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Repainting-Thread doesn't repaint Inner-Class JPanel

I want to make a little rain program in swing, but for some reason I cannot repaint the panel from another class. I tried using an inner class for the panel this time, but it doesn't seem to work with repainting it from another class/thread. Does someone know why?
sscce:
import javax.swing.JPanel;
import javax.swing.Timer;
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.JFrame;
public class UI extends JFrame {
public static void main(String[] args) {
UI myProgram = new UI();
myProgram.setVisible(true);
}
public UI() {
this.setSize(new Dimension(500,300));
this.setBackground(Color.WHITE);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
UserPanel p = new UserPanel(this);
}
public class UserPanel extends JPanel implements ActionListener {
private Timer time = new Timer(1, this);
private UI myFrame;
public UserPanel(UI myFrame) {
this.myFrame = myFrame;
this.setSize(myFrame.getSize());
time.start();
}
#Override
public void actionPerformed(ActionEvent e) {
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("painting");
g.setColor(Color.BLACK);
g.fillRect(this.getWidth()/2, this.getHeight()/2, 50,50);
}
}
}
UI Class (with inner class JPanel):
package Rain;
import javax.swing.JPanel;
import javax.swing.Timer;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
public class UI extends JFrame {
public UI() {
this.setSize(new Dimension(500,300));
this.setBackground(Color.WHITE);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
UserPanel p = new UserPanel(this);
}
private class UserPanel extends JPanel implements ActionListener {
private Timer time = new Timer(1, this);
private UI myFrame;
private ArrayList<Raindrop> rain = new ArrayList<Raindrop>();
private static final int AMOUNT = 50;
private Random rand = new Random();
public UserPanel(UI myFrame) {
this.myFrame = myFrame;
this.setSize(myFrame.getSize());
for(int i = 0; i < AMOUNT; i++) {
createRain();
}
new Painter(this);
time.start();
}
public void createRain() {
float distance = rand.nextFloat() * 90 + 10;
int x = rand.nextInt(this.getWidth());
int y = 100;
rain.add(new Raindrop(distance,x,y));
}
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("tick");
for(Raindrop r : rain) {
r.fall();
}
}
public void paintComponent(Graphics g) {
System.out.println("painting");
g.setColor(this.getBackground());
g.fillRect(0,0,this.getWidth(),this.getHeight());
for(Raindrop r : rain) {
r.draw(g);
}
}
}
}
Painter:
package Rain;
import javax.swing.JPanel;
public class Painter extends Thread {
private JPanel p;
public Painter(JPanel p) {
this.p = p;
this.start();
}
public void run() {
while(true) {
System.out.println("trying to paint..");
p.repaint();
}
}
}
Console Output:
trying to paint..
tick
trying to paint..
tick
...
Expected Output:
trying to paint..
painting
tick
trying to paint..
...
The thread does work but it never calls the paintComponent(Graphics g) function in the panel

All Swing applications must run on their own thread, called EDT. (Hopefully, you start your application by calling SwingUtilities#invokelater method). So, repainting a component outside of Event Dispatch Thread is really bad bad (bad) idea. Instead of creating new Thread, repaint the component inside javax.swing.Timer's action listener since it will run in EDT.
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("tick");
for(Raindrop r : rain) {
r.fall();
}
repaint(); //repaint in EDT
}
Also, when you #Override paintComponent method, always start by calling super.paintComponent(g);
public void paintComponent(Graphics g) {
super.paintComponent(g);//let component get painted normally
System.out.println("painting");
g.setColor(this.getBackground());
g.fillRect(0,0,this.getWidth(),this.getHeight());
for(Raindrop r : rain) {
r.draw(g);
}
}
UPDATE after your SSCCE
In order a component to get painted, it must have a parent. You UserPanel p = new UserPanel(this); but you never add it to the frame:
UserPanel p = new UserPanel(this);
getContentPane().setLayout(new BorderLayout());
getContentPane().add(p);
The complete SSCCE:
public class UI extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> { //Run in EDT
UI myProgram = new UI();
myProgram.setVisible(true);
});
}
public UI() {
super("title");//call super for frame
this.setSize(new Dimension(500, 300));
this.setBackground(Color.WHITE);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
UserPanel p = new UserPanel(this);
//Use border layout to make p fit the whole frame
getContentPane().setLayout(new BorderLayout());
getContentPane().add(p, BorderLayout.CENTER);
}
public class UserPanel extends JPanel implements ActionListener {
private Timer time = new Timer(1, this);
private UI myFrame;
public UserPanel(UI myFrame) {
this.myFrame = myFrame;
this.setSize(myFrame.getSize());
time.start();
}
#Override
public void actionPerformed(ActionEvent e) {
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("painting");
g.setColor(Color.BLACK);
g.fillRect(this.getWidth() / 2, this.getHeight() / 2, 50, 50);
}
}
}
Don't ignore the SwingUtilities.invokeLater.

