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paintComponent not called when I scroll both Horizontal and Vertical scrollbars in a JScrollPane

I am having trouble with Swing and the JScrollPane.
I am having a strange behaviour.
I extended JScrollPane. I display an image in it and draw rectangles over it to define areas.
With a big image, I have an Horizontal and a Vertical scrollbars.
I - ok - When I move one scrollbar or the other I see my image move too as it should.
II - not ok - When I move one scrollbar an leave it in between max and min position, then when I move my second scrollbar my image disappears.
With some debug prints, I found out that paintComponent, is not called when in case II.
I would like to know why it is not calling paintComponent and how I can fix it.
Here below is my class:
package GUI;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import javax.swing.JScrollPane;
public class DrawingPanel extends JScrollPane {
private static final long serialVersionUID = 1L;
private static final Color DRAWING_COLOR = new Color(255, 100, 200);
private static final Color FINAL_DRAWING_COLOR = Color.red;
private static final double ZOOMING_STEP = 1.1;
private Image sImg;
private Point startPt;
private Point endPt;
private Point currentPt;
private int prefW;
private int prefH;
private double zoomFactor = 1;
private boolean zoomer = false;
private boolean loaded = false;
public DrawingPanel() {
setFocusable(true);
setFocusTraversalKeysEnabled(false);
}
public void loadImage(Image img) {
sImg = img;
prefW = sImg.getWidth(null);
prefH = sImg.getHeight(null);
zoomFactor = getSize().getWidth() / prefW;
zoomer = true;
loaded = true;
repaint();
revalidate();
}
int countPaint = 0;
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("paintComponent " + countPaint);
if (loaded) {
int zoomWidth = (int) (prefW * zoomFactor);
int zoomHeight = (int) (prefH * zoomFactor);
if (zoomer) {
((Graphics2D) g).scale(zoomFactor, zoomFactor);
setSize(zoomWidth, zoomHeight);
zoomer = false;
}
g.drawImage(sImg, 0, 0, zoomWidth, zoomHeight, null);
drawRectangle(g);
}
g.dispose();
countPaint++;
}
#Override
public Dimension getPreferredSize() {
return loaded ?
this.getSize() :
new Dimension((int) (prefW*zoomFactor), (int) (prefH*zoomFactor));
}
private void drawRectangle(Graphics g) {
Point secondPoint = (currentPt != null) ? currentPt : endPt;
Color color = (currentPt != null) ? DRAWING_COLOR : FINAL_DRAWING_COLOR;
if (startPt!=null && secondPoint!=null) {
int x = Math.min(startPt.x, secondPoint.x);
int y = Math.min(startPt.y, secondPoint.y);
int rectangleWidth = Math.abs(startPt.x - secondPoint.x);
int rectangleHeight = Math.abs(startPt.y - secondPoint.y);
g.setColor(color);
g.drawRect(x, y, rectangleWidth, rectangleHeight);
}
}
public void deleteRectangle(){
startPt = null;
endPt = null;
}
public void increaseZoom(Point p) {
double oldZoom = zoomFactor;
zoomFactor *= ZOOMING_STEP;
repositonPointAfterZoom(oldZoom, zoomFactor);
}
public void decreaseZoom(Point p) {
double oldZoom = zoomFactor;
zoomFactor /= ZOOMING_STEP;
repositonPointAfterZoom(oldZoom, zoomFactor);
}
public void repositonPointAfterZoom(double oldZoom, double newZoom) {
double evolution = newZoom/oldZoom;
if (startPt!=null) {
startPt.setLocation(startPt.x * evolution, startPt.y * evolution);
}
if (endPt!=null) {
endPt.setLocation(endPt.x * evolution, endPt.y * evolution);
}
repaint();
}
// Getter et setter
public void setStartPt(Point startPt) {
this.startPt = startPt;
}
public void setEndPt(Point endPt) {
this.endPt = endPt;
}
public void setCurrentPt(Point currentPt) {
this.currentPt = currentPt;
}
public int getZoomCalculateX(int value){
return (int) (value / zoomFactor);
}
public int getZoomCalculateY(int value){
return (int) (value / zoomFactor);
}
