Develop Reference

Keeping Shapes on Screen Help, can't figure out how to keep track of X,Y coordinates

I have tried and tried, I looked up many examples for keeping Shapes on the screen but can't seem to adapt to my code. In Summary, a left click prints a square, a right click prints a circle. I would like to fill the window with squares (rects) and circles. Any help and explanation so I can learn the concept would be great. I understand I have to keep track on the coordinates, perhaps in a loop but can seem to get it to work. Thanks again.
import java.awt.*;
import javax.swing.JFrame;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
public class MouseButtonTester extends JFrame implements MouseListener
{
private int mouseX, mouseY;
private int mouseButton;
private boolean isFirstRun;
private static final int WIDTH = 640;
private static final int HEIGHT = 480;
private static final long serialVersionUID = 0; //use this if you do not like warnings
public MouseButtonTester() //constructor
{
super("Mouse Button Tester");
//set up all variables
mouseX = mouseY = 0;
mouseButton = 0;
isFirstRun = true;
//set up the Frame
setSize(WIDTH,HEIGHT);
setBackground(Color.WHITE);
setVisible(true);
//start trapping for mouse clicks
addMouseListener(this);
}
public void mouseClicked(MouseEvent e)
{
mouseX=e.getX(); //Tracks x coordinates
mouseY=e.getY(); //Tracker y coordinates
mouseButton = e.getButton(); //gets button number
repaint();
}
public void paint( Graphics window ) // Draws the Window
{
if(isFirstRun)
{
window.setColor(Color.WHITE);
window.fillRect(0,0,WIDTH, HEIGHT);
//change isFirstRun
}
window.setFont(new Font("TAHOMA",Font.BOLD,12));
window.setColor(Color.BLUE);
window.drawString("MOUSE BUTTON TESTER", 420,55);
draw(window);
}
public void draw(Graphics window)
{
if(mouseButton==MouseEvent.BUTTON1) //left mouse button pressed
{
//window.drawString("BUTTON1", 50,200); //debug code
window.setColor(Color.RED);
window.drawRect(mouseX,mouseY,10,10);
}
//right mouse button pressed
{
if (mouseButton == MouseEvent.BUTTON2)
window.setColor(Color.BLUE);
window.drawOval(mouseX,mouseY,10,10);
}
//any other mouse button pressed
{
}
}
public void mouseEntered(MouseEvent e) { }
public void mouseExited(MouseEvent e) { }
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) { }
}
------ Main Method --------------
public class MouseButtonTesterRunner
{
public static void main(String[] args)
{ MouseButtonTester prog = new MouseButtonTester();
}
}

First, start by having a read through:
Performing Custom Painting
Painting in AWT and Swing
So you can get a understanding how painting in Swing works, how you can work with it and your responsibilities when doing so.
Next, have a read through:
How can I set in the midst?
Java JFrame .setSize(x, y) not working?
How to get the EXACT middle of a screen, even when re-sized
Graphics rendering in title bar
for reasons why you should avoid overriding paint of top level containers like JFrame
Finally...
Painting in Swing is destructive, that is, every time your component is painted, you are expected to completely repaint the component state from scratch.
In order to achieve your goal, you will need to maintain a cache of the items you want to paint.
The concept itself it's very difficult, but there might be some "gotchas" along the way
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private List<Point> circles;
private List<Point> squares;
public TestPane() {
circles = new ArrayList<>();
squares = new ArrayList<>();
addMouseListener(new MouseAdapter() {
#Override
public void mouseReleased(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
circles.add(e.getPoint());
} else if (SwingUtilities.isRightMouseButton(e)) {
squares.add(e.getPoint());
}
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// I'm picky
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.RED);
for (Point p : circles) {
g2d.drawOval(p.x, p.y, 10, 10);
}
g2d.setColor(Color.BLUE);
for (Point p : squares) {
g2d.drawRect(p.x, p.y, 10, 10);
}
g2d.setFont(new Font("TAHOMA", Font.BOLD, 12));
g2d.setColor(Color.BLUE);
FontMetrics fm = g2d.getFontMetrics();
String text = "MOUSE BUTTON TESTER";
int x = getWidth() - fm.stringWidth(text) - 10;
int y = getHeight() - (fm.getAscent() - fm.getHeight()) - 10;
g2d.drawString(text, x, y);
g2d.dispose();
}
}
}

