HarmonyOS 鸿蒙Next如何实现瀑布流布局

HarmonyOS 鸿蒙Next 瀑布流布局也可以参考下面代码

//Index.ets
import { WaterFlowDataSource } from './WaterFlowDataSource'

@Entry
@Component
struct WaterFlowDemo {
  @State minSize: number = 80
  @State maxSize: number = 180
  @State fontSize: number = 24
  @State colors: number[] = [0xFFC0CB, 0xDA70D6, 0x6B8E23, 0x6A5ACD, 0x00FFFF, 0x00FF7F]
  scroller: Scroller = new Scroller()
  datasource: WaterFlowDataSource = new WaterFlowDataSource()
  private itemWidthArray: number[] = []
  private itemHeightArray: number[] = []

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

  // 保存flow item宽/高
  getItemSizeArray() {
    for (let i = 0; i < 1000; i++) {
      this.itemWidthArray.push(this.getSize())
      this.itemHeightArray.push(this.getSize())
    }
  }

  aboutToAppear() {
    this.getItemSizeArray()
  }

  @Builder
  itemFoot() {
    Column() {
      Text(`Footer`)
        .fontSize(10)
        .backgroundColor(Color.Red)
        .width(50)
        .height(50)
        .align(Alignment.Center)
        .margin({ top: 2 })
    }
  }

  build() {
    Column({ space: 2 }) {
      WaterFlow() {
        LazyForEach(this.datasource, (item: number, index: number) => {
          FlowItem() {
            Column() {
              if (this.itemWidthArray[index] > 100) {
                Grid() {
                  GridItem() {
                    Text("N" + item)
                      .fontSize(16)
                      .width('100%')
                      .height('100%')
                      .textAlign(TextAlign.Center)
                  }.columnStart(1).columnEnd(2)
                }
              } else {
                Grid() {
                  GridItem() {
                    Text("N" + item)
                      .fontSize(16)
                      .width('100%')
                      .height('100%')
                      .textAlign(TextAlign.Center)
                      .borderStyle(BorderStyle.Dashed)
                      .borderWidth(5)
                      .borderColor(Color.Red)
                      .borderRadius(10)
                  }

                  GridItem() {
                    Text("N1" + item)
                      .fontSize(16)
                      .width('100%')
                      .height('100%')
                      .textAlign(TextAlign.Center)
                      .borderStyle(BorderStyle.Dashed)
                      .borderWidth(5)
                      .borderColor(Color.Green)
                      .borderRadius(10)
                  }
                }
                .columnsTemplate('1fr 1fr')
              }
            }
          }
          .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")
      .columnsGap(10)
      .rowsGap(5)
      .backgroundColor(0xFAEEE0)
      .width('100%')
      .height('100%')
    }
  }
}

//WaterFlowDataSource.ets
export class WaterFlowDataSource implements IDataSource {
  private dataArray: number[] = []
  private listeners: DataChangeListener[] = []

  constructor() {
    for (let i = 0; i < 1000; 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)
    })
  }

  // 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)
  }

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