Flutter 倒数计时器(自定义时间)

我使用了倒数计时器的基本代码，并想知道如何让用户自定义他们想要的时间量，而不是将其设为默认值(在我的情况下为30分钟或1800秒).我只想让他们 Select 他们想要的任何时间，比如5分钟、30分钟、1小时等等.单击该按钮后，可能会出现另一个按钮，或者可能会出现一个弹出窗口，让他们 Select 时间？老实说，在这一点上有任何帮助，谢谢！

class timer extends StatefulWidget {
  const timer({Key? key}) : super(key: key);

  @override
  State<timer> createState() => _timerState();
}

class _timerState extends State<timer> {
   final int _duration = 1800;
  final CountDownController _controller = CountDownController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
          child: CircularCountDownTimer(
        // Countdown duration in Seconds.
        duration: _duration,

        // Countdown initial elapsed Duration in Seconds.
        initialDuration: 0,

        // Controls (i.e Start, Pause, Resume, Restart) the Countdown Timer.
        controller: _controller,

        // Width of the Countdown Widget.
        width: MediaQuery.of(context).size.width / 2,

        // Height of the Countdown Widget.
        height: MediaQuery.of(context).size.height / 2,

        // Ring Color for Countdown Widget.
        ringColor: Colors.grey[300]!,

        // Ring Gradient for Countdown Widget.
        ringGradient: null,

        // Filling Color for Countdown Widget.
        fillColor: Color(0XFFffadad),

        // Filling Gradient for Countdown Widget.
        fillGradient: null,

        // Background Color for Countdown Widget.
        backgroundColor: Color(0XFFFDE2E4),

        // Background Gradient for Countdown Widget.
        backgroundGradient: null,

        // Border Thickness of the Countdown Ring.
        strokeWidth: 20.0,

        // Begin and end contours with a flat edge and no extension.
        strokeCap: StrokeCap.round,

        // Text Style for Countdown Text.
        textStyle: const TextStyle(
          fontSize: 33.0,
          color: Colors.white,
          fontWeight: FontWeight.bold,
        ),

        // Format for the Countdown Text.
        textFormat: CountdownTextFormat.S,

        // Handles Countdown Timer (true for Reverse Countdown (max to 0), false for Forward Countdown (0 to max)).
        isReverse: false,

        // Handles Animation Direction (true for Reverse Animation, false for Forward Animation).
        isReverseAnimation: false,

        // Handles visibility of the Countdown Text.
        isTimerTextShown: true,

        // Handles the timer start.
        autoStart: false,

        // This Callback will execute when the Countdown Starts.
        onStart: () {
          // Here, do whatever you want
          debugPrint('Countdown Started');
        },

        // This Callback will execute when the Countdown Ends.
        onComplete: () {
          // Here, do whatever you want
          debugPrint('Countdown Ended');
        },
      )),
      floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          const SizedBox(
            width: 30,
          ),
          _button(title: "Start", onPressed: () => _controller.start()),
          const SizedBox(
            width: 10,
            height: 200
          ),
          _button(title: "Pause", onPressed: () => _controller.pause()),
          const SizedBox(
            width: 10,
            height: 200
          ),
          _button(title: "Resume", onPressed: () => _controller.resume()),
          const SizedBox(
            width: 10,
            height: 200
          ),
          _button(title: "Restart",onPressed: () => _controller.restart(duration: _duration)),
          const SizedBox(
            width: 10,
            height: 200
          ),
        ],
      ),
    );
  }

  Widget _button({required String title, VoidCallback? onPressed}) {
    return Expanded(
        child: ElevatedButton(
      child: Text(
        title,
        style: const TextStyle(color: Colors.white),
      ),
      style: ButtonStyle(
        backgroundColor: MaterialStateProperty.all(Color(0XFFBCD4E6)),
      ),
      onPressed: onPressed,
    ));
  }
}