貪吃蛇

貪吃蛇這一款小游戲，在以前的諾基亞手機中基本都會帶有這款，曾經風靡一時，
那么我們如何將這一款小游戲實作出來呢？
在這里，我們會使用到javaFX圖形化編程，將圖形化界面列印出來，通過用戶的實際操作，來控制游戲，如下圖：

這就是，游戲最終實作的情況，
我們可以通過蛇的速度來控制游戲難度，通過控制方向左右移動，實作游戲的邏輯，最后完成，
首先我們會匯入很多的包，大多數都是javafx的，因為需要圖形化界面，我們需要匯入它，javafx是jdk自帶的，

import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.stage.Stage;
import java.util.Arrays;
import java.util.Random;

我們定義貪吃蛇的身體初始為3，食物隨機生成，每次吃完食物速度會增加，同時獲得一分，當頭部撞墻，或者頭部撞到身體后，游戲結束，當游戲結束，按R從新開始游戲，
具體看原始碼，參照注釋閱讀：

原始碼：

public class Point {
    public int x;
    public int y;

    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }
}

package snake;

import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.stage.Stage;
import java.util.Arrays;
import java.util.Random;

public class SnakeAPP extends Application {
    //定義變數
    //游戲區域大小，格子的的寬和高
    private static final int WIDTH = 20;
    private static final int HEIGHT = 20;
    //繪制圖形的時候，格子所占的大小
    private static final int GRID_SIZE = 40;
    private static final int CANVAS_WIDTH = WIDTH * GRID_SIZE;
    private static final int CANVAS_HEIGHT = HEIGHT * GRID_SIZE;
    //定義游戲本身
    //移動速度
    //speed,每秒的幀數
    private static int speed;
    //食物
    private static Point food = new Point(-1, -1);
    //蛇,最多長1000節
    private static Point[] snake = new Point[1000];
    //現在多少節
    private static int snakeLength = 0;

    //朝向
    enum Direction {
        UP, LEFT, DOWN, RIGHT
    }

    private static Direction direction;
    //隨機生成器
    private static Random random = new Random();
    //游戲結束標志
    private static boolean gameOver;

    //初始化游戲資料
    private static void newGame() {
        speed = 3;
        //蛇的初始有3節
        Arrays.fill(snake, null);
        snakeLength = 0;
        snake[snakeLength++] = new Point(WIDTH / 2, HEIGHT / 2);
        snake[snakeLength++] = new Point(WIDTH / 2, HEIGHT / 2);
        snake[snakeLength++] = new Point(WIDTH / 2, HEIGHT / 2);
        //生成食物
        newFood();
        direction = Direction.LEFT;
        //游戲未結束
        gameOver = false;
    }

    //在地圖上隨機生成食物
    private static void newFood() {
        //1，不能生成在外面
        //2.不能和蛇的身體碰撞
        int x, y;
        do {
            x = random.nextInt(WIDTH);
            y = random.nextInt(HEIGHT);
        } while (isCollision(x, y));

        food.x = x;
        food.y = y;
    }

    private static boolean isCollision(int x, int y) {
        //遍歷蛇
        //不要用foreach
        for (int i = 0; i < snakeLength; i++) {
            Point point = snake[i];
            if (point.x == x && point.y == y) {
                return true;
            }
        }
        return false;
    }

    //每一幀做的動作
    private static void frame() {
        //移動身體
        for (int i = snakeLength - 1; i >= 1; i--) {
            //變成前一個坐標
            snake[i].x = snake[i - 1].x;
            snake[i].y = snake[i - 1].y;
        }
        //移動頭
        Point head = snake[0];
        switch (direction) {
            case UP:
                head.y--;
                break;
            case DOWN:
                head.y++;
                break;
            case LEFT:
                head.x--;
                break;
            case RIGHT:
                head.x++;
                break;
        }
        //判斷頭是否出邊界
        if (head.x < 0 || head.x >= WIDTH || head.y < 0 || head.y >= HEIGHT) {
            gameOver = true;
            return;
        }
        //判斷是否碰到身體
        for (int i = 1; i < snakeLength; i++) {
            Point point = snake[i];
            if (head.x == point.x && head.y == point.y) {
                gameOver = true;
                return;
            }
        }
        //判斷是否吃到食物
        // 如果吃到食物
        // 1.身體增加1節    2.重新生成食物    3. 速度增加
        if (head.x == food.x && head.y == food.y) {
            snake[snakeLength++] = new Point(-1, -1);
            newFood();
            speed++;
        }
    }

    //每一幀繪制作業，渲染
    private static void render(GraphicsContext gc) {
        //1.從新繪制背景
        gc.setFill(Color.BLACK);
        gc.fillRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);
        //2.蛇的繪制
        for (int i = 0; i < snakeLength; i++) {
            Point point = snake[i];
            gc.setFill(Color.GREEN);
            gc.fillRect(point.x * GRID_SIZE + 1, point.y * GRID_SIZE + 1, GRID_SIZE - 2, GRID_SIZE - 2);
        }
        //3.食物的繪制
        gc.setFill(Color.YELLOW);
        gc.fillOval(food.x * GRID_SIZE + 1, food.y * GRID_SIZE + 1, GRID_SIZE, GRID_SIZE);
        //3.進行游戲結束繪制
        if (gameOver) {
            gc.setFill(Color.RED);
            gc.setFont(new Font(40));
            gc.fillText("游戲結束,按R繼續", 200, 200);
        }

        //得分
        gc.setFill(Color.AQUAMARINE);
        gc.setFont(new Font(20));
        gc.fillText("當前得分"+ (speed-3)+"分", 40, 40);
        //作者
        gc.setFill(Color.AQUA);
        gc.setFont(new Font(15));
        gc.fillText("版本：v1.0    作者：H485301267 ", 20, 740);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        //游戲的初始化
        newGame();
        Pane pane = new Pane();
        Canvas canvas = new Canvas(CANVAS_WIDTH, CANVAS_HEIGHT);
        pane.getChildren().add(canvas);

        Scene scene = new Scene(pane);

        final GraphicsContext gc = canvas.getGraphicsContext2D();
        AnimationTimer timer = new AnimationTimer() {
            long lastTiick;

            @Override
            public void handle(long now) {
                if (gameOver) {
                    return;
                }
                if (lastTiick == 0 || now - lastTiick > 1e9 / speed) {
                    lastTiick = now;
                    frame();
                    render(gc);
                }
            }
        };
        timer.start();
        scene.setOnKeyPressed(new EventHandler<KeyEvent>() {
            @Override
            public void handle(KeyEvent event) {
                switch (event.getCode()) {
                    case W:
                    case UP:
                        if (direction != Direction.DOWN) {
                            direction = Direction.UP;
                        }
                        break;
                    case A:
                    case LEFT:
                        if (direction != Direction.RIGHT) {
                            direction = Direction.LEFT;
                        }
                        break;
                    case S:
                    case DOWN:
                        if (direction != Direction.UP) {
                            direction = Direction.DOWN;
                        }
                        break;
                    case D:
                    case RIGHT:
                        if (direction != Direction.LEFT) {
                            direction = Direction.RIGHT;
                        }
                        break;
                    case R:
                        if (gameOver) {
                            newGame();
                        }
                        break;
                }
            }
        });
        primaryStage.setScene(scene);
        primaryStage.setTitle("貪吃蛇");
        primaryStage.setResizable(false);
        primaryStage.sizeToScene();
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}