I am trying to develop a game in Java. It is a 2D game with not much logic in it.
I wondered if JFrame , JPanel or Canvas should be used for this? Has one benefits over the others
One popular approach is to override paintComponent in a JPanel like so:
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// put drawing code here
}
You can invoke this by calling repaint
method elsewhere in the JPanel, usually in response to Key events for user-provided input, or from a Timer
for fixed interval updates.
Here is some code you can use to get you started:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.WindowConstants;
public class GameFrame extends JFrame {
private static final long serialVersionUID = 1L;
public GameFrame() {
super("Game Frame");
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
getContentPane().add(new GamePanel(), BorderLayout.CENTER);
pack();
setResizable(false);
setLocationRelativeTo(null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame frame = new GameFrame();
frame.setVisible(true);
}
});
}
}
class GamePanel extends JPanel implements ActionListener, KeyListener {
private static final long serialVersionUID = 1L;
private static final Dimension PANEL_SIZE = new Dimension(640, 480);
private static final int REFRESH_RATE = 1000;
private static final int CHARACTER_WIDTH = 32;
private static final int CHARACTER_HEIGHT = 64;
private Timer timer = new Timer(REFRESH_RATE, this);
private int currentRow = 0;
private int currentCol = 0;
private int randomRow = 0;
private int randomCol = 0;
public GamePanel() {
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
timer.start();
}
public Dimension getPreferredSize() {
return PANEL_SIZE;
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawOval(randomCol, randomRow, CHARACTER_WIDTH, CHARACTER_HEIGHT);
g.drawRect(currentCol, currentRow, CHARACTER_WIDTH, CHARACTER_HEIGHT);
}
public void actionPerformed(ActionEvent e) {
int min = 0;
int maxRow = (int)PANEL_SIZE.getHeight() - CHARACTER_HEIGHT;
int maxCol = (int)PANEL_SIZE.getWidth() - CHARACTER_WIDTH;
Random rand = new Random();
randomRow = rand.nextInt((maxRow - min) + 1) + min;
randomCol = rand.nextInt((maxCol - min) + 1) + min;
repaint();
}
public void keyPressed(KeyEvent e) {
int code = e.getKeyCode();
int rowIncrement = 0;
int colIncrement = 0;
if(code == KeyEvent.VK_LEFT) {
colIncrement--;
}
else if(code == KeyEvent.VK_RIGHT) {
colIncrement++;
}
else if(code == KeyEvent.VK_UP) {
rowIncrement--;
}
else {
if(code == KeyEvent.VK_DOWN) {
rowIncrement++;
}
}
if(isInBounds(rowIncrement, colIncrement)) {
currentRow += rowIncrement;
currentCol += colIncrement;
repaint();
}
}
private boolean isInBounds(int rowIncrement, int colIncrement) {
int top = currentRow + rowIncrement;
int left = currentCol + colIncrement;
int right = left + CHARACTER_WIDTH;
int bottom = top + CHARACTER_HEIGHT;
return (top >= 0 && left >= 0 && right <= PANEL_SIZE.getWidth() && bottom <= PANEL_SIZE.getHeight());
}
public void keyTyped(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}
}