Flutter Desktop Apps: Getting Started

Android Studio

Let’s test this out by deleting our todos and writing the import code.

Back in menus.dart, find the handleImport method. Add:

final result = await FilePicker.platform.pickFiles(
  dialogTitle: 'Open file',
  allowedExtensions: ['todo'],
  type: FileType.custom

);
if (result == null || result.files.isEmpty) {
  return;
}
final path = result.files[0].path;

Similar to saving, we use the open command with a title and set the extension to be ‘.todo’. Now add:

// 1
if (path != null) {
  // 2
  final file = File(path);
  // 3
  if (await file.exists()) {
    // 4
    final repository = ref.read(repositoryProvider);
    // 5
    file.readAsString().then((String contents) async {
      // 6
      final jsonArray = jsonDecode(contents) as List<dynamic>;
      // 7
      await Future.forEach(jsonArray, (value) async  {
        final map = value as Map<String, dynamic>;
        var list = TodoList.fromJson(map);
        // 8
        list = list.copyWith(id: -1);
        // 9
        final todoListId = await repository.addTodoList(list);
        // 10
        await Future.forEach(list.categories, (category) async {
          // 11
          category = category.copyWith(id: -1, todoList: todoListId);
          // 12
          final categoryId = await repository.addCategory(category);
          await Future.forEach(category.todos, (todo) async {
          	todo = todo.copyWith(id: -1, category: categoryId);
            await repository.addTodo(todo);
          });
        });
      });
    });
  }
}

First check to see if there is a path, create a file object and make sure it exists. Using Riverpod, you get the repository, then read the file as a string. Next, decode it into a dynamic list. Then for each list, convert it to a real TodoList class. Since the json contains the ids of the items, you want to set the ids to -1 to let the database know to assign a new id. Next add the todo list to the repository. Then for each category set it’s id to -1 and then add it to the repository. Do the same for all of the todos.

Hot reload the app. Now choose Todo -> import. It should recreate the screen the way it was.

You now have a way of either importing and exporting files or saving and opening files.