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Using repaint() in different class instances in one panel

I have a draw class that extends JPanel and has a void method called drawing with repaint() in it.
public class draw extends JPanel {
public draw(int position_x, int position_y, int width, int height) {
positionx = position_x;
positiony = position_y;
this.width = width;
this.height = height;
}
public void drawing() {
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(positionx, positiony, width, height);
}
}
So, my intention is create a lot of this rectangles in a JPanel so they create a graphic bar.
public class coin_launcher {
public static void main(String[] args) {
JFrame frame = new JFrame("Coin Launcher");
frame.setVisible(true);
frame.setSize(1920, 1080);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
draw object = new draw(2,2,100,2);
frame.add(object);
object.drawing();
draw object2 = new draw(2,6,200,2);
frame.add(object2);
object2.drawing();
}
}
The problem is that when I call drawing() in both of the objects only one gets drawn.
If use the debugger its only the first one, if I dont, its only the second one. I need to make 100 bars but it literally repaints the JPanel every time, how can I add different draw class in one JPanel without erasing the others?

JFrame uses a BorderLayout by default, this means that only the last component added (to the default centre position) will be managed by the layout.
See BorderLayout for more details.
An immediate solution might be to use a different layout manager, but I would argue that's the wrong solution.
Instead, you should have ONE component, which is capable of paint multiple bars, based on the data available from a "model"
This decouples the source of the data from the presentation of the data, allowing to produce multiple different implementations of these, which shouldn't break the other.
In this case, the "view" shouldn't care how the data is obtained or marinated, only that it conforms to a specified contract, like wise the data doesn't care how its presented.
See Model-View-Controller for more details

This answer is a very basic and simplified example of
"you should have ONE component, which is capable of paint multiple
bars, based on the data available from a "model"
quoted from MadProgrammer's answer.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Arrays;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class CoinLauncher {
public static void main(String[] args) {
JFrame frame = new JFrame("Coin Launcher");
frame.setSize(920, 480);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//data to be painted. for better implementation use a model class that
//encapsulates the data
Rectangle[] bars = {
new Rectangle(2,2,100,2),
new Rectangle(2,6,200,2),
};
Draw object = new Draw(Arrays.asList(bars));
frame.add(object);
frame.setVisible(true);
}
}
class Draw extends JPanel {
private final List<Rectangle> bars;
Draw(List<Rectangle> bars) {
this.bars = bars;
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
for(Rectangle bar : bars){
g.fillRect(bar.x, bar.y, bar.width, bar.height);
}
}
}
Implementing a model to encapsulate data need for the view, can be as simple as :
public class CoinLauncher {
public static void main(String[] args) {
JFrame frame = new JFrame("Coin Launcher");
frame.setSize(920, 480);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Model model = new Model();
model.addBar( new Rectangle(2,2,100,2) );
model.addBar( new Rectangle(2,6,200,2) );
Draw object = new Draw(model);
frame.add(object);
frame.setVisible(true);
}
}
class Draw extends JPanel {
private final List<Rectangle> bars;
Draw(Model model) {
bars = model.getBars();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
for(Rectangle bar : bars){
g.fillRect(bar.x, bar.y, bar.width, bar.height);
}
}
}
class Model {
private final List<Rectangle> bars;
Model(){
bars = new ArrayList<>();
}
void addBar(Rectangle rectangle){
bars.add(rectangle);
}
List<Rectangle> getBars() { return bars; }
}

Relation and implementation of Graphics and paint? [duplicate]