I suggest creating 2 classes.
1) Circle class
2) Square Class
Those classes will store info that you need, like X, y etc..
Initialize an array list that stores those objects & read from it in your paint method, proceed with painting them just like you do in your code.
(On a click event you simply create new object (circle/square) and add it into your array list)

So here's how i understand how your code works so far: The user left clicks, those coordinates are recorded, and a square is rendered on the screen at those coordinates.
When we click the coordinates are updated and on the next draw, the square is moved to a new position.
You were on the right track about needing a loop.
Here's the logic you need to implement:
Create an ArrayList as a member variable. The type can be a pair<int,int> object. So this arraylist will hold a list of X,Y coordinates. This arraylist will look something like this:
ArrayList<pair<int,int>> myRightClickCoords;
Once you make that list, every time the user clicks, record the click coordinates and insert them into the arraylist. That will look something like this:
myRightClickCoords.insert(new pair<int,int>(e.getX(),e.getY()));
Then, once that is added to your code, in your draw function, you can have a look that runs through the entire myRightClickCoords list and runs drawRect for each set of coordinates.
Once you get that working, you can do the same thing for left click and circles. Good luck!

What is the correct way to use createBufferStrategy()?

Even after using Java Swing for over a year, it still seems like magic to me. How do I correctly use a BufferStrategy, in particular, the method createBufferSrategy()?
I would like to have a JFrame and a Canvas that gets added to it and then painted. I would also like to be able to resize (setSize()) the Canvas. Every time I resize the Canvas it seems my BufferStrategy gets trashed or rather, turns useless, since using show() on the BufferStrategy does not actually do anything. Also, createBufferStrategy() has a weird non-deterministic behaviour and I don't know how to synchronize it correctly.
Here's what I mean:
public class MyFrame extends JFrame {
MyCanvas canvas;
int i = 0;
public MyFrame() {
setUndecorated(false);
setVisible(true);
setSize(1100, 800);
setLocation(100, 100);
setDefaultCloseOperation(EXIT_ON_CLOSE);
canvas = new MyCanvas();
add(canvas);
canvas.makeBufferStrat();
}
#Override
public void repaint() {
super.repaint();
canvas.repaint();
//the bigger threshold's value, the more likely it is that the BufferStrategy works correctly
int threshold = 2;
if (i < threshold) {
i++;
canvas.makeBufferStrat();
}
}
}
MyCanvas has a method makeBufferStrat() and repaint():
public class MyCanvas extends Canvas {
BufferStrategy bufferStrat;
Graphics2D g;
public MyCanvas() {
setSize(800, 600);
setVisible(true);
}
public void makeBufferStrat() {
createBufferStrategy(2);
//I'm not even sure whether I need to dispose() those two.
if (g != null) {
g.dispose();
}
if (bufferStrat != null) {
bufferStrat.dispose();
}
bufferStrat = getBufferStrategy();
g = (Graphics2D) (bufferStrat.getDrawGraphics());
g.setColor(Color.BLUE);
}
#Override
public void repaint() {
g.fillRect(0, 0, 100, 100);
bufferStrat.show();
}
}
I simply call MyFrame's repaint() method from a while(true) loop in the main method.
When threshold is small (i.e. 2), bufferStrat.show() in about 70% of all cases doesn't do anything - the JFrame just remains gray upon starting the program. The remaining 30% it paints the rectangle how it's supposed to. If I do threshold = 200;, the painting succeeds close to 100% of the time I execute the program. Javadoc says that createBufferStrategy() may take a while, so I assume that's the issue here. However, how do I synchronize and use it properly? Clearly, I'm doing something wrong here. I can't imagine that's how it's supposed to be used.
Does anyone have a minimal working example?

