We Keep Coding

i can't see circle moving

While using Swing in java, I am trying to move a circle slowly from a starting position to an end position when clicking a button. However, I can't see the circle moving. It just moves from start to end in an instant.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class MyApp {
private int x = 10;
private int y = 10;
private JFrame f;
private MyDraw m;
private JButton b;
public void go() {
f = new JFrame("Moving circle");
b = new JButton("click me to move circle");
m = new MyDraw();
f.add(BorderLayout.SOUTH, b);
f.add(BorderLayout.CENTER, m);
f.setSize(500, 500);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
b.addActionListener(new Bute());
}
public static void main(String[] args) {
MyApp m = new MyApp();
m.go();
}
private class Bute implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
for (int i = 0; i < 150; i++) {
++x;
++y;
m.repaint();
Thread.sleep(50);
}
}
}
private class MyDraw extends JPanel {
#Override
public void paintComponent(Graphics g) {
g.setColor(Color.white);
g.fillRect(0, 0, 500, 500);
g.setColor(Color.red);
g.fillOval(x, y, 40, 40);
}
}
}
I think the problem is with the action listener because when I'm doing it without using button it is working. Any suggestions?

As Andrew Thompson said, calling Thread.sleep() without defining a second thread freezes everything, so the solution is to define and run another thread like so:
class Bute implements ActionListener, Runnable {
//let class implement Runnable interface
Thread t; // define 2nd thread
public void actionPerformed(ActionEvent e) {
t = new Thread(this); //start a new thread
t.start();
}
#Override //override our thread's run() method to do what we want
public void run() { //this is after some java-internal init stuff called by start()
//b.setEnabled(false);
for (int i = 0; i < 150; i++) {
x++;
y++;
m.repaint();
try {
Thread.sleep(50); //let the 2nd thread sleep
} catch (InterruptedException iEx) {
iEx.printStackTrace();
}
}
//b.setEnabled(true);
}
}
The only problem with this solution is that pressing the button multiple times will speed up the circle, but this can be fixed by making the button unclickable during the animation via b.setEnabled(true/false). Not the best solution but it works.

As said in the comments and another answer, don't block the EDT. Thead.sleep(...) will block it, so you have two options:
Create and manage your own (new) thread.
Use a Swing Timer
In this answer I'll be using a Swing Timer, since it's easier to use. I also changed the paintComponent method to use the Shape API and change the button text to start and stop accordingly as well as reusing the same ActionListener for the button and the timer:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class MovingCircle {
private JFrame frame;
private CustomCircle circle;
private Timer timer;
private JButton button;
public static void main(String[] args) {
SwingUtilities.invokeLater(new MovingCircle()::createAndShowGui);
}
private void createAndShowGui() {
frame = new JFrame(this.getClass().getSimpleName());
circle = new CustomCircle(Color.RED);
timer = new Timer(100, listener);
button = new JButton("Start");
button.addActionListener(listener);
circle.setBackground(Color.WHITE);
frame.add(circle);
frame.add(button, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private ActionListener listener = (e -> {
if (!timer.isRunning()) {
timer.start();
button.setText("Stop");
} else {
if (e.getSource().equals(button)) {
timer.stop();
button.setText("Start");
}
}
circle.move(1, 1);
});
#SuppressWarnings("serial")
class CustomCircle extends JPanel {
private Color color;
private int circleX;
private int circleY;
public CustomCircle(Color color) {
this.color = color;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(color);
g2d.fill(new Ellipse2D.Double(circleX, circleY, 50, 50));
}
#Override
public Dimension preferredSize() {
return new Dimension(100, 100);
}
public void move(int xGap, int yGap) {
circleX += xGap;
circleY += yGap;
revalidate();
repaint();
}
public int getCircleX() {
return circleX;
}
public void setCircleX(int circleX) {
this.circleX = circleX;
}
public int getCircleY() {
return circleY;
}
public void setCircleY(int circleY) {
this.circleY = circleY;
}
}
}
I'm sorry, I can't post a GIF as I wanted but this example runs as expected.

