HarmonyOS 提供一个下载图片，然后保存到图库的demo，不用savebutton的那种

使用http模块下的request方法下载图片，并在该方法的回调函数中保存到相册先申请以下权限：

ohos.permission.INTERNET 
ohos.permission.WRITE_IMAGEVIDEO 

其中ohos.permission.WRITE_IMAGEVIDEO推荐使用临时授权方式，https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/user-file-uri-intro-V5

保存网络图片代码如下：

// xxx.ets
@Entry
@Component
struct RefreshExample {
  @State isRefreshing: boolean = false
  @State arr: String[] = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10']

  @Builder
  customRefreshComponent() {
    Stack() {
      Row() {
        LoadingProgress().height(32)
        Text("正在刷新...").fontSize(16).margin({ left: 20 })
      }.alignItems(VerticalAlign.Center)
    }.width("100%").align(Alignment.Center)
  }

  build() {
    Column() {
      Refresh({ refreshing: $$this.isRefreshing, builder: this.customRefreshComponent() }) {
        List() {
          ForEach(this.arr, (item: string) => {
            ListItem() {
              Text('' + item)
                .width('100%')
                .height(100)
                .fontSize(16)
                .textAlign(TextAlign.Center)
                .borderRadius(10)
                .backgroundColor(0xFFFFFF)
            }
          }, (item: string) => item)
        }
        .onScrollIndex((first: number) => {
          console.info(first.toString())
        })
        .width('100%')
        .height('100%')
        .divider({
          strokeWidth: 1,
          color: Color.Yellow,
          startMargin: 10,
          endMargin: 10
        })
        .scrollBar(BarState.Off)
      }.onStateChange((refreshStatus: RefreshStatus) => {
        console.info('Refresh onStatueChange state is ' + refreshStatus)
      }).onRefreshing(() => {
        setTimeout(() => {
          this.isRefreshing = false
        }, 2000)
        console.log('onRefreshing test')
      }).backgroundColor(0x89CFF0)
    }
  }
}
import { http } from '@kit.NetworkKit'
import { BusinessError } from '@kit.BasicServicesKit';
import ResponseCode from '@ohos.net.http';
import { photoAccessHelper } from '@kit.MediaLibraryKit';
import fs from '@ohos.file.fs';

@Entry
@Component
struct Index {
  loadImageWithUrl(url: string) {
    // 使用request下载图片并在回调函数中保存图片到相册
    http.createHttp().request(url,
      {
        method:http.RequestMethod.GET,
        connectTimeout:60000,
        readTimeout:60000
      },
      async (error: BusinessError, data: http.HttpResponse) => {
        if (error) {
          console.error(`http reqeust failed with. Code: ${error.code}, message: ${error.message}`);
        } else {
          if (ResponseCode.ResponseCode.OK === data.responseCode) {
            let imageBuffer: ArrayBuffer = data.result as ArrayBuffer;
            try {
              // 获取相册路径
              const context = getContext(this);
              let helper = photoAccessHelper.getPhotoAccessHelper(context);
              let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'jpg')
              let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
              // 写入文件
              await fs.write(file.fd, imageBuffer);
              // 关闭文件
              await fs.close(file.fd);
            } catch (error) {
              console.error("error is "+ JSON.stringify(error))
            }
          } else {
            console.error("error occurred when image downloaded!")
          }
        }
      })
  }
}