The way you create the BufferStrategy is "okay", you could have a look at the JavaDocs for BufferStrategy which has a neat little example.
The way you're using it, is questionable. The main reason for using a BufferStrategy is because you want to take control of the painting process (active painting) away from Swing's painting algorithm (which is passive)
BUT, you seem to trying to do both, which is why it's causing your issues. Instead, you should have a "main" loop which is responsible for deciding what and when the buffer should paint, for example...
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferStrategy;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
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();
}
TestPane testPane = new TestPane();
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(testPane);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
// The component needs to be attached to displayed window before
// the buffer can be created
testPane.startPainting();
}
});
}
public class TestPane extends Canvas {
private AtomicBoolean painting = new AtomicBoolean(true);
private PaintCycle paintCycle;
private Rectangle clickBounds;
public TestPane() {
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
if (clickBounds != null && clickBounds.contains(e.getPoint())) {
painting.set(false);
}
}
});
}
public void startPainting() {
if (paintCycle == null) {
createBufferStrategy(2);
painting.set(true);
paintCycle = new PaintCycle();
Thread t = new Thread(paintCycle);
t.setDaemon(true);
t.start();
}
}
public void stopPainting() {
if (paintCycle != null) {
painting.set(false);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
public class PaintCycle implements Runnable {
private BufferStrategy strategy;
private int xDelta = 2;
private int yDelta = 2;
#Override
public void run() {
System.out.println("Painting has started");
int x = (int) (Math.random() * (getWidth() - 40));
int y = (int) (Math.random() * (getHeight() - 40));
do {
xDelta = (int) (Math.random() * 8) - 4;
} while (xDelta == 0);
do {
yDelta = (int) (Math.random() * 8) - 4;
} while (yDelta == 0);
clickBounds = new Rectangle(x, y, 40, 40);
strategy = getBufferStrategy();
while (painting.get()) {
// Update the state of the model...
update();
// Paint the state of the model...
paint();
try {
// What ever calculations you want to use to maintain the framerate...
Thread.sleep(40);
} catch (InterruptedException ex) {
}
}
System.out.println("Painting has stopped");
}
protected void update() {
int x = clickBounds.x + xDelta;
int y = clickBounds.y + yDelta;
if (x + 40 > getWidth()) {
x = getWidth() - 40;
xDelta *= -1;
} else if (x < 0) {
x = 0;
xDelta *= -1;
}
if (y + 40 > getHeight()) {
y = getHeight() - 40;
yDelta *= -1;
} else if (y < 0) {
y = 0;
yDelta *= -1;
}
clickBounds.setLocation(x, y);
}
protected void paint() {
// Render single frame
do {
// The following loop ensures that the contents of the drawing buffer
// are consistent in case the underlying surface was recreated
do {
// Get a new graphics context every time through the loop
// to make sure the strategy is validated
Graphics2D graphics = (Graphics2D) strategy.getDrawGraphics();
// Render to graphics
// ...
graphics.setColor(Color.BLUE);
graphics.fillRect(0, 0, getWidth(), getHeight());
graphics.setColor(Color.RED);
graphics.fill(clickBounds);
// Dispose the graphics
graphics.dispose();
// Repeat the rendering if the drawing buffer contents
// were restored
} while (strategy.contentsRestored());
// Display the buffer
strategy.show();
// Repeat the rendering if the drawing buffer was lost
} while (strategy.contentsLost());
}
}
}
}
You should also remember, Swing's been using either DirectX or OpenGL pipelines since about 1.4 (or maybe 1.5). The main reasons for using BufferStrategy are more direct access to the hardware (which Swing is pretty close to anyway) AND direct control over the painting process (which is now really the only reason to use it)