Java Fade In and Out two JPanels at the same time

I have a list of JPanels that I want to display as a "slideshow" where one JPanel fades out and the next JPanel in the list fades in. This is the code I am fiddling with:
public float opacity = 0f;
private Timer fadeTimer;
private boolean out;
public void fadeIn()
{
out = false;
beginFade();
}
public void fadeOut ()
{
out = true;
beginFade();
}
private void beginFade()
{
fadeTimer =
new javax.swing.Timer(75,this);
fadeTimer.setInitialDelay(0);
fadeTimer.start();
}
public void actionPerformed(ActionEvent e)
{
if (out)
{
opacity -= .03;
if(opacity < 0)
{
opacity = 0;
fadeTimer.stop();
fadeTimer = null;
}
}
else
{
opacity += .03;
if(opacity > 1)
{
opacity = 1;
fadeTimer.stop();
fadeTimer = null;
}
}
repaint();
}
public void paintComponent(Graphics g)
{
((Graphics2D) g).setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity));
g.setColor(getBackground());
g.fillRect(0,0,getWidth(),getHeight());
}
The problem is that it fades some times, and other times it does not, and other times the transition is very laggy. What I would prefer is that there is a fraction of a second where the screen goes white, between when one JPanel fades out and the next JPanel fades in. Does anyone know how I can solve this? Thanks in advance.

So, when dealing with these types of problems, it's generally a better idea to reduce the number of Timers you have, as each timer will be posting multiple events to the Event Dispatching Queue (there own tick updates as well as repaint events). All this activity could reduce the performance of the system.
Animation is also the illusion of change over time, to this end, rather the trying to loop from a start point to an end point, you should decide how long you want the animation to run for and calculate the progress of time and update the values accordingly (this more of a "timeline" based animation cycle). This can help reduce the appearance of "lagging"
Normally I'd use the Timing Framework to accomplish this, but you could also have a look at the Trident framework or the Universal Tween Engine which also provide complex animation support for Swing.
This example is very tightly coupled to it's goal. Personally, I'd normally have a abstract concept of an "animatiable" object, which would probably just have the update(float) method, which would then be expanded to support other objects, but I'll leave that you to nut out.
Another issue is making sure that the component is fully transparent to begin with (setOpaque(false)), this allows us to fake the translucency of the component during the animation.
Normally, I'd always encourage you to override paintComponent, but there a few times when this is not adequate, this is one of them. Basically, in order to facilitate the transition from one component to the other, we need to control the alpha level of ALL the child components within the component, this is when overriding paint will be a better choice.
nb: The code is set to run at around 25fps, but the screen capture software captures at roughly 8fps
import java.awt.AlphaComposite;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class FadeTest {
public static void main(String[] args) {
new FadeTest();
}
public FadeTest() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
BufferedImage img1 = ImageIO.read(new File("C:\\Users\\shane\\Dropbox\\Ponies\\sillydash-small.png"));
BufferedImage img2 = ImageIO.read(new File("C:\\Users\\shane\\Dropbox\\Ponies\\SmallPony.png"));
AlphaPane pane1 = new AlphaPane();
pane1.add(new JLabel(new ImageIcon(img1)));
pane1.setAlpha(1f);
AlphaPane pane2 = new AlphaPane();
pane2.add(new JLabel(new ImageIcon(img2)));
pane2.setAlpha(0f);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 1;
gbc.gridy = 1;
gbc.weightx = 1;
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
frame.add(pane1, gbc);
frame.add(pane2, gbc);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
MouseAdapter ma = new MouseAdapter() {
private AnimationController controller;
#Override
public void mouseClicked(MouseEvent e) {
try {
if (controller != null) {
controller.stop();
}
controller = new AnimationController(4000);
boolean fadeIn = pane1.getAlpha() < pane2.getAlpha();
controller.add(controller.new AlphaRange(pane1, fadeIn));
controller.add(controller.new AlphaRange(pane2, !fadeIn));
controller.start();
} catch (InvalidStateException ex) {
ex.printStackTrace();
}
}
};
pane1.addMouseListener(ma);
pane2.addMouseListener(ma);
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
}
public class AnimationController {
private List<AlphaRange> animationRanges;
private Timer timer;
private Long startTime;
private long runTime;
public AnimationController(int runTime) {
this.runTime = runTime;
animationRanges = new ArrayList<>(25);
}
public void add(AlphaRange range) {
animationRanges.add(range);
}
public void start() throws InvalidStateException {
if (timer == null || !timer.isRunning()) {
timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (startTime == null) {
startTime = System.currentTimeMillis();
}
long duration = System.currentTimeMillis() - startTime;
float progress = (float) duration / (float) runTime;
if (progress > 1f) {
progress = 1f;
stop();
}
System.out.println(NumberFormat.getPercentInstance().format(progress));
for (AlphaRange range : animationRanges) {
range.update(progress);
}
}
});
timer.start();
} else {
throw new InvalidStateException("Animation is running");
}
}
public void stop() {
if (timer != null) {
timer.stop();
}
}
public class AlphaRange {
private float from;
private float to;
private AlphaPane alphaPane;
public AlphaRange(AlphaPane alphaPane, boolean fadeIn) {
this.from = alphaPane.getAlpha();
this.to = fadeIn ? 1f : 0f;
this.alphaPane = alphaPane;
}
public float getFrom() {
return from;
}
public float getTo() {
return to;
}
public float getValueBasedOnProgress(float progress) {
float value = 0;
float distance = to - from;
value = (distance * progress);
value += from;
return value;
}
public void update(float progress) {
float alpha = getValueBasedOnProgress(progress);
alphaPane.setAlpha(alpha);
}
}
}
public class InvalidStateException extends Exception {
public InvalidStateException(String message) {
super(message);
}
public InvalidStateException(String message, Throwable cause) {
super(message, cause);
}
}
public class AlphaPane extends JPanel {
private float alpha;
public AlphaPane() {
setOpaque(false);
}
#Override
public void paint(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.SrcOver.derive(alpha));
super.paint(g2d);
g2d.dispose();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Fake the background
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
}
public void setAlpha(float value) {
if (alpha != value) {
this.alpha = Math.min(1f, Math.max(0, value));
repaint();
}
}
public float getAlpha() {
return alpha;
}
}
}

How does repaint() method behave inside an infinite for loop?

I have this code,
import java.awt.*;
import java.applet.*;
public class FirstApplet extends Applet
{
int len;
char ch;
String msg="Hello World ";
public void init()
{
setBackground(Color.CYAN);
setForeground(Color.WHITE);
}
public void start()
{
System.out.println("Inside Start");
repaint();
}
public void paint(Graphics g)
{
System.out.println("Inside paint");
g.drawString(msg,200,200);
}
}
It outputs a CYAN coloured background with Hello World on it.And on the console(cmd),it outputs-
Inside Start
Inside paint
Now if I modify the code to this-
import java.awt.*;
import java.applet.*;
public class FirstApplet extends Applet
{
String msg="Hello World ";
int len;
char ch;
public void init()
{
setBackground(Color.CYAN);
setForeground(Color.WHITE);
}
public void start()
{
System.out.println("Inside Start");
for(;;)
{
repaint();
}
}
public void paint(Graphics g)
{
System.out.println("Inside paint");
g.drawString(msg,200,200);
}
}
It outputs a white coloured screen with no text on it,and on the console it just outputs-
Inside Start
I am unable to understand the output of second program,Although I am calling the repaint() inside the for loop every time yet why the colour of the applet window is not changing to CYAN colour and why its not printing "Inside paint" on the console?Can somebody please help me out.

You're tying up the GUI's event thread with your infinite loop, so that although repaint() is being called, the GUI's event thread is unable to act on it. Consider using a Swing Timer or a background thread instead.
For example, and continuing with your 1890's Applet example:
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.*;
public class PaintEg extends Applet {
String msg = "Hello World ";
int len;
char ch;
public void init() {
setBackground(Color.CYAN);
setForeground(Color.WHITE);
}
public void start() {
System.out.println("Inside Start");
new Thread(new Runnable() {
public void run() {
for (;;) {
repaint();
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
public void paint(Graphics g) {
System.out.println("Inside paint");
g.drawString(msg, 10, 20);
}
}
Better maybe is a Swing example that uses a Swing Timer and performs basic animation:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class PaintEg2 extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = PREF_W;
private static final int TIMER_DELAY = 30;
private String msg = "Hello World ";
private int msgX = 0;
private int msgY = 0;
public PaintEg2() {
setBackground(Color.CYAN);
setForeground(Color.WHITE);
setFont(new Font(Font.SANS_SERIF, Font.BOLD, 20));
new Timer(TIMER_DELAY, new TimerListener()).start();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString(msg, msgX, msgY);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
msgX++;
msgY++;
repaint();
}
}
private static void createAndShowGui() {
PaintEg2 mainPanel = new PaintEg2();
JFrame frame = new JFrame("PaintEg2");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Note that in your code repaint() is being called and is being executed, but the paint manager is unable to act on this because it does so on the GUI's event thread. If the GUI's event thread is tied up, no painting can be done.
For more on how painting is done in Swing and AWT, please read Painting in AWT and Swing

java graphics isn't drawing anything

The program draws a bunch of rectangles for a bar graph. I know the bar class works perfectly fine because I've got it working before adding in the graph panel class. I was drawing straight onto the frame instead of the graph panel. I assume its a problem in the way my set visible methods are called as it was pointed out to me before. I tried looking into it but I've had no luck after playing around and reading documentation.
import java.awt.Color;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.util.concurrent.Semaphore;
#SuppressWarnings("serial")
public class GraphPanel extends JPanel {
private ArrayList<Bar> graphBars;
private int nBars;
public GraphPanel(int nBars, JFrame mainFrame) {
this.setSize(400, 400);
this.graphBars = new ArrayList<Bar>(nBars);
this.nBars = nBars;
this.initBars(mainFrame.getWidth());
for(Bar b: this.graphBars) {
this.add(b);
}
}
private void initBars(int frameW) {
Random random = new Random();
float hue;
Color color;
int barPadding = frameW/this.nBars;
for(int i = 0; i < this.nBars; i++) {
hue = random.nextFloat();
color = Color.getHSBColor(hue, 0.9f, 1.0f);
this.graphBars.add(new Bar(i*barPadding + 30, 350, color));
}
}
public ArrayList<Bar> getBarList() {
return this.graphBars;
}
}
#SuppressWarnings("serial")
public class Bar extends JPanel implements Runnable {
int height = 0;
Color barColor;
Rectangle bar;
private final int WIDTH = 20;
Thread bartender;
private Semaphore s;
public Bar(int x, int y, Color barColor) {
this.barColor= barColor;
this.bar = new Rectangle(x, y, this.WIDTH, this.height);
this.bartender= new Thread(this);
this.s = new Semaphore(1);
}
public boolean setNewHeight(int h) {
try {
this.s.acquire();
this.height = h;
this.s.release();
return true;
} catch (InterruptedException e) {
e.printStackTrace();
return false;
}
}
#SuppressWarnings("deprecation")
public void update() {
if (this.bar.height < this.height) {
bar.reshape(this.bar.x, --this.bar.y, this.bar.width, ++this.bar.height);
} else {
bar.reshape(this.bar.x, ++this.bar.y, this.bar.width, --this.bar.height);
}
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(this.barColor);
g2d.fill(this.bar);
}
#SuppressWarnings("deprecation")
public void callBarTender() {
this.bartender.resume();
}
#SuppressWarnings("deprecation")
#Override
public void run() {
System.out.println("sdf");
while(true) {
if (this.bar.height < this.height) {
for(int i = this.bar.height; i<this.height; i++ ) {
try {
update();
repaint();
Thread.sleep(15);
} catch(Exception e) {
System.out.println(e);
}
}
} else if (this.height < this.bar.height) {
for(int i = this.bar.height; i>this.height; i-- ) {
try {
update();
repaint();
Thread.sleep(15);
} catch(Exception e) {
System.out.println(e);
}
}
}
this.bartender.suspend();
}
}
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(400, 400);
frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GraphPanel gPane = new GraphPanel(3, frame);
frame.add(gPane);
gPane.getBarList().get(0).setVisible(true);
gPane.getBarList().get(1).setVisible(true);
gPane.getBarList().get(2).setVisible(true);
gPane.setVisible(true);
frame.setVisible(true);
gPane.getBarList().get(0).setNewHeight(100);
gPane.getBarList().get(1).setNewHeight(100);
gPane.getBarList().get(2).setNewHeight(100);
gPane.getBarList().get(0).bartender.start();
gPane.getBarList().get(1).bartender.start();
gPane.getBarList().get(2).bartender.start();
}

