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Thread: Is Key Pressed statements

  1. #1
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    Default Is Key Pressed statements

    Hi,

    I am making a game like pong. I made a Jframe for the start menu:

     
    import java.awt.Dimension;
    import java.awt.Graphics;
    import java.awt.Image;
     
    import javax.swing.ImageIcon;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
     
      class ImageTest {
     
      public static void main(String[] args) {
        ImagePanel panel = new ImagePanel(new ImageIcon("pongintropage.png").getImage());
     
        JFrame frame = new JFrame();
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true);
      }
    }
     
    class ImagePanel extends JPanel {
     
      private Image img;
     
      public ImagePanel(String img) {
        this(new ImageIcon(img).getImage());
      }
     
      public ImagePanel(Image img) {
        this.img = img;
        Dimension size = new Dimension(img.getWidth(null), img.getHeight(null));
        setPreferredSize(size);
        setMinimumSize(size);
        setMaximumSize(size);
        setSize(size);
        setLayout(null);
      }
     
      public void paintComponent(Graphics g) {
        g.drawImage(img, 0, 0, null);
      }
    }


    I tried to do an is key pressed statement to change backgrounds:

    if(isKeyPressed(KeyEvent.VK_SPACE)
     
    {
           setBackground(newBackground);
    }


    Is set background the right command or will I have to do the whole Jframe thing shown up above again in the if statement?
    Also, is SPACE the right command for spacebar?

    What I am trying to do is get the background to change when the key spacebar is pressed.


  2. #2
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    Default Re: Is Key Pressed statements

    each key has different Key Code for example space is 32
    you should add KeyListener to your component
    and the you can check which key is pressed like
    if(event.getKeyCode()==32)

  3. #3
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    Default Re: Is Key Pressed statements

    Thanks. What about the background?

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    Default Re: Is Key Pressed statements

    And, how do i find out all the different key codes? Is there some website I can look at?

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    Default Re: Is Key Pressed statements

    @ serdar
    if(event.getKeyCode()==32)
    That code can be made to be self documentating. When I read 32 it has no meaning.
    What is the variable that defines the value for that key press? Use that instead!

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    Default Re: Is Key Pressed statements

    find out all the different key codes
    Read the API doc for KeyEvent. Go to this site and find KeyEvent
    Java Platform SE 6

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    Default Re: Is Key Pressed statements

    to change background image you should have

    *array with image names on ImageTest class
    *setImg() method on ImagePanel class
    * I'm using ImageHelper.class to load Images
    *counter to go to next index of array
    *repaint() method calls paintComponent() method
    frame.addKeyListener(new KeyAdapter() {
        public void keyReleased(java.awt.event.KeyEvent evt) {
            if(evt.getKeyCode()==KeyEvent.VK_SPACE)
                    panel.setImg(ImageHelper.loadImage(array[counter]).getImage());
                    panel.repaint();
                    counter++;
                }
        });
    ImageHelper.class:
     
    import java.net.*;
    import java.awt.*;
    import javax.swing.*;
     
    public class ImageHelper {
     
        private ImageHelper() {
        }
     
        public static ImageIcon loadImage(String name) {
            ImageIcon image = null;
            try {
                URL url = ImageHelper.class.getResource(name);
                if (url != null) {
                    java.awt.Image img = Toolkit.getDefaultToolkit().createImage(url);
                    if (img != null) {
                        image = new ImageIcon(img);
                    }
                }
            } catch (Throwable ex) {
                System.out.println("ERROR: loading image " + name + " failed");
            }
            return image;
        }
    }

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