HarmonyOS 下拉图片放大效果如何实现

参考示例如下：

// xxx.ets
@Entry
@Component
struct RefreshExample {
  @State isRefreshing: boolean = false
  @State arr: String[] = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10']
  @State heightNum: number = 0
  @State marginNum: number = 0
  @State imageH: number = 0
  scroller = new Scroller()

  @Builder
  freshArea() {
    Image($r("app.media.startIcon"))
      .width("100%")
      .height(this.heightNum)
      .margin({ top: this.marginNum, bottom: -this.marginNum })
  }

  build() {
    Refresh({ refreshing: $$this.isRefreshing, builder: this.freshArea() }) {
      Scroll(this.scroller) {
        Column() {
          Image($r("app.media.startIcon"))
            .width("100%")
            .onSizeChange((old, newValue) => {
              this.imageH = Number(newValue.height)
              this.marginNum = this.imageH
              this.heightNum = this.imageH
            })
            .opacity(0)
          List({}) {
            ForEach(this.arr, (item: string) => {
              ListItem() {
                Text('' + item)
                  .width('70%')
                  .height(80)
                  .fontSize(16)
                  .margin(10)
                  .textAlign(TextAlign.Center)
                  .borderRadius(10)
                  .backgroundColor(0xFFFFFF)
              }
            }, (item: string) => item)
          }
          .nestedScroll({
            scrollForward: NestedScrollMode.PARENT_FIRST,
            scrollBackward: NestedScrollMode.SELF_FIRST
          })
          .onScrollIndex((first: number) => {
            console.info(first.toString())
          })
          .width('100%')
          .height('100%')
          .alignListItem(ListItemAlign.Center)
          .scrollBar(BarState.Off)
        }
      }
      .onDidScroll((scrollOffset: number) => {
        console.info("进入onDidScroll:", this.scroller.currentOffset().yOffset)
        if (this.scroller.currentOffset().yOffset <= 0) {
          this.marginNum = this.imageH
          return
        }
        // 获取List上滑的高度，控制图片上滑的高度
        let offset =
          this.scroller.currentOffset().yOffset > this.imageH ? this.imageH : this.scroller.currentOffset().yOffset
        this.marginNum = this.imageH - offset;
      })
    }
    .height("100%")
    .onStateChange((refreshStatus: RefreshStatus) => {
      console.info('Refresh onStatueChange state is ' + refreshStatus)
    })
    .onOffsetChange((value: number) => {
      this.heightNum = this.imageH + value
    })
    .onRefreshing(() => {
      setTimeout(() => {
        this.isRefreshing = false
      }, 2000)
      console.log('onRefreshing test')
    })
    .backgroundColor(0x89CFF0)
    .refreshOffset(64)
    .pullToRefresh(false)
  }
}
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