harmony 鸿蒙Saving User Files

2023-06-24
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Saving User Files

When a user needs to download a file from the network to a local directory or save a user file into another directory, use FilePicker to save the file.

The operations for saving images, audio or video clips, and documents are similar. Call save() of the corresponding picker instance and pass in saveOptions. No permission is required if your application uses FilePicker to access files.

Currently, all the save() APIs of FilePicker can be perceived by users. Specifically, FilePicker is started to save the files to a directory managed by FileManager. The files are isolated from the assets managed by Gallery and cannot be viewed in Gallery.

To enable the saved image or video to be viewed in Gallery, create the media asset using a security component.

Saving Images or Video Files

For example, select an image from Gallery and save it to the file manager.

Import the picker, fs, photoAccessHelper, and dataSharePredicates modules.

   import picker from '@ohos.file.picker';
   import fs from '@ohos.file.fs';
   import photoAccessHelper from '@ohos.file.photoAccessHelper';
   import dataSharePredicates from '@ohos.data.dataSharePredicates';

Obtain the thumbnail of the first image on the device. Before performing this operation, ensure that at least one image exists on the device.

   import common from '@ohos.app.ability.common';
   import image from '@ohos.multimedia.image';
   import { BusinessError } from '@ohos.base';

   let context = getContext(this) as common.UIAbilityContext;
   let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(context);

   let pixelmapArrayBuffer: ArrayBuffer;
   async function getPixelmap(): Promise<void> {
      try {
         let predicates = new dataSharePredicates.DataSharePredicates();
         let fetchOption: photoAccessHelper.FetchOptions = {
            fetchColumns: [],
            predicates: predicates
         };
         let fetchResult = await phAccessHelper.getAssets(fetchOption);
         console.info('[picker] getThumbnail fetchResult: ' + fetchResult);
         const asset = await fetchResult.getFirstObject();
         console.info('[picker] getThumbnail asset displayName = ', asset.displayName);
         asset.getThumbnail().then((pixelMap: image.PixelMap) => {
            let pixelBytesNumber = pixelMap.getPixelBytesNumber();
            const readBuffer = new ArrayBuffer(pixelBytesNumber);
            pixelMap.readPixelsToBuffer(readBuffer).then(() => {
               pixelmapArrayBuffer = readBuffer;
            })
         }).catch((err: BusinessError) => {
            console.error('[picker] getThumbnail failed with error: ' + JSON.stringify(err));
         });
      } catch (error) {
         let err: BusinessError = error as BusinessError;
         console.error('[picker] getThumbnail error = ' + JSON.stringify(err));
      }
   }

Create a photoViewPicker instance and call save() to open the FilePicker page to save the image. After the user selects the destination folder, the image is saved and the URI of the saved image is returned.

The permission on the URI returned by save() is read/write. Further operations on the file can be performed based on the URI in the result set. Note that the URI cannot be directly used in the picker callback to open a file. You need to define a global variable to save the URI and use a button to trigger file opening.

   import { BusinessError } from '@ohos.base';

   let uris: Array<string> = [];
   async function photoViewPickerSave(): Promise<void>{
      try {
         const photoSaveOptions = new picker.PhotoSaveOptions(); // Create a photoSaveOptions instance.
         photoSaveOptions.newFileNames = ["PhotoViewPicker01.png"]; // (Optional) Name of the file to be saved. The file name in the square brackets can be customized and must be unique. If the file name already exists on the device, change the file name. Otherwise, an error will be returned.

         const photoViewPicker = new picker.PhotoViewPicker();
         try {
            let photoSaveResult = await photoViewPicker.save(photoSaveOptions);
            if (photoSaveResult != undefined) {
               uris = photoSaveResult;
               console.info('photoViewPicker.save to file succeed and uris are:' + uris);
            }
         } catch (error) {
            let err: BusinessError = error as BusinessError;
            console.error(`[picker] Invoke photoViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
         }
      } catch (error) {
         let err: BusinessError = error as BusinessError;
         console.info("[picker] photoViewPickerSave error = " + JSON.stringify(err));
      }
   }

After the UI is returned from the FilePicker page, use a button to trigger API calling. Use fs.openSync() to open the file based on the URI and obtain the FD. Note that the mode parameter of fs.openSync() must be fs.OpenMode.READ_WRITE.

