HarmonyOS 鸿蒙Next 保存网络图片到手机图库？

参考以下demo：

import http from '[@ohos](/user/ohos).net.http';
import { BusinessError } from '[@ohos](/user/ohos).base';
import common from '[@ohos](/user/ohos).app.ability.common';
import photoAccessHelper from '[@ohos](/user/ohos).file.photoAccessHelper';
import fs from '[@ohos](/user/ohos).file.fs';
import promptAction from '[@ohos](/user/ohos).promptAction';
@Entry
@Component
export struct SaveNetWorkPictures {
imageBuffer: ArrayBuffer | undefined = undefined; // 图片ArrayBuffer
async aboutToAppear(): Promise<void> {
//请求网络图片
//this.getPicture();
}
build() {
Column() {
Column() {
SaveButton({ icon: SaveIconStyle.FULL_FILLED })
.iconSize(60)
.iconColor("#888888")
.width(99)
.height(99)
.onClick(async () => {
// if (this.imageBuffer !== undefined) {
// await this.getPicture();
await this.saveImage(this.imageBuffer);
promptAction.showToast({
message: ‘图片保存成功’,
duration: 2000
})
// }
})
}
.height(‘100%’)
.padding(100)
}
}
// * 通过http的request方法从网络下载图片资源
getPicture(): Promise<void> {
return new Promise((resolve)=>{
http.createHttp()// 显示网络图片的地址
.request(‘https://gitee.com/harmonyos-cases/cases/raw/master/CommonAppDevelopment/feature/variablewatch/src/main/resources/base/media/variablewatch_grape.png’,
(error: BusinessError, data: http.HttpResponse) => {
if (error) {
// 下载失败时弹窗提示检查网络，不执行后续逻辑
promptAction.showToast({
message: ‘图片加载失败，请检查网络’,
duration: 2000
})
return;
}
// this.transcodePixelMap(data);
// 判断网络获取到的资源是否为ArrayBuffer类型
if (data.result instanceof ArrayBuffer) {
this.imageBuffer = data.result as ArrayBuffer;
}
resolve();
}
)
})
}
// * 保存ArrayBuffer到图库
async saveImage(buffer: ArrayBuffer | string | undefined): Promise<void> {
if(this.imageBuffer == undefined ){
await this.getPicture()
}
try {
const context = getContext(this) as common.UIAbilityContext; // 获取getPhotoAccessHelper需要的context
const helper = photoAccessHelper.getPhotoAccessHelper(context); // 获取相册管理模块的实例
const uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, ‘jpg’); // 指定待创建的文件类型、后缀和创建选项，创建图片或视频资源
const file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
await fs.write(file.fd, this.imageBuffer);
await fs.close(file.fd);
} catch (e) {
console.log(JSON.stringify(e))
}
}
}<button style="position: absolute; padding: 4px 8px 0px; cursor: pointer; top: 8px; right: 8px; font-size: 14px;">复制</button>