public void setZoomer(boolean zoomer) {
this.zoomer = zoomer;
}
}
EDIT : Bellow is the class (simplified) that uses DrawingPanel so you can have a reproducible exemple.
package GUI;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import org.apache.commons.io.FilenameUtils;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import fileHandler.*;
public class GUI {
private JFrame frame;
private MenuBar menubar;
private DrawingPanel panelImage;
private JScrollPane scroll;
private GroundTruth openFile;
private int[] panelImageDown = new int[2];
private int[] panelImageUp = new int[2];
private Menu CoordinateMenu1 = new Menu();
private Menu CoordinateMenu2 = new Menu();
private int actualPagePdf;
private PDFRenderer renderer;
public static void main(String[] args) throws IOException {
new GUI();
}
public GUI() throws IOException {
JFrame frame = CreateFrame();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private JFrame CreateFrame() throws IOException {
frame = new JFrame();
frame.setMenuBar(CreateMenuBar());
frame.setContentPane(SplitScreen());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("GTA - Ground Truth Annotator");
frame.setExtendedState(frame.getExtendedState() | JFrame.MAXIMIZED_BOTH);
return frame;
}
private MenuBar CreateMenuBar() {
menubar = new MenuBar();
menubar.add(CreateFileMenu());
menubar.add(new Menu("Selection coordinates:"));
menubar.add(CoordinateMenu1);
menubar.add(new Menu("Width/Height:"));
menubar.add(CoordinateMenu2);
return menubar;
}
private Menu CreateFileMenu() {
Menu mFile = new Menu("File");
MenuItem miOpenImage = new MenuItem("Open Image/PDF File");
mFile.add(miOpenImage);
miOpenImage.addActionListener(OpenFileActionListener);
mFile.addSeparator();
MenuItem miExit = new MenuItem("Exit Program");
mFile.add(miExit);
miExit.addActionListener(ExitActionListener);
return mFile;
}
private JPanel SplitScreen() throws IOException {
JPanel splittedScreen = new JPanel(new GridLayout(1, 2));
splittedScreen.add(CreateLeftPanel());
splittedScreen.add(CreateRightPanel());
return splittedScreen;
}
private JLayeredPane CreateLeftPanel() throws IOException {
JLayeredPane panel = new JLayeredPane();
panel.setLayout(new BorderLayout());
panel.setBorder(BorderFactory.createLineBorder(Color.gray));
panel.add(CreateImageScrollPane());
return panel;
}
private JScrollPane CreateImageScrollPane() throws IOException {
scroll = new JScrollPane(CreateImagePanel((String) null));
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
scroll.getViewport().setScrollMode(JViewport.BLIT_SCROLL_MODE);
return scroll;
}
private DrawingPanel CreateImagePanel(String path) throws IOException {
if (panelImage == null) {
panelImage = new DrawingPanel();
}
if (path != null) {
panelImage.loadImage(ImageIO.read(new File(path)));
}
panelImage.addMouseListener(PanelImageMouseListener);
panelImage.addMouseWheelListener(PanelImageMouseWheelListener);
panelImage.addMouseMotionListener(PanelImageMouseMotionAdapter);
panelImage.setOpaque(false);
panelImage.revalidate();
panelImage.repaint();
panelImage.requestFocus();
return panelImage;
}
private DrawingPanel CreateImagePanel(Image image) throws IOException {
if (panelImage == null) {
panelImage = new DrawingPanel();
}
panelImage.loadImage(image);
panelImage.addMouseListener(PanelImageMouseListener);
panelImage.addMouseWheelListener(PanelImageMouseWheelListener);
panelImage.addMouseMotionListener(PanelImageMouseMotionAdapter);
panelImage.setOpaque(false);
panelImage.revalidate();
panelImage.repaint();
return panelImage;
}
private JPanel CreateRightPanel() {
JPanel panel = new JPanel(new GridLayout(0, 1));
//...
return panel;
}
ActionListener OpenFileActionListener = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
OpenFile();
}
};
