java - Snake Game -- Can't steer snake

问题描述

Actual question on the bottom of the post!
At first, I want to explain my problem.

I'm writing a basic Snake game and I got the snake to move automatically. It moves automatically to the right of the window when you execute the code, just like intended. However, I can't steer my snake the way I want, it doesn't change its direction at all.

To avoid confusion, player is an instance of the class Snake.

To explain the movement of the snake:

The Snake object has a coordinates property which is an ArrayList holding SnakePart objects. Each SnakePart object has the property x and y. Using this ArrayList, the snake is moving by drawing little rectangles on a canvas by using the x and y properties on the y- and x-axis of the canvas.

The Snake object also has a dx and a dy property that gets added (or subtracted -- depending on the direction of the snake) to the x and y property of the SnakePart object to move the snake in a direction.

To update the ArrayList in Snake.java:

public void move() {
  SnakePart head = new SnakePart(this.coordinates.get(0).x + this.dx, this.coordinates.get(0).y + this.dy);

  this.coordinates.add(0, head);
  this.coordinates.remove(this.coordinates.size() - 1);
}

To draw the snake on the canvas in Board.java (partly, rest of the method is not necessary for now):

@Override
public void paintComponent(Graphics g) {
  this.player.coordinates.forEach(snakePart -> {
    g.setColor(Color.BLUE);
    g.fillRect(snakePart.x, snakePart.y, 10, 10);
  });
}

To steer the snake, I want to use the arrow keys. Depending on which arrow key is pressed, the snake's x and y coordinates/properties get modified (Board.java):

@Override
public void keyPressed(KeyEvent event) {
  int keyCode = event.getKeyCode();

  if (keyCode == 37) {
    this.player.dx = -10;
    this.player.dy = 0;
  } else if (keyCode == 38) {
    this.player.dx = 0;
    this.player.dy = -10;
  } else if (keyCode == 39) {
    this.player.dx = 10;
    this.player.dy = 0;
  } else if (keyCode == 40) {
    this.player.dx = 0;
    this.player.dy = 10;
  }
}

Whole code:

Snake.java:

package com.codef0x.snake;
import java.util.ArrayList;

public class Snake {
  ArrayList < SnakePart > coordinates;
  int dx = 10;
  int dy = 0;

  public Snake(ArrayList < SnakePart > coords) {
    this.coordinates = coords;
  }

  public void move() {
    SnakePart head = new SnakePart(this.coordinates.get(0).x + this.dx, this.coordinates.get(0).y + this.dy);

    this.coordinates.add(0, head);
    this.coordinates.remove(this.coordinates.size() - 1);
  }

  public void grow() {
    SnakePart newPart = new SnakePart(0, 0);
    newPart.x = this.coordinates.get(this.coordinates.size() - 1).x - 10;
    newPart.y = this.coordinates.get(this.coordinates.size() - 1).y;

    this.coordinates.add(this.coordinates.size() - 1, newPart);
  }
}

Board.java (showing only relevant parts, otherwise it would be too much code)

package com.codef0x.snake;

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.Timer;
import java.util.TimerTask;


public class Board extends JPanel implements KeyListener {
  Snake player;
  ArrayList<SnakePart> snakeCoordinates;

  public Board() {

    this.snakeCoordinates = new ArrayList<>();

    snakeCoordinates.add(new SnakePart(150, 150));
    snakeCoordinates.add(new SnakePart(140, 150));
    snakeCoordinates.add(new SnakePart(130, 150));
    snakeCoordinates.add(new SnakePart(120, 150));

    this.player = new Snake(snakeCoordinates);

    this.food = new Food();
  }

  @Override
  public void paintComponent(Graphics g) {
    clear(g);

    this.player.coordinates.forEach(snakePart - > {
      g.setColor(Color.BLUE);
      g.fillRect(snakePart.x, snakePart.y, 10, 10);
    });
  }

  public void clear(Graphics g) {
    g.clearRect(0, 0, getHeight(), getWidth());
  }

  @Override
  public void update(Graphics g) {
    paintComponent(g);
  }

  @Override
  public void keyPressed(KeyEvent event) {
    int keyCode = event.getKeyCode();

    if (keyCode == 37) {
      this.player.dx = -10;
      this.player.dy = 0;
    } else if (keyCode == 38) {
      this.player.dx = 0;
      this.player.dy = -10;
    } else if (keyCode == 39) {
      this.player.dx = 10;
      this.player.dy = 0;
    } else if (keyCode == 40) {
      this.player.dx = 0;
      this.player.dy = 10;
    }
  }

  @Override
  public void keyTyped(KeyEvent event) {
    return;
  }

  @Override
  public void keyReleased(KeyEvent event) {
    return;
  }

  public void run(Board board) {
    Timer game = new Timer();
    game.schedule(new TimerTask() {
      boolean initiallySpawned = false;
      @Override
      public void run() {
        Graphics g = board.getGraphics();

        if (hitSomething()) { // removed method hitSomething, not relevant
          game.cancel();
          return;
        }

        player.move();
        update(g);
      }
    }, 0, 500);
  }
}

SnakePart.java:

package com.codef0x.snake;

public class SnakePart {
  int x;
  int y;

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

What am I doing wrong and what do I need to change to steer the snake properly?

In case you still want / need to see all files as a whole, you can have a look at them here:

Snake.java
Board.java
SnakePart.java
Food.java <- Not related, but may prevent confusion about the Food object

标签： javaswingawt

java - Snake Game -- Can't steer snake

问题描述

What am I doing wrong and what do I need to change to steer the snake properly?

解决方案

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