Snake Game Complete

main.dart

import 'dart:async';
import 'dart:math';

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

void main() {
  runApp(const SnakeGame());
}

class SnakeGame extends StatelessWidget {
  const SnakeGame({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: "Snake Game",
      home: Center(
        child: Game(),
      ),
    );
  }
}

class Snake {
  List<Point<int>> snake = [const Point(0, 0)];
  Point<int> direction = Constants.right;

  Point<int> get head {
    return snake[0];
  }

  bool didBiteItself() {
    for (int i = 1; i < snake.length; i++) {
      if (snake[i] == head) {
        return true;
      }
    }
    return false;
  }

  bool pointOnSnake(Point<int> point) {
    for (Point body in snake) {
      if (body == point) {
        return true;
      }
    }
    return false;
  }

  void update() {
    // For moving in a direction, move all body parts to the location of the
    // part before them
    for (int i = snake.length - 1; i > 0; --i) {
      snake[i] = snake[i - 1];
    }
    // Then update in the direction snake is moving
    snake[0] = Point((head.x + direction.x) % 50, (head.y + direction.y) % 50);
  }

  void eatFood() {
    // Since food is added to the end and snake would ultimately
    // Update one position, save the last location and append it again.
    var foodLoc = snake.last;
    update();
    snake.add(foodLoc);
  }
}

class Constants {
  // Canvas
  static const double canvasSize = 500;
  static const double blockSize = 10;

  // Directions
  static const up = Point(0, -1);
  static const down = Point(0, 1);
  static const right = Point(1, 0);
  static const left = Point(-1, 0);
}

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

  @override
  State<Game> createState() => _GameState();
}

class _GameState extends State<Game> {
  late Snake snake;
  late Point<int> food;
  Random random = Random();

  @override
  void initState() {
    initGame();
    Timer.periodic(const Duration(milliseconds: 50), (t) {
      gameUpdate();
    });
    super.initState();
  }

  initGame() {
    snake = Snake();
    foodUpdate();
  }

  void gameUpdate() {
    // update this
    if (food == snake.head) {
      snake.eatFood();
      foodUpdate();
    } else {
      snake.update();
    }
    if (snake.didBiteItself()) {
      initGame();
    }
    setState(() {});
  }

  void foodUpdate() {
    do {
      food = Point(random.nextInt(Constants.canvasSize ~/ Constants.blockSize),
          random.nextInt(Constants.canvasSize ~/ Constants.blockSize));
    } while (snake.pointOnSnake(food));
  }

  void keyHandler(RawKeyEvent event) {
    if (event.logicalKey == LogicalKeyboardKey.arrowDown) {
      if (snake.direction != Constants.up) {
        snake.direction = Constants.down;
      }
    } else if (event.logicalKey == LogicalKeyboardKey.arrowUp) {
      if (snake.direction != Constants.down) {
        snake.direction = Constants.up;
      }
    } else if (event.logicalKey == LogicalKeyboardKey.arrowRight) {
      if (snake.direction != Constants.left) {
        snake.direction = Constants.right;
      }
    } else if (event.logicalKey == LogicalKeyboardKey.arrowLeft) {
      if (snake.direction != Constants.right) {
        snake.direction = Constants.left;
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return RawKeyboardListener(
      focusNode: FocusNode(),
      onKey: keyHandler,
      autofocus: true,
      child: Container(
        width: Constants.canvasSize,
        height: Constants.canvasSize,
        color: Colors.black,
        child: Stack(
          children: snake.snake // Update This
                  .map((e) => Positioned(
                        top: Constants.blockSize * e.y,
                        left: Constants.blockSize * e.x,
                        child: Container(
                          height: Constants.blockSize,
                          width: Constants.blockSize,
                          color: Colors.green,
                        ),
                      ))
                  .toList() +
              [
                Positioned(
                  top: Constants.blockSize * food.y,
                  left: Constants.blockSize * food.x,
                  child: Container(
                    height: Constants.blockSize,
                    width: Constants.blockSize,
                    color: Colors.red,
                  ),
                )
              ],
        ),
      ),
    );
  }
}