java - AWT fillOval 不绘制新对象

Question

我正在尝试通过向面板添加第二个球作为练习来修改网站上旧 ping-pong game 的示例代码。到目前为止，我正在重复生成第一个球的步骤。然而，不知何故我失败了。虽然程序是可执行的，但我添加的第二个球没有出现。我不知道问题出在哪里。 ball 方法位于PanelPelota 类下。到目前为止，我只是复制了变量和一些函数。这是代码:

主类

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Main extends JFrame {

private static final long serialVersionUID = 1L; // Eclipse added this automatically

private JPanel jContentPane = null;

private PanelPelota panel = null; // This is the panel of the game class

private PanelPelota getPanel() {
    if (panel == null) {
        panel = new PanelPelota(); // The panel is created
    }
    return panel;
}

/**
 * This is the default constructor
 */
public Main() {
    super();
    initialize();
    // Listeners for the keyboard
    this.addKeyListener(new KeyAdapter() {
        // Method for the key pressed
        public void keyPressed(KeyEvent evt) {
            formKeyPressed(evt);
        }

        // Method for the key released
        public void keyReleased(KeyEvent evt) {
            formKeyReleased(evt);
        }
    });

}

// Here i'm stating the method that will send the key pressed to the game class
private void formKeyPressed(KeyEvent evt) {
    panel.keyPressed(evt);
}

// Here i'm stating the method that will send the key released to the game class
private void formKeyReleased(KeyEvent evt) {
    panel.keyReleased(evt);
}

/**
 * This method initializes this
 *
 * @return void
 */
private void initialize() {
    this.setResizable(false);
    this.setBounds(new Rectangle(312, 184, 250, 250)); // Position on the desktop
    this.setMinimumSize(new Dimension(250, 250));
    this.setMaximumSize(new Dimension(250, 250));
    this.setContentPane(getJContentPane());
    this.setTitle("Pong");
}

/**
 * This method initializes jContentPane
 *
 * @return javax.swing.JPanel
 */
private JPanel getJContentPane() {
    if (jContentPane == null) {
        jContentPane = new JPanel();
        jContentPane.setLayout(new BorderLayout());
        jContentPane.add(getPanel(), BorderLayout.CENTER);
    }
    return jContentPane;
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            Main thisClass = new Main();
            thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            thisClass.setVisible(true);
        }
    });
}
}

PanelPelota 类

import java.awt.*;
import java.awt.event.KeyEvent;
import javax.swing.*;

public class PanelPelota extends JPanel implements Runnable {

private static final long serialVersionUID = 1L;
// Positions on X and Y for the ball, player 1 and player 2
private int pelotaX = 10, pelotaY = 100, pelota2X = 230, pelota2Y = 100, jug1X = 10, jug1Y = 100, jug2X = 230, jug2Y = 100;
Thread hilo;
int derecha = 5;// to the right
int izquierda = -5; // to the left
int arriba = 5; // upward
int abajo = -5; // down
int ancho, alto; // Width and height of the ball
int ancho2, alto2;
// Scores
int contPlay1 = 0, contPlay2 = 0;
boolean player1FlagArr, player1FlagAba, player2FlagArr, player2FlagAba;
boolean juego, gameOver;

public PanelPelota() {
    juego = true;
    hilo = new Thread(this);
    hilo.start();
}

// Draw ball and ships
public void paintComponent(Graphics gc) {
    setOpaque(false);
    super.paintComponent(gc);

    // Draw ball
    gc.setColor(Color.black);
    gc.fillOval(pelotaX, pelotaY, 8, 8);
    gc.fillOval(pelota2X, pelota2Y, 8, 8);

    // Draw ships
    gc.fillRect(jug1X, jug1Y, 10, 25);
    gc.fillRect(jug2X, jug2Y, 10, 25);