java simple bouncing ball flickers

This is just a simple red ball going up and down and i see it flickering. I already saw few subjects about that but did not find any answer that helped me.
Thank you :)
The Window class with the go method that makes the ball goes up and down.
The panel that also contains the ball positions and that just repaints.
Window.java
import java.awt.Dimension;
import javax.swing.JFrame;
public class Window extends JFrame
{
public static void main(String[] args)
{
new Window();
}
public Panel pan = new Panel();
public Window()
{
this.setSize(600, 600);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.setContentPane(pan);
this.setVisible(true);
go();
}
private void go()
{
int vecY = 1;
while (true)
{
if (pan.y <= 100)
{
vecY = 1;
}
else if (pan.y >= 400)
{
vecY = -1;
}
pan.y += vecY;
pan.repaint();
try
{
Thread.sleep(10);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
}
Panel.java
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Panel extends JPanel
{
public int x = 300;
public int y = 300;
public void paintComponent(Graphics g)
{
g.setColor(Color.white);
g.fillRect(0, 0, this.getWidth(), this.getHeight());
g.setColor(Color.red);
g.fillOval(x, y, 50, 50);
}
}

There are a number of possible issues. The primary issue is likely to be a thread race condition between your while-loop and the paintComponent method.
Your while-loop is capable of change the state of the y position before the paintComponent has a chance to paint it's state. Painting is done at the leisure of the paint sub system, so calling repaint simply makes a request to the RepaintManager which decides what and when an actual paint cycle might take place, this means that you could be dropping frames.
For most animations in Swing, a Swing Timer is more the capable. It's safe to update the UI from within, as the ActionListener is called within the context of the EDT but won't block the EDT
For example:
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.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class Window extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Window();
}
});
}
public Panel pan = new Panel();
public Window() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setContentPane(pan);
pack();
this.setLocationRelativeTo(null);
this.setVisible(true);
go();
}
private void go() {
Timer timer = new Timer(10, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
pan.updateAnmationState();
}
});
timer.start();
}
public class Panel extends JPanel {
private int x = 300;
private int y = 300;
private int vecY = 1;
public void updateAnmationState() {
if (y <= 100) {
vecY = 1;
} else if (y >= 400) {
vecY = -1;
}
y += vecY;
repaint();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.white);
g.fillRect(0, 0, this.getWidth(), this.getHeight());
g.setColor(Color.red);
g.fillOval(x, y, 50, 50);
}
}
}
This example worked fine for me on MiniMac

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, animate a still image in a JApplet

I am working on an assignment and I'm essentially done with the assignment, it was just a simple program to create an image map and add some audio to hot spots, I have a couple more days left and was going to try and "animate" the image.
It's a picture of a car dash board and when the user clicked on the ignition I was going to see if there is a way to make the image shake for a second. I've tried looking around here and on google but every time I searched I was getting articles from the 90's for applet's and not JApplet's.
If you could point my in the right direction on how to "animate" the image or even to a place where there may be tutorials I'd appreciate it!
Here is my code if you want to see what I'm talking about and can help me out in anyway.
public class ImageMap extends JApplet implements MouseListener{
private Image pic;
private Container contentPane;
private JLabel directions;
private Rectangle horn;
private Rectangle vent;
private Rectangle doorLocksUpper;
private Rectangle window;
private Rectangle radio;
private Rectangle ignition;
private int x, y;
private AudioClip hornSound, airSound, radioClip, lockSound1, lockSound2, ignitionSound;
public void init() {
pic = getImage(getCodeBase(), "CarDash.jpg");
horn = new Rectangle(250, 142, 105,104);
vent = new Rectangle(514, 159, 204, 72);
doorLocksUpper = new Rectangle(80, 167, 104, 58);
window = new Rectangle(122, 243, 88, 55);
radio = new Rectangle(514, 234, 176, 171);
ignition = new Rectangle(465, 217, 42, 43);
directions = new JLabel("CLICK ON: Horn, Door Locks, Air Vents, Radio & Ignition Push Start");
//Create components
contentPane = getContentPane();
contentPane.setLayout(new FlowLayout());
contentPane.add(directions, BorderLayout.NORTH);
contentPane.addMouseListener(this);
}
//Display image on applet window
public void paint(Graphics g) {
g.drawImage(pic, 0, 40, this);
}
public void mouseClicked(MouseEvent me) {
//Play horn clip when car horn is clicked.
if(horn.contains(me.getX(), me.getY())) {
play(getCodeBase(), "HornSound.wav");
}
if(vent.contains(me.getX(), me.getY())) {
play(getCodeBase(), "AirVent.wav");
}
if(ignition.contains(me.getX(), me.getY())) {
play(getCodeBase(), "Ignition.wav");
}
if(doorLocksUpper.contains(me.getX(), me.getY())) {
play(getCodeBase(), "DoorLocks.wav");
}
if(radio.contains(me.getX(), me.getY())) {
play(getCodeBase(), "BrownSugar.mid");
}
if(window.contains(me.getX(), me.getY())) {
play(getCodeBase(), "Window.wav");
}
}
public void mouseReleased(MouseEvent me) {}
public void mouseEntered(MouseEvent me) {}
public void mouseExited(MouseEvent me) {}
public void mousePressed(MouseEvent me) {}
}

