Develop Reference

Repaint method not working on JComponent java swing

I want to have a text field to input an integer, then select 1) Grow or 2) Shrink, and then click the button so that the circle gets redrawn on the screen based on the selected options.
I don't know why it isn't repaining. (Don't worry about the layout, just want to get it to work first)
My Frame:
public class Main {
public static void main(String[] args) {
var frame = new JFrame();
frame.setSize(400,400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
var circleComp = new circleComponent();
var panel1 = new JPanel();
var multiplierLabel = new JLabel("Grow Multiplier");
var multiplierField = new JTextField(20);
var radio1 = new JRadioButton("Grow Circle");
var radio2 = new JRadioButton("Shrink Circle");
var bg = new ButtonGroup();
bg.add(radio1);
bg.add(radio2);
JButton button = new JButton("Rivizato");
button.addActionListener(
new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if(radio1.isSelected()){
rrComp.repaint(0,0,Integer.parseInt(multiplierField.getText())*rrComp.getWidth(), Integer.parseInt(multiplierField.getText())*rrComp.getHeight());
}
else if(radio2.isSelected()){
rrComp.repaint(0,0,Integer.parseInt(multiplierField.getText())/rrComp.getWidth(), Integer.parseInt(multiplierField.getText())/rrComp.getHeight());
}
}
}
);
panel1.add(multiplierLabel);
panel1.add(multiplierField);
panel1.add(button);
panel1.add(radio1);
panel1.add(radio2);
frame.add(panel1);
frame.add(circleComp);
}
}
My CircleComponent class:
public class CircleComponent extends JComponent {
public void paintComponent(Graphics g){
super.paintComponent(g);
var g2 = (Graphics2D) g;
var circle = new Ellipse2D.Double(0,0,100,100);
g2.draw(circle);
}
}

var circle = new Ellipse2D.Double(0,0,100,100); means that your circle will never change size.
You should also be careful with repaint(x, y, width, height) as it could leave regions of your component "dirty". Better to just use repaint.
As a conceptual example...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public final class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new MainPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MainPane extends JPanel {
private CirclePane circlePane;
public MainPane() {
setLayout(new BorderLayout());
JPanel actionsPane = new JPanel(new GridBagLayout());
JButton growButton = new JButton("Grow");
growButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
circlePane.grow();
}
});
JButton shrinkButton = new JButton("Shrink");
shrinkButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
circlePane.shrink();
}
});
actionsPane.add(growButton);
actionsPane.add(shrinkButton);
circlePane = new CirclePane();
add(circlePane);
add(actionsPane, BorderLayout.SOUTH);
}
}
public class CirclePane extends JPanel {
private Ellipse2D circle;
public CirclePane() {
circle = new Ellipse2D.Double(0, 0, 100, 100);
}
public void grow() {
double width = circle.getWidth() + 10;
double height = circle.getHeight() + 10;
circle.setFrame(0, 0, width, height);
repaint();
}
public void shrink() {
double width = Math.max(0, circle.getWidth() - 10);
double height = Math.max(0, circle.getHeight() - 10);
circle.setFrame(0, 0, width, height);
repaint();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
double x = (getWidth() - circle.getWidth()) / 2d;
double y = (getHeight() - circle.getHeight()) / 2d;
g2d.translate(x, y);
g2d.draw(circle);
g2d.dispose();
}
}
}
nb: I know I've not used JTextField to specify the size of the circle, that's on purpose. You will need to adapt your requirements to work in a similar way - can you see where you might pass parameters to the CirclePane?

I cannot Get the Background Color of my JPanel in main class

The Problem is I make a class that extends JPanel with gradient Color background but the problem is when I am getting the background of it to use it to other component is I cannot get the color of it. I want to set the background color of components same to other components
I had tried to use .getBackground(); But it doesn't work on it. what should I do so that I can get the background of it?
import javax.swing.*;
import java.awt.*;
public class GradientPaintDemo extends JPanel {
private static final int scale = 2;
private static final Color c1 = Color.decode("#00F260");
private static final Color c2 = Color.decode("#0575E6");
private static final int size = (c2.getRed() - c1.getRed()) * scale;
#Override
public Dimension getPreferredSize() {
return new Dimension(size, size);
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(20, 0, c1, 20, h, c2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
}
}
then when in my Main Class
GradientPaintDemo gpd = new GradientPaintDemo();
JPanel panel1 = new JPanel();
gpd.add(panel1);
panel.getBackground();
I want that to have only one background on all of my panels and buttons I want to look like this image below

At a "guess" I would say you need to make the child component transparent, using panel1.setOpaque(false), so the parent will show through it.
Also, at a "guess", the use of size in your getPreferredSize method could be causing you issues. Instead, I'd set the component's default layout manager to BorderLayout and let the child dictate the required size.
For example, opaque...
Transparent...
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.HeadlessException;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
public class Test extends JFrame {
public static void main(String[] args) {
new Test();
}
public Test() throws HeadlessException {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
GradientPaintDemo gpd = new GradientPaintDemo();
gpd.setBorder(new EmptyBorder(20, 20, 20, 20));
JPanel panel = new JPanel();
panel.setBorder(new EmptyBorder(20, 20, 20, 20));
panel.add(new JLabel("This is a test"));
panel.setOpaque(false);
gpd.add(panel);
frame.add(gpd);
frame.pack();
frame.setVisible(true);
}
});
}
public static class GradientPaintDemo extends JPanel {
private static final int scale = 2;
private static final Color c1 = Color.decode("#00F260");
private static final Color c2 = Color.decode("#0575E6");
private static final int size = (c2.getRed() - c1.getRed()) * scale;
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(20, 0, c1, 20, h, c2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
}
}
}

Java Doesn't draw on JPanel

This is my main class:
public class Sad {
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Sad window = new Sad();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Sad() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 512, 399);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(new CardLayout(0, 0));
JPanel panel = new JPanel();
frame.getContentPane().add(panel, "name_12361565901507");
panel.setLayout(null);
JButton btnNes = new JButton("Nes");
btnNes.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Grafik grafik = new Grafik(20, 20, 100);
panel.add(grafik);
}
});
btnNes.setBounds(90, 146, 89, 23);
panel.add(btnNes);
}
}
And this is drawing class
public class Grafik extends JPanel{
private int x;
private int y;
private int r;
public Grafik(int x, int y, int r){
this.x = x;
this.y = y;
this.r = r;
}
public void paintComponent(Graphics g) {
Graphics2D g2 =(Graphics2D) g;
Ellipse2D circ = new Ellipse2D.Float(x, y, r, r);
g2.setColor(Color.RED);
g2.draw(circ);
}
}
They are in same package. And when i click button its suposed to draw Ellipse in red color, but it doesn't show anything. Can someone help me? BTW Sorry for bad english

It's because you don't call panel.setBounds(), revalidate() and repaint().
But you shouldn't use a null layout anyway: Use layout
managers.
You should call super.paintComponent(g) at the beginning of
the paintComponent method.
Rather than adding a new component to the panel after every button press you might want to just toggle a boolean value inside the Grafik instance which determines wheter the ellipse should be visible or not.
If you want the ellipse to be "smooth", you can call g2.setRenderingHint(hintKey, hintValue).
Modified code including my suggestions:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Sad {
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Sad window = new Sad();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Sad() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 512, 399);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Grafik grafik = new Grafik(20, 20, 100);
JPanel panel = new JPanel();
panel.setLayout(new BorderLayout());
panel.add(grafik);
JButton btnNes = new JButton("Nes");
btnNes.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
grafik.setEllipseVisible(true);
panel.repaint();
}
});
JPanel btnPanel = new JPanel();
btnPanel.add(btnNes);
panel.add(btnPanel, BorderLayout.SOUTH);
frame.setContentPane(panel);
}
}
class Grafik extends JPanel {
private int x;
private int y;
private int r;
private boolean ellipseVisible;
public Grafik(int x, int y, int r) {
this.x = x;
this.y = y;
this.r = r;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (isEllipseVisible()) {
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Ellipse2D circ = new Ellipse2D.Float(x, y, r, r);
g2.setColor(Color.RED);
g2.draw(circ);
}
}
public boolean isEllipseVisible() {
return ellipseVisible;
}
public void setEllipseVisible(boolean ellipseVisible) {
this.ellipseVisible = ellipseVisible;
}
}

