选中图库的资源，然后获取资源的pixeMap

import picker from '@ohos.file.picker'; 
import photoAccessHelper from '@ohos.file.photoAccessHelper'; 
import dataSharePredicates from '@ohos.data.dataSharePredicates'; 
import { BusinessError } from '@ohos.base'; 
 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World' 
 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
        Button("点我") 
          .onClick(async()=>{ 
            try { 
              let PhotoSelectOptions = new picker.PhotoSelectOptions(); 
              PhotoSelectOptions.MIMEType = picker.PhotoViewMIMETypes.IMAGE_VIDEO_TYPE; 
              PhotoSelectOptions.maxSelectNumber = 5; 
              //在使用PhotoAccessHelper的PhotoViewPicker前，需要先创建PhotoViewPicker实例 
              let photoPicker = new picker.PhotoViewPicker(); 
              photoPicker.select(PhotoSelectOptions).then((PhotoSelectResult: picker.PhotoSelectResult) => { 
 
                //此处获取的phAccessHelper实例为全局对象，后续使用到phAccessHelper的地方默认为使用此处获取的对象，如未添加此段代码报phAccessHelper未定义的错误请自行添加 
                let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(getContext(this)); 
 
                let predicates:dataSharePredicates.DataSharePredicates = new dataSharePredicates.DataSharePredicates(); 
                predicates.equalTo(photoAccessHelper.PhotoKeys.URI,PhotoSelectResult.photoUris[0]) 
                let fetchoptions:photoAccessHelper.FetchOptions ={ 
                  fetchColumns:[], 
                  predicates:predicates 
                }; 
 
                phAccessHelper.getAssets(fetchoptions,async (err,fetchResult)=>{ 
                  if (fetchResult !=undefined){ 
                    let photoAsset:photoAccessHelper.PhotoAsset = await fetchResult.getFirstObject(); 
                    photoAsset.getThumbnail((err,pixelMap)=>{ 
                      if(pixelMap == undefined){ 
                        console.log('getThumbnail fail' + err); 
                      }else { 
                        console.log('getThumbnail'+pixelMap); 
                      } 
                    }) 
                  } 
                }) 
 
              }).catch((err: BusinessError) => { 
                console.error('PhotoViewPicker.select failed with err: ' + JSON.stringify(err)); 
              }); 
            } catch (error) { 
              let err: BusinessError = error as BusinessError; 
              console.error('PhotoViewPicker failed with err: ' + JSON.stringify(err)); 
            } 
 
          }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
}