Creating animated text that loops on itself

I'm trying to make a news ticker type thing where a string is entered and inside of a JPanel the text is looped.
I know it moves currently at about 90 pixels a second and that there is about 16 pixels per char in this font. So what I am asking is how I can use this information to make it so that after a timer runs for a certain time, a new animated text is spawned, and how after the 1st animated text leaves the screen completely, how to delete it from the memory.
This is what I got so far, the code is borrowed heavily from here : Java Animate JLabel, So also if you see any unneeded code in there, let me know.
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.EnumMap;
import javax.swing.*;
#SuppressWarnings("serial")
public class AnimateExample extends JPanel {
private static final int TIMER_DELAY = 20;
private static final String KEY_DOWN = "key down";
public static final int TRANSLATE_SCALE =2;
private static final Font BG_STRING_FONT = new Font(Font.SANS_SERIF,
Font.BOLD, 32);
private EnumMap<Direction, Boolean> dirMap =
new EnumMap<AnimateExample.Direction, Boolean>(Direction.class);
private BufferedImage image = null;
private int posX = 100;
private int posY = 50;
Timer t;
public AnimateExample() {
for (Direction dir : Direction.values()) {
dirMap.put(dir, Boolean.TRUE);
}
t = new Timer(TIMER_DELAY, new TimerListener());
t.start();
ActionMap actionMap = getActionMap();
for (final Direction dir : Direction.values()) {
actionMap.put(dir.Left + KEY_DOWN, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
dirMap.put(dir, true);
}
});
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g.setFont(BG_STRING_FONT);
g.setColor(Color.LIGHT_GRAY);
g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
String s = "Hi, I'm trying to make a news ticker type thing where a string is entered and inside of a JPanel the text is looped.I know it moves currently at about 90 pixels a second and that there is about 16 pixels per char in this font. So what I am asking is how I can use this information to make it so that after a timer runs for a certain time, a new animated text is spawned, and how after the 1st animated text leaves the screen completely, how to delete it from the memory.";
g.drawString(s, posX, posY);
}
private class TimerListener implements ActionListener {
public void actionPerformed(java.awt.event.ActionEvent e) {
for (Direction dir : Direction.values()) {
if (dirMap.get(dir)) {
posX += dir.getX() * TRANSLATE_SCALE;
posY += dir.getY() * TRANSLATE_SCALE;
}
}
repaint();
if(posX<-500)
{
t.stop();
}
};
}
enum Direction {
Left( KeyEvent.VK_LEFT, -1, 0);
private int keyCode;
private int x;
private int y;
private Direction(int keyCode, int x, int y) {
this.keyCode = keyCode;
this.x = x;
this.y = y;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
}
private static void createAndShowGui() {
AnimateExample mainPanel = new AnimateExample();
JFrame frame = new JFrame("Animate Example");
frame.setUndecorated(true);
frame.setSize(1600, 900);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.add(mainPanel);
mainPanel.setBounds(new Rectangle(1600,400));
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
EDIT:
I was also thinking that perhaps resetting the X position after a certain amount of time or distance, but the problem with that would be that it would require that the area would be blank for one screen length. If you have a work around for that, it would also be great.

You could check out the Marquee Panel. It uses a different approach than most scrollers. You add actual components to the panel and the components scroll.
This allows you to scroll text or images. You can use labels with HTML so you can have colored text etc. The message will continue to scroll until you manually stop the scrolling.
Currently there is no automatic mechanism for replacing a scrolling message. Although you could easily create a List or Queue of messages. Then when a message has finished scrolling completely you just remove the current message and add a new one.
Following is the section code from the MarqueePanel class you would need to change:
public void actionPerformed(ActionEvent ae)
{
scrollOffset = scrollOffset + scrollAmount;
int width = super.getPreferredSize().width;
if (scrollOffset > width)
{
scrollOffset = isWrap() ? wrapOffset + scrollAmount : - getSize().width;
// add code here to swap component from the List or Queue
}
repaint();
}
Of course you would also need to add a method to the class to add a component to the List or Queue.

