HarmonyOS鸿蒙Next中截图保存问题

可参考如下代码(需要在module.json5中声明"ohos.permission.WRITE_IMAGEVIDEO"权限)：

import { componentSnapshot, promptAction } from '@kit.ArkUI';
import { image } from '@kit.ImageKit';
import { photoAccessHelper } from '@kit.MediaLibraryKit';
import { fileIo as fs } from '@kit.CoreFileKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { abilityAccessCtrl, bundleManager, common, PermissionRequestResult, Permissions } from '@kit.AbilityKit';

@Entry
@Component
struct Index {
  @State pixmap: image.PixelMap | undefined = undefined

  build() {
    Column() {
      Row() {
        Image(this.pixmap).width(200).height(200).border({ color: Color.Black, width: 2 }).margin(5)
        Image($r('app.media.startIcon')).autoResize(true).width(200).height(200).margin(5).id("root")
      }
      Button("click to generate UI snapshot")
        .onClick(() => {
          componentSnapshot.get("root", (error: Error, pixmap: image.PixelMap) => {
            if (error) {
              console.log("error: " + JSON.stringify(error))
              return;
            }
            this.pixmap = pixmap
            const imagePackerApi: image.ImagePacker = image.createImagePacker();
            let packOpts: image.PackingOption = { format: "image/jpeg", quality: 98 }

            grantPermission().then(() => {
              imagePackerApi.packing(this.pixmap, packOpts).then(async (buffer: ArrayBuffer) => {
                try {
                  const context = getContext(this)
                  let helper = photoAccessHelper.getPhotoAccessHelper(context)
                  let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'png')
                  let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
                  await fs.write(file.fd, buffer);
                  // 关闭文件
                  await fs.close(file.fd);
                  promptAction.showToast({ message: `截图保存成功` })
                } catch (error) {
                  console.error("error is " + JSON.stringify(error))
                }

              }).catch((error: BusinessError) => {
                console.error('Failed to pack the image. And the error is: ' + error);
              })
            })

          }, {scale : 2, waitUntilRenderFinished : true})
        }).margin(10)
    }
    .width('100%')
    .height('100%')
    .alignItems(HorizontalAlign.Center)
  }
}

const context = getContext(this) as common.UIAbilityContext;

const TAG: string = '[Permission]';

const PERMISSIONS: Array<Permissions> = [
  "ohos.permission.WRITE_IMAGEVIDEO",
];

export default async function grantPermission(): Promise<boolean> {
  try {
    let bundleInfo: bundleManager.BundleInfo =
      await bundleManager.getBundleInfoForSelf(
        bundleManager.BundleFlag.GET_BUNDLE_INFO_WITH_APPLICATION
      );
    let appInfo: bundleManager.ApplicationInfo = bundleInfo.appInfo;
    let tokenId = appInfo.accessTokenId;
    let atManager = abilityAccessCtrl.createAtManager();
    let pems: Array<Permissions> = [];
    for (let i = 0; i < PERMISSIONS.length; i++) {
      let state = await atManager.checkAccessToken(tokenId, PERMISSIONS[i]);
      if (state !== abilityAccessCtrl.GrantStatus.PERMISSION_GRANTED) {
        pems.push(PERMISSIONS[i]);
      }
    }
    if (pems.length > 0) {
      let ctx = context
      let result: PermissionRequestResult = await atManager.requestPermissionsFromUser(ctx, pems);
      let grantStatus: Array<number> = result.authResults;
      let length: number = grantStatus.length;
      for (let i = 0; i < length; i++) {
        if (grantStatus[i] !== 0) {
          return false;
        }
      }
    }
    return true;
  } catch (error) {
    return false;
  }
}