You should override getPreferredSize of your GraphPanel to ensure that they are laid out correctly
The x/y positions you are passing to the Bar class are irrelevant, as this is causing your Rectangle to paint outside of the visible context of the Bar pane. Painting is done from within the context of the component (0x0 been the top/left corner of the component)
The use of Rectangle or the way you are using it, is actually causing issues. It's impossible to know exactly how big you component will be until it's layed or painted
There is a reason why resume and suspend are deprecated, this could cause no end of "weird" (and wonderful) issues
Take a look at Laying Out Components Within a Container for why you're bars aren't been updated correctly and why the x/y coordinates are pointless
Take a look at How to use Swing Timers for an alternative to your use of Thread
Possibly, something more like...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame();
frame.setSize(400, 400);
// frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GraphPanel gPane = new GraphPanel(3, frame);
frame.add(gPane);
gPane.getBarList().get(1).setFill(false);
gPane.getBarList().get(0).start();
gPane.getBarList().get(1).start();
gPane.getBarList().get(2).start();
frame.setVisible(true);
}
});
}
public class GraphPanel extends JPanel {
private ArrayList<Bar> graphBars;
private int nBars;
public GraphPanel(int nBars, JFrame mainFrame) {
this.graphBars = new ArrayList<Bar>(nBars);
this.nBars = nBars;
this.initBars(mainFrame.getWidth());
for (Bar b : this.graphBars) {
this.add(b);
}
}
private void initBars(int frameW) {
Random random = new Random();
float hue;
Color color;
for (int i = 0; i < this.nBars; i++) {
hue = random.nextFloat();
color = Color.getHSBColor(hue, 0.9f, 1.0f);
this.graphBars.add(new Bar(color));
}
}
public ArrayList<Bar> getBarList() {
return this.graphBars;
}
}
#SuppressWarnings("serial")
public class Bar extends JPanel {
private Color barColor;
private boolean fill = true;
private float fillAmount = 0;
private float delta = 0.01f;
private Timer timer;
private Rectangle bar;
public Bar(Color barColor) {
bar = new Rectangle();
setBorder(new LineBorder(Color.RED));
this.barColor = barColor;
timer = new Timer(15, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
fillAmount += isFill() ? delta : -delta;
// System.out.println(fillAmount);
if (fillAmount < 0) {
fillAmount = 0;
((Timer) e.getSource()).stop();
} else if (fillAmount > 1.0f) {
fillAmount = 1f;
((Timer) e.getSource()).stop();
}
repaint();
}
});
}
public void start() {
timer.start();
}
public void stop() {
timer.stop();
}
public void setFill(boolean fill) {
this.fill = fill;
if (!timer.isRunning()) {
if (fill && fillAmount == 1) {
fillAmount = 0;
} else if (!fill && fillAmount == 0) {
fillAmount = 1;
}
}
}
public boolean isFill() {
return fill;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(20, 100);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(this.barColor);
int height = Math.round(getHeight() * fillAmount);
bar.setSize(getWidth(), height);
bar.setLocation(0, getHeight() - height);
g2d.fill(bar);
g2d.dispose();
}
}
}

