flutter - Flutter-如何开始列表中的下一个倒数

我有一个倒数计时器的秒表。
当列表中的第一个倒数结束时，我要开始下一个倒数，依此类推。
我怎样才能做到这一点？
谢谢!
我的代码到现在为止

import 'dart:async';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:timer_count_down/timer_controller.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      themeMode: ThemeMode.dark,
      home: Ex(),
    );
  }
}

class Ex extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => ExpandableListView();
}

class ExpandableListView extends State<Ex> {
  final CountdownController controller = CountdownController();
  List<int> list = [3, 4, 5, 6];
  Timer _timer;
  int counter = 3;

  void _startTimer(seconds) {

    if (_timer != null) {
      _timer.cancel();
    }

    _timer = Timer.periodic(Duration(hours:0, minutes: 0, seconds: seconds), (timer) {
      setState(() {
        if (counter > 0) {
          counter--;
        } else {
          _timer.cancel();
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: Container(
        height: 500,
        width: 200,
        child: Column(
          children: [
            Container(
              height: 200,
              width: 200,
              child: ListView.builder(
                itemCount: list.length,
                itemBuilder: (context, index) {
                  return Text(list[index].toString());
                },
              ),
            ),
            RaisedButton(
              onPressed: () {
                setState(() {
                  _startTimer(list[0]);
                });
              },
            ),
          ],
        ),
      ),
    );
  }
}

最佳答案

这样的一种方法就是这样。

class _MyWidgetState extends State<MyWidget> {
  List<int> list = [3, 4, 5, 6];
  Timer _timer;
  int currentIndex = 0;           //<-- to track which timer is running at the moment

  void _startTimer() {
    _timer = Timer.periodic(Duration(seconds: 1), (_) {
      setState(() {
        if (list[currentIndex] > 0) {
          list[currentIndex]--;
        } else {
          if (currentIndex != (list.length - 1)) {
            currentIndex++;
            list[currentIndex]--;
          }
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Expanded(
            child: ListView.builder(
              itemCount: list.length,
              itemBuilder: (context, index) {
                return Text('${list[index]}');
              },
            ),
          ),
          RaisedButton(
            child: Text('Start'),
            onPressed: _startTimer,
          ),
        ],
      ),
    );
  }

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

链接到dartpad上的演示-https://dartpad.dev/ca29e0b73e1d919d941e113174b747cf
要在完成后删除计时器，您可以这样做。

itemBuilder: (context, index) {
                if(list[index] == 0){
                  return const SizedBox();
                }
                else{
                  return Text('${list[index]}');
                }
              }