import package:flutter/material.dart;
import dart:async;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
	return MaterialApp(
  	title: Timer Mundur,
  	home: CountdownTimer(),
	);
  }
}

class CountdownTimer extends StatefulWidget {
  @override
  _CountdownTimerState createState() => _CountdownTimerState();
}

class _CountdownTimerState extends State<CountdownTimer> {
  int _start = 10; // waktu dalam detik
  late Timer _timer;

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

  @override
  Widget build(BuildContext context) {
	return Scaffold(
  	appBar: AppBar(
    	title: Text(Timer Mundur),
  	),
  	body: Center(
    	child: Column(
      	mainAxisAlignment: MainAxisAlignment.center,
      	children: [
        	Text(Waktu tersisa: $_start detik),
        	ElevatedButton(
          	onPressed: startTimer,
          	child: Text(Mulai Timer),
        	),
      	],
    	),
  	),
	);
  }

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