How do I move a graphic across the screen with arrow keys?

Question

I'm trying to create the beginning of a simple game. The first thing I am trying to do is import a graphic into my code and move it across the screen. I was able to draw a ball on the screen and move it around but when I import a graphic from a file I am unable to move it around. What am I missing or doing wrong?

import javax.swing.*;
import java.awt.Graphics;
import java.awt.*;
import java.awt.event.*;
import javax.swing.ImageIcon;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyListener;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Game extends JPanel implements ActionListener, KeyListener {

    Timer t = new Timer(5, this);
    double x = 0, y = 0, velX = 0, velY = 0;
    private ImageIcon image;


    public Game(){
        setBackground(Color.WHITE);
        t.start();
        addKeyListener(this);
        this.setFocusable(true);
        setFocusTraversalKeysEnabled(false);
        image = new ImageIcon ("ship.gif");

    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        ImageIcon i = new ImageIcon("C:\\Users\\Bryan\\Pictures\\ship.gif");
        i.paintIcon(this, g, 0, 0);

    }

    public void actionPerformed(ActionEvent e){
        repaint();
        x += velX;
        y += velY;

        if(x<0){
            velX = 0;
            x = 0;
        }

        if(x>750){
            velX = 0;
            x = 750;
        }

        if(y<0);{
            velY = 0;
            y = 0;
        }

        if(y>550){
            velY = 0;
            y = 550;
        }
    }

    public void up(){
        velY = -1.5;
        velX = 0;
    }

    public void down(){
        velY = 1.5;
        velX = 0;
    }

    public void left(){
        velX = -1.5;
        velY = 0;
    }

    public void right(){
        velX = 1.5;
        velY = 0;
    }

    public void keyPressed(KeyEvent e){
        int code = e.getKeyCode();

        if (code == KeyEvent.VK_UP){
            up();
        }

        if (code == KeyEvent.VK_DOWN){
            down();
        }

        if (code == KeyEvent.VK_LEFT){
            left();
        }

        if (code == KeyEvent.VK_RIGHT){
            right();
        }
    }

    public void keyTyped(KeyEvent e){}

    public void keyReleased(KeyEvent e){

//      velX = 0;
//      velY = 0;
        int code = e.getKeyCode();

        if (code == KeyEvent.VK_UP){
            velY = 0;
        }
        if (code == KeyEvent.VK_DOWN){
            velY = 0;
        }
        if (code == KeyEvent.VK_LEFT){
            velX = 0;
        }
        if (code == KeyEvent.VK_RIGHT){
            velX = 0;
        }
    }

}

My driver is in another class as follows:

import java.awt.Color;

import javax.swing.JFrame;

public class GameDriver {

    public static void main(String[] args) {

        JFrame f = new JFrame();
        Game  g = new Game();
        f.add(g);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(800,600);

    }
}

Solution

Two big problems here:

public void paintComponent(Graphics g){
    super.paintComponent(g);
    ImageIcon i = new ImageIcon("C:\\Users\\Bryan\\Pictures\\ship.gif");
    i.paintIcon(this, g, 0, 0);
}

1. You're reading from a file from within paintComponent(...). Never do this as this will slow your drawing unnecessarily. Read the image once, perhaps in a constructor, and then use the stored image variable in drawing. The paintComponent method should be for painting only, and it should be lean, mean and fast.
2. You're drawing at 0, 0 always. If you want to move something, draw at a variable position, and then change the values held by the variable and repaint.

Also: You should use Key Bindings to accept key strokes in a Swing application as this will help solve focus issues.

For example, please have a look at my code in this answer.

Comments

[MadProgrammer]

(cough)key bindings(cough) ;) +1

[Hovercraft Full Of Eels]

@MadProgrammer: You should have that cough looked into (thanks).

[Bfrank]

Okay thank you. One more question for you then. Instead of using a paintComponent method, what should I use and how should I import the image? Sorry I'm a newbie (:

[Hovercraft Full Of Eels]

@Bfrank: Yes, use a paintComponent method for painting, but again, read in the images once wherever it makes the most sense to do so. Again, a constructor perhaps.