封装lazyforeach懒加载方法

export class Evaluate {
  userId:string
  userIcon: Resource
  userNumber: string
  rating:number
  desc: string
}

import { BasicDataSource } from './BasicDataSource';

export class MyDataSource<T> extends BasicDataSource<T> {

  private dataArray: T[] = [];

  public totalCount(): number {
    return this.dataArray.length;
  }

  public getData(index: number): T {
    return this.dataArray[index];
  }

  public addData(index:number,data: T): void {
    this.dataArray.splice(index,0,data);
    this.notifyDataAdd(index)
  }


  public pushData(data: T): void {
    this.dataArray.push(data);
    this.notifyDataAdd(this.dataArray.length - 1)
  }

  public pushAllData(data: T[]): void {
    for (let i = 0; i <= this.dataArray.length; i++) {
      this.pushData(data[i]);
    }
  }

}
----------

export class BasicDataSource<T> implements IDataSource {
  private listeners: DataChangeListener[] = [];
  private originDataArray: T[] = [];

  public totalCount(): number {
    return 0;
  }

  public getData(index: number): T {
    return this.originDataArray[index];
  }

  // 该方法为框架侧调用，为LazyForEach组件向其数据源处添加listener监听
  registerDataChangeListener(listener: DataChangeListener): void {
    if (this.listeners.indexOf(listener) < 0) {
      console.info('add listener');
      this.listeners.push(listener);
    }
  }

  // 该方法为框架侧调用，为对应的LazyForEach组件在数据源处去除listener监听
  unregisterDataChangeListener(listener: DataChangeListener): void {
    const pos = this.listeners.indexOf(listener);
    if (pos >= 0) {
      console.info('remove listener');
      this.listeners.splice(pos, 1);
    }
  }

  // 通知LazyForEach组件需要重载所有子组件
  notifyDataReload(): void {
    this.listeners.forEach(listener => {
      listener.onDataReloaded();
    })
  }

  // 通知LazyForEach组件需要在index对应索引处添加子组件
  notifyDataAdd(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataAdd(index);
    })
  }

  // 通知LazyForEach组件在index对应索引处数据有变化，需要重建该子组件
  notifyDataChange(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataChange(index);
    })
  }

  // 通知LazyForEach组件需要在index对应索引处删除该子组件
  notifyDataDelete(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataDelete(index);
    })
  }

  // 通知LazyForEach组件将from索引和to索引处的子组件进行交换
  notifyDataMove(from: number, to: number): void {
    this.listeners.forEach(listener => {
      listener.onDataMove(from, to);
    })
  }
}

-----------------

import { MyDataSource } from '../utils/MyDataSource';
import { Evaluate } from '../viewModel/DetailsModel';


@Entry
@Component
struct MyComponent {
  private data:MyDataSource<Evaluate> = new MyDataSource();

  aboutToAppear() {

    const evaluate:Evaluate[] = [
      {
        userId:'1',
        userIcon: $r('app.media.icon'),
        userNumber:'18522679763',
        rating:5,
        desc:'和描述相符。质量挺好，很喜欢呀'
      },
      {
        userId:'2',
        userIcon: $r('app.media.icon'),
        userNumber:'18522679796',
        rating:5,
        desc:'和描述相符。质量挺好，很喜欢呀,真心推荐'
      }
    ]

    for (let i = 0; i <= 100; i++) {
      this.data.pushData({
          userId:( i + 1) + '' ,
          userIcon: $r('app.media.icon'),
          userNumber:'18522679796',
          rating:5,
          desc:'和描述相符。质量挺好，很喜欢呀,真心推荐'
        })
    }

  }

  build() {
    List({ space: 3 }) {
      LazyForEach(this.data, (item: Evaluate) => {
        ListItem() {
          Row() {
            Text(item.userId).fontSize(50)
              .onAppear(() => {
                console.info("appear:" + item)
              })
          }.margin({ left: 10, right: 10 })
        }
      }, (item: Evaluate) => item.userId)
    }.cachedCount(5)
  }
}