I tried few source codes of drawing in java and they were working fine, but when i tried to make one of my own I could not get the paint(Grahpics g) method to work! I looked again at the codes I have and checked some of the tutorials in Oracle's pages but i don't seem to be able to know why it would not work.
can someone please check it and tell me what is wrong here??
main method:
public class main
{
public static void main(String[] args)
{
new board();
}
}
board:
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class board implements ActionListener
{
private JFrame f = new JFrame("Speedy");
private JPanel gamePanel = new JPanel();
private Image bg = new ImageIcon(this.getClass().getResource("road.png")).getImage();
private Timer t;
private car myCar = new car();
public board()
{
t = new Timer(50,this);
t.start();
gamePanel.setSize(600,400);
gamePanel.setDoubleBuffered(true);
gamePanel.setFocusable(true);
gamePanel.addKeyListener(new TAdapter());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(gamePanel,BorderLayout.CENTER);
//f.addKeyListener(new TAdapter());
f.setBounds(200,100,600,400);
f.setVisible(true);
f.revalidate();
f.repaint();
}
public void paint(Graphics g) {
gamePanel.paint(g);
Graphics2D g2d = (Graphics2D)g;
g2d.drawImage(bg,0,0,null);
g2d.drawImage(myCar.getImg(), myCar.xPos, myCar.yPos, null);
System.out.println("Painted");
g.dispose();
}
public void actionPerformed(ActionEvent e)
{
gamePanel.repaint();
//System.out.println("Painting..");
}
private class TAdapter extends KeyAdapter {
public void keyReleased(KeyEvent e) {}
public void keyPressed(KeyEvent e)
{
myCar.keyPressed(e);
System.out.println("You pressed: "+e);
}
}
}
car.java:
import java.awt.Image;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import javax.swing.ImageIcon
;
public class car
{
private Image image;
public int xPos,yPos;
public car()
{
image = new ImageIcon(this.getClass().getResource("car.png")).getImage();
xPos = 300;
yPos = 200;
System.out.println(image.getWidth(null));
}
public Image getImg() {return image;}
public void move() {}
public void keyPressed(KeyEvent e)
{
int key = e.getKeyCode();
if (key == KeyEvent.VK_LEFT) xPos -= 1;
if (key == KeyEvent.VK_RIGHT)xPos += 1;
if (key == KeyEvent.VK_UP) yPos -= 1;
if (key == KeyEvent.VK_DOWN) yPos += 1;
}
}
There are no errors, it shows me the width of the image which is right, also the timer triggers the ActionListener, also KeyListener is working, but the images would not draw! the paint(Graphics g) method just does not want to get triggered!
Googling it did not help.. I thought this would be a common problem but nobody has the problem I have, all solutions failed me.
help please?
If someone can explain it would be most appreciated!

Your class Board does not extend the JPanel class. So the paint() method is never called by the Swing.
Also, the statement gamePanel.repaint() will only execute the default JPanel paint() method of gamePanel. Instead you want the overridden paint method to be executed, so might want to do this:
public class Board extends JPanel implements ActionListener {
....
public void paint(Graphics g) {
this.paint(g);
Graphics2D g2d = (Graphics2D)g;
g2d.drawImage(bg,0,0,null);
g2d.drawImage(myCar.getImg(), myCar.xPos, myCar.yPos, null);
System.out.println("Painted");
g2d.dispose();
}
....
}
Replace your action functionality with this:
public void actionPerformed(ActionEvent e) {
this.repaint();
}
Alternative solution:
If you do not want your Board class to extend JPanel, you can also override the paint() method of the gamePanel as you initialize it.
gamePanel = new JPanel() {
#Override
public void paint(Graphics g) {
this.paint(g);
Graphics2D g2d = (Graphics2D)g;
g2d.drawImage(bg,0,0,null);
g2d.drawImage(myCar.getImg(), myCar.xPos, myCar.yPos, null);
g2d.dispose();
}
};
However, I would recommend the first solution rather than this one with anonymous classes.

When you call repaint on some container, then what happens is that Swing looks at all the components in that container and calls their paint method.
However, your board class (you should be calling it Board, by the way. Class names should always start with a capital) is not a component of your JFrame. When you call repaint, Swing will attempt to call the paint method of the JPanel that is a component of that JFrame. But you didn't override that method. You just added a paint method to your board, and board is not a component of the JFrame.
For this reason, usually you are supposed to create a class that extnds JPanel or some other component, and then add the current object of that class as a component to the JFrame. This way, your paint method will be called when the JFrame is repainted.

