Download files

There are three ways of getting data that was previously uploaded:

Download File

You can download file to a local directory using Amplify.Storage.downloadFile.

You can use the path_provider package to create a local file in the user's documents directory where you can store the downloaded data.

1import 'package:path_provider/path_provider.dart';
2
3Future<void> downloadToLocalFile(String key) async {
4  final documentsDir = await getApplicationDocumentsDirectory();
5  final filepath = documentsDir.path + '/example.txt';
6  try {
7    final result = await Amplify.Storage.downloadFile(
8      key: key,
9      localFile: AWSFile.fromPath(filepath),
10      onProgress: (progress) {
11        safePrint('Fraction completed: ${progress.fractionCompleted}');
12      },
13    ).result;
14
15    safePrint('Downloaded file is located at: ${result.localFile.path}');
16  } on StorageException catch (e) {
17    safePrint(e.message);
18  }
19}

On Web, the download process will be handled by the browser. You can provide the downloaded file name by specifying the path parameter of AWSFile.fromPath. E.g. this instructs the browser to download the file download.txt.

1Future<void> downloadToLocalFileOnWeb(String key) async {
2  try {
3    final result = await Amplify.Storage.downloadFile(
4      key: key,
5      localFile: AWSFile.fromPath('download.txt'),
6    ).result;
7
8    safePrint('Downloaded file: ${result.downloadedItem.key}');
9  } on StorageException catch (e) {
10    safePrint(e.message);
11  }
12}

Download data

You can download a file to in-memory buffer with Amplify.Storage.downloadData:

1Future<void> downloadToMemory(String key) async {
2  try {
3    final result = await Amplify.Storage.downloadData(
4      key: key,
5      onProgress: (progress) {
6        safePrint('Fraction completed: ${progress.fractionCompleted}');
7      },
8    ).result;
9
10    safePrint('Downloaded data: ${result.bytes}');
11  } on StorageException catch (e) {
12    safePrint(e.message);
13  }
14}

Generate a download URL

You can get a downloadable URL for the file in storage by its key and access level.

When creating a downloadable URL, you can choose to check if the file exists by setting validateObjectExistence to true in S3GetUrlPluginOptions. If the file is inaccessible or does not exist, a StorageException is thrown. This allows you to check if an object exists during generating the presigned URL, which you can then use to download that object.

1Future<String> getDownloadUrl({
2  required String key,
3  required StorageAccessLevel accessLevel,
4}) async {
5  try {
6    final result = await Amplify.Storage.getUrl(
7      key: key,
8      options: const StorageGetUrlOptions(
9        accessLevel: accessLevel,
10        pluginOptions: S3GetUrlPluginOptions(
11          validateObjectExistence: true,
12          expiresIn: Duration(days: 1),
13        ),
14      ),
15    ).result;
16    return result.url.toString();
17  } on StorageException catch (e) {
18    safePrint('Could not get a downloadable URL: ${e.message}');
19    rethrow;
20  }
21}

Upload files

Get file properties