ActionListener ExitActionListener = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Object[] options = {"Yes, quit now", "No, go back"};
int n = JOptionPane.showOptionDialog(
frame, "ATTENTION: closing without saving will cause any unsaved files to be lost. Do you want to proceed?",
"Warning", JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE, null, options, options[0]
);
switch (n) {
case JOptionPane.YES_OPTION:
System.exit(0);
case JOptionPane.NO_OPTION:
case JOptionPane.CANCEL_OPTION:
}
}
};
MouseListener PanelImageMouseListener = new MouseListener() {
public void mousePressed(MouseEvent me) {
panelImageDown = new int[]{
panelImage.getZoomCalculateX(me.getX()), panelImage.getZoomCalculateY(me.getY())
};
panelImageUp = null;
CoordinateMenu1.setLabel(String.format("%s:%s", panelImageDown[0], panelImageDown[1]));
CoordinateMenu2.setLabel("");
panelImage.setStartPt(me.getPoint());
panelImage.repaint();
}
public void mouseReleased(MouseEvent me) {
panelImageUp = new int[]{
Math.abs(panelImage.getZoomCalculateX(me.getX()) - panelImageDown[0]),
Math.abs(panelImageDown[1] - panelImage.getZoomCalculateY(me.getY()))
};
CoordinateMenu2.setLabel(String.format("%s:%s", panelImageUp[0], panelImageUp[1]));
panelImage.setEndPt(me.getPoint());
panelImage.setCurrentPt(null);
panelImage.repaint();
}
public void mouseClicked(MouseEvent arg0) {
}
public void mouseEntered(MouseEvent arg0) {
}
public void mouseExited(MouseEvent arg0) {
}
};
MouseMotionAdapter PanelImageMouseMotionAdapter = new MouseMotionAdapter() {
#Override
public void mouseDragged(MouseEvent me) {
panelImageUp = new int[]{
Math.abs(panelImage.getZoomCalculateX(me.getX()) - panelImageDown[0]),
Math.abs(panelImageDown[1] - panelImage.getZoomCalculateY(me.getY()))
};
CoordinateMenu2.setLabel(String.format("%s:%s", panelImageUp[0], panelImageUp[1]));
panelImage.setCurrentPt(me.getPoint());
panelImage.repaint();
}
};
MouseWheelListener PanelImageMouseWheelListener = new MouseWheelListener() {
public void mouseWheelMoved(MouseWheelEvent me) {
if (me.isAltDown()) {
if (me.getWheelRotation() < 0) {
panelImage.setZoomer(true);
panelImage.increaseZoom();
panelImage.repaint();
panelImage.requestFocus();
//scroll.repaint();
//Zoom out
} else if(me.getWheelRotation() > 0) {
panelImage.setZoomer(true);
panelImage.decreaseZoom();
panelImage.repaint();
panelImage.requestFocus();
//scroll.repaint();
}
}
}
};
private void OpenFile() {
openFile = new GroundTruth();
JFileChooser fileChooser = new JFileChooser();
fileChooser.setCurrentDirectory(new File(System.getProperty("user.home")));
fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
fileChooser.setAcceptAllFileFilterUsed(false);
fileChooser.addChoosableFileFilter(new FileNameExtensionFilter(
"Images / PDF Scan",
"bmp", "jpeg", "jpg", "png", "tif", "tiff", "pdf"
));
if (fileChooser.showOpenDialog(frame) != 0) {
return;
}
openFile.setFilename(fileChooser.getSelectedFile().getAbsolutePath());
if (getExtension(fileChooser.getSelectedFile().getName()).equals("pdf")) {
try {
PDDocument doc = PDDocument.load(fileChooser.getSelectedFile());
numberPagePdf = doc.getNumberOfPages();
actualPagePdf = 0;
renderer = new PDFRenderer(doc);
setPdfPage(actualPagePdf);
} catch (IOException e) {
e.printStackTrace();
}
} else {
try {
CreateImagePanel(fileChooser.getSelectedFile().getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void setPdfPage(int pageNumber){
try {
BufferedImage bim = renderer.renderImageWithDPI(pageNumber, 300);
refreshInfoPageSection();
CreateImagePanel(bim);
} catch (IOException e) {
e.printStackTrace();
}
}
// refresh the label who indicate the page display and set visible or inivisble the previous and next button
private void refreshInfoPageSection(){
panelImage.deleteRectangle();
}
public String getExtension(String filename) {
return FilenameUtils.getExtension(filename);
}
}

