List滚动条时长时短，求解决方案？

@Entry 
@Component 
struct ListExample { 
  private arr: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 
  private arrItem: string[] = ["我是评论1", "我是评论2", "我是评论3", "我是评论4", 
    "我是评论5", "我是评论6"] 
  private arrItem2: string[] = ["我是评论1"] 
 
  @Builder 
  itemList(aa: number) { 
    List({ space: 20, initialIndex: 0 }) { 
      if (aa % 2 == 0) { 
        ForEach(this.arrItem, (item: string) => { 
          ListItem() { 
            Text('' + item) 
              .width('100%') 
              .height(50) 
              .fontSize(16) 
              .textAlign(TextAlign.Center) 
              .borderRadius(10) 
              .backgroundColor(0xFFFFFF) 
          } 
        }, (item: string) => item) 
      } else { 
        ForEach(this.arrItem2, (item: string) => { 
          ListItem() { 
            Text('' + item) 
              .width('100%') 
              .height(50) 
              .fontSize(16) 
              .textAlign(TextAlign.Center) 
              .borderRadius(10) 
              .backgroundColor(0xFFFFFF) 
          } 
        }, (item: string) => item) 
      } 
    } 
    .margin({ left: 20 }) 
    .listDirection(Axis.Vertical) 
    .scrollBar(BarState.Off) 
    .width('100%') 
  } 
 
  build() { 
    Column() { 
      List({ space: 20, initialIndex: 0 }) { 
        ForEach(this.arr, (item: number) => { 
          ListItem() { 
            Column({ space: 3 }) { 
              Text('' + item) 
                .width('100%') 
                .height(100) 
                .fontSize(16) 
                .textAlign(TextAlign.Center) 
                .borderRadius(10) 
                .backgroundColor(0xFFFFFF) 
              this.itemList(item) 
            } 
          } 
        }, (item: string) => item) 
      } 
      .listDirection(Axis.Vertical) 
      .scrollBar(BarState.On) 
      .friction(0.6) 
      .edgeEffect(EdgeEffect.Spring) 
      .width('90%') 
    } 
    .width('100%') 
    .height('100%') 
    .backgroundColor(0xDCDCDC) 
    .padding({ top: 5 }) 
  } 
}