Add writeToFile, writeToFileAsBytes, writeToFileAsString

android/src/main/kotlin/io/lakscastro/sharedstorage/storageaccessframework/DocumentFileApi.kt

@@ -74,6 +74,13 @@ internal class DocumentFileApi(private val plugin: SharedStoragePlugin) :
                 call.argument<ByteArray>("content")!!
             )
           }
+      WRITE_TO_FILE ->
+          writeToFile(
+              result,
+              call.argument<String>("uri")!!,
+              call.argument<ByteArray>("content")!!,
+              call.argument<String>("mode")!!
+          )
       PERSISTED_URI_PERMISSIONS ->
         persistedUriPermissions(result)
       RELEASE_PERSISTABLE_URI_PERMISSION ->
@@ -311,6 +318,25 @@ internal class DocumentFileApi(private val plugin: SharedStoragePlugin) :
     }
   }
 
+  private fun writeToFile(
+    result: MethodChannel.Result,
+    uri: String,
+    content: ByteArray,
+    mode: String
+  ) {
+    try {
+      plugin.context.contentResolver.openOutputStream(Uri.parse(uri), mode)?.apply {
+        write(content)
+        flush()
+        close()
+
+        result.success(true)
+      }
+    } catch (e: Exception) {
+      result.success(false)
+    }
+  }
+
   @RequiresApi(API_19)
   private fun persistedUriPermissions(result: MethodChannel.Result) {
     val persistedUriPermissions = plugin.context.contentResolver.persistedUriPermissions

android/src/main/kotlin/io/lakscastro/sharedstorage/storageaccessframework/lib/StorageAccessFrameworkConstant.kt

@@ -23,6 +23,7 @@ const val OPEN_DOCUMENT_TREE = "openDocumentTree"
 const val PERSISTED_URI_PERMISSIONS = "persistedUriPermissions"
 const val RELEASE_PERSISTABLE_URI_PERMISSION = "releasePersistableUriPermission"
 const val CREATE_FILE = "createFile"
+const val WRITE_TO_FILE = "writeToFile"
 const val FROM_TREE_URI = "fromTreeUri"
 const val CAN_WRITE = "canWrite"
 const val CAN_READ = "canRead"

docs/Usage/Storage Access Framework.md

@@ -217,6 +217,33 @@ final DocumentFile? createdFile = createFileAsBytes(
 );
 ```
 
+### <samp>writeToFileAsBytes</samp>
+
+Write to a file using raw bytes `Uint8List`.
+
+Given the document uri, opens the file in the specified `mode` and writes the `bytes` to it.
+
+`mode` represents the mode in which the file will be opened for writing. Use `FileMode.write` for truncating (overwrite) and `FileMode.append` for appending to the file.
+
+```dart
+final Uri documentUri = ...
+final String fileContent = 'My File Content';
+
+/// Write to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFileAsBytes(
+  documentUri,
+  bytes: Uint8List.fromList(fileContent.codeUnits),
+  mode: FileMode.write,
+);
+
+/// Append to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFileAsBytes(
+  documentUri,
+  bytes: Uint8List.fromList(fileContent.codeUnits),
+  mode: FileMode.write,
+);
+```
+
 ### <samp>canRead</samp>
 
 <samp>Mirror of [`DocumentFile.canRead`](<https://developer.android.com/reference/androidx/documentfile/provider/DocumentFile#canRead()>)</samp>
@@ -485,6 +512,31 @@ final DocumentFile? createdFile = createFileAsString(
 );
 ```
 
+### <samp>writeToFileAsString</samp>
+
+<samp>Alias for `writeToFileAsBytes`</samp>
+
+Convenient method to write to a file using `content` as `String` instead `Uint8List`.
+
+```dart
+final Uri documentUri = ...
+final String fileContent = 'My File Content';
+
+/// Write to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFileAsString(
+  documentUri,
+  content: fileContent,
+  mode: FileMode.write,
+);
+
+/// Append to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFileAsBytes(
+  documentUri,
+  content: fileContent,
+  mode: FileMode.write,
+);
+```
+
 ### <samp>createFile</samp>
 
