width(20).height(20)
    }
    .width(100)
    .height(60)
    .borderRadius({ topLeft: 10, topRight: 10 })
    .onClick(() => {
      this.controller.changeIndex(tabIndex)
      this.focusIndex = tabIndex
    })
    .backgroundColor(tabIndex === this.focusIndex ? "#ffffffff" : "#ffb7b7b7")
  }

  build() {
    Column() {
      Column() {
        // 页签
        Row({ space: 7 }) {
          Scroll() {
            Row() {
              ForEach(this.tabArray, (item: number, index: number) => {
                this.Tab("页" + item, item, index)
              })
            }
            .justifyContent(FlexAlign.Start)
          }
          .align(Alignment.Start)
          .scrollable(ScrollDirection.Horizontal)
          .scrollBar(BarState.Off)
          .width('80%')
          .backgroundColor("#ffb7b7b7")

        }
        .width('100%')
        .backgroundColor("#ffb7b7b7")

        //tabs
        Tabs({ barPosition: BarPosition.Start, controller: this.controller }) {
          ForEach(this.tabArray, (item: number, index: number) => {
            TabContent() {
              Text('我是页面 ' + item + " 的内容")
                .height(300)
                .width('100%')
                .fontSize(30)
            }

            .backgroundColor(Color.Blue)
          })
        }

        .barHeight(0)
        .animationDuration(100)
        .onChange((index: number) => {
          console.log('foo change')
          this.focusIndex = index
        })
      }
      .alignItems(HorizontalAlign.Start)
      .width('100%')
    }
    .height('100%')
  }
}