Your "main" class (board) should extend JPanel to work as expected.
With your way, paint would never be called. it acts like any normal self-written function.
If you want to keep things as they are, you can do something ike that:
gamePanel = new JPanel()
{
#Override
public void paint(Graphics g)
{
//your code here
}
};
Please keep in mind that a Class name should start with a capital letter. It won't make any errors but it is a naming convention as you can see here:
http://www.oracle.com/technetwork/java/codeconventions-135099.html

drawing with multiple classes in java "applet not initialized"

I am trying to draw to a single panel from multiple sources in java. However when I try this test code I get applet not initialized. Keeping in mind I am fairly new to this. How would I get rid of this error and or draw to a panel from multiple sources.
import java.awt.Graphics;
import javax.swing.JPanel;
class Surface extends JPanel {
public void init() {
}
public void paintComponent(Graphics g){
super.paintComponent(g);
DrawRect d = new DrawRect(this);
d.draw( g );
}
}
class DrawRect {
Surface surface;
Graphics g;
public DrawRect(Surface surface)
{
g = surface.getGraphics();
}
public void draw( Graphics g )
{
g.fillRect(20,20,100,50); // (now this will work).
}
}

Java: Repaint in Swing Not Working

I am learning java swing and am having trouble with the following program. It creates a small frame with a quit button at top. The objective is to display coordinates wherever the mouse is clicked. When I click the mouse 2 unwanted things are happening:
the quit button is overridden by the mouse clicks and it no longer responds (instead of responding to event and quitting, it displays coordinates on top of the quit button).
when I click at a new location, the coordinates from the old location persist.
I used removeAll() and revalidate() before doing repaint() based on this discussion but that has not helped. This code is taken from here and the code to says to research online documentation for why this is happening.
Any pointers?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
public class QuitCoordinateTest {
public static void main(String[] args){
GUI gui = new GUI();
}
}
class MyFrame extends JFrame implements ActionListener{
int clickX;
int clickY;
public void paint(Graphics g){
g.drawString("" + clickX + ", " + clickY, clickX, clickY);
}
public void actionPerformed(ActionEvent e){
System.exit(0);
}
}
//=======================================================//
class GUI extends MyFrame {
JButton quitButton = new JButton("Quit");
public GUI(){
MyFrame displayWindow = new MyFrame();
displayWindow.setTitle("Title");
/*
JPanel buttonPanel = new JPanel();
buttonPanel.add(quitButton);
displayWindow.getContentPane().add(buttonPanel,BorderLayout.NORTH);
JPanel textPanel = new JPanel();
*/
displayWindow.getContentPane().add(quitButton,BorderLayout.NORTH);
quitButton.addActionListener(displayWindow);
displayWindow.setSize(201,201);
displayWindow.setVisible(true);
// displayWindow.pack();
displayWindow.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
displayWindow.addMouseListener(new MouseProc(displayWindow));
}//end constructor
}//end class GUI definition
//=======================================================//
//This listener class monitors for mouse presses and
// displays the coordinates of the mouse pointer when the
// mouse is pressed on the source object.
class MouseProc extends MouseAdapter{
MyFrame refToWin;
MouseProc(MyFrame inWin){
refToWin = inWin;
}
//Override the mousePressed method to determine and
// display the coordinates when the mouse is pressed.
public void mousePressed(MouseEvent e){
refToWin.removeAll();
refToWin.clickX = e.getX();
refToWin.clickY = e.getY();
//Force the JFrame object to be repainted in order to
// display the coordinate information.
refToWin.removeAll();
refToWin.validate();
refToWin.repaint();
}
}