Then, use fs.write to modify the file based on the FD, and close the FD after the modification is complete.

   import { BusinessError } from '@ohos.base';

   async function writeOnly(uri: string): Promise<void> {
      try {
         let file = fs.openSync(uri, fs.OpenMode.WRITE_ONLY);
         let writeLen = await fs.write(file.fd, pixelmapArrayBuffer);
         fs.closeSync(file);
         console.info("[picker] writeOnly writeLen = " + writeLen);
      } catch (error) {
         let err: BusinessError = error as BusinessError;
         console.info("[picker] writeOnly error: " + JSON.stringify(err));
      }
   }

Saving Documents

Import the picker and fs modules.

   import picker from '@ohos.file.picker';
   import fs from '@ohos.file.fs';
   import { BusinessError } from '@ohos.base';

Create a documentSaveOptions instance.

   const documentSaveOptions = new picker.DocumentSaveOptions(); // Create a documentSaveOptions instance.
   documentSaveOptions.newFileNames = ["DocumentViewPicker01.txt"]; // (Optional) Set the name of the document to save.
   documentSaveOptions.fileSuffixChoices = ['.png', '.txt', '.mp4']; // (Optional) Types of the documents to save.

Create a documentViewPicker instance, and call save() to open the FilePicker page to save the document. After the user selects the destination folder, the document is saved and the URI of the document saved is returned.

   import { BusinessError } from '@ohos.base';

   let uris: Array<string> = [];
   const documentViewPicker = new picker.DocumentViewPicker(); // Create a documentViewPicker instance.
   documentViewPicker.save(documentSaveOptions).then((documentSaveResult: Array<string>) => {
     uris = documentSaveResult;
     console.info('documentViewPicker.save to file succeed and uris are:' + uris);
   }).catch((err: BusinessError) => {
     console.error(`Invoke documentViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
   })

After the UI is returned from the FilePicker page, use a button to trigger API calling. Use fs.openSync() to open the file based on the URI and obtain the FD. Note that the mode parameter of fs.openSync() must be fs.OpenMode.READ_WRITE.

   import fs from '@ohos.file.fs';

   const uri = '';
   let file = fs.openSync(uri, fs.OpenMode.READ_WRITE);
   console.info('file fd: ' + file.fd);

Use fs.writeSync() to edit the document based on the FD, and then close the FD.

   import fs from '@ohos.file.fs';

   let writeLen: number = fs.writeSync(file.fd, 'hello, world');
   console.info('write data to file succeed and size is:' + writeLen);
   fs.closeSync(file);

Saving Audio Files

Import the picker and fs modules.

   import picker from '@ohos.file.picker';
   import fs from '@ohos.file.fs';
   import { BusinessError } from '@ohos.base';

Create an audioSaveOptions instance.

   const audioSaveOptions = new picker.AudioSaveOptions(); // Create an audioSaveOptions instance.
   audioSaveOptions.newFileNames = ['AudioViewPicker01.mp3']; // (Optional) Set the name of the audio file to save.

Create an audioViewPicker instance, and call save() to open the FilePicker page to save the file. After the user selects the destination folder, the audio file is saved and the URI of the document saved is returned.

   let uri: string = '';
   const audioViewPicker = new picker.AudioViewPicker();
   audioViewPicker.save(audioSaveOptions).then((audioSelectResult: Array<string>) => {
     uri = audioSelectResult[0];
     console.info('audioViewPicker.save to file succeed and uri is:' + uri);
   }).catch((err: BusinessError) => {
     console.error(`Invoke audioViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
   })

After the UI is returned from the FilePicker page, use a button to trigger API calling. Use fs.openSync() to open the file based on the URI and obtain the FD. Note that the mode parameter of fs.openSync() must be fs.OpenMode.READ_WRITE.

   let file = fs.openSync(uri, fs.OpenMode.READ_WRITE);
   console.info('file fd: ' + file.fd);

Use fs.writeSync() to edit the document based on the FD, and then close the FD.

   let writeLen = fs.writeSync(file.fd, 'hello, world');
   console.info('write data to file succeed and size is:' + writeLen);
   fs.closeSync(file);