Don't worry about the character width, as different fonts can produce variable character widths. Instead use FontMetrics to measure the String width and determine it the xPos <= -stringWidth, this is when the text would be fully off the left hand side of the screen.
You could use a Queue of some kind to manage text, popping of the next one as you need it. This example simply pops the last message onto the end of the queue, so it will keep repeating
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.LinkedList;
import java.util.Queue;
import javax.swing.JFrame;
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();
}
Queue<String> queue = new LinkedList<>();
queue.add("I have something to say, it's better to burn out then fade away");
queue.add("Banana peels");
queue.add("Don't worry if plan A fails, there are 25 more letters in the alphabet");
queue.add("When the past comes knocking, don't answer. It has nothing new to tell you");
queue.add("I know the voices in my head aren't real..... but sometimes their ideas are just absolutely awesome!");
TickerTapPane pane = new TickerTapPane();
pane.setMessages(queue);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(pane);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TickerTapPane extends JPanel {
private Queue<String> queue;
private String message;
private int xPos;
public TickerTapPane() {
Timer timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (message == null) {
message = queue.remove();
xPos = getWidth();
}
xPos -= 4;
FontMetrics fm = getFontMetrics(getFont());
int stringWidth = fm.stringWidth(message);
if (xPos <= -stringWidth) {
queue.add(message);
xPos = getWidth();
message = queue.remove();
}
repaint();
}
});
timer.start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (message != null) {
Graphics2D g2d = (Graphics2D) g.create();
FontMetrics fm = g2d.getFontMetrics();
int yPos = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
g2d.drawString(message, xPos, yPos);
g2d.dispose();
}
}
protected void setMessages(Queue<String> queue) {
this.queue = queue;
}
}
}

Trouble with for loop

I have a for loop that iterates within an actionPerformed method. Basically, I have a car game. I have a panel where car images travel from side to side in a JPanel. I am trying to have the cars stop at the finish line (I am doing that by sleeping when the image reaches a certain x value) display the race results, leave the screen and race again. I need to do that four times until we have a winner.
private class RaceDisplay extends JPanel implements ActionListener{
private Image img1,img2;
private int velX1,velX2;
private int x1,x2;
private Timer tm;
private JTextArea text1 = new JTextArea();
public RaceDisplay(){
tm = new Timer(30,this);
x1=0;
x2=0;
velX1=2;
velX2 =2;
}
public void paintComponent(Graphics g){
super.paintComponent(g);
ImageIcon car1 = new ImageIcon("...");
ImageIcon car2 = new ImageIcon("...");
img1 = car1.getImage();
img2 = car2.getImage();
g.drawImage(img1,x1,100,null);
g.drawImage(img2,x2,200,null);
tm.start();
}
public void actionPerformed(ActionEvent e) {
x1=x1+velX1;
velX2= x2+velX2;
repaint();
for(int count = 0;count<=4;count++){//<-----loop with issues.
if(count == 1){
text1.setText(result());
}
if(x1>=650 && x2>=650){ //does this when both cars reach the line
velX1=0;
velX2=0;
try {
Thread.sleep(2500);
} catch (InterruptedException ex) {
Logger.getLogger(Display.class.getName()).log(Level.SEVERE, null, ex);
}
x1=0;
x2=0;
repaint();
velX1= x1+velX1;
velX2= x2+velX2;
}
}
repaint();
}
I created the for loop that should check the if statements when it reaches the last counter it displays the winner(method for winner in the code). I was expecting the images to travel from side to four times and display the results four times.
But it only display anything if i set the if(counter==1) to (counter==0).
Can anyone help?
Thanks.

