Question

当我从列表视图中删除项目时，尽管添加项目工作正常，但在颤振中重置删除项目下方的计时器。如何在删除项目上保持计时器状态？示例：如果我删除项目 2，项目 0 和项目 1 的计时器仍保持其状态，但项目 3 的计时器重置为其原始值。这是我的代码...

class MyListView extends StatefulWidget {


@override
  _MyListViewState createState() => _MyListViewState();
}

class _MyListViewState extends State<MyListView> {
  List<Todo> todos = [
    Todo("120", "Item 0", 10),
    Todo("121", "Item 1", 15),
    Todo("122", "Item 2", 20),
  ];
// adding item on click add
  void _addTodoItem() {
    setState(() {
      int index = todos.length;
      todos.add(Todo("12$index", "Item $index", 30));
    });
  }
// build list view
  Widget _buildTodoList() {
    return new ListView.builder(
      itemBuilder: (context, index) {
        if (index < todos.length) {
          return _buildTodoItem(todos[index], index);
        } else
          return null;
      },
    );
  }
// build listview item
  Widget _buildTodoItem(Todo todo, int index) {
    return GestureDetector(
      key: ValueKey(todo.key),
      onTap: () => _removeTodoItem(index),
      child: todo.text != null
          ? Row(
              children: [
                Text(todo.text),
                SizedBox(
                  width: 20,
                ),
                TimerWidget(
                  duration: todo.duration,
                )
              ],
            )
          : Text("Loading Time"),
    );
  }
// remove item when click on list item
  void _removeTodoItem(int index) {
    setState(() => todos.removeAt(index));
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text('Todo List')),
      body: _buildTodoList(),
      floatingActionButton: new FloatingActionButton(
          onPressed: _addTodoItem,
          tooltip: 'Add task',
          child: new Icon(Icons.add)),
    );
  }
}

我的计时器小工具

class _TimerWidgetState extends State<TimerWidget> {
  Timer _timer;

  int _start = 0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _start = widget.duration;
    this.startTimer();
  }

  void startTimer() {
    const oneSec = const Duration(seconds: 1);
    _timer = new Timer.periodic(
      oneSec,
      (Timer timer) {
        if (_start == 0) {
          setState(() {
            timer.cancel();
          });
        } else {
          setState(() {
            _start--;
          });
        }
      },
    );
  }

  @override
  void dispose() {
    _timer.cancel();
    super.dispose();
  }

  Widget build(BuildContext context) {
    return Text("$_start");
  }
}

Todo 模型

class Todo {
  String key;
  String text;
  int duration;

  Todo(key, text, duration) {
    this.key = key;
    this.text = text;
    this.duration = duration;
  }
}

在颤动中从列表视图中删除项目

0 个答案: