I am trying to make a project based on Hilbert Curve. I was able to use the code in Applet, but I need it to work in JFrame, because I will be needing to open more than 1 frame at once to present my project. I have the code in applet below, but I don't know how to change to JFrame.
In the applet form, it is like the code below:
import java.awt.*;
import java.applet.*;
public class HilbertCurve extends Applet{
private SimpleGraphics sg = null;
private int dist0=256;
private int dist=dist0;
public void init(){
resize(dist0, dist0);
sg = new SimpleGraphics(getGraphics());}
public void paint(Graphics g){
int level = 4;
dist = dist0;
for(int i=level; i>0; i--) dist/=2;
sg.goToXY (dist/2, dist/2);
HilbertU(level);
}
private void HilbertU(int level){
if(level>0){
HilbertD(level-1); sg.lineRel(0,dist);
HilbertU(level-1); sg.lineRel(dist,0);
HilbertU(level-1); sg.lineRel(0,-dist);
HilbertC(level-1);
}
}
private void HilbertD(int level){
if(level>0){
HilbertU(level-1); sg.lineRel(dist,0);
HilbertD(level-1); sg.lineRel(0,dist);
HilbertD(level-1); sg.lineRel(-dist,0);
HilbertA(level-1);
}
}
private void HilbertC(int level){
if(level>0){
HilbertA(level-1); sg.lineRel(-dist,0);
HilbertC(level-1); sg.lineRel(0,-dist);
HilbertC(level-1); sg.lineRel(dist,0);
HilbertU(level-1);
}
}
private void HilbertA(int level){
if(level>0){
HilbertC(level-1); sg.lineRel(0,-dist);
HilbertA(level-1); sg.lineRel(-dist,0);
HilbertA(level-1); sg.lineRel(0,dist);
HilbertD(level-1);
}
}
import java.awt.*;
import javax.swing.*;
class SimpleGraphics{
private Graphics g = null;
private int x =0, y = 0;
public SimpleGraphics(Graphics g) {
this.g = g;}
public void goToXY(int x, int y){
this.x =x;
this.y= y;
}
public void lineRel(int deltaX, int deltaY){
g.drawLine(x, y, x+deltaX, y+deltaY);
x+=deltaX;
y+=deltaY;}
}
I tried putting it to JFrame by myself, but I wasn't able to. The JFrame opens, but the HilbertCurve doesn't start. Below is my code, and I didn't change the class SimpleGraphics
import java.awt.*;
import javax.swing.*;
public class HilbertCurve extends JPanel {
JFrame frame;
private SimpleGraphics sg = null;
private int dist0=256;
private int dist=dist0;
public static void main(String[] args){
HilbertCurve exemplo1 = new HilbertCurve();
exemplo1.fireUpScreen();
}
public void fireUpScreen(){
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(512,512);
frame.setVisible(true);
frame.add(this);
}
public void paint(Graphics g){
int level = 4;
dist = dist0;
for(int i=level; i>0; i--) dist/=2;
sg.goToXY (dist/2, dist/2);
HilbertU(level);
}
private void HilbertU(int level){
if(level>0){
HilbertD(level-1); sg.lineRel(0,dist);
HilbertU(level-1); sg.lineRel(dist,0);
HilbertU(level-1); sg.lineRel(0,-dist);
HilbertC(level-1);
}
}
private void HilbertD(int level){
if(level>0){
HilbertU(level-1); sg.lineRel(dist,0);
HilbertD(level-1); sg.lineRel(0,dist);
HilbertD(level-1); sg.lineRel(-dist,0);
HilbertA(level-1);
}
}
private void HilbertC(int level){
if(level>0){
HilbertA(level-1); sg.lineRel(-dist,0);
HilbertC(level-1); sg.lineRel(0,-dist);
HilbertC(level-1); sg.lineRel(dist,0);
HilbertU(level-1);
}
}
private void HilbertA(int level){
if(level>0){
HilbertC(level-1); sg.lineRel(0,-dist);
HilbertA(level-1); sg.lineRel(-dist,0);
HilbertA(level-1); sg.lineRel(0,dist);
HilbertD(level-1);
}
}
}
First, I would suggest you start by reading through Performing Custom Painting and Painting in AWT and Swing to better understand how painting works in Swing.
The example Applet is actually a bad example of how to perform painting, as you should never maintain a reference to Graphics and it should be passed to the methods which need it when the component is painted.
You should also end up with a NullPointerException as sg is never initialised.
As a general rule, establish the UI first, then call setVisible last, it will solve a number of simple issues.
There's no reason HilbertCurve needs a reference to the JFrame, the frame can be instantiated in the main method instead.
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class HilbertCurve extends JPanel {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
HilbertCurve exemplo1 = new HilbertCurve();
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(exemplo1);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
private SimpleGraphics sg = null;
private int dist0 = 256;
private int dist = dist0;
public HilbertCurve() {
sg = new SimpleGraphics();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(512, 512);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
int level = 4;
dist = dist0;
for (int i = level; i > 0; i--) {
dist /= 2;
}
sg.goToXY(dist / 2, dist / 2);
Graphics2D g2d = (Graphics2D) g.create();
hilbertU(g2d, level);
g2d.dispose();
}
private void hilbertU(Graphics2D g, int level) {
if (level > 0) {
hilbertD(g, level - 1);
sg.lineRel(g, 0, dist);
hilbertU(g, level - 1);
sg.lineRel(g, dist, 0);
hilbertU(g, level - 1);
sg.lineRel(g, 0, -dist);
hilbertC(g, level - 1);
}
}
private void hilbertD(Graphics2D g, int level) {
if (level > 0) {
hilbertU(g, level - 1);
sg.lineRel(g, dist, 0);
hilbertD(g, level - 1);
sg.lineRel(g, 0, dist);
hilbertD(g, level - 1);
sg.lineRel(g, -dist, 0);
hilbertA(g, level - 1);
}
}
private void hilbertC(Graphics2D g, int level) {
if (level > 0) {
hilbertA(g, level - 1);
sg.lineRel(g, -dist, 0);
hilbertC(g, level - 1);
sg.lineRel(g, 0, -dist);
hilbertC(g, level - 1);
sg.lineRel(g, dist, 0);
hilbertU(g, level - 1);
}
}
private void hilbertA(Graphics2D g, int level) {
if (level > 0) {
hilbertC(g, level - 1);
sg.lineRel(g, 0, -dist);
hilbertA(g, level - 1);
sg.lineRel(g, -dist, 0);
hilbertA(g, level - 1);
sg.lineRel(g, 0, dist);
hilbertD(g, level - 1);
}
}
class SimpleGraphics {
// private Graphics g = null;
private int x = 0, y = 0;
public SimpleGraphics() {
}
public void goToXY(int x, int y) {
this.x = x;
this.y = y;
}
public void lineRel(Graphics2D g, int deltaX, int deltaY) {
g.drawLine(x, y, x + deltaX, y + deltaY);
x += deltaX;
y += deltaY;
}
}
}