Here's a simplified example of a drawing JPanel that's larger than the scrolling JPanel.
You can see in the image that the drawing JPanel is larger both horizontally and vertically than the scrolling JPanel.
I don't call the paintComponent method at all in this code. Because I set up the GUI properly, Swing itself calls the repaint method when you move the scroll bars.
Here are the important things I did.
I started the Swing GUI with a call to the SwingUtilities invokeLater method. This method makes sure that the Swing components are created and executed on the Event Dispatch Thread.
I used a JFrame, two JPanels, and a JScrollPane. I extended JPanel to create the drawing panel. I used a JScrollPane, JPanel, and JFrame. The only time you extend a Swing component, or any Java class, is when you want to override one or more class methods.
I used Swing layout managers. I used a BorderLayout for the JFrame and scrolling JPanel.
Here's the complete runnable code. Why, you can even call it a minimal reproducible example!
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
public class LargeDrawingPanel implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new LargeDrawingPanel());
}
#Override
public void run() {
JFrame frame = new JFrame("Large Drawing Panel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
panel.setPreferredSize(new Dimension(400, 400));
JScrollPane scrollPane = new JScrollPane(new DrawingPanel());
panel.add(scrollPane, BorderLayout.CENTER);
return panel;
}
public class DrawingPanel extends JPanel {
private static final long serialVersionUID = 1L;
public DrawingPanel() {
this.setBackground(Color.WHITE);
this.setPreferredSize(new Dimension(2000, 2000));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
int x = 100;
int y = 100;
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 10; j++) {
g.fillRect(x, y, 100, 100);
x += 200;
}
y += 200;
x = 100;
}
}
}
}
Edited to add: The OP posted additional questions in a comment.
Thanks for the example but it doesn't show me how to print an image in
a JPanel.
Pretty simple. Read an image using the ImageIO class, save the image in an application model consisting of one or more plain Java getter / setter classes and use the Graphics drawImage method to draw the image.
Your preview has only one scrollbar moved not both - which is my
problem.
Did you actually run the code I provided? I can only move one scrollbar at a time. The drawing JPanel extends both horizontally and vertically.
And it doesn't explain why my example doesn't work.
Your example is riddled with errors. Start over, building a Swing application one Swing component at a time using sound principles. The Oracle tutorial, Creating a GUI With JFC/Swing, will show you the correct way to create a Swing application. You can skip the Netbeans section.

Adding animations to JPanel

I've written some code that essentially animates a sequence of images and adds them to a frame when I run the file.
I want to implement a functionality where I can add this animation to two different areas of a JPanel that has a BorderLayout (North and West).
I want to do this using a button but I don't know how to do that. I am new to event handling and layout managers.
How do I go about this?
My code for the animation:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ImageSequence extends JPanel implements ActionListener {
private ImageSQPanel imageSQPanel;
private static int frameNumber = -1;
private Timer timer;
private void buildUI(Container container, Image[] arrows) {
int fps = 10;
int delay = 1000 / fps;
timer = new Timer(delay, this);
timer.setInitialDelay(0);
timer.setCoalesce(true);
imageSQPanel = new ImageSQPanel(arrows);
container.add(imageSQPanel, BorderLayout.CENTER);
}
private synchronized void startAnimation() {
if (!timer.isRunning()) {
timer.start();
}
}
public void actionPerformed(ActionEvent e) {
frameNumber++;
imageSQPanel.repaint();
}
class ImageSQPanel extends JPanel {
Image arrowAnimation[];
ImageSQPanel(Image[] arrowAnimation) {
this.arrowAnimation = arrowAnimation;
}
//Draw the current frame of animation.
public void paintComponent(Graphics g) {
super.paintComponent(g); //paint background
//Paint the frame into the image.
try {
g.drawImage(arrowAnimation[ImageSequence.frameNumber % 10], 0, 0, this);
} catch (ArrayIndexOutOfBoundsException e) {
//On rare occasions, this method can be called
//when frameNumber is still -1. Do nothing.
}
}
}
//Invoked only when this is run as an application.
public static void main(String[] args) {
Image[] waving = new Image[7];
for (int i = 1; i <= 7; i++) {
waving[i - 1] = Toolkit.getDefaultToolkit().getImage(
"/Users/sarthaksachdeva/Documents/IntelliJ Projects/Animation/src/images/Arrow" + i + ".png");
}
JFrame f = new JFrame("ImageSequenceTimer");
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
ImageSequence controller = new ImageSequence();
controller.buildUI(f.getContentPane(), waving);
controller.startAnimation();
f.setSize(new Dimension(200, 200));
f.setVisible(true);
}
}

Strange JFrame Behavior

I have the following program which has some very strange and unwanted behavior when it runs. Its supposed to have two buttons, "Start" and "Stop, but when I click "Start" another button shows up right below "Start". Here's a print screen of what I'm talking about:
What am I doing wrong and how do I fix this ugly problem?
Here's the code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
public class TwoButtonsTest {
JFrame frame;
Timer timer;
boolean isClicked;
public static void main(String[] args) {
TwoButtonsTest test = new TwoButtonsTest();
test.go();
}
public void go() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
JButton startButton = new JButton("Start");
startButton.addActionListener(new StartListener());
JButton stopButton = new JButton("Stop");
stopButton.addActionListener(new StopListener());
final DrawPanel myDraw = new DrawPanel();
frame.getContentPane().add(BorderLayout.CENTER, myDraw);
frame.getContentPane().add(BorderLayout.NORTH, startButton);
frame.getContentPane().add(BorderLayout.SOUTH, stopButton);
frame.setVisible(true);
timer = new Timer(50, new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
myDraw.repaint();
}
});
}
class StartListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//needs to be implemented
if(!isClicked) {
}
isClicked = true;
timer.start();
}
}
class StopListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//needs to be implemented
timer.stop();
isClicked = false;
}
}
class DrawPanel extends JPanel {
public void paintComponent(Graphics g) {
int red = (int)(Math.random()*256);
int blue = (int)(Math.random()*256);
int green = (int)(Math.random()*256);
g.setColor(new Color(red, blue, green));
Random rand = new Random();
// following 4 lines make sure the rect stays within the frame
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth()-wd);
int y = rand.nextInt(getHeight()-ht);
g.fillRect(x,y,wd,ht);
}
} // close inner class
}
Also I'm trying to get the Start button to do two things. One is to of course start the animation but when the Stop button is pressed and I press Start again, I want it to clean the screen so to speak and start the animation again a new. Any tips on that?