    // Draw scores
    gc.drawString("Jugador1: " + contPlay1, 25, 10);
    gc.drawString("Jugador2: " + contPlay2, 150, 10);

    if (gameOver) {
        //gc.drawString("Game Over", 100, 125);
        Restart replay = new Restart();
        JPanel midPanel = new JPanel();
        replay.setVisible(true);
        if(contPlay1 == 6)
            midPanel.add(new JLabel("Player1 wins!"));
        if(contPlay2 == 6)
            midPanel.add(new JLabel("Player2 wins!"));
        replay.setTitle("Game Over!");
        replay.setSize(300, 100);
        replay.setLocationRelativeTo(null);

        midPanel.add(new JLabel(""));
        replay.add(midPanel, BorderLayout.CENTER);
        replay.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

// Positions on X and Y for the ball
public void dibujarPelota(int nx, int ny) {
    pelotaX = nx;
    pelotaY = ny;
    this.ancho = this.getWidth();
    this.alto = this.getHeight();
    repaint();
}

public void dibujarPelota2(int nx, int ny) {
    pelotaX = nx;
    pelotaY = ny;
    this.ancho2 = this.getWidth();
    this.alto2 = this.getHeight();
    repaint();
}

// Here we receive from the game container class the key pressed
public void keyPressed(KeyEvent evt) {
    switch (evt.getKeyCode()) {
    // Move ship 1
    case KeyEvent.VK_W:
        player1FlagArr = true;
        break;
    case KeyEvent.VK_S:
        player1FlagAba = true;
        break;

    // Move ship 2
    case KeyEvent.VK_UP:
        player2FlagArr = true;
        break;
    case KeyEvent.VK_DOWN:
        player2FlagAba = true;
        break;
    }
}

// Here we receive from the game container class the key released
public void keyReleased(KeyEvent evt) {
    switch (evt.getKeyCode()) {
    // Mover Nave1
    case KeyEvent.VK_W:
        player1FlagArr = false;
        break;
    case KeyEvent.VK_S:
        player1FlagAba = false;
        break;

    // Mover nave 2
    case KeyEvent.VK_UP:
        player2FlagArr = false;
        break;
    case KeyEvent.VK_DOWN:
        player2FlagAba = false;
        break;
    }
}

// Move player 1
public void moverPlayer1() {
    if (player1FlagArr == true && jug1Y >= 0)
        jug1Y += abajo;
    if (player1FlagAba == true && jug1Y <= (this.getHeight() - 25))
        jug1Y += arriba;
    dibujarPlayer1(jug1X, jug1Y);
}

// Move player 2
public void moverPlayer2() {
    if (player2FlagArr == true && jug2Y >= 0)
        jug2Y += abajo;
    if (player2FlagAba == true && jug2Y <= (this.getHeight() - 25))
        jug2Y += arriba;
    dibujarPlayer2(jug2X, jug2Y);
}

// Position on Y for the player 1
public void dibujarPlayer1(int x, int y) {
    this.jug1X = x;
    this.jug1Y = y;
    repaint();
}

// Position on Y for the player 2
public void dibujarPlayer2(int x, int y) {
    this.jug2X = x;
    this.jug2Y = y;
    repaint();
}

public void run() {
    // TODO Auto-generated method stub
    boolean izqDer = false;
    boolean arrAba = false;
    boolean izqDer2 = false;
    boolean arrAba2 = false;

    while (true) {

        if (juego) {

            // The ball move from left to right
            if (izqDer) {
                // a la derecha
                pelotaX += derecha;
                if (pelotaX >= (ancho - 8))
                    izqDer = false;
            } else {
                // a la izquierda
                pelotaX += izquierda;
                if (pelotaX <= 0)
                    izqDer = true;
            }

            // The ball moves from up to down
            if (arrAba) {
                // hacia arriba
                pelotaY += arriba;
                if (pelotaY >= (alto - 8))
                    arrAba = false;

            } else {
                // hacia abajo
                pelotaY += abajo;
                if (pelotaY <= 0)
                    arrAba = true;
            }
            dibujarPelota(pelotaX, pelotaY);