Don't call tm.start(); from within the paintComponent method, this is just asking for trouble. Painting may occur for any number of reasons, many of which you don't control or have knowledge about
Don't call Thread.sleep from within the context of the Event Dispatching Thread. This isn't stopping the Timer, but is prevent the EDT from processing the Event Queue, which includes things like repaint events and timer events...
Instead, once you've detected that a car has passed the finish line, you can either, stop updating that car's position and/or stop the Timer
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.awt.image.BufferedImage;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
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 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 Map<BufferedImage, Rectangle> carBounds;
private BufferedImage blueCar;
private BufferedImage redCar;
public TestPane() {
carBounds = new HashMap<>(25);
try {
blueCar = ImageIO.read(getClass().getResource("/BlueCar.png"));
redCar = ImageIO.read(getClass().getResource("/RedCar.png"));
int x = 0;
int y = (200 / 2 ) - blueCar.getHeight();
carBounds.put(blueCar, new Rectangle(x, y, blueCar.getWidth(), blueCar.getHeight()));
y = (200 / 2);
carBounds.put(redCar, new Rectangle(x, y, redCar.getWidth(), redCar.getHeight()));
} catch (IOException ex) {
ex.printStackTrace();
}
Timer timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
for (BufferedImage img : carBounds.keySet()) {
Rectangle bounds = carBounds.get(img);
int xDelta = (int)Math.round((Math.random() * 7) + 1);
bounds.x += xDelta;
if (bounds.x + bounds.width > getWidth()) {
bounds.x = getWidth() - bounds.width;
((Timer)e.getSource()).stop();
}
}
repaint();
}
});
timer.start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
for (BufferedImage img : carBounds.keySet()) {
Rectangle bounds = carBounds.get(img);
g2d.drawImage(img, bounds.x, bounds.y, this);
}
g2d.dispose();
}
}
}
Take a closer look at Concurrency in Swing for more details

Custom JComponent(s) refuse to paint (if added to an ArrayList)

here's the relevant code from the form where JComponents should be drawn - this code creates and adds to the form a JComponent and also adds it to an ArrayList, as I need to be able to destroy the components later.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JOptionPane;
public class frmMain extends javax.swing.JFrame implements ActionListener {
ArrayList<Pocitadlo> poc;
Random rnd;
/**
* Creates new form frmMain
*/
public frmMain() {
initComponents();
poc = new ArrayList<Pocitadlo>();
rnd = new Random();
// Pocitadlo tmp = new Pocitadlo(100, 40, 40, getFont());
// tmp.addActionListener(this);
// this.add(tmp);
// tmp.start();
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int val, x, y;
val = 20;
x = (this.getWidth() / 2) - 10 + rnd.nextInt(20);
y = (this.getHeight() / 2) - 10 + rnd.nextInt(20);
try{
val = Integer.parseInt(txtCounterValue.getText());
Pocitadlo tmp = new Pocitadlo(val, x, y, getFont());
tmp.addActionListener(this);
poc.add(tmp);
tmp.setVisible(true);
tmp.start();
this.add(tmp);
this.setTitle("Počet počítadiel: " + this.getComponentCount());
repaint();
tmp.repaint();
} catch(Exception e){
