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Changing a shape and a colour after a click (GUI, Java)

I'm just learning how GUI works and I wanted to write a code where following happens:
firstly we see red rectangle
after a click it changes into a circle in gradient (I picked orange and pink) + the background is black.
The problem is, I don't know how to notify the change when I use repaint(), I tried creating the first picture with another method - fail, maybe I lack some knowledge. Currently we get just the second output that doesn't change after the click.
This is the code at the moment I got stuck:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class SimpleGUI implements ActionListener {
JButton button;
JFrame frame;
public void work() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
button = new JButton("Color change");
button.addActionListener(this);
mojpanel panel = new mojpanel();
frame.getContentPane().add(BorderLayout.SOUTH, button);
frame.getContentPane().add(BorderLayout.CENTER, panel);
frame.setSize(300,300);
frame.setVisible(true);
}
public void actionPerformed(ActionEvent event) {
frame.repaint();
}
}
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import javax.swing.*;
import java.awt.Graphics2D;
public class mojpanel extends JPanel {
public void paintComponent(Graphics g) {
g.setColor(Color.black);
g.fillRect(0, 0, this.getWidth(), this.getHeight());
GradientPaint gradient = new GradientPaint(70,70, Color.orange, 150,150, Color.pink);
((Graphics2D) g).setPaint(gradient);
g.fillOval(100, 100, 100, 100);
}
}
import javax.swing.JFrame;
public class Test {
public static void main(String[] args) {
SimpleGUI aplGUI = new SimpleGUI();
JFrame frame = new JFrame();
mojpanel panel = new mojpanel();
frame.add(panel);
aplGUI.work();
}
}
import java.awt.*;
public class Painting extends SimpleGUI {
public void paint(Graphics g) {
g.setColor(Color.red);
g.drawRect(100, 100, 100, 100);
g.fillRect(100, 100, 100, 100);
}
}

When you create new classes, you short invest more thought into them. You have two classes which are supposed to be interchangeable, one painting a red rectangle, the other painting a circle with a color gradient, with the ability to switch from the former to the latter.
So when you have one class extending JPanel and the other extending SimpleGUI, there is no way to exchange one for the other. Further, the names mojpanel and Painting do not reflect their purposes.
Besides that, you have it backward. Don’t implement an action that calls repaint(), followed by an attempt to recognize that repaint() has been called, to modify the GUI afterwards. Instead, change the GUI’s state and after the GUI has changed in a way that the visual appearance needs to be updated, call repaint. Note that most properties of the Swing components do already trigger an according repaint automatically when you change them.
You may create two classes extending JComponent having a custom paintComponent method and replace one with the other when the action has been triggered. But there’s a less intrusive way. Let the classes implement Icon and set the icon property of a component, e.g. a JLabel. This is one of the properties that will trigger the painting automatically:
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class SimpleGUI {
static class GradientOval implements Icon {
#Override
public void paintIcon(Component c, Graphics g, int x, int y) {
GradientPaint gradient
= new GradientPaint(70,70, Color.orange, 150,150, Color.pink);
((Graphics2D)g).setPaint(gradient);
g.fillOval(100, 100, 100, 100);
}
#Override
public int getIconWidth() {
return 200;
}
#Override
public int getIconHeight() {
return 200;
}
}
static class RedRectangle implements Icon {
#Override
public void paintIcon(Component c, Graphics g, int x, int y) {
g.setColor(Color.RED);
g.fillRect(100, 100, 100, 100);
}
#Override
public int getIconWidth() {
return 200;
}
#Override
public int getIconHeight() {
return 200;
}
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel content = new JLabel(new RedRectangle());
JButton button = new JButton("Change To Circle");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
content.setIcon(new GradientOval());
}
});
frame.getContentPane().add(BorderLayout.SOUTH, button);
frame.getContentPane().add(BorderLayout.CENTER, content);
frame.setSize(300, 300);
frame.setVisible(true);
}
}
I don’t know which level of Java knowledge you have. The code
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
content.setIcon(new GradientOval());
}
});
creates an instance of an anonymous inner class implementing ActionListener. You can simplify this code using a lambda expression:
button.addActionListener(e -> content.setIcon(new GradientOval()));
To demonstrate the interaction between component properties and repaints, here an approach using a custom component:
import java.awt.*;
import javax.swing.*;
public class SimpleGUI {
static class DualAppearance extends JComponent {
private boolean first = true;
public boolean isFirst() {
return first;
}
public void setFirst(boolean shouldBeFirst) {
if(shouldBeFirst != first) {
first = shouldBeFirst;
repaint();
}
}
public void next() {
if(first) {
first = false;
repaint();
}
}
#Override
protected void paintComponent(Graphics g) {
if(first) {
g.setColor(Color.RED);
g.fillRect(100, 100, 100, 100);
}
else {
GradientPaint gradient
= new GradientPaint(70,70, Color.orange, 150,150, Color.pink);
((Graphics2D)g).setPaint(gradient);
g.fillOval(100, 100, 100, 100);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
public Dimension getMinimumSize() {
return new Dimension(200, 200);
}
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DualAppearance content = new DualAppearance();
JButton button = new JButton("Change To Second");
button.addActionListener(e -> content.next());
frame.getContentPane().add(BorderLayout.SOUTH, button);
frame.getContentPane().add(BorderLayout.CENTER, content);
frame.setSize(300, 300);
frame.setVisible(true);
}
}
This DualAppearance component follows the usual pattern. When being requested to paint itself, it will always paint itself according to the current state. This may happen multiple times without a state change, due to other reasons, e.g. being requested by the system. When its own state changes and requires a repaint, which only this component can know, it will invoke repaint.
You can easily modify this example code to toggle between both appearances by replacing
JButton button = new JButton("Change To Second");
button.addActionListener(e -> content.next());
with
JButton button = new JButton("Toggle");
button.addActionListener(e -> content.setFirst(!content.isFirst()));

