LazyForEach的使用,以及数据改变,更新UI页面

创建BaseLazyForEachDataSource文件

import { RefreshDataSource } from "@abner/refresh";

export class BaseLazyForEachDataSource<DataElement> implements IDataSource {
  private listeners: DataChangeListener[] = [];
  protected datas: DataElement[] = [];

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

  public getData(index: number): DataElement {
    return this.datas[index];
  }

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

  public pushDatas(datas: DataElement[]): void {
    const insertCount = datas.length;
    for (let index = 0; index < insertCount; index++) {
      const element = datas[index];
      this.datas.push(element);
      this.notifyDataAdd(this.datas.length - 1);
    }
  }

  public resetAllData(newDatas?: DataElement[]): void {
    if (undefined != newDatas && newDatas.length > 0) {
      this.datas = newDatas;
    }else {
      this.datas = [];
    }
    this.notifyDataReload();
  }

  registerDataChangeListener(listener: DataChangeListener): void {
    if (this.listeners.indexOf(listener) < 0) {
      console.info('add listener');
      this.listeners.push(listener);
    }
  }

  unregisterDataChangeListener(listener: DataChangeListener): void {
    const pos = this.listeners.indexOf(listener);
    if (pos >= 0) {
      console.info('remove listener');
      this.listeners.splice(pos, 1);
    }
  }

  notifyDataReload(): void {
    this.listeners.forEach(listener => {
      listener.onDataReloaded();
    })
  }

  notifyDataAdd(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataAdd(index);
    })
  }

  notifyDataChange(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataChange(index);
    })
  }

  notifyDataDelete(index: number): void {
    this.listeners.forEach(listener => {
      listener.onDataDelete(index);
    })
  }

  notifyDataMove(from: number, to: number): void {
    this.listeners.forEach(listener => {
      listener.onDataMove(from, to);
    })
  }

  notifyDatasetChange(operations: DataOperation[]): void {
    this.listeners.forEach(listener => {
      listener.onDatasetChange(operations);
    })
  }
}


export class ListViewLazyForEachDataSource extends RefreshDataSource {

  constructor() {
    super();
    super.initData([]);
  }

  pushDatas(datas: Object[]): void {
    super.pushDataArray(datas);
  }

  resetAllData(newDatas?: Object[]): void {
    super.deleteAllAfterPushArray(newDatas);
  }
}

使用方式 在需要用到的页面继承

class CommentListPageDataSource extends BaseLazyForEachDataSource<CommentList> {
}

在用到的组件或者页面中声明

@State commentListPageDataSource: CommentListPageDataSource = new CommentListPageDataSource();

UI页面使用

LazyForEach(this.commentListPageDataSource, (item:CommentList,index:number) => {

}, (item: Array<CommentList>, index) => `${index}_${JSON.stringify(item)}`)

(item: Array, index) => ${index}_${JSON.stringify(item)} 这句话是必须要写的. 更新数据的时候

let itemData = this.commentListPageDataSource.getData(pos);
itemData.praiseFlag = true
itemData.praises = this.commentListPageDataSource.getData(pos).praises as number + 1
this.commentListPageDataSource.notifyDataChange(pos);

重点是this.commentListPageDataSource.notifyDataChange(pos);这句代码. ListView使用的是ListViewLazyForEachDataSource这个,用法差不多,在此不一一复述.