You do not call super.paintComponent(Graphics g) in overriden paintComponent(..) method which you should in order to honor the paint chain and thus the painting of other components.
This call should also be the first call within the method:
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
//do painting here
}
A probem might arise that drawings are not persistent. You must than have a way to store drawings and redraw every time. The most common is an ArrayList which will hold objects to be drawn (thus you cann add to the list remove etc), you would than iterate over the list and redraw each object in paintComponent. See my answer here for an example.
Also please remember to create and manipulate Swing components on Event Dispatch Thread :
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
//create UI and components here
}
});
Dont call setSize(..) on JFrame rather override getPreferredSize() of JPanel and return an appropriate height which fits all components, than call JFrame#pack() before setting JFrame visible (but after adding all components).
No need for getContentPane().add(..) as of Java 6+ add(..) defaults to contentPane
Do not re declare Random i.e Random r=new Random() each time paintComponent is called as this will make the distributions of the values less random rather initiate it once when class is created and call methods on the instance
Here is the fixed code (with above fixes implemented):
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.*;
public class TwoButtonsTest {
JFrame frame;
Timer timer;
boolean isClicked;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
TwoButtonsTest test = new TwoButtonsTest();
test.go();
}
});
}
final DrawPanel myDraw = new DrawPanel();
public void go() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton startButton = new JButton("Start");
startButton.addActionListener(new StartListener());
JButton stopButton = new JButton("Stop");
stopButton.addActionListener(new StopListener());
frame.add(myDraw, BorderLayout.CENTER);
frame.add(startButton, BorderLayout.NORTH);
frame.add(stopButton, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
timer = new Timer(50, new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
myDraw.repaint();
}
});
}
class StartListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
//needs to be implemented
if (!isClicked) {
}
myDraw.clearRects();
isClicked = true;
timer.start();
}
}
class StopListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//needs to be implemented
timer.stop();
isClicked = false;
}
}
class DrawPanel extends JPanel {
private ArrayList<MyRectangle> rects = new ArrayList<>();
private Random rand = new Random();
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
addRect();
for (MyRectangle r : rects) {
g.setColor(r.getColor());
g.fillRect(r.x, r.y, r.width, r.height);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
public void clearRects() {
rects.clear();
}
public void addRect() {
// following 4 lines make sure the rect stays within the frame
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
int red = (int) (Math.random() * 256);
int blue = (int) (Math.random() * 256);
int green = (int) (Math.random() * 256);
rects.add(new MyRectangle(x, y, wd, ht, new Color(red, blue, green)));
}
} // close inner class
}
class MyRectangle extends Rectangle {
Color color;
public MyRectangle(int x, int y, int w, int h, Color c) {
super(x, y, w, h);
this.color = c;
}
public Color getColor() {
return color;
}
}

I wish I could offer a solution, but as of yet I haven't found one. I can tell you the root of the "problem" here lies in the way you are drawing the Center section of your BorderLayout. You are overriding the whole paintComponent() function for this program and having whatever it creates put into the Center of your BoarderLayout. In this case, each time you click a button, the program calls the repaint to draw the image of a clicked button, but since you have also added ANY of the drawn objects to the Center panel, it also is drawn there. Since this specific repaint doesn't specify a location, it goes in the upper left corner.

I fixed your button problem on my Windows XP computer by invoking SwingUtilities.
I formatted your Java code.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class TwoButtonsTest implements Runnable {
JFrame frame;
Timer timer;
boolean isClicked;
public static void main(String[] args) {
SwingUtilities.invokeLater(new TwoButtonsTest());
}
#Override
public void run() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
JButton startButton = new JButton("Start");
startButton.addActionListener(new StartListener());
JButton stopButton = new JButton("Stop");
stopButton.addActionListener(new StopListener());
final DrawPanel myDraw = new DrawPanel();
frame.getContentPane().add(BorderLayout.CENTER, myDraw);
frame.getContentPane().add(BorderLayout.NORTH, startButton);
frame.getContentPane().add(BorderLayout.SOUTH, stopButton);
frame.setVisible(true);
timer = new Timer(50, new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
myDraw.repaint();
}
});
}
class StartListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
// needs to be implemented
if (!isClicked) {
}
isClicked = true;
timer.start();
}
}
class StopListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
// needs to be implemented
timer.stop();
isClicked = false;
}
}
class DrawPanel extends JPanel {
#Override
public void paintComponent(Graphics g) {
int red = (int) (Math.random() * 256);
int blue = (int) (Math.random() * 256);
int green = (int) (Math.random() * 256);
g.setColor(new Color(red, blue, green));
Random rand = new Random();
// following 4 lines make sure the rect stays within the frame
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
g.fillRect(x, y, wd, ht);
}
} // close inner class
}
To clean the screen when you press the Start button, you're going to have to add some methods to your DrawPanel class.
Here's one way to do it.
class DrawPanel extends JPanel {
protected boolean eraseCanvas;
public void setEraseCanvas(boolean eraseCanvas) {
this.eraseCanvas = eraseCanvas;
}
#Override
public void paintComponent(Graphics g) {
if (eraseCanvas) {
g.setColor(Color.WHITE);
g.fillRect(0, 0, getWidth(), getHeight());
} else {
int red = (int) (Math.random() * 256);
int blue = (int) (Math.random() * 256);
int green = (int) (Math.random() * 256);
g.setColor(new Color(red, blue, green));
Random rand = new Random();
// following 4 lines make sure the rect stays within the frame
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
g.fillRect(x, y, wd, ht);
}
}
} // close inner class