why repeated call to repaint() method did not work

My objective is to put a button and a circle on the JFrame. When i click the button the circle should move randomly on the panel/frame.
But when i click the button the circle just move once only and after putting SOP statements i found that "frame.repaint()" is getting called multiple times but this call is triggering the "paintComponent" method only once, the very first time (defined in class Panel1). Its very strange!
I have also provided another code which works as expected but has no buttons to trigger the animation. I have read that repaint() requests are coalesced together and executed once, then how come the second program works?
import java.awt.event.*;
import java.awt.Graphics.*;
import javax.swing.*;
import java.awt.*;
public class SimpleGui3c_4 {
public static void main(String args[]) {
Frame1 frame = new Frame1();
frame.go();
}
}
class Frame1 {
JFrame frame;
Panel1 p;
void go() {
frame = new JFrame();
JButton button1 = new JButton("Color Change");
p = new Panel1();
frame.setSize(500,500);
frame.setVisible(true);
frame.getContentPane().add(BorderLayout.SOUTH, button1);
frame.getContentPane().add(BorderLayout.CENTER, p);
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
button1.addActionListener(new ColorActionListener());
}
class ColorActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
for(int i=0;i<130;i++) {
System.out.println("Frame repaint started");
frame.repaint();
try {
Thread.sleep(5000);
}catch(Exception ex) {}
System.out.println("Frame repaint ended");
}
}
}
class Panel1 extends JPanel {
public void paintComponent(Graphics g) {
System.out.println("Inside the paint Component method");
int x = (int)(Math.random()*100);
int y = (int)(Math.random()*100);
g.setColor(Color.BLUE);
g.fillOval(x,y,100,100);
System.out.println("Exiting the paint component method");
}
}
}
Code which works but has no button to trigger the animation, it works as soon as i run the code. I am not sure why the below program works and the above program fails!
import javax.swing.*;
import java.awt.*;
public class SimpleAnimation {
int x = 70;
int y = 70;
public static void main(String args[]) {
SimpleAnimation gui = new SimpleAnimation();
gui.go();
}
public void go() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MyDrawPanel drawPanel = new MyDrawPanel();
frame.getContentPane().add(drawPanel);
frame.setSize(300,300);
frame.setVisible(true);
for(int i = 0;i<130;i++) {
//x++;
//y++;
drawPanel.repaint();
try {
Thread.sleep(50);
}catch(Exception ex) {}
}
}//close go
class MyDrawPanel extends JPanel {
public void paintComponent(Graphics g) {
g.setColor(Color.WHITE);
g.fillRect(0,0,this.getWidth(), this.getHeight());
int x = (int)(Math.random()*70);
int y = (int)(Math.random()*70);
g.setColor(Color.green);
g.fillOval(x,y,40,40);
}
}
}

I have also provided another code which works as expected but has no buttons to trigger the animation.
The difference between the two pieces of code is context within which they are been called.
The code that "works" is actually been updated out side the context of the Even Dispatching Thread, in the "main" thread, which means that doing something like Thread.sleep won't prevent the UI from been updated.
The code which does not work is been updated from with the content of the Event Dispatching Thread (from within the ActionListener), which is prevent the EDT from processing new paint requests until after the actionPerformed method returns
Another issue you will face relates to when you decide to update the position of the circle.
paintComponent can be called for all a number of different reasons, many which you don't control. Painting should focus on painting the current state and should never modify it (directly or indirectly). Instead, you should use some kind of update method, whose job it is, is to update the x/y position of the circle and trigger a new paint cycle.
I would highly recommend that you stop and take the time to read through:
Concurrency in Swing for a more detail explanation
How to use Swing Timers for a possible solution
Performing Custom Painting and Painting in AWT and Swing for a better understanding into how painting actually works in Swing.
Your problem is rookie mistake which comes about from not understanding how the API actually works and not understanding the tools available to solve it
There are a number of other "issues" which would result in undesirable behaviour, like not calling setVisible last, so the UI doesn't need be updated again to ensure that the components been added are visible.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class SimpleGui3c_4 {
public static void main(String args[]) {
new SimpleGui3c_4();
}
public SimpleGui3c_4() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
Frame1 frame = new Frame1();
frame.go();
}
});
}
public interface Animatable {
public void update();
}
public class Frame1 {
JFrame frame;
Panel1 p;
void go() {
frame = new JFrame();
JButton button1 = new JButton("Color Change");
p = new Panel1();
frame.getContentPane().add(BorderLayout.SOUTH, button1);
frame.getContentPane().add(BorderLayout.CENTER, p);
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
button1.addActionListener(new ColorActionListener(p));
frame.pack();
frame.setVisible(true);
}
class ColorActionListener implements ActionListener {
private Animatable parent;
public ColorActionListener(Animatable parent) {
this.parent = parent;
}
public void actionPerformed(ActionEvent e) {
JButton btn = (JButton) e.getSource();
btn.setEnabled(false);
Timer timer = new Timer(5000, new ActionListener() {
private int counter = 0;
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Frame repaint started");
parent.update();
counter++;
if (counter >= 130) {
((Timer)e.getSource()).stop();
btn.setEnabled(true);
}
}
});
timer.setInitialDelay(0);
timer.start();
}
}
class Panel1 extends JPanel implements Animatable {
private int xPos, yPos;
public Panel1() {
update();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("Inside the paint component method");
g.setColor(Color.BLUE);
g.fillOval(xPos, yPos, 100, 100);
System.out.println("Exiting the paint component method");
}
#Override
public void update() {
System.out.println("Inside the update method");
xPos = (int) (Math.random() * 100);
yPos = (int) (Math.random() * 100);
repaint();
}
}
}
}

I'm trying to draw a string in JFrame, but it won't work.. Help please

I'm trying to display a string when a button is pressed, but it does not work. I do not know what the problem is. I get no error, but that does not bother me. I'm missing something fundamental, I suppose. Please help!!
//I'm trying to draw a string in the frame when a button is pressed, but it won't work..
//Can't figure out what the problem is.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class AppletTwo extends JFrame implements ActionListener
{
JFrame frameOne;
JButton btnOne;
AppletTwo()
{
frameOne = new JFrame("frameOne");
frameOne.setSize(320,240);
frameOne.setLayout(new FlowLayout(FlowLayout.LEFT));
frameOne.setVisible(true);
frameOne.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
btnOne = new JButton("Print");
btnOne.addActionListener(this);
frameOne.add(btnOne);
}
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource() == btnOne)
{
repaint();
}
}
public void paint(Graphics g)
{
g.drawString("Never Works",150,150);
}
public static void main(String[] args)
{
AppletTwo frame1 = new AppletTwo();
}
}

" I'm missing something fundamental, I suppose. "
Yes, you are:
Main problem:
Your class is JFrame which is the component for which you are overriding the paint method. But you create another instance of a JFrame, which is the one you setVisible to. Keep in mind, you haven't drawn anything to this frame. So you are seeing the new instance of frame, not the class frame for which you are painting (and for which you never set visible).
Other problems:
You should always call super.paint[Component] after a paint[Component] override
#Override
public void paint(Graphics g) {
super.paint(g);
}
Don't paint on top level container like JFrame. Instead paint on a JPanel or JComponent and override is paintComponent method and call super.paintComponent, then add that component to the frame. See Performing Custom Painting
Swing apps should be run on the event dispatch thread (EDT). You can do so by wrapping your main code in a SwingUtilities.invokeLater(...). See Initial Threads
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run() {
AppletTwo frame1 = new AppletTwo();
}
});
}
Generally, you always want to set the frame visible after adding your components.
Other notes:
See Extends JFrame vs. creating it inside the the program
UPDATE
Example with all the above mentioned points.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class SimpleDrawing {
public SimpleDrawing() {
final DrawingPanel panel = new DrawingPanel();
final JTextField field = new JTextField(15);
JButton button = new JButton("Change name");
button.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e) {
String someString = field.getText();
if (!someString.isEmpty()) {
panel.setString(someString);
}
}
});
JPanel bottomPanel = new JPanel();
bottomPanel.add(field);
bottomPanel.add(button);
JFrame frame = new JFrame();
frame.add(panel);
frame.add(bottomPanel, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public class DrawingPanel extends JPanel {
private String someString = "Stackoverflow";
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString(someString, 75, 75);
}
#Override
public Dimension getPreferredSize() {
return new Dimension (300, 100);
}
public void setString(String someString) {
this.someString = someString;
repaint();
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run() {
new SimpleDrawing();
}
});
}
}

Using java timer in JFrame

when handset button pressed I want to green button color change red.After a certain time,again
I want to green button.I dont use timer class.Please help me.
For example my code
if (e.getSource() == handsetbutton) {
text1.setBackground(Color.RED);
// What l have to add here?
}

Run this example. I use a Swing Timer and set the delay to 4 seconds. When the button is pressed, it fires an action to change the color and start the timer. When the 4 seconds is up, the color changes back
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class GreenToRed extends JPanel {
private Color color = Color.RED; // global color object
static JButton button = new JButton("Change");
private Timer timer = null;
public GreenToRed(){
timer = new Timer(4000, new ActionListener(){ // Timer 4 seconds
public void actionPerformed(ActionEvent e) {
color = Color.RED; // after 4 seconds change back to red
repaint();
}
});
button.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
color = Color.GREEN; // change to green
repaint(); // repaint
timer.start(); // start timer
}
});
}
private static void createAndShowGui() {
JFrame frame = new JFrame();
frame.add(new GreenToRed(), BorderLayout.CENTER);
frame.add(button, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(color);
g.fillOval(getWidth() / 2 - 50, getHeight() / 2 - 50, 100, 100);
}
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

JPanel wont repaint

My JPanel wont repaint, I am calling the repaint method from a loop using a thread. I am 100% sure that the loop works but when calling repaint(); nothing happens
package jgame.org.game;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class GamePanel extends JPanel implements Runnable
{
#Override
public void paint(Graphics g)
{
if (gameState == 0)
{
g.drawImage(new ImageIcon(System.getProperty("user.home")
+ "/jGame/FruitSlayer/Sprites/splash.png").getImage(), 0,
0, null);
} else
{
g.drawImage(new ImageIcon(System.getProperty("user.home")
+ "/jGame/FruitSlayer/Sprites/white.png").getImage(), 0,
0, null);
}
System.out.println("REPAINT");
}
public int currentLoopTime, gameState;
#Override
public void run()
{
while (true)
{
if (gameState != 1)
{
currentLoopTime += 1;
if (currentLoopTime == 2000)
{
gameState = 1;
}
}
repaint();
}
}
}
And my Game class:
package jgame.org.game;
import java.awt.Dimension;
import javax.swing.JFrame;
#SuppressWarnings("serial")
public class Game extends JFrame
{
public Dimension size = new Dimension(605, 625);
public Game()
{
super("Fruit Slayer");
setSize(size);
setResizable(false);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setVisible(true);
(new Thread(new GamePanel())).start();
add(new GamePanel());
}
public static void main(String[] args)
{
new Game();
}
}
REPAINT isn't printing in the console but when I add it to the loop it works perfectly. What is causing it not to call paint(Graphics); even though im using repaint();???

there are a few the remains of the ancient past, no good idea build
override public void paintComponent (Graphics g) instead of public void paint(Graphics g) for Swing JPanel
next line should be super.paint()/super.paintComponent()
don't load any Objects inside paint/paintComponent, nor FileIO (doesn't matter if is from resources) prepare Image, etc... to local variable(s)
override getPreferredSize for JPanel, otherwise painting returns zero dimension
use Swing Timer for todays Java6/7 instead of Runnable#Thread

Try this
public Game()
{
super("Fruit Slayer");
setSize(size);
setResizable(false);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setVisible(true);
GamePanel panel = new GamePanel();
(new Thread(panel)).start();
setContentPane(panel);
}