Java graphic not painting properly

I've written the following code
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
final public class Test
{
JFrame frame;
DrawPanel drawPanel;
boolean up = false;
boolean down = true;
boolean left = false;
boolean right = true;
private int timeStep = 0;
private int ballYTravel = 100;
private int BALL_NUM = 24;
public static void main(String... args)
{
new Test().go();
}
private void go()
{
frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
drawPanel = new DrawPanel();
frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
frame.setResizable(false);
frame.setSize(800, 600);
frame.setLocationByPlatform(true);
frame.setVisible(true);
moveIt();
}
class DrawPanel extends JPanel
{
private static final long serialVersionUID = 1L;
public double getY(int i, int t) {
return 200 + ballYTravel / 2 * (Math.sin(timeStep * (i / 200 + 0.08)));
}
public void paintComponent(Graphics g)
{
for (int k = 0; k < BALL_NUM; k++ ) {
g.fillRect(100 + 20 *k , (int) getY(k, timeStep), 6, 6);
}
timeStep++;
}
}
private void moveIt()
{
while (true)
{
try
{
Thread.sleep(10);
}
catch (Exception e)
{
e.printStackTrace();
}
frame.repaint();
}
}
}
It runs and animates, however it is not animating in the same fashion as the Javascript code I referenced it from which can be found here http://codepen.io/anon/pen/ZYQoQZ
any help in understanding why is appreciated

There are (possibly) two basic problems...
In getY, you are ignoring the parameter t and using timeStep instead, while, technically, this probably isn't going to make a MASSIVE difference, it is an area of concern
You have an integer division issue. i/200 will result in int result, where you really want a double. Change it to i/200d
For example...
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.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
final public class Test {
private int timeStep = 0;
private final int ballYTravel = 100;
private final int BALL_NUM = 24;
public static void main(String... args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new DrawPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
class DrawPanel extends JPanel {
private static final long serialVersionUID = 1L;
public DrawPanel() {
new Timer(10, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
timeStep++;
repaint();
}
}).start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 200);
}
public double getY(int i, int t) {
return 100 + ballYTravel / 2 * (Math.sin(t * (i / 200d + 0.08)));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
for (int k = 0; k < BALL_NUM; k++) {
g.fillRect(10 + 20 * k, (int) getY(k, timeStep), 6, 6);
}
}
}
}
You're also breaking the paint chain, which is going to cause you issues in the long run, make sure you are calling super.paintComponent...
For more details see...
Performing Custom Painting
Painting in AWT and Swing
Concurrency in Swing
How to use Swing Timers
Initial Threads

Your transliteration reveals several problems:
Swing GUI objects should be constructed and manipulated only on the event dispatch thread.
Don't use setSize() when you really mean to override getPreferredSize().
Invoke pack() to let the container adopt its preferred size.
Use javax.swing.Timer to pace the animation.
Revised code, incorporating #Mad's fix and using drawOval():
import java.awt.BorderLayout;
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.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
final public class Test {
JFrame frame;
DrawPanel drawPanel;
private int timeStep = 0;
private int ballYTravel = 100;
private int BALL_NUM = 24;
public static void main(String... args) {
new Test().go();
}
private void go() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
drawPanel = new DrawPanel();
frame.add(BorderLayout.CENTER, drawPanel);
frame.setResizable(false);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
Timer t = new Timer(10, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
drawPanel.repaint();
}
});
t.start();
}
});
}
private class DrawPanel extends JPanel {
public double getY(int i, int t) {
return 200 + ballYTravel / 2 * (Math.sin(t * (i / 200d + 0.08)));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
for (int k = 0; k < BALL_NUM; k++) {
g.drawOval(100 + 20 * k, (int) getY(k, timeStep), 8, 8);
}
timeStep++;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(700, 500);
}
}
}