AWT and Swing component together, simultaneous display?

I have to use both AWT and Swing component in my application. At displaying the AWT first appear on the screen then come the Swing component (with LAF style)
Is it possible that and make them appear simutaneously ? Like before paint, a kind of buffer ?
Thank you

1) since as of the JDK 6 update 12 and JDK7 build 19 releases, you can seamlessly mix heavyweight (AWT) and lightweight (Swing) components,But I don't suggest mixing AWT with Swing,
2) its hard change Look and Feel for AWT Components, I never saw good one, by default is there Look and Feel that came from Native OS, Look and Feel is about usage Swing JComponents
3) since is possible put JComponents with different Look and Feel, I'd suggest to create something similair
import java.awt.event.*;
import java.awt.Color;
import java.awt.AlphaComposite;
import javax.swing.*;
import javax.swing.UIManager.LookAndFeelInfo;
public class ButtonTest {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ButtonTest().createAndShowGUI();
}
});
}
private JFrame frame;
private JButton opaqueButton1;
private JButton opaqueButton2;
private SoftJButton softButton1;
private SoftJButton softButton2;
public void createAndShowGUI() {
opaqueButton1 = new JButton("Opaque Button");
opaqueButton2 = new JButton("Opaque Button");
softButton1 = new SoftJButton("Transparent Button");
softButton2 = new SoftJButton("Transparent Button");
opaqueButton1.setBackground(Color.GREEN);
softButton1.setBackground(Color.GREEN);
frame = new JFrame();
frame.getContentPane().setLayout(new java.awt.GridLayout(2, 2, 10, 10));
frame.add(opaqueButton1);
frame.add(softButton1);
frame.add(opaqueButton2);
frame.add(softButton2);
frame.setSize(567, 350);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
Timer alphaChanger = new Timer(30, new ActionListener() {
private float incrementer = -.03f;
#Override
public void actionPerformed(ActionEvent e) {
float newAlpha = softButton1.getAlpha() + incrementer;
if (newAlpha < 0) {
newAlpha = 0;
incrementer = -incrementer;
} else if (newAlpha > 1f) {
newAlpha = 1f;
incrementer = -incrementer;
}
softButton1.setAlpha(newAlpha);
softButton2.setAlpha(newAlpha);
}
});
alphaChanger.start();
Timer uiChanger = new Timer(3500, new ActionListener() {
private LookAndFeelInfo[] laf = UIManager.getInstalledLookAndFeels();
private int index = 1;
#Override
public void actionPerformed(ActionEvent e) {
try {
UIManager.setLookAndFeel(laf[index].getClassName());
SwingUtilities.updateComponentTreeUI(frame);
} catch (Exception exc) {
exc.printStackTrace();
}
index = (index + 1) % laf.length;
}
});
uiChanger.start();
}
public static class SoftJButton extends JButton {
private static final JButton lafDeterminer = new JButton();
private static final long serialVersionUID = 1L;
private boolean rectangularLAF;
private float alpha = 1f;
public SoftJButton() {
this(null, null);
}
public SoftJButton(String text) {
this(text, null);
}
public SoftJButton(String text, Icon icon) {
super(text, icon);
setOpaque(false);
setFocusPainted(false);
}
public float getAlpha() {
return alpha;
}
public void setAlpha(float alpha) {
this.alpha = alpha;
repaint();
}
#Override
public void paintComponent(java.awt.Graphics g) {
java.awt.Graphics2D g2 = (java.awt.Graphics2D) g;
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha));
if (rectangularLAF && isBackgroundSet()) {
Color c = getBackground();
g2.setColor(c);
g.fillRect(0, 0, getWidth(), getHeight());
}
super.paintComponent(g2);
}
#Override
public void updateUI() {
super.updateUI();
lafDeterminer.updateUI();
rectangularLAF = lafDeterminer.isOpaque();
}
}
}

How to add Window's Aero effects to a JPanel?