repaint() is working fine.
Avoid drawing directly on the JFrame.
Instead draw in the protected void paintComponent(Graphics g) method override of a JPanel that is then displayed in your JFrame.
Be sure to call the super's paintComponent(g) method inside of your paintComponent override -- this will erase the old images and is the reason for one of your problems.
Use reasonable comments in your code. Too many comments and too much text distracts and makes understanding your code harder, not easier.
Calling removeAll() on your JFrame will do just that -- remove all components including your button. Why are you calling this? Are you sure that you want to call this method?
A minor nitpick -- you'll want to avoid directly setting the fields of another class, such as your clickX and clickY fields. Instead, make them private, and only allow outside classes to modify them through public methods. While it may not matter much for this small program, it will matter greatly when you start scaling up your programming and create large programs with complex interactions. The key to success here will be to limit and control all communication between classes to avoid hard to detect side effects.
For example, something like...
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
String str = String.format("[%d, %d]", clickX, clickY);
g.drawString(str, clickX, clickY);
}
public int getClickX() {
return clickX;
}
public void setClickX(int clickX) {
this.clickX = clickX;
}
public int getClickY() {
return clickY;
}
public void setClickY(int clickY) {
this.clickY = clickY;
}
For example
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class DetectClicks extends JPanel {
private static final int PREF_W = 800;
private static final int PREF_H = 650;
private int clickX;
private int clickY;
public DetectClicks() {
MyMouseListener mouseAdapter = new MyMouseListener(this);
addMouseListener(mouseAdapter);
addMouseMotionListener(mouseAdapter); // to allow dragging!
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
String str = String.format("[%d, %d]", clickX, clickY);
g.drawString(str, clickX, clickY);
}
public int getClickX() {
return clickX;
}
public void setClickX(int clickX) {
this.clickX = clickX;
}
public int getClickY() {
return clickY;
}
public void setClickY(int clickY) {
this.clickY = clickY;
}
private static void createAndShowGui() {
DetectClicks mainPanel = new DetectClicks();
JFrame frame = new JFrame("DetectClicks");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class MyMouseListener extends MouseAdapter {
private DetectClicks detectClicks;
public MyMouseListener(DetectClicks detectClicks) {
this.detectClicks = detectClicks;
}
#Override
public void mousePressed(MouseEvent evt) {
showPoint(evt);
}
#Override
public void mouseDragged(MouseEvent evt) {
showPoint(evt);
}
private void showPoint(MouseEvent evt) {
detectClicks.setClickX(evt.getX());
detectClicks.setClickY(evt.getY());
detectClicks.repaint();
}
}

Your event is getting consumed by the handler that prints the coordinates, you need to redispatch the event so that the button can see it. You can do it like this, inside the coordinate display event handler:
Component c = e.getComponent();
c.getParent().dispatchEvent( e );
Also, I'd be tempted to use the glass pane of the frame, and put a JLabel on it with the co-ordinates rather than messing with the paint method.

you don't have to use any of repaint(),invalidate() etc.
i highly recommend to use
SwingUtilities.invokeLater(new Runnable() {
public void run() {
//TODO udpdate UI compontents, layouts etc.
}
});
this guarantees that UI components update on real time. Because we don't know when the system update UI hierarchy so we can't force it. This allow system to determine by it's self.

Troubles with a piechart applet

Alright the deal is I am trying to use the drawPie method to create my pie chart in an applet. After attempting google searches I find multiple tutorials that explain part of the process but not all of it. While trying to knit together partial information I am not getting the results I want.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JApplet;
import javax.swing.JComponent;
public class JLW_PieApplet extends JApplet {
class PieData extends JComponent {
PieValue[] slices = new PieValue[4];
PieData() {
slices[0] = new PieValue(35, Color.red);
slices[1] = new PieValue(33, Color.green);
slices[2] = new PieValue(20, Color.pink);
slices[3] = new PieValue(12, Color.blue);
}
public void paint(Graphics g) {
drawPie((Graphics2D)g, getBounds(), slices);
}
}
}

Ther isn't such method in Swing called drawPie. Without the contents of this method, we have no idea of how to help you
Try having a read through 2D Graphics and have a look at Ellipse2D in particular
The other problem I can see is you don't call super.paint(g) in your paint method. This is VERY, VERY, VERY important

You have a PieData component within your applet but you never add it, so you need to add it in init and bring in drawPie from your link above:
public class JLW_PieApplet extends JApplet {
public void init() {
add(new PieData());
}
class PieData extends JComponent {
PieValue[] slices = new PieValue[4];
PieData() {
slices[0] = ...
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
drawPie((Graphics2D) g, getBounds(), slices);
}
public void drawPie(Graphics2D g, Rectangle area, PieValue[] slices) {
...