如何为与 Provider 合作的列表实施 ChangeNotifier？

Question

我想为我的应用程序实现 Provider，在做了一些研究后，我发现我必须为我的 Data 类实现 ChangeNotifier 以在“天数”发生变化时更新 UI。

我见过有人在 setter 方法中编写 notifyListeners()，但总是针对单个属性，从不针对列表。什么是正确的实现？

谢谢！

这是我的班级和名单：

class Data with ChangeNotifier {
  List<Day> days = [
    Day(
      name: 'Monday',
      transactions: [
        Transaction(
          isExpense: true,
          name: 'Pizza',
          transactionType: TransactionType.food,
          amount: '120€',
        ),
        Transaction(
          isExpense: true,
          name: 'EDEKA',
          transactionType: TransactionType.payment,
          amount: '120€',
        ),
      ],
    ),
    Day(
      name: 'Tuesday',
      transactions: [
        Transaction(
          isExpense: true,
          name: 'Sushi',
          transactionType: TransactionType.food,
          amount: '120€',
        ),
        Transaction(
          isExpense: true,
          name: 'Lidl',
          transactionType: TransactionType.payment,
          amount: '120€',
        ),
        Transaction(
          isExpense: false,
          name: 'Einkommen',
          transactionType: TransactionType.payment,
          amount: '120€',
        ),
      ],
    ),
  ];
}

Answer 1

Todo App 是处理List<Taks> 的一个很好的例子
可以参考https://dev.to/shakib609/create-a-todos-app-with-flutter-and-provider-jdh
完整示例github代码https://github.com/shakib609/todos-flutter/tree/master/lib

代码sn-p

class Task {
  String title;
  bool completed;

  Task({@required this.title, this.completed = false});

  void toggleCompleted() {
    completed = !completed;
  }
}

class TodosModel extends ChangeNotifier {
  final List<Task> _tasks = [];

  UnmodifiableListView<Task> get allTasks => UnmodifiableListView(_tasks);
  UnmodifiableListView<Task> get incompleteTasks =>
      UnmodifiableListView(_tasks.where((todo) => !todo.completed));
  UnmodifiableListView<Task> get completedTasks =>
      UnmodifiableListView(_tasks.where((todo) => todo.completed));

  void addTodo(Task task) {
    _tasks.add(task);
    notifyListeners();
  }

  void toggleTodo(Task task) {
    final taskIndex = _tasks.indexOf(task);
    _tasks[taskIndex].toggleCompleted();
    notifyListeners();
  }

  void deleteTodo(Task task) {
    _tasks.remove(task);
    notifyListeners();
  }
}

工作演示

Answer 2

制作2种添加和删除项目的方法。

void add(Day day) {
  days.add(day);
  notifyListeners();
}

void remove(int index) {
  days.removeAt(index);
  notifyListeners();
}