I'm trying to have Aero Glass look in my JPanel. Is it possible do such a thing?
How to add Aero effect to JFrame - like this picture?

please read tutorials How to Create Translucent, How to Create Translucent and Shaped Windows, then by using javax.swing.Timer is possible (for example)
import java.awt.event.*;
import java.awt.Color;
import java.awt.AlphaComposite;
import javax.swing.*;
import javax.swing.UIManager.LookAndFeelInfo;
public class ButtonTest {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ButtonTest().createAndShowGUI();
}
});
}
private JFrame frame;
private JButton opaqueButton1;
private JButton opaqueButton2;
private SoftJButton softButton1;
private SoftJButton softButton2;
public void createAndShowGUI() {
opaqueButton1 = new JButton("Opaque Button");
opaqueButton2 = new JButton("Opaque Button");
softButton1 = new SoftJButton("Transparent Button");
softButton2 = new SoftJButton("Transparent Button");
opaqueButton1.setBackground(Color.GREEN);
softButton1.setBackground(Color.GREEN);
frame = new JFrame();
frame.getContentPane().setLayout(new java.awt.GridLayout(2, 2, 10, 10));
frame.add(opaqueButton1);
frame.add(softButton1);
frame.add(opaqueButton2);
frame.add(softButton2);
frame.setSize(567, 350);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
Timer alphaChanger = new Timer(30, new ActionListener() {
private float incrementer = -.03f;
#Override
public void actionPerformed(ActionEvent e) {
float newAlpha = softButton1.getAlpha() + incrementer;
if (newAlpha < 0) {
newAlpha = 0;
incrementer = -incrementer;
} else if (newAlpha > 1f) {
newAlpha = 1f;
incrementer = -incrementer;
}
softButton1.setAlpha(newAlpha);
softButton2.setAlpha(newAlpha);
}
});
alphaChanger.start();
Timer uiChanger = new Timer(3500, new ActionListener() {
private LookAndFeelInfo[] laf = UIManager.getInstalledLookAndFeels();
private int index = 1;
#Override
public void actionPerformed(ActionEvent e) {
try {
UIManager.setLookAndFeel(laf[index].getClassName());
SwingUtilities.updateComponentTreeUI(frame);
} catch (Exception exc) {
exc.printStackTrace();
}
index = (index + 1) % laf.length;
}
});
uiChanger.start();
}
public static class SoftJButton extends JButton {
private static final JButton lafDeterminer = new JButton();
private static final long serialVersionUID = 1L;
private boolean rectangularLAF;
private float alpha = 1f;
public SoftJButton() {
this(null, null);
}
public SoftJButton(String text) {
this(text, null);
}
public SoftJButton(String text, Icon icon) {
super(text, icon);
setOpaque(false);
setFocusPainted(false);
}
public float getAlpha() {
return alpha;
}
public void setAlpha(float alpha) {
this.alpha = alpha;
repaint();
}
#Override
public void paintComponent(java.awt.Graphics g) {
java.awt.Graphics2D g2 = (java.awt.Graphics2D) g;
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha));
if (rectangularLAF && isBackgroundSet()) {
Color c = getBackground();
g2.setColor(c);
g.fillRect(0, 0, getWidth(), getHeight());
}
super.paintComponent(g2);
}
#Override
public void updateUI() {
super.updateUI();
lafDeterminer.updateUI();
rectangularLAF = lafDeterminer.isOpaque();
}
}
}

Maybe this blog post will help you more. The author describes an approach where he rebuilds the whole Windows Aero effect. Here is his working example:
(source: centigrade.de)