Pong Controls With KeyListener

问题:

I have ran into a bit of trouble getting my pong game to work, this project started simply with making a ball have physics but then i decided to do some more work

I have that ball bounce back and forth and all but the keys W and S wont control player one and the up and down arrow keys dont control player 2

public void keyPressed(KeyEvent e){  
            if(e.getKeyCode() == e.VK_UP){  
                p2Y -= 3; 
                System.out.println("UP");
            }   
            if(e.getKeyCode() == e.VK_DOWN){  
                p2Y += 3;  
                System.out.println("Down");
            }  
            if(e.getKeyCode() == e.VK_W){  
                p1Y -= 3; 
                System.out.println("Up");
            }   
            if(e.getKeyCode() == e.VK_S){  
                p1Y += 3;  
                System.out.println("down");
            }
            repaint();
        } 

It wont even show the system print messages

I dont know if its just this part of the code that is the problem or if its somewhere else

If it is somewhere else here is the link to the rest of this file http://pastebin.com/TJbLBxL7

The entire code:

import javax.swing.*;


import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;

public class Pong extends JPanel
{
    Circle circle1;
    javax.swing.Timer timer;
    ArrayList<Point> points = new ArrayList<Point>();
    int p1X=10, p1Y=320;
    int p2X=760, p2Y = 320;
    int y, y1;

    int p1Score, p2Score;

    boolean playing = true;

    public Pong(Color backcolor, int Width, int Height)
    {
        setBackground(backcolor);
        setPreferredSize(new Dimension(Width, Height));

        //first circle

        circle1 = new Circle(Width / 2, 360, 15, Color.white);
        circle1.setVelocity(4);
        circle1.setDirection(180);

        timer =  new javax.swing.Timer(5, new MoveListener());
        addKeyListener(new KeyWatcher());
        timer.start();
    }

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        //first circle
        circle1.draw(g);
        circle1.fill(g);

        // Draw Players
        g.setColor(Color.red);
        g.fillRect(p1X, p1Y, 10, 75);
        g.setColor(Color.blue);
        g.fillRect(p2X, p2Y, 10, 75);

        //Draw Scores
        g.setColor(Color.white);
        g.drawString("Player 1's Score: " + p1Score, 10, 10);
        g.drawString("Player 2's Score: " + p2Score, getWidth() - 120, 10);
        repaint();

        if(!playing)
        {
            g.setColor(Color.red);
            g.drawString("GAMEOVER!!!", (getWidth() / 2) - 15, 10);
        }
        else
        {
        }
    }

    private class MoveListener extends MouseAdapter implements ActionListener
    {
        public void actionPerformed(ActionEvent arg0)
        {

            int x1 = circle1.getX();
            int y1 = circle1.getY();
            int width = getWidth();
            int height = getHeight();
            int radius1 = circle1.getRadius();

            //first circle

            if(x1 - radius1 <= 0)
            {
                p2Score++;
                circle1.setX(getWidth()/2);
                circle1.setY(getHeight()/2);
            }
            if(x1 + radius1 >= width)
            {
                p1Score++;

                circle1.setX(getWidth()/2);
                circle1.setY(getHeight()/2);
            }
            if(y1 - radius1 <= 0 || y1 + radius1 >= height )
            {
                circle1.turnY();

            }

            if((x1 - radius1 == p1X) || (x1 + radius1 == p2X))
            {
                circle1.turnX();
            }

            circle1.move();
            repaint();
        }

        public void GameOver()
        {
            playing = false;
        }

    }
    private class KeyWatcher implements KeyListener
    {

        @Override
        public void keyPressed(KeyEvent e){  
            if(e.getKeyCode() == e.VK_UP){  
                p2Y -= 3; 
                System.out.println("UP");
            }   
            if(e.getKeyCode() == e.VK_DOWN){  
                p2Y += 3;  
                System.out.println("Down");
            }  
            if(e.getKeyCode() == e.VK_W){  
                p1Y -= 3; 
                System.out.println("Up");
            }   
            if(e.getKeyCode() == e.VK_S){  
                p1Y += 3;  
                System.out.println("down");
            }
            repaint();
        }  

        @Override
        public void keyReleased(KeyEvent e){  
             //if(e.getKeyCode() == e.VK_UP){  
            //        y1 = p2Y;  
             //       repaint();
             //   }   
             //   if(e.getKeyCode() == e.VK_DOWN){  
             //       y1 = p2Y;  
            //        repaint();
            //    } 
             //if(e.getKeyCode() == e.VK_W){  
             //       y = p1Y;  
            //        repaint();
            //    }   
            //    if(e.getKeyCode() == e.VK_S){  
            //        y = p1Y;  
            //        repaint();
             //   } 
        }  

