瀑布流布局，实现LazyForEach不设置高度的时候，笔记流随页面滚动，交互体验和主端一致。

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.onDataAdded(index) 
    }) 
  } 
  
  // 通知控制器数据变化 
  notifyDataChange(index: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataChanged(index) 
    }) 
  } 
  
  // 通知控制器数据删除 
  notifyDataDelete(index: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataDeleted(index) 
    }) 
  } 
  
  // 通知控制器数据位置变化 
  notifyDataMove(from: number, to: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataMoved(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() 
  } 
} 
  
import { WaterFlowDataSource } from './WaterFlowDataSource' 
@Entry 
@Component 
struct KALLScroll { 
  @State message: string = 'Hello World' 
  @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 < 100; i++) { 
      this.itemWidthArray.push(this.getSize()) 
      this.itemHeightArray.push(this.getSize()) 
    } 
  } 
  
  aboutToAppear() { 
    this.getItemSizeArray() 
  } 
  
  build() { 
    Scroll() { 
      Column() { 
        Text("Scroll Area") 
          .width("100%") 
          .height("40%") 
          .backgroundColor(Color.Red) 
          .textAlign(TextAlign.Center) 
  
        WaterFlow() { 
          LazyForEach(this.datasource, (item: number) => { 
            FlowItem() { 
              Column() { 
                Text("N" + item).fontSize(12).height('16') 
                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 
              console.error("lizhouze:onAppear") 
              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%') 
        .nestedScroll({ 
          scrollForward: NestedScrollMode.PARENT_FIRST, 
          scrollBackward: NestedScrollMode.SELF_FIRST 
        }) 
  
      }.width("100%") 
    } 
    .edgeEffect(EdgeEffect.Spring) 
    .friction(0.6) 
    .backgroundColor('#DCDCDC') 
    .scrollBar(BarState.Off) 
    .width('100%') 
    .height('100%') 
  } 
}
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