Gallery/lib/data_provider/data_provider.dart

import 'package:flutter/material.dart';

class Item {
  bool isFolder;
  Uri uri;
  String name;

  Item(this.isFolder, this.uri, this.name);

  @override
  String toString() {
    return 'Item{isFolder: $isFolder, uri: $uri, name: $name}';
  }
}

class Folder {
  List<Item> items;
  Uri self;
  Uri parent;

  Folder(this.items, this.self, this.parent);

  @override
  String toString() {
    return 'Folder{items: $items, self: $self, parent: $parent}';
  }
}

abstract class DataProvider {
  final List<String> validSuffix = [".jpg", ".jpeg", ".png"];

  Future<void> connect();
  Future<Folder> listOfFiles({Uri? uri});
  ImageProvider getImageProvider(Uri uri);
}