Add with_data support to FilePicker

Add support for returning file contents (bytes) from FilePicker via a new with_data flag. Dart changes: introduce withData handling, include bytes in FilePickerFile map, and toggle withReadStream accordingly. Python SDK: add bytes field and docstring to FilePickerFile, expose with_data parameter in pick_files payload, normalize incoming byte arrays to bytes, and update returned objects. Also add an example script (pick_and_save_text_content.py) demonstrating picking and saving text content.

Author: FeodorFitsner

packages/flet/lib/src/services/file_picker.dart

@@ -34,6 +34,7 @@ class FilePickerService extends FletService {
     var allowedExtensions = (args["allowed_extensions"] as List?)
         ?.map((e) => e.toString())
         .toList();
+    var withData = args["with_data"] == true;
     var srcBytes = args["src_bytes"];
 
     if (allowedExtensions != null && allowedExtensions.isNotEmpty) {
@@ -53,16 +54,17 @@ class FilePickerService extends FletService {
                 type: fileType,
                 allowedExtensions: allowedExtensions,
                 allowMultiple: args["allow_multiple"],
-                withData: false,
-                withReadStream: true))
+                withData: withData,
+                withReadStream: !withData))
             ?.files;
         return _files != null
             ? _files!.asMap().entries.map((file) {
                 return FilePickerFile(
                         id: file.key, // use entry's index as id
                         name: file.value.name,
                         path: kIsWeb ? null : file.value.path,
-                        size: file.value.size)
+                        size: file.value.size,
+                        bytes: withData ? file.value.bytes : null)
                     .toMap();
               }).toList()
             : [];

packages/flet/lib/src/utils/file_picker.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:file_picker/file_picker.dart';
 import 'enums.dart';
 
@@ -20,15 +22,22 @@ class FilePickerFile {
   final String name;
   final String? path;
   final int size;
+  final Uint8List? bytes;
 
   FilePickerFile(
       {required this.id,
       required this.name,
       required this.path,
-      required this.size});
+      required this.size,
+      required this.bytes});
 
-  Map<String, dynamic> toMap() =>
-      <String, dynamic>{'id': id, 'name': name, 'path': path, 'size': size};
+  Map<String, dynamic> toMap() => <String, dynamic>{
+        'id': id,
+        'name': name,
+        'path': path,
+        'size': size,
+        'bytes': bytes
+      };
 }
 
 class FilePickerUploadFile {

sdk/python/examples/services/file_picker/pick_and_save_text_content.py

@@ -0,0 +1,75 @@
+#
+# Example of picking and saving text content with FilePicker.
+#
+# Run this example with:
+#    uv run flet run --web examples/services/file_picker/pick_and_save_text_content.py
+#
+import flet as ft
+
+
+def main(page: ft.Page):
+    selected_file_name = ft.Text("No file selected")
+    selected_file_content = ft.TextField(
+        label="Selected file content",
+        multiline=True,
+        min_lines=8,
+        max_lines=14,
+    )
+    save_status = ft.Text()
+
+    async def pick_text_file(_: ft.Event[ft.Button]):
+        files = await ft.FilePicker().pick_files(
+            allow_multiple=False,
+            with_data=True,
+            file_type=ft.FilePickerFileType.CUSTOM,
+            allowed_extensions=["txt", "md"],
+        )
+        if not files:
+            selected_file_name.value = "Selection cancelled"
+            selected_file_content.value = ""
+            page.update()
+            return
+
+        selected = files[0]
+        selected_file_name.value = f"Selected: {selected.name} ({selected.size} bytes)"
+        selected_file_content.value = (
+            selected.bytes.decode("utf-8", errors="replace") if selected.bytes else ""
+        )
+        save_status.value = ""
+        page.update()
+
+    async def save_text_file(_: ft.Event[ft.Button]):
+        file_name = "flet_text_content.txt"
+        file_path = await ft.FilePicker().save_file(
+            file_name=file_name,
+            file_type=ft.FilePickerFileType.CUSTOM,
+            allowed_extensions=["txt"],
+            src_bytes=selected_file_content.value.encode("utf-8"),
+        )
+        if page.web:
+            save_status.value = f"Downloaded as {file_name}"
+        else:
+            save_status.value = (
+                f"Saved to: {file_path}" if file_path else "Save cancelled"
+            )
+        page.update()
+
+    page.add(
+        ft.Text("Pick a .txt/.md file and load its text from FilePickerFile.bytes"),
+        ft.Button(
+            content="Pick text file",
+            icon=ft.Icons.UPLOAD_FILE,
+            on_click=pick_text_file,
+        ),
+        selected_file_name,
+        selected_file_content,
+        ft.Button(
+            content="Save / Download text",
+            icon=ft.Icons.DOWNLOAD,
+            on_click=save_text_file,
+        ),
+        save_status,
+    )
+
+
+ft.run(main)

sdk/python/packages/flet/src/flet/controls/services/file_picker.py

@@ -1,6 +1,6 @@
 from dataclasses import dataclass
 from enum import Enum
-from typing import Optional
+from typing import Any, Optional
 
 from flet.controls.base_control import control
 from flet.controls.control_event import Event, EventHandler
@@ -131,6 +131,14 @@ class FilePickerFile:
             does not expose a filesystem path.
     """
 
+    bytes: Optional[bytes] = None
+    """
+    File contents.
+
+    Returned only when [`pick_files()`][(c).pick_files] is called with
+    `with_data=True`. Otherwise this value is `None`.
+    """
+
 
 @dataclass
 class FilePickerUploadEvent(Event["FilePicker"]):
@@ -299,6 +307,7 @@ async def pick_files(
         file_type: FilePickerFileType = FilePickerFileType.ANY,
         allowed_extensions: Optional[list[str]] = None,
         allow_multiple: bool = False,
+        with_data: bool = False,
     ) -> list[FilePickerFile]:
         """
         Opens a pick file dialog.
@@ -312,6 +321,8 @@ async def pick_files(
             initial_directory: The initial directory where the dialog should open.
             file_type: The file types allowed to be selected.
             allow_multiple: Allow the selection of multiple files at once.
+            with_data: Read selected file contents into
+                [`FilePickerFile.bytes`][flet.FilePickerFile.].
             allowed_extensions: The allowed file extensions. Has effect only if
                 `file_type` is [`FilePickerFileType.CUSTOM`][flet.].
 
@@ -326,7 +337,14 @@ async def pick_files(
                 "file_type": file_type,
                 "allowed_extensions": allowed_extensions,
                 "allow_multiple": allow_multiple,
+                "with_data": with_data,
             },
             timeout=3600,
         )
-        return [FilePickerFile(**file) for file in files]
+        return [FilePickerFile(**self._normalize_file(file)) for file in files]
+
+    def _normalize_file(self, file: dict[str, Any]) -> dict[str, Any]:
+        value = file.get("bytes")
+        if isinstance(value, list):
+            file["bytes"] = bytes(value)
+        return file