        @Override
        public void keyTyped(KeyEvent arg0) {
            // TODO Auto-generated method stub

        }


    }
}

My New Code The problem with this one is that only one player can be controlled at a time

It also has my foolish attempt to fix it by making 2 MyKeyAction but it didnt change it at all

package Bouncy;

import javax.swing.*;


import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;

public class Pong extends JPanel
{
    Circle circle1;
    javax.swing.Timer timer;
    ArrayList<Point> points = new ArrayList<Point>();
    int p1X=10, p1Y=320;
    int p2X=760, p2Y = 320;
    int y, y1;

    int p1Score, p2Score;

    boolean playing = true;

    public Pong(Color backcolor, int Width, int Height)
    {
        setBackground(backcolor);
        setPreferredSize(new Dimension(Width, Height));

        //first circle

        circle1 = new Circle(Width / 2, 360, 15, Color.white);
        circle1.setVelocity(4);
        circle1.setDirection(180);

        timer =  new javax.swing.Timer(5, new MoveListener());
        setupKeyBinding();
        setupKeyBinding2();
        timer.start();
    }
    private void setupKeyBinding() {
          int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
          InputMap inMap = getInputMap(condition);
          ActionMap actMap = getActionMap();

          // this uses an enum of Direction that holds ints for the arrow keys
          for (DirectionP1 direction : DirectionP1.values()) {
             int key = direction.getKey();
             String name = direction.name();

             // add the key bindings for arrow key and shift-arrow key
             inMap.put(KeyStroke.getKeyStroke(key, 0), name);
             inMap.put(KeyStroke.getKeyStroke(key, InputEvent.SHIFT_DOWN_MASK), name);
             actMap.put(name, new MyKeyAction(direction));
          }
       }
    private void setupKeyBinding2() {
          int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
          InputMap inMap = getInputMap(condition);
          ActionMap actMap = getActionMap();

          // this uses an enum of Direction that holds ints for the arrow keys
          for (DirectionP2 direction : DirectionP2.values()) {
             int key = direction.getKey();
             String name = direction.name();

             // add the key bindings for arrow key and shift-arrow key
             inMap.put(KeyStroke.getKeyStroke(key, 0), name);
             inMap.put(KeyStroke.getKeyStroke(key, InputEvent.SHIFT_DOWN_MASK), name);
             actMap.put(name, new MyKeyAction2(direction));
          }
       }
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        //first circle
        circle1.draw(g);
        circle1.fill(g);

        // Draw Players
        g.setColor(Color.red);
        g.fillRect(p1X, p1Y, 10, 75);
        g.setColor(Color.blue);
        g.fillRect(p2X, p2Y, 10, 75);

        //Draw Scores
        g.setColor(Color.white);
        g.drawString("Player 1's Score: " + p1Score, 10, 10);
        g.drawString("Player 2's Score: " + p2Score, getWidth() - 120, 10);
        repaint();

        if(!playing)
        {
            g.setColor(Color.red);
            g.drawString("GAMEOVER!!!", (getWidth() / 2) - 15, 10);
        }
        else
        {
        }
    }

    private class MoveListener extends MouseAdapter implements ActionListener
    {
        public void actionPerformed(ActionEvent arg0)
        {

            int x1 = circle1.getX();
            int y1 = circle1.getY();
            int width = getWidth();
            int height = getHeight();
            int radius1 = circle1.getRadius();

            //first circle

            if(x1 - radius1 <= 0)
            {
                p2Score++;
                circle1.setX(getWidth()/2);
                circle1.setY(getHeight()/2);
            }
            if(x1 + radius1 >= width)
            {
                p1Score++;

                circle1.setX(getWidth()/2);
                circle1.setY(getHeight()/2);
            }
            if(y1 - radius1 <= 0 || y1 + radius1 >= height )
            {
                circle1.turnY();

            }

            if((x1 - radius1 <= p1X) || (x1 + radius1 >= p2X))
            {
                circle1.turnX();
            }

            circle1.move();
            repaint();
        }

        public void GameOver()
        {
            playing = false;
        }



    }

    enum DirectionP1 {
           W(KeyEvent.VK_W), S(KeyEvent.VK_S);

           private int key;

           private DirectionP1(int key) {
              this.key = key;
           }

           public int getKey() {
              return key;
           }
        }
    enum DirectionP2 {
           UP(KeyEvent.VK_UP), DOWN(KeyEvent.VK_DOWN);

           private int key;

           private DirectionP2(int key) {
              this.key = key;
           }

           public int getKey() {
              return key;
           }
        }

    class MyKeyAction extends AbstractAction {
           private DirectionP1 direction;

