Question

我设计了一款在Windows上完美运行的基本乒乓球游戏，但它可以在Mac OS X上编译和运行，但它不会绘制任何东西。

JFrame的代码：

import javax.swing.JFrame;
public class Interface extends JFrame {

/**
 * Creates a reference to a new Interface object. Sets all the parameters of the window
 */
public Interface() {
    setTitle("Pong");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(600, 250, 506, 500); //setBounds(x, y, width, height)
    setResizable(false);
    setVisible(true);
}

/**
 * The main method that the program is run from.
 * @param args Command line arguments that are ignored by this method
 */
public static void main(String[] args) {
    Interface window = new Interface();
    Display d = new Display();

    window.getContentPane().add(d);
    window.addKeyListener(d); //allows the user to do a certain function from the object "d", if a specified key is pressed
    d.run(); 
}

JPanel的基本代码：

public void paint(Graphics g) {
    //set the background
    g.setColor(Color.BLACK);
    g.fillRect(0, 0, 500, 500);

    //draws the net
    g.setColor(Color.WHITE);
    int yCoord = 0;
    for (int i = 0; i < 16; i ++) {
        g.fillRect(248, yCoord, 4, 15);
        yCoord += 30;
    }

    //draws the players paddles
    player1.draw(g);        
    player2.draw(g);

    //draws the ball
    ball.draw(g);

    //draws the player scores
    g.setColor(Color.WHITE);
    g.drawString(player1.getScore()+"            "+player2.getScore(), 224, 10);
}

//Constructor
public Display() {
    player1 = new Player(10, 10, 1);
    player2 = new Player(480, 10, 2);
    ball = new Ball();
}

@Override
public void run() {
    boolean running = true;
    long startloop;
    long wait;
    long elapsed = 0;

    System.out.println("Game is running");

    while (running) {
        startloop = System.nanoTime(); //starts the timer

        //if (elapsed >= 1) {

            //checks to see if there is a winner and updates the location and drawing of the ball
            int win = ball.update();

            //checks to see if the ball has collided with anyone
            if (ball.checkPlayerCollision(player1)) {
                ball.collideWithPlayer(player1);
            } else if (ball.checkPlayerCollision(player2)) {
                ball.collideWithPlayer(player2);
            }

            if (win == 1) {
                player1.scored();
                ball.reset();
            } else if (win == 2) {
                player2.scored();
                ball.reset();
            }

            repaint(); //redraws the entire panel
            elapsed = 0;
        //}

        elapsed += (System.nanoTime() - startloop);

        wait = targetTime - elapsed / 1000000;

        if(wait < 0) {
            wait = 5;
        }

        //makes the while loop pause 
        try {
            Thread.sleep(wait);
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

我尝试将print语句放在任何地方，一切正常，它只是不会访问paint方法。我该如何解决这个问题？

Answer 1

您的代码：

public static void main(String[] args) {
    Interface window = new Interface();
    Display d = new Display();

    window.getContentPane().add(d);
    window.addKeyListener(d); 
    d.run();  // ***************** here ***************
}

您似乎正在调用Thread的run()方法或runnable（您不会显示类标题，因此无法知道），这可以保证不会有后台线程制作。而是调用包含Runnable的Thread的start()方法。

所以也许你会想要改变

d.run();

为：

new Thread(d).start();

但是，在将来，当问及为什么我的代码无法正常运行＆＃34;时，请考虑创建并发布minimal example program，一个小程序，尽可能小的，为我们编译和运行，无需图像，这向我们展示了您的问题。

暂且不说：

一般情况下，请勿覆盖JPanel的paint(...)方法，而应覆盖其paintComponent(...)方法。
并在你的覆盖中调用超级方法。
通常情况下，使用Key Bindings更好，而不是使用Swing程序的KeyListeners。

Java：绘制到Windows而不是mac

1 个答案: