Snake不会出现在Java游戏框架中

Question

I am trying to make snake game in java but the snake doesn't shown up on the screen and I don't know why ... here is my code ... I've made it in three classes

 public class SnakeGame extends JFrame {

 public SnakeGame(){
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBackground(Color.green);
    setSize(WIDTH, HEIGHT);
    setTitle("Snake Game");
    setVisible(true);
    setResizable(false);
     play p = new play();
     add(p);
     pack();
}

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



public class play extends JPanel implements Runnable{

public static final int WIDTH = 700,HEIGHT = 700;
private ArrayList<SnakeDesign> snake;

public play(){
    setPreferredSize(new Dimension(WIDTH, HEIGHT));
    snake = new ArrayList<SnakeDesign>();

}

public void paint(Graphics g){
    for(int i=0;i<snake.size();i++){
        snake.get(i).paintSnake(g);
       }
     }

@Override
public void run() {
    repaint();
}

}

 public class SnakeDesign {

private int Xcoor, Ycoor, width, height;

public SnakeDesign(int Xcoor, int Ycoor,int tileSize){
    this.Xcoor = Xcoor;
    this.Ycoor = Ycoor;
    width = tileSize;
    height = tileSize;

}
public void paintSnake (Graphics g){
    g.setColor(Color.red);
    g.drawRect(Xcoor*width, Xcoor*height, width, height);
}

so please can anyone say why the snake doesn't appear ... thanks in advance

Answer 1

1. don't override the JPanel's paint(Graphics g) method but rather override its paintComponent(Graphics g) method. There are many reasons for this, and some include
   • The paint method is responsible for drawing the component and drawing its borders and children, and so if its Graphics object is changed, you may cause unwanted and hard to debug side effects on a component's borders and child components.
   • A JPanel or JComponent's paintComponent method uses double buffering by default, and so if you use this for animation (and you are) using this will give you a noticeable much smoother animation.
2. Call the super's super.paintComponent(g) method in your paintComponent(Graphics g) override.
3. You've created a Runnable, but I don't see you putting it in a Thread or starting the Thread.
4. Always call setVisible(true) last after adding all components, not before.
5. Class names should start with an upper case letter.
6. Where do you add elements into your ArrayList, ie, where do you have snake.add(...) where you pass a body element into the snake? If you give your snake no body, what will it show?
7. Use a Swing Timer to drive your animation. This will allow you to get rid of the need for a Runnable interface (which is currently only calling run() and so it is essentially doing nothing).