How can I draw vertical line when I press the button?

I am unable to draw line when I press the component in Java Swing. How can I do this? I already used paint method, my problem is when program executes paint method invoke automatically, DrawLine() method will be there in paint method, so is there any way that I can get the lines other than paint method?
Please give some suggestion.
Below code I have tried, it's displaying lines but I want to display the lines when I click the component.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class ReferenceLink1 extends JFrame
{
JLabel l1;
JLabel l2;
JPanel p1;
ReferenceLink1()
{
p1 = new JPanel();
p1.setLayout(null);
p1.setBackground(Color.ORANGE);
p1.setOpaque(true);
p1.setBounds(0,0,300,400);
setLayout(null);
l1 = new JLabel();
l1.setText("l1");
l1.setBounds(20, 40, 100, 40);
l1.setHorizontalAlignment(SwingConstants.CENTER);
l1.setBackground(Color.GREEN);
l1.setOpaque(true);
l2 = new JLabel(); ;
l2.setText("l2");
l2.setBounds(20, 100,100,40);
l2.setBackground(Color.BLUE);
l2.setHorizontalAlignment(SwingConstants.CENTER);
l2.setOpaque(true);
p1.add(l1);
p1.add(l2);
add(p1);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
setBounds(0,0,400,400);
}
public void paint(Graphics g)
{
super.paint(g);
g.drawLine(77,110,77,130);
}
public static void main(String args[])
{
ReferenceLink1 rf = new ReferenceLink1();
}
}

class Surface extends JPanel {
private void doDrawing(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.blue);
Dimension size = getSize();
Insets insets = getInsets();
int w = size.width - insets.left - insets.right;
int h = size.height - insets.top - insets.bottom;
Random r = new Random();
for (int i = 0; i < 1000; i++) {
int x = Math.abs(r.nextInt()) % w;
int y = Math.abs(r.nextInt()) % h;
g2d.drawLine(x, y, x, y);
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
doDrawing(g);
}
}
public class Points extends JFrame {
public Points() {
initUI();
}
private void initUI() {
setTitle("Points");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(new Surface());
setSize(350, 250);
setLocationRelativeTo(null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
Points ps = new Points();
ps.setVisible(true);
}
});
}
}

You could simply add a mouse listener to the label that represents your button.
l2.addMouseListener(new MouseAdapter()
{
public void mouseClicked(MouseEvent e)
{
p1.getGraphics().drawLine(77,110,77,130);
}
});

public class ReferenceLink1 extends JFrame {
JLabel l1;
JButton l2;
JPanel p1;
public static class MyListener implements ActionListener{
Graphics g;
public MyListener(Graphics g) {
this.g = g;
}
#Override
public void actionPerformed(ActionEvent e) {
g.drawLine(77, 110, 77, 130);
}
}
public ReferenceLink1() {
p1 = new JPanel();
setVisible(true);
p1.setLayout(null);
p1.setBackground(Color.ORANGE);
p1.setOpaque(true);
p1.setBounds(0,0,300,400);
setLayout(null);
l1 = new JLabel();
l1.setText("l1");
l1.setBounds(20, 40, 100, 40);
l1.setHorizontalAlignment(SwingConstants.CENTER);
l1.setBackground(Color.GREEN);
l1.setOpaque(true);
l2 = new JButton();
l2.addActionListener(new MyListener(this.getGraphics()));
l2.setText("l2");
l2.setBounds(20, 100,100,40);
l2.setBackground(Color.BLUE);
l2.setHorizontalAlignment(SwingConstants.CENTER);
l2.setOpaque(true);
p1.add(l1);
p1.add(l2);
add(p1);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(0,0,400,400);
}
public static void main(String args[]) {
ReferenceLink1 rf = new ReferenceLink1();
}
}