JOptionPane.showMessageDialog(this, "Nesprávne zadaná alebo prázdna hodnota počítadla. Hodnota musí byť celé číslo.", "Chyba", JOptionPane.ERROR_MESSAGE);
}
}
#Override
public void actionPerformed(ActionEvent e){
if(e.getActionCommand().equals("counterFinished")){
Pocitadlo tmp = (Pocitadlo)e.getSource();
poc.remove(tmp);
this.setTitle("Počet počítadiel: " + poc.size());
this.remove(tmp);
}
}
and here is the code of the JComponents i'm adding and naiively expect to be drawn:
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JComponent;
import javax.swing.Timer;
public class Pocitadlo extends JComponent implements MouseListener, ActionListener {
private int maxValue, value;
private Boolean isRunning, isDisplayed;
private Timer valueTimer, blinkTimer;
private ActionListener actionListener;
private Font font;
public Pocitadlo(int timeout, int x, int y, Font f){
isRunning = false;
isDisplayed = true;
maxValue = value = timeout;
valueTimer = new Timer(1000, this);
valueTimer.setActionCommand("valueTimer");
blinkTimer = new Timer(200, this);
blinkTimer.setActionCommand("blinkTimer");
this.setBounds(x, y, 100, 50);
}
public void start(){
isRunning = true;
valueTimer.start();
}
public void stop(){
isRunning = false;
valueTimer.stop();
}
#Override
public void actionPerformed(ActionEvent e){
if(e.getActionCommand().equals("valueTimer")){
value--;
if(actionListener != null){
repaint();
actionListener.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "counterTick"));
}
if(value == 0 && actionListener != null){
isRunning = false;
valueTimer.stop();
actionListener.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "counterFinished"));
}
if(value < maxValue / 2 && !blinkTimer.isRunning()) blinkTimer.start();
}
if(e.getActionCommand().equals("blinkTimer")){
isDisplayed = !isDisplayed;
repaint();
}
}
public void addActionListener(ActionListener listener){
actionListener = listener;
}
#Override
public void mouseClicked(MouseEvent e) {
value += 5000;
if(value > maxValue) value = maxValue;
repaint();
}
#Override
public void paintComponent(Graphics g){
g.setColor(Color.red);
g.fillRect(getX(), getY(), getWidth(), getHeight());
if(isDisplayed){
g.setColor(Color.green);
g.fillRect(getX(), getY(), getWidth(), getHeight());
g.setColor(Color.black);
//g.setFont(font);
g.drawString(value + "/" + maxValue, 0, 0);
}
//super.paintComponent(g);
}
}
this results in nothing - the JComponents are created and correctly added at least to the ArrayList, and its paintComponent method run, as well as the timer events, components are also correctly removed at least from the ArrayList when the countdown reaches 0, but doesn't draw anything and I have no idea why.
please note that the commented code in frmMain constructor kind of works, and if uncommented, it draws the JComponent... well... just the rectangles, doesn't draw any text, but I suppose that's another problem, however, if you're willing to help with that one too, I'd be glad.
also, if I'm using action events and listeners incorrectly, please ignore that, I'm a beginner at Java and would like to know how to do it correctly, but later, right now I just need to get this code to work so please focus on the issue, thank you.
yes, there's some dead things, like the font passed to the component, those are remains of my attempts to get the drawString to work.

