Lean File Picker

Pick a single file using the native file explorer.

Motivation

Why do we need another file picker for Flutter if there is already a plugin for file selection available? The existing file_picker plugin has two serious problems on iOS:

• The file_picker plugin requires you to build your Flutter app with frameworks (use_frameworks!) instead of using static linking. This results in substantially larger binaries.
• The file_picker plugin has a considerable list of large dependencies (DKImagePickerController, DKPhotoGallery, SDWebImage, SwiftyGif) that yet again increase your binary size.

By using lean_file_picker instead of file_picker I managed to reduce the installation size of an app from 81.3 MB to 31.3 MB — a reduction of 50 MB or more than 60%!

If the native file explorer behavior on Android and iOS is sufficient for your needs then replace file_picker with lean_file_picker for a much reduced installation size and memory consumption (especially on iOS).

Usage

import 'package:lean_file_picker/lean_file_picker.dart';
final file = await pickFile(
  allowedExtensions: ['zip'],
  allowedMimeTypes: ['image/jpeg', 'text/*'],
);
if (file != null) {
  print(file.path);
}

If the user selects a large file or if the selected file is stored on a virtual file system such as OneDrive or iCloud, copying the file to a temporary location might take a while. To inform the user about the file being copied, e.g. by displaying a progress dialog, you can add a listener to the pickFile() function call:

import 'package:lean_file_picker/lean_file_picker.dart';
final file = await pickFile(
  listener: (status) {
    if (status == FilePickerStatus.copying) {
      print('Selected file is being copied to a temporary location…');
    } else {
      print('Copy process has completed.');
    }
  },
);

Because on iOS the operating system automatically copies the selected file to a temporary location and does so inside the native file explorer UI, the selected file is always ready when the file explorer returns to the Flutter app. Therefore the aforementioned listener is never called on iOS.