            // The second ball move from left to right
            if (izqDer2) {
                // a la derecha
                pelota2X += derecha;
                if (pelota2X >= (ancho - 8))
                    izqDer2 = false;
            } else {
                // a la izquierda
                pelota2X += izquierda;
                if (pelota2X <= 0)
                    izqDer2 = true;
            }

            // The ball moves from up to down
            if (arrAba2) {
                // hacia arriba
                pelota2Y += arriba;
                if (pelota2Y >= (alto - 8))
                    arrAba2 = false;

            } else {
                // hacia abajo
                pelota2Y += abajo;
                if (pelota2Y <= 0)
                    arrAba2 = true;
            }
            dibujarPelota2(pelota2X, pelota2Y);

            // Delay
            try {
                Thread.sleep(50);
            } catch (InterruptedException ex) {

            }

            // Move player 1
            moverPlayer1();

            // Move player 2
            moverPlayer2();

            // The score of the player 1 increase
            if (pelotaX >= (ancho - 8))
                contPlay1++;

            // The score of the player 2 increase
            if (pelotaX == 0)
                contPlay2++;

            // Game over. Here you can change 6 to any value
            // When the score reach to the value, the game will end
            if (contPlay1 == 6 || contPlay2 == 6) {
                juego = false;
                gameOver = true;
            }

            // The ball stroke with the player 1
            if (pelotaX == jug1X + 10 && pelotaY >= jug1Y && pelotaY <= (jug1Y + 25))
                izqDer = true;

            // The ball stroke with the player 2
            if (pelotaX == (jug2X - 5) && pelotaY >= jug2Y && pelotaY <= (jug2Y + 25))
                izqDer = false;

            // The ball2 stroke with the player 1
            if (pelota2X == jug1X + 10 && pelota2Y >= jug1Y && pelota2Y <= (jug1Y + 25))
                izqDer2 = true;

            // The ball2 stroke with the player 2
            if (pelota2X == (jug2X - 5) && pelota2Y >= jug2Y && pelota2Y <= (jug2Y + 25))
                izqDer2 = false;
        }
    }
}
}

重新启动类(class)(由我创建)

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Restart extends JFrame{
private static final long serialVersionUID = 1L;

public JButton restart = new JButton("Restart");

public Restart() {
    Container cp = getContentPane(); 
    cp.setLayout(new BorderLayout());

    JPanel bottomPanel = new JPanel();
    bottomPanel.add(restart);
    cp.add(bottomPanel, BorderLayout.SOUTH);

    restart.addActionListener(new ActionListener() {

          public void actionPerformed(ActionEvent e) {
            //Creating the window with all its awesome snaky features
            Main thisClass= new Main();
            thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            thisClass.setVisible(true);

            //Close Menu once select
            String cmd = e.getActionCommand();
            if(cmd.equals("Restart"))
            {
                dispose();
            }
          };
      });
}
}

如果重要的话，我正在使用 eclipse IDE。

提前谢谢您。

Answer 1

dibujarPelota 和 dibujarPelota2 正在将值分配给相同的实例字段，从而有效地覆盖它们。

public void dibujarPelota(int nx, int ny) {
    pelotaX = nx;
    pelotaY = ny;
    this.ancho = this.getWidth();
    this.alto = this.getHeight();
    repaint();
}

public void dibujarPelota2(int nx, int ny) {
    pelotaX = nx;
    pelotaY = ny;
    this.ancho2 = this.getWidth();
    this.alto2 = this.getHeight();
    repaint();
}

所以，是的，你的第二个球已更新并绘制，但位置与第一个球相同。

更改 dibujarPelota2，将 nx 分配给 pelota2X，将 ny 分配给 pelota2Y

public void dibujarPelota2(int nx, int ny) {
    pelota2X = nx;
    pelota2Y = ny;
    this.ancho2 = this.getWidth();
    this.alto2 = this.getHeight();
    repaint();
}

此外，请注意，您使用的示例不是最好的示例，因为它正在更新 UI 依赖于 EDT 上下文之外的状态信息，虽然这可能只是一个小问题，但它可以迅速升级