You project is suffering from a number of really basic misconceptions about how painting in Swing works.
Because (at the time I tested it) you hadn't provided the full code, I had to make some assumptions.
Your expection is that the content pane of the JFrame is using a null layout. I'd find it difficult to see how you would mange this and have other components on the frame. In any case, I would isolate a separate container to act as the "main" view for your Pocitadlo. This allows you to continue using layout managers to manage the other components as well.
I'm a little concerned that you trap the entire Pocitadlo generation code in a try-catch simply to catch a numeric conversion. Since you've already applied a default value, it would be reasonable to trap the conversion in its own try-catch and ignore it if it fails (displaying a message as required). Now I'm coming in from the outside, so you may see a need for this, it just caught my eye...
Your valueTimer actionPerformed code is slightly erronous, as it's possible for the blinkTimer to continue running even after the valueTimer has completed. I corrected this by merging two of you if statements into a if-else statement instead...
if (value == 0 && actionListener != null) {
isRunning = false;
valueTimer.stop();
actionListener.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "counterFinished"));
blinkTimer.stop();
} else if (value < maxValue / 2 && !blinkTimer.isRunning()) {
blinkTimer.start();
}
I, personally, would use a JPanel over a JComponent. JPanel is opaque to start with.
The main problem is in you paintComponent method.
You should always call super.paintComponent, and on opaque components it should be called first.
You seem to think you have to correct for the components position when painting, for example g.fillRect(getX(), getY(), getWidth(), getHeight());. This is actually wrong. The graphics context has already been translated so that the x/y position of the component/graphics is now equal to 0x0. Have a read through Painting in AWT and Swing for a better explanation, but basically, this means, the top/left corner of you paint area is now 0x0.
You seem to think that text is painted from the top/left corner of the first character. This is actually wrong. Text is painted along it's base line. You need to compenstate for this by adjusting the y-position by the Fonts ascent value.
.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestRepaint01 {
public static void main(String[] args) {
new TestRepaint01();
}
public TestRepaint01() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
MainFrame frame = new MainFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MainFrame extends javax.swing.JFrame implements ActionListener {
ArrayList<Pocitadlo> poc;
Random rnd;
private JPanel body;
/**
* Creates new form frmMain
*/
public MainFrame() {
setLayout(new BorderLayout());
poc = new ArrayList<Pocitadlo>();
rnd = new Random();
body = new JPanel(null);
add(body);
JButton btn = new JButton("Add");
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
int val, x, y;
val = 20;
x = (getWidth() / 2) - 10 + rnd.nextInt(20);
y = (getHeight() / 2) - 10 + rnd.nextInt(20);
// try {
// val = Integer.parseInt(txtCounterValue.getText());
Pocitadlo tmp = new Pocitadlo(val, x, y, getFont());
tmp.addActionListener(MainFrame.this);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.weightx = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
poc.add(tmp);
tmp.start();
body.add(tmp);
body.repaint();
setTitle("Počet počítadiel: " + getComponentCount());
// } catch (Exception e) {
// JOptionPane.showMessageDialog(this, "Nesprávne zadaná alebo prázdna hodnota počítadla. Hodnota musí byť celé číslo.", "Chyba", JOptionPane.ERROR_MESSAGE);
// }
}
});
add(btn, BorderLayout.SOUTH);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("counterFinished")) {
System.out.println("Counter finished");
Pocitadlo tmp = (Pocitadlo) e.getSource();
poc.remove(tmp);
this.setTitle("Počet počítadiel: " + poc.size());
body.remove(tmp);
// body.revalidate();
body.repaint();
}
}
}
public class Pocitadlo extends JPanel implements MouseListener, ActionListener {
private int maxValue, value;
private Boolean isRunning, isDisplayed;
private Timer valueTimer, blinkTimer;
private ActionListener actionListener;
private Font font;
public Pocitadlo(int timeout, int x, int y, Font f) {
isRunning = false;
isDisplayed = true;
maxValue = value = timeout;
valueTimer = new Timer(1000, this);
valueTimer.setActionCommand("valueTimer");
blinkTimer = new Timer(200, this);
blinkTimer.setActionCommand("blinkTimer");
this.setBounds(x, y, 100, 50);
}
#Override
public void removeNotify() {
super.removeNotify();
stop();
blinkTimer.stop();
}
public void start() {
isRunning = true;
valueTimer.start();
}
public void stop() {
isRunning = false;
valueTimer.stop();
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("valueTimer")) {
value--;
System.out.println("value = " + value);
if (actionListener != null) {
repaint();
actionListener.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "counterTick"));
}
if (value == 0 && actionListener != null) {
isRunning = false;
valueTimer.stop();
actionListener.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "counterFinished"));
blinkTimer.stop();
} else if (value < maxValue / 2 && !blinkTimer.isRunning()) {
blinkTimer.start();
}
}
if (e.getActionCommand().equals("blinkTimer")) {
System.out.println("Blink");
isDisplayed = !isDisplayed;
repaint();
}
}
public void addActionListener(ActionListener listener) {
actionListener = listener;
}
#Override
public void mouseClicked(MouseEvent e) {
value += 5000;
if (value > maxValue) {
value = maxValue;
}
repaint();
}
#Override
public void mouseExited(MouseEvent e) {
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.red);
// location bad
g.fillRect(0, 0, getWidth(), getHeight());
if (isDisplayed) {
g.setColor(Color.green);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(Color.black);
//g.setFont(font);
FontMetrics fm = g.getFontMetrics();
g.drawString(value + "/" + maxValue, 0, fm.getAscent());
}
g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
}
#Override
public void mousePressed(MouseEvent e) {
}
#Override
public void mouseReleased(MouseEvent e) {
}
#Override
public void mouseEntered(MouseEvent e) {
}
}
}
None of the problems you've encountered are super critical (sure, you program doesn't do what you want) and suggest that you've reached a pinnacle moment in your code abilities. I say this, because I made the exact same mistakes... ;)
Take a closer look at 2D Graphics and Custom Painting
I'd also take a look at Code Conventions for the Java Programming Language as you simply annoy people if you don't follow them ;)