Here's a really quick and useful tip, don't paint directly to a top level container like a applet. It traps you into a single use case, which doesn't always make it easier to modify or re-use.
Instead, start by using something like a JPanel as your primary container, with this, you can add it to what ever you like, applet, window, some other container.
While there are a number of ways you can do animation in Swing, one of the simplest (and generally safest) is to use a Swing Timer.
This example simply uses a Swing Timer, set to update every 16ms (which is to fast for my capture software :P) which is started when you click the panel. The timer simply updates a offset value which isolates between a positive and negative value. The Timer makes use of LocalTime to calculate the length of time the Timer has been running at stops it after one second
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
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.IOException;
import java.time.Duration;
import java.time.LocalTime;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ShakeAnimation {
public static void main(String[] args) {
new ShakeAnimation();
}
public ShakeAnimation() {
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 ShakePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class ShakePane extends JPanel {
private Timer timer;
private LocalTime startTime;
private int xOffset = 0;
private int delta = 8;
private BufferedImage img;
public ShakePane() {
try {
img = ImageIO.read(getClass().getResource("Duke-Thumbs.jpg"));
} catch (IOException exp) {
exp.printStackTrace();
}
timer = new Timer(16, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Duration duration = Duration.between(startTime, LocalTime.now());
if (duration.getSeconds() >= 1) {
timer.stop();
xOffset = 0;
} else {
xOffset *= -1;
}
repaint();
}
});
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
if (!timer.isRunning()) {
xOffset = delta;
startTime = LocalTime.now();
timer.start();
}
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
Graphics2D g2d = (Graphics2D) g.create();
int x = ((getWidth() - img.getWidth()) / 2) + xOffset;
int y = (getHeight() - img.getHeight()) / 2;
g2d.drawImage(img, x, y, this);
g2d.dispose();
}
}
}
}
See How to use Swing Timers for more details

Repaint without painting every component again

i have an application containing a jframe, this jframe then adds a jpanel which constains an image. the jpanel is displayed for a given time, then removed from the jframe and another jpanel is added.
I want to fade in and out between the images, and ive done this using a timer
private void fadeOut() {
ActionListener fadeOutAc = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
opacity += 10;
if (opacity >= 255) {
opacity = 255;
fadeOutT.stop();
}
repaint();
}
};
fadeOutT = new Timer(20, fadeOutAc);
fadeOutT.start();
}
private void fadeIn() {
ActionListener fadeInAc = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
opacity -= 10;
if (opacity <= 0) {
opacity = 0;
fadeInT.stop();
}
repaint();
}
};
fadeInT = new Timer(10, fadeInAc);
fadeInT.setInitialDelay(200);
fadeInT.start();
}
public void paint(Graphics g) {
super.paintComponent(g);
g.setColor(new Color(picColor.getRed(), picColor.getGreen(), picColor.getBlue(), opacity));
g.fillRect(0, 0, presWin.getWidth(), presWin.getHeight());
}
i recently moved the fading in/out from the jpanel to the jframe instead. The problem is, that in the jpanel, the repaint only had to draw an image, now it has to repaint the entire jpanel each time. Is there a way to call repaint without having the paint the components, only the rectangel?

