HarmonyOS 相册多选场景pixelMap转ArrayBuffer只有异步方法导致只有一张图片生效

这边提供有批量选择相册图片，并且将图片压缩，转成base64格式的demo：

页面：

import { photoAccessHelper } from '@kit.MediaLibraryKit';
import { buffer } from '@kit.ArkTS';
import { PictureUtils } from '../utils/PictureUtils';

@Entry
@Component
struct Index {
  @State pictures: Array<string> = [];

  @Styles
  butStyle(){
    .width(200)
    .height(50)
    .margin({ top: 30 })
  }

  async selectAndCompressPicture() {
    this.pictures = [];
    let selectResult: photoAccessHelper.PhotoSelectResult = await PictureUtils.selectPicture(2);
    let pictureUriArr: Array<string> = selectResult.photoUris;
    pictureUriArr.forEach(uri => {
      PictureUtils.compressPicture(uri, "image/jpeg", 20).then((data: ArrayBuffer) => {
        // 将图片转成base64
        let base64Str = buffer.from(data).toString('base64')
        let resultBase64Str = "data:image/png;base64," + base64Str
        this.pictures.push(resultBase64Str)

      })
    });
  }

  build() {
    Column() {
      ForEach(this.pictures, (uri: string) => {
        Image(uri)
          .width(200)
          .height(200)
          .padding({ top: 30 })
      }, (item: string) => item)

      Button("选择图片并压缩", { type: ButtonType.Capsule, stateEffect: false })
        .fontSize('15fp')
        .fontColor('#ffffff')
        .butStyle()
        .onClick(() => {
          this.selectAndCompressPicture()
        })
    }
    .width('100%')
    .height('100%')
    .alignItems(HorizontalAlign.Center)
    .justifyContent(FlexAlign.Center)
  }
}

util：

import { photoAccessHelper } from '@kit.MediaLibraryKit';
import fs from '@ohos.file.fs';
import { image } from '@kit.ImageKit';

export class PictureUtils {
  /**
   * 选择图片
   *
   * @param selectNumber 选择图片的最大数量
   * @returns PhotoSelectResult
   */
  static async selectPicture(selectNumber: number): Promise<photoAccessHelper.PhotoSelectResult> {
    let photoSelectOptions = new photoAccessHelper.PhotoSelectOptions();
    // 设置要选择的媒体文件类型
    photoSelectOptions.MIMEType = photoAccessHelper.PhotoViewMIMETypes.IMAGE_TYPE;
    // 设置选择文件最大数量
    photoSelectOptions.maxSelectNumber = selectNumber;
    let photoPicker = new photoAccessHelper.PhotoViewPicker();
    return await photoPicker.select(photoSelectOptions)
  }

  /**
   * 图片压缩
   *
   * @param pictureUri 图片uri
   * @param format 压缩后的目标格式，支持jpg、webp和png
   * @param quality 压缩质量，取值范围0-100，压缩质量数字越大，图片越大
   * @returns ArrayBuffer
   */
  static async compressPicture(pictureUri: string, format: string, quality: number): Promise<ArrayBuffer> {
    let file = fs.openSync(pictureUri, fs.OpenMode.READ_ONLY);
    let size = fs.statSync(file.fd).size;
    let buf = new ArrayBuffer(size);
    fs.readSync(file.fd, buf);
    fs.closeSync(file);
    let imageSource = image.createImageSource(buf);

    const imagePackerApi: image.ImagePacker = image.createImagePacker();
    let packOpts: image.PackingOption = { format: format, quality: quality };
    return await imagePackerApi.packing(imageSource, packOpts)
  }
}