HarmonyOS 鸿蒙Next 外层Scroll或Refresh组件内WaterFlow跟随滑动实现

[@Entry](/user/Entry)
[@ComponentV2](/user/ComponentV2)
struct Index {
  [@Local](/user/Local) minSize: number = 80
  [@Local](/user/Local) maxSize: number = 180
  [@Local](/user/Local) fontSize: number = 24
  [@Local](/user/Local) colors: number[] = [0xFFC0CB, 0xDA70D6, 0x6B8E23, 0x6A5ACD, 0x00FFFF, 0x00FF7F]
  scroller: Scroller = new Scroller()
  dataSource: WaterFlowDataSource = new WaterFlowDataSource()
  private itemWidthArray: number[] = []
  private itemHeightArray: number[] = []

  // 计算FlowItem宽/高
  getSize() {
    let ret = Math.floor(Math.random() * this.maxSize)
    return (ret > this.minSize ? ret : this.minSize)
  }

  // 设置FlowItem的宽/高数组
  setItemSizeArray() {
    for (let i = 0; i < 100; i++) {
      this.itemWidthArray.push(this.getSize())
      this.itemHeightArray.push(this.getSize())
    }
  }

  aboutToAppear() {
    this.setItemSizeArray()
  }

  build() {
    Scroll() {
      Column() {
        Row() {
          Text('1')
          Text('2')
          Text('3')
          Text('4')
        }.width('100%')
        .height('15%')
        .backgroundColor(Color.Blue)
        .justifyContent(FlexAlign.SpaceBetween)

        WaterFlow() {
          LazyForEach(this.dataSource, (item: number) => {
            FlowItem() {
              Column() {
                Text("N" + item).fontSize(12).height('16')
                // 存在对应的jpg文件才会显示图片
                // Image('res/waterFlowTest(' + item % 5 + ').jpg')
                //   .objectFit(ImageFit.Fill)
                //   .width('100%')
                //   .layoutWeight(1)
              }
            }
            .onAppear(() => {
              // 即将触底时提前增加数据
              if (item + 20 == this.dataSource.totalCount()) {
                for (let i = 0; i < 100; i++) {
                  this.dataSource.addLastItem()
                }
              }
            })
            .width('100%')
            .height(this.itemHeightArray[item % 100])
            .backgroundColor(this.colors[item % 5])
          }, (item: string) => item)
        }
        .columnsTemplate("1fr 1fr")
        .columnsGap(10)
        .rowsGap(5)
        .backgroundColor(0xFAEEE0)
        .width('100%')
        .height('100%')
        .height('100%')
        .backgroundColor(Color.Orange)
        .nestedScroll({
          scrollForward: NestedScrollMode.PARENT_FIRST,
          scrollBackward: NestedScrollMode.SELF_FIRST,
        })
      }
    }
    .size({ width: '100%', height: '100%' })
    .scrollBar(BarState.Off)
  }
}

// WaterFlowDataSource.ets

// 实现IDataSource接口的对象，用于瀑布流组件加载数据
export class WaterFlowDataSource implements IDataSource {
  private dataArray: number[] = []
  private listeners: DataChangeListener[] = []

  constructor() {
    for (let i = 0; i < 100; i++) {
      this.dataArray.push(i)
    }
  }

  // 获取索引对应的数据
  public getData(index: number): number {
    return this.dataArray[index]
  }

  // 通知控制器数据重新加载
  notifyDataReload(): void {
    this.listeners.forEach(listener => {
      listener.onDataReloaded()
    })
  }

  // 通知控制器数据增加
  notifyDataAdd(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataAdd(index)
    })
  }

  // 通知控制器数据变化
  notifyDataChange(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataChange(index)
    })
  }

  // 通知控制器数据删除
  notifyDataDelete(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataDelete(index)
    })
  }

  // 通知控制器数据位置变化
  notifyDataMove(from: number, to: number): void {
    this.listeners.forEach(listener => {
      listener.onDataMove(from, to)
    })
  }

  //通知控制器数据批量修改
  notifyDatasetChange(operations: DataOperation[]): void {
    this.listeners.forEach(listener => {
      listener.onDatasetChange(operations);
    })
  }

  // 获取数据总数
  public totalCount(): number {
    return this.dataArray.length
  }

  // 注册改变数据的控制器
  registerDataChangeListener(listener: DataChangeListener): void {
    if (this.listeners.indexOf(listener) < 0) {
      this.listeners.push(listener)
    }
  }

  // 注销改变数据的控制器
  unregisterDataChangeListener(listener: DataChangeListener): void {
    const pos = this.listeners.indexOf(listener)
    if (pos >= 0) {
      this.listeners.splice(pos, 1)
    }
  }

  // 增加数据
  public add1stItem(): void {
    this.dataArray.splice(0, 0, this.dataArray.length)
    this.notifyDataAdd(0)
  }

  // 在数据尾部增加一个元素
  public addLastItem(): void {
    this.dataArray.splice(this.dataArray.length, 0, this.dataArray.length)
    this.notifyDataAdd(this.dataArray.length - 1)
  }

  // 在指定索引位置增加一个元素
  public addItem(index: number): void {
    this.dataArray.splice(index, 0, this.dataArray.length)
    this.notifyDataAdd(index)
  }

  // 删除第一个元素
  public delete1stItem(): void {
    this.dataArray.splice(0, 1)
    this.notifyDataDelete(0)
  }

  // 删除第二个元素
  public delete2ndItem(): void {
    this.dataArray.splice(1, 1)
    this.notifyDataDelete(1)
  }

  // 删除最后一个元素
  public deleteLastItem(): void {
    this.dataArray.splice(-1, 1)
    this.notifyDataDelete(this.dataArray.length)
  }

  // 在指定索引位置删除一个元素
  public deleteItem(index: number): void {
    this.dataArray.splice(index, 1)
    this.notifyDataDelete(index)
  }

  // 重新加载数据
  public reload(): void {
    this.dataArray.splice(1, 1)
    this.dataArray.splice(3, 2)
    this.notifyDataReload()
  }
}