Timekeeper

main.dart

import 'dart:async';

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: MyApp(),
      ),
    );

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  Timer timer;
  int secondsLeft = 0;
  int teamOneScore = 0;
  int teamTwoScore = 0;

  void _restartGame() {
    setState(() {
      secondsLeft = 60;
      timer = Timer.periodic(Duration(seconds: 1), (t) {
        setState(() {
          secondsLeft--;
          if (secondsLeft == 0) {
            timer.cancel();
          }
        });
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: (secondsLeft != 0)
          ? Theme.of(context).scaffoldBackgroundColor
          : Color(0xffff8080),
      body: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          GestureDetector(
            onTap: () => _restartGame(),
            child: SizedBox(
              height: 150,
              width: 175,
              child: Center(
                child: Text(
                  '$secondsLeft',
                  style: Theme.of(context)
                      .textTheme
                      .headline1
                      .copyWith(fontWeight: FontWeight.bold),
                ),
              ),
            ),
          ),
          Column(children: [
            SizedBox(
              height: 100,
              width: 50,
              child: GestureDetector(
                onTap: () {
                  setState(() => teamOneScore++);
                },
                onLongPress: () {
                  setState(() => teamOneScore--);
                },
                child: Center(
                  child: Text(
                    '$teamOneScore',
                    style: Theme.of(context).textTheme.headline4,
                  ),
                ),
              ),
            ),
            SizedBox(
              height: 50,
              width: 50,
              child: GestureDetector(
                onTap: () {
                  setState(() => teamTwoScore++);
                },
                onLongPress: () {
                  setState(() => teamTwoScore--);
                },
                child: Center(
                  child: Text(
                    '$teamTwoScore',
                    style: Theme.of(context).textTheme.headline4,
                  ),
                ),
              ),
            ),
          ])
        ],
      ),
    );
  }
}