How to setup desired Coordinates in Graphics2D

I want to set up a mathematical (where y grows up not down) coordinate space from (-1, -1) to (+1, +1) and have it fit in the window regardless of the window size.
I am using an anonymous JComponent subclass in Java SE 7 and casting the incoming Graphics in paintComponent to Graphics2D and then drawing on the Graphics2D
But the Graphics2D is set to a computer coordinate space that changes with the size of the window. How to get it to rescale according to window size and have Y go upwards? The following program should show a dark square in upper right quadrant.
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JComponent;
import javax.swing.JFrame;
public class G {
public static void main (String [] args) {
JFrame frame = new JFrame(G.class.getCanonicalName());
frame.setUndecorated(true);
JComponent component = new JComponent() {
private static final long serialVersionUID = 1L;
#Override
protected void paintComponent (Graphics g) {
super.paintComponent(g);
paint2D((Graphics2D)g);
}
protected void paint2D (Graphics2D g2) {
g2.draw(new Rectangle2D.Double(0.1, 0.1, 0.9, 0.9));
}
};
frame.add(component);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setVisible(true);
}
}

Setup the coordinate system how you want, using transform() and translate(). So:
you want the origin to be at (0, height); bottom left.
then you want to flip the Y axis.
Example code:
AffineTransform tform = AffineTransform.getTranslateInstance( 0, height);
tform.scale( 1, -1);
g2.setTransform( tform);
[My edited version]:
public static void main (String [] args) {
JFrame frame = new JFrame( G2dTransform_Question.class.getCanonicalName());
JComponent component = new JComponent() {
private static final long serialVersionUID = 1L;
#Override
protected void paintComponent (Graphics g) {
super.paintComponent(g);
paint2D((Graphics2D)g);
}
protected void paint2D (Graphics2D g2) {
AffineTransform tform = AffineTransform.getTranslateInstance( 0, getHeight());
tform.scale( getWidth(), -getHeight()); // NOTE -- to make 1.0 'full width'.
g2.setTransform( tform);
g2.setColor( Color.BLUE); // NOTE -- so we can *see* something.
g2.fill( new Rectangle2D.Double(0.1, 0.1, 0.8, 0.8)); // NOTE -- 'fill' works better than 'draw'.
}
};
frame.setLayout( new BorderLayout()); // NOTE -- make the component size to frame.
frame.add( component, BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setVisible(true);
}
[Hovercraft's version]: Thanks Hover!
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;
import javax.swing.JComponent;
import javax.swing.JFrame;
public class G {
public static final int PREF_W = 400;
public static final int PREF_H = PREF_W;
public static void main (String [] args) {
JFrame frame = new JFrame(G.class.getCanonicalName());
frame.setUndecorated(true);
JComponent component = new JComponent() {
private static final long serialVersionUID = 1L;
#Override
protected void paintComponent (Graphics g) {
super.paintComponent(g);
AffineTransform tform = AffineTransform.getTranslateInstance( 0, getHeight());
tform.scale( 1, -1);
Graphics2D g2 = (Graphics2D) g.create();
g2.setTransform( tform);
paint2D(g2);
g2.dispose();
}
protected void paint2D (Graphics2D g2) {
g2.draw(new Rectangle2D.Double(10, 10, 20, 30));
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
};
frame.add(component);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}