HarmonyOS 鸿蒙Next showAssetsCreationDialog 保存图片失败

请参考demo：

import { common } from '@kit.AbilityKit';
import { fileIo as fs, fileUri, ReadOptions, WriteOptions } from '@kit.CoreFileKit'
import { photoAccessHelper } from '@kit.MediaLibraryKit';
import json from '@ohos.util.json';
@Entry
@Component
struct Index {
    @State message: string = 'Hello World';
    filePath: string = '';
    build() {
        Column() {
            Button("复制文件到沙箱")
                .onClick(() => {
                console.log('开始复制文件到沙箱')
                this.copyFile()
                console.log('复制文件到沙箱完成')
            })
            Button('沙箱文件保存到相册')
                .onClick(()=>{
                console.log('开始沙箱文件保存到相册')
                this.syncToSysAlbum(photoAccessHelper.PhotoType.IMAGE,'png', this.filePath)
                })
            Button('沙箱文件保存到相册')
                .onClick(() => {
                console.log('开始沙箱文件保存到相册')
                this.example()
            })
        }
        .height('100%')
        .width('100%')
    }
    copyFile() {
        console.log("开发复制文件")
        let context = getContext(this) as common.UIAbilityContext;
        let srcFileDescriptor = context.resourceManager.getRawFdSync('background.png'); //这里填rawfile文件夹下的文件名（包括后缀）
        let stat = fs.statSync(srcFileDescriptor.fd)
        console.log(`stat isFile:${stat.isFile()}`);
        // 通过UIAbilityContext获取沙箱地址filesDir，以Stage模型为例
        let pathDir = context.filesDir;
        console.log("沙箱文件目录路径:", pathDir)
        let dstPath = pathDir + "/background.png";
        this.filePath = fileUri.getUriFromPath(dstPath)
        console.log("沙箱文件URI" + this.filePath);
        let dest = fs.openSync(dstPath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE)
        let bufsize = 4096
        let buf = new ArrayBuffer(bufsize)
        let off = 0, len = 0, readedLen = 0
        while (len = fs.readSync(srcFileDescriptor.fd, buf, { offset: srcFileDescriptor.offset + off, length: bufsize })) {
        readedLen += len
        fs.writeSync(dest.fd, buf, { offset: off, length: len })
        off = off + len
        if ((srcFileDescriptor.length - readedLen) < bufsize) {
            bufsize = srcFileDescriptor.length - readedLen
        }   
        }
        fs.close(dest.fd)
    }
    async syncToSysAlbum(fileType: photoAccessHelper.PhotoType, extension: string, ...filePath: string[]) {
        //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 context = getContext(this);
        let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(context);
        try {
            const srcFileUris: string[] = []
                filePath.forEach((path) => {
                srcFileUris.push(path)
                })
            const config: photoAccessHelper.PhotoCreationConfig[] = []
            config.push({
                title: 'background', // 可选
                fileNameExtension: extension,
                photoType: fileType,
                subtype: photoAccessHelper.PhotoSubtype.DEFAULT, // 可选
            })
            console.log("syncToSysAlarm fileUri:" + json.stringify(srcFileUris) + ",config:" + json.stringify(config))
            const desFileUris = await phAccessHelper.showAssetsCreationDialog(srcFileUris, config)
            console.debug(`目标图片 uri is : ${JSON.stringify(desFileUris)}`)
            if (desFileUris.length > 0) {
            for (let index = 0; index < desFileUris.length; index++) {
                this.copyFileContentTo(srcFileUris[index], desFileUris[index])
                }
            }
        } catch (err) {
        console.log("syncToSysAlarm filePath:" + filePath + ",error:" + json.stringify(err))
        }
    }
    async example() {
    console.info('ShowAssetsCreationDialogDemo.');
    let context = getContext(this) as common.UIAbilityContext
    let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(context);
    try {
        // 获取需要保存到媒体库的位于应用沙箱的图片/视频uri
        // let srcFileUris: Array<string> = [
        // // 实际场景请使用真实的uri
        // // 'file://com.example.test35/data/storage/el2/base/haps/entry/files/background.png'
        // this.filePath
        // ];
        let srcFileUri: Array<string> = [this.filePath]
        console.debug(`图片 uri is : ${JSON.stringify(srcFileUri)}`)
        let photoCreationConfigs: Array<photoAccessHelper.PhotoCreationConfig> = [
        {
            title: 'background', // 可选
            fileNameExtension: 'png',
            photoType: photoAccessHelper.PhotoType.IMAGE,
            subtype: photoAccessHelper.PhotoSubtype.DEFAULT, // 可选
            }
        ];
        console.log("syncToSysAlarm fileUri:" + JSON.stringify(srcFileUri) + ",config:" +
        JSON.stringify(photoCreationConfigs))
        let desFileUris: Array<string> = await phAccessHelper.showAssetsCreationDialog(srcFileUri, photoCreationConfigs);
        console.debug(`目标图片 uri is : ${JSON.stringify(desFileUris)}`)
        if (desFileUris.length > 0) {
            for (let index = 0; index < desFileUris.length; index++) {
                this.copyFileContentTo(srcFileUri[index], desFileUris[index])
                }
            }
        } catch (err) {
            console.error('showAssetsCreationDialog failed, errCode is ' + err.code + ', errMsg is ' + err.message);
        }
    }
    /**
    * 复制文件内容到目标文件
    * @param srcFilePath 源文件路径
    * @param destFilePath 目标文件路径
    */
    copyFileContentTo(srcFilePath: string, destFilePath: string) {
        let srcFile = fs.openSync(srcFilePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
        let destFile = fs.openSync(destFilePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
        // 读取源文件内容并写入至目的文件
        let bufSize = 4096;
        let readSize = 0;
        let buf = new ArrayBuffer(bufSize);
        let readOptions: ReadOptions = {
            offset: readSize,
            length: bufSize
        };
        let readLen = fs.readSync(srcFile.fd, buf, readOptions);
        while (readLen > 0) {
            readSize += readLen;
            let writeOptions: WriteOptions = {
                length: readLen
            };
            fs.writeSync(destFile.fd, buf, writeOptions);
            readOptions.offset = readSize;
            readLen = fs.readSync(srcFile.fd, buf, readOptions);
        }
        // 关闭文件
        fs.closeSync(srcFile);
        fs.closeSync(destFile);
    }
}