 <samp>Alias for `createFileAsBytes` and `createFileAsString`</samp>
@@ -514,6 +566,49 @@ final DocumentFile? createdFile = createFile(
 );
 ```
 
+### <samp>writeToFile</samp>
+
+<samp>Alias for `writeToFileAsBytes` and `writeToFileAsString`</samp>
+
+Convenient method to write to a file using `content` as `String` **or** `bytes` as `Uint8List`.
+
+You should provide either `content` or `bytes`, if both `bytes` will be used.
+
+`mode` represents the mode in which the file will be opened for writing. Use `FileMode.write` for truncating and `FileMode.append` for appending to the file.
+
+```dart
+final Uri documentUri = ...
+final String fileContent = 'My File Content';
+
+/// Write to a file using a [String] as file contents [content]
+final bool? success = writeToFile(
+  documentUri,
+  content: fileContent,
+  mode: FileMode.write,
+);
+
+/// Append to a file using a [String] as file contents [content]
+final bool? success = writeToFile(
+  documentUri,
+  content: fileContent,
+  mode: FileMode.append,
+);
+
+/// Write to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFile(
+  documentUri,
+  content: Uint8List.fromList(fileContent.codeUnits),
+  mode: FileMode.write,
+);
+
+/// Append to a file using a [Uint8List] as file contents [bytes]
+final bool? success = writeToFile(
+  documentUri,
+  content: Uint8List.fromList(fileContent.codeUnits),
+  mode: FileMode.append,
+);
+```
+
 ## External APIs (deprecated)
 
 These APIs are from external Android libraries.

example/lib/screens/file_explorer/file_explorer_card.dart

@@ -198,6 +198,13 @@ class _FileExplorerCardState extends State<FileExplorerCard> {
                 }
               },
             ),
+            if (!_isDirectory)
+              DangerButton(
+                'Write to File',
+                onTap: () async {
+                  await writeToFile(widget.partialFile.metadata!.uri!, content: 'Hello World!');
+                },
+              ),
           ],
         ),
       ],

lib/src/saf/document_file.dart

@@ -1,3 +1,4 @@
+import 'dart:io';
 import 'dart:typed_data';
 
 import '../common/functional_extender.dart';
@@ -155,6 +156,41 @@ class DocumentFile {
         displayName: displayName,
         content: content,
       );
+
+  /// {@macro sharedstorage.saf.writeToFileAsBytes}
+  Future<bool?> writeToFileAsBytes({
+    required Uint8List bytes,
+    FileMode? mode,
+  }) =>
+      saf.writeToFileAsBytes(
+        uri,
+        bytes: bytes,
+        mode: mode,
+      );
+
+  /// {@macro sharedstorage.saf.writeToFile}
+  Future<bool?> writeToFile({
+    String? content,
+    Uint8List? bytes,
+    FileMode? mode,
+  }) =>
+      saf.writeToFile(
+        uri,
+        content: content,
+        bytes: bytes,
+        mode: mode,
+      );
+
+  /// Alias for [writeToFile] with [content] param
+  Future<bool?> writeToFileAsString({
+    required String content,
+    FileMode? mode,
+  }) =>
+      saf.writeToFile(
+        uri,
+        content: content,
+        mode: mode,
+      );
 
   /// {@macro sharedstorage.saf.length}
   Future<int?> get length => saf.documentLength(uri);

lib/src/saf/saf.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:io';
 import 'dart:typed_data';
 
 import '../../saf.dart';
@@ -201,7 +202,7 @@ Future<DocumentFile?> createDirectory(Uri parentUri, String displayName) async {
 }
 
 /// {@template sharedstorage.saf.createFile}
-/// Convenient method to create files using either String or raw bytes.
+/// Convenient method to create files using either [String] or raw bytes [Uint8List].
 ///
 /// Under the hood this method calls `createFileAsString` or `createFileAsBytes`
 /// depending on which argument is passed.
@@ -281,6 +282,79 @@ Future<DocumentFile?> createFileAsString(
   );
 }
 
+/// {@template sharedstorage.saf.writeToFile}
+/// Convenient method to write to a file using either [String] or raw bytes [Uint8List].
+///
+/// Under the hood this method calls `writeToFileAsString` or `writeToFileAsBytes`
+/// depending on which argument is passed.
+///
+/// If both (bytes and content) are passed, the bytes will be used and the content will be ignored.
+/// {@endtemplate}
+Future<bool?> writeToFile(
+  Uri uri, {
+  Uint8List? bytes,
+  String? content,
+  FileMode? mode,
+}) {
+  assert(
+    bytes != null || content != null,
+    '''Either [bytes] or [content] should be provided''',
+  );
+
+  return bytes != null
+      ? writeToFileAsBytes(
+          uri,
+          bytes: bytes,
+          mode: mode,
+        )
+      : writeToFileAsString(
+          uri,
+          content: content!,
+          mode: mode,
+        );
+}
+
+/// {@template sharedstorage.saf.writeToFileAsBytes}
+/// Write to a file.
+/// - `uri` is the URI of the file.
+/// - `bytes` is the content of the document as a list of bytes `Uint8List`.
+/// - `mode` is the mode in which the file will be opened for writing. Use `FileMode.write` for truncating and `FileMode.append` for appending to the file.
+///
+/// Returns `true` if the file was successfully written to.
+/// {@endtemplate}
+Future<bool?> writeToFileAsBytes(
+  Uri uri, {
+  required Uint8List bytes,
+  FileMode? mode,
+}) async {
+  final writeMode =
+      mode == FileMode.append || mode == FileMode.writeOnlyAppend ? 'wa' : 'wt';
+
+  final args = <String, dynamic>{
+    'uri': '$uri',
+    'content': bytes,
+    'mode': writeMode,
+  };
+
+  return kDocumentFileChannel.invokeMethod<bool>('writeToFile', args);
+}
+
+/// {@template sharedstorage.saf.writeToFileAsString}
+/// Convenient method to write to a file.
+/// using `content` as [String] instead [Uint8List].
+/// {@endtemplate}
+Future<bool?> writeToFileAsString(
+  Uri uri, {
+  required String content,
+  FileMode? mode,
+}) {
+  return writeToFileAsBytes(
+    uri,
+    bytes: Uint8List.fromList(content.codeUnits),
+    mode: mode,
+  );
+}
+
 /// {@template sharedstorage.saf.length}
 /// Equivalent to `DocumentFile.length`.
 ///