HarmonyOS waterFlow用sections模式，delete某个元素后列表就不能动？

Question

public deleteData(index: number,): void {
  this.dataArray.splice(index, 1);
  this.notifyDataDelete(index);
}

waterFlow 用sections模式，delete某个元素后列表就不能动

Answer 1

waterFlow在使用sections模式后，在删除后需要调用update方法更新，以下是根据官网案例3，做出修改的demo：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-container-waterflow-V5\#%E7%A4%BA%E4%BE%8B3

参考示例：

import { WaterFlowDataSource } from './WaterFlowDataSource'

@Reusable
@Component
struct ReusableFlowItem {
  @State item: number = 0

  // 从复用缓存中加入到组件树之前调用，可在此处更新组件的状态变量以展示正确的内容
  aboutToReuse(params: Record<string, number>) {
    this.item = params.item;
    console.info('Reuse item:' + this.item)
  }

  aboutToAppear() {
    console.info('new item:' + this.item)
  }

  build() {
    Text("N" + this.item).fontSize(16).height('100%')
  }
}

@Entry
@Component
struct WaterFlowDemo {
  minSize: number = 80
  maxSize: number = 180
  fontSize: number = 24
  colors: number[] = [0xFFC0CB, 0xDA70D6, 0x6B8E23, 0x6A5ACD, 0x00FFFF, 0x00FF7F]
  scroller: Scroller = new Scroller()
  dataSource: WaterFlowDataSource = new WaterFlowDataSource()
  dataCount: number = this.dataSource.totalCount()
  private itemHeightArray: number[] = []
  @State sections: WaterFlowSections = new WaterFlowSections()
  sectionMargin: Margin = { top: 10, left: 5, bottom: 10, right: 5 }
  oneColumnSection: SectionOptions = {
    itemsCount: 4,
    crossCount: 1,
    columnsGap: '5vp',
    rowsGap: 10,
    margin: this.sectionMargin,
    onGetItemMainSizeByIndex: (index: number) => {
      return this.itemHeightArray[index % 100]
    }
  }
  twoColumnSection: SectionOptions = {
    itemsCount: 2,
    crossCount: 2,
    onGetItemMainSizeByIndex: (index: number) => {
      return 100
    }
  }
  lastSection: SectionOptions = {
    itemsCount: 20,
    crossCount: 2,
    onGetItemMainSizeByIndex: (index: number) => {
      return this.itemHeightArray[index % 100]
    }
  }

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

  // 设置FlowItem的高度数组
  setItemSizeArray() {
    for (let i = 0; i < 100; i++) {
      this.itemHeightArray.push(this.getSize())
    }
  }

  aboutToAppear() {
    this.setItemSizeArray()
    // 初始化瀑布流分组信息
    let sectionOptions: SectionOptions[] = []
    let count = 0
    let oneOrTwo = 0
    while (count < this.dataCount) {
      if (this.dataCount - count < 20) {
        this.lastSection.itemsCount = this.dataCount - count
        sectionOptions.push(this.lastSection)
        break;
      }
      if (oneOrTwo++ % 2 == 0) {
        sectionOptions.push(this.oneColumnSection)
        count += this.oneColumnSection.itemsCount
      } else {
        sectionOptions.push(this.twoColumnSection)
        count += this.twoColumnSection.itemsCount
      }
    }
    this.sections.splice(0, 0, sectionOptions)
  }

  build() {
    Column({ space: 2 }) {
      Row() {
        Button('删除某一项')
          .height('5%')
          .onClick(() => {

            let newSection: SectionOptions = {
              itemsCount: 1,
            }
            this.dataSource.deleteItem(4)
            //newSection中需要确保itemsCount为删除一项后的数据
            this.sections.update(1, newSection)
          })
          .margin({ top: 10, left: 20 })
      }.margin({ bottom: 20 })

      WaterFlow({ scroller: this.scroller, sections: this.sections }) {
        LazyForEach(this.dataSource, (item: number) => {
          FlowItem() {
            ReusableFlowItem({ item: item })
          }
          .width('100%')
          // 以onGetItemMainSizeByIndex为准
          // .height(this.itemHeightArray[item % 100])
          .backgroundColor(this.colors[item % 5])
        }, (item: string) => item)
      }
      .columnsTemplate('1fr 1fr') // 瀑布流使用sections参数时该属性无效
      .columnsGap(10)
      .rowsGap(5)
      .backgroundColor(0xFAEEE0)
      .width('100%')
      .height('100%')
      .layoutWeight(1)
      .onScrollIndex((first: number, last: number) => {
        // 即将触底时提前增加数据
        if (last + 20 >= this.dataSource.totalCount()) {
          for (let i = 0; i < 100; i++) {
            this.dataSource.addLastItem()
          }
          // 更新数据源后同步更新sections，修改最后一个section的FlowItem数量
          this.lastSection.itemsCount += 100
          this.sections.update(-1, this.lastSection);
        }
      })
    }
  }
}


export class WaterFlowDataSource implements IDataSource {
  private dataArray: number[] = []
  private listeners: DataChangeListener[] = []
  private index:number = 0
  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)
    })
  }

  // 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)
  }
  // 删除某一个元素
  public deleteItem(index:number): void {
    this.dataArray.splice(index, 1)
    this.notifyDataDelete(0)
  }

  // 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()
  }
}