           public MyKeyAction(DirectionP1 direction) {

              this.direction = direction;
           }

           @Override
           public void actionPerformed(ActionEvent e) {
               switch (direction) {
                  case W:
                        p1Y -= 6; 
                     break;
                  case S:
                        p1Y += 6; 
                     break;

                  default:
                     break;
                  }
           }
        }
    class MyKeyAction2 extends AbstractAction {
           private DirectionP2 direction2;

           public MyKeyAction2(DirectionP2 direction2) {

              this.direction2 = direction2;
           }

           @Override
           public void actionPerformed(ActionEvent e) {

               switch (direction2) {
                  case UP:
                        p2Y -= 6; 
                     break;
                  case DOWN:
                        p2Y += 6; 
                     break;

                  default:
                     break;
                  }
           }
        }
}

回答1:

You have a focus issue. You're adding a KeyListener to a JPanel: but the JPanel never has focus and so the KeyListener won't work:

public class Pong extends JPanel
{
    //...


    public Pong(Color backcolor, int Width, int Height)
    {
        // ...

        timer =  new javax.swing.Timer(5, new MoveListener());
        addKeyListener(new KeyWatcher());

But the JPanel never gets the focus, and KeyListeners only work if the component being listened to has the focus.

A a better solution is not to relay on KeyListeners but instead to use a Swing Timer and Key Bindings. Please see this link for an example of this.

Edit: Or an even better link -- Java KeyListener Not Registering Arrow Keys.

Edit 2
Perhaps a better solution is to use Key Bindings but use them to set fields of the class on key press or key release, and then use a Swing Timer as the game loop to poll those fields.

For example, this doesn't show the animation (that's up to you) but shows that this technique will allow response to simultaneous key presses:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.EnumMap;

import javax.swing.*;

public class NewArrowTest extends JPanel {
   private static final String PRESSED = "pressed";
   private static final String RELEASED = "released";
   private static final int TIMER_DELAY = 20;
   private EnumMap<Key, Boolean> keyMap = new EnumMap<NewArrowTest.Key, Boolean>(Key.class);

   public NewArrowTest() {
      keyMap.put(Key.W, false);
      keyMap.put(Key.S, false);
      keyMap.put(Key.UP, false);
      keyMap.put(Key.DOWN, false);

      // set up key binding
      ActionMap actionMap = getActionMap();
      int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
      InputMap inputMap = getInputMap(condition);

      for (Key key : Key.values()) {
         KeyStroke pressedKeyStroke = KeyStroke.getKeyStroke(key.getKeyCode(), 0, false);
         KeyStroke releasedKeyStroke = KeyStroke.getKeyStroke(key.getKeyCode(), 0, true);

         inputMap.put(pressedKeyStroke, key.getText() + PRESSED);
         inputMap.put(releasedKeyStroke, key.getText() + RELEASED);
         actionMap.put(key.getText() + PRESSED, new MyArrowBinding(key, false));
         actionMap.put(key.getText() + RELEASED, new MyArrowBinding(key, true));
      }

      // start polling timer or game loop
      new Timer(TIMER_DELAY, new TimerListener()).start();
   }

   private static void createAndShowGui() {
      NewArrowTest mainPanel = new NewArrowTest();

      JFrame frame = new JFrame("NewArrowTest");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }

   private class TimerListener implements ActionListener {
      public void actionPerformed(java.awt.event.ActionEvent e) {
         for (Key key : keyMap.keySet()) {
            System.out.printf("%6s %b%n", key, keyMap.get(key));
            // here we'd move things based on which key is true
         }
         System.out.println();

      };
   }

   private class MyArrowBinding extends AbstractAction {
      private Key key;
      private boolean released;

      public MyArrowBinding(Key key, boolean released) {
         this.key = key;
         this.released = released;
      }

      @Override
      public void actionPerformed(ActionEvent aEvt) {
         keyMap.put(key, !released);
      }
   }

   enum Direction {
      UP("Up"), DOWN("Down"), NEUTRAL("Neutral");
      private String text;

      private Direction(String text) {
         this.text = text;
      }
      public String getText() {
         return text;
      }
   }

   enum Key {
      W("W", Direction.UP, KeyEvent.VK_W), S("S", Direction.DOWN, KeyEvent.VK_S), 
      UP("Up", Direction.UP, KeyEvent.VK_UP), DOWN("Down", Direction.DOWN, KeyEvent.VK_DOWN);

      private String text;
      private Direction direction;
      private int keyCode;

      private Key(String text, Direction direction, int keyCode) {
         this.text = text;
         this.direction = direction;
         this.keyCode = keyCode;
      }

      public String getText() {
         return text;
      }

      public Direction getDirection() {
         return direction;
      }

      public int getKeyCode() {
         return keyCode;
      }

   }
}