在应用栏中获取小部件的值

Question

如果时间还没有结束，我需要将控件的倒计时值每秒获取一秒，以便进行控制。我不知道该怎么办...我如何获得小部件的价值？我如何获得每秒的价值？对于其他小部件的集成，我想我可以做到。

我的倒数计时小部件：

class _CountdownState extends State<Countdown> {

  Countdown c = new Countdown();
  Timer _timer;
  int seconds = 0;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(constructTime(seconds), style: TextStyle(fontSize: 18, color: Colors.white, fontStyle: FontStyle.italic),),
    );
  }

  String constructTime(int seconds) {
    if(seconds == 0){
      return "";
    }
    int hour = seconds ~/ 3600;
    int minute = seconds % 3600 ~/ 60;
    int second = seconds % 60;
    return formatTime(hour) + ":" + formatTime(minute) + ":" + formatTime(second);
  }

  String formatTime(int timeNum) {
    return timeNum < 10 ? "0" + timeNum.toString() : timeNum.toString();
  }

  @override
  initState(){
    super.initState();
    getDate();
    startTimer();
  }

  void getDate() async{
    var now = DateTime.now();
    /*String creationDate = await Poll().getCreationDateToSF();
    DateTime creationDateTime = DateTime.parse(creationDate);*/
    var creationDateTime = DateTime.now().add(new Duration(seconds: 15));
    seconds = creationDateTime.difference(now).inSeconds;
  }

  void startTimer() {
    const period = const Duration(seconds: 1);
    _timer = Timer.periodic(period, (timer) {
      setState(() {
        seconds--;
      });
      if (seconds == 0) {
        cancelTimer();
      }
    });
  }

  void cancelTimer() {
    if (_timer != null) {
      _timer.cancel();
      _timer = null;
      c.onCountDownComplete();
    }
  }

  @override
  void dispose() {
    super.dispose();
    cancelTimer();
  }
}

[我添加了在其他页面上打印消息的方法，并在我的投票状态类中调用了Countdown（onCountDownComplete：onCountDown）

我想在其他页面中进行控制，当我的倒数结束后，我停止我的应用程序。

Answer 1

尝试此代码：

像这样更改您的倒计时课程：

class Countdown extends StatefulWidget {
  final Function onCountDownComplete;
  Countdown({this.onCountDownComplete});
  @override
  _CountdownState createState() => _CountdownState();
}

class _CountdownState extends State<Countdown> {
  Timer _timer;
  int seconds = 0;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(
        constructTime(seconds),
        style: TextStyle(
            fontSize: 18, color: Colors.white, fontStyle: FontStyle.italic),
      ),
    );
  }

  String constructTime(int seconds) {
    int hour = seconds ~/ 3600;
    int minute = seconds % 3600 ~/ 60;
    int second = seconds % 60;
    return formatTime(hour) +
        ":" +
        formatTime(minute) +
        ":" +
        formatTime(second);
  }

  String formatTime(int timeNum) {
    return timeNum < 10 ? "0" + timeNum.toString() : timeNum.toString();
  }

  @override
  initState() {
    getDate();
    //startTimer();
    super.initState();
  }

  void getDate() async {
    var now = DateTime.now();
    String creationDate = '12:20:11';
    DateTime creationDateTime = DateTime.parse(creationDate);
    seconds = creationDateTime.difference(now).inSeconds;
    startTimer();
  }

  void startTimer() {
    const period = const Duration(seconds: 1);
    _timer = Timer.periodic(period, (timer) {
      setState(() {
        seconds--;
      });
      if (seconds == 0) {
        cancelTimer();
      }
    });
  }

  void cancelTimer() {
    if (_timer != null) {
      _timer.cancel();
      _timer = null;
      widget.onCountDownComplete();
    }
  }

  @override
  void dispose() {
    super.dispose();
    cancelTimer();
  }
}

用于倒数计时：

 void onCountDown() {
    print('Complete Count down');
  }


Countdown(onCountDownComplete: onCountDown)