To me, it seems a bit silly to put the functionality in the JFrame when what you seem to want is a container which can fade it's content in and out. This way you can isolate the responsibility to a single container/class which can be placed or used in what ever way you want in isolation to the rest of the UI.
Basically, this example uses a FadingPane (based on a JPanel) to control the fading process, but onto which I place JLabel which holds the actual images.
Fading is controlled through the use of a AlphaComposite, meaning that this panel will actually physically fade in and out, not just change fill color ;)
There is also a FadingListener which provides additional notifications about the fading process, really only interested in fadeOutDidComplete, so you can switch the images and fade the panel back in, but you never know...
import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
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 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("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JLabel label;
private FadingPane fadingPane;
private File[] pictures;
private int index;
public TestPane() {
// Just for show
setBackground(Color.RED);
fadingPane = new FadingPane(new FadeListener() {
#Override
public void fadeDidStart(FadingPane panel) {
}
#Override
public void fadeDidStop(FadingPane panel) {
}
#Override
public void fadeOutDidComplete(FadingPane panel) {
nextPicture();
fadingPane.fadeIn();
}
#Override
public void fadeInDidComplete(FadingPane panel) {
}
});
setLayout(new BorderLayout());
fadingPane.setLayout(new BorderLayout());
label = new JLabel();
fadingPane.add(label);
add(fadingPane);
JButton next = new JButton("Next");
add(next, BorderLayout.SOUTH);
next.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
fadingPane.fadeOut();
}
});
pictures = new File("/Volumes/Disk02/Dropbox/MegaTokyo/thumnails").listFiles(new FileFilter() {
#Override
public boolean accept(File pathname) {
String name = pathname.getName().toLowerCase();
return name.endsWith(".jpg") || name.endsWith(".png");
}
});
nextPicture();
}
protected void nextPicture() {
index++;
if (index >= pictures.length) {
index = 0;
}
try {
BufferedImage img = ImageIO.read(pictures[index]);
label.setIcon(new ImageIcon(img));
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
public interface FadeListener {
public void fadeDidStart(FadingPane panel);
public void fadeDidStop(FadingPane panel);
public void fadeOutDidComplete(FadingPane panel);
public void fadeInDidComplete(FadingPane panel);
}
public class FadingPane extends JPanel {
private float delta;
private float alpha = 1f;
private Timer timer;
private FadeListener fadeListener;
public FadingPane(FadeListener fadeListener) {
this.fadeListener = fadeListener;
// This is important, as we may not always be opaque
// and we don't want to stuff up the painting process
setOpaque(false);
timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
float alpha = getAlpha() + delta;
if (alpha < 0.001f) {
alpha = 0f;
timer.stop();
fadeListener.fadeOutDidComplete(FadingPane.this);
} else if (alpha >= 1.0f) {
alpha = 1.0f;
timer.stop();
fadeListener.fadeInDidComplete(FadingPane.this);
}
setAlpha(alpha);
}
});
}
public float getAlpha() {
return alpha;
}
public void setAlpha(float value) {
if (alpha != value) {
this.alpha = Math.min(1.0f, Math.max(0.0f, value));
repaint();
}
}
#Override
public void paint(Graphics g) {
// I don't normally recomamned overriding paint, but in this case,
// I want to affect EVERYTHING that might be added to this panel
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.SrcOver.derive(getAlpha()));
super.paint(g2d);
g2d.dispose();
}
public void fadeIn() {
timer.stop();
fadeListener.fadeDidStop(FadingPane.this);
delta = 0.05f;
timer.restart();
fadeListener.fadeDidStart(FadingPane.this);
}
public void fadeOut() {
timer.stop();
fadeListener.fadeDidStop(FadingPane.this);
delta = -0.05f;
timer.restart();
fadeListener.fadeDidStart(FadingPane.this);
}
}
}

Thats totaly normal, moving your function to the JFrame and calling repaint function would actualy call repaint of your JFrame.
I think the best solution would be to pass panel as an argument to your fadeIn and fadeOut function and call its repaint methode for example fadeIn :
private void fadeIn(JPanel panelParam) {
ActionListener fadeInAc = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
opacity -= 10;
if (opacity <= 0) {
opacity = 0;
fadeInT.stop();
}
panelParam.repaint(); // here call repaint of the panel.
}
};
fadeInT = new Timer(10, fadeInAc);
fadeInT.setInitialDelay(200);
fadeInT.start();
}
With that you can apply your effect on any other panel.
Hope it helped.