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The repaint method stops working for short delays

I'm trying to create a simple panel where a 2-dimensional ball is bouncing up and down. I can't get it to work because for some reason I can't call the repaint method more than once a second. The design is basically that there is an object that can be given "an impulse" with the method move(). Everytime the evaluatePosition method is called, the current position will be calculated through the time that has passed, the velocity and the acceleration. The code for the panel is:
public class Display extends JPanel {
private MovableObject object = new MovableObject(new Ellipse2D.Double(5,5,50,50));
private static final int DELAY = 1000;
public Display(){
object.move(50,50);
Timer timer = new Timer(DELAY, new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
object.evaluatePosition();
repaint();
}
});
timer.start();
}
}
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g.drawOval((int)object.getPosition().getX(), (int)object.getPosition.getY()
(int)object.getShape().getWidth(), object.getShape().getHeight());
}
This code works for DELAY=1000 but not for DELAY=100 or DELAY=10 and so on. I read some example code here on SO but they all seem to me like what I already did. So why is my code not working?
EDIT (2016-01-30):
Since it really seems to be a performance issue, here's the code for the MovableObject (I just thought it would be irrelevant and you will probably see why):
public class MovableObject {
// I would really like to use Shape instead of Ellipse2D so that
// objects of any shape can be created
private Ellipse2D.Double shape;
private Point position;
// Vector is my own class. I want to have some easy vector addition and
// multiplication and magnitude methods
private Vector velocity = new Vector(0, 0);
private Vector acceleration = new Vector(0, 0);
private Date lastEvaluation = new Date();
public MovableObject(Ellipse2D.Double objectShape){
shape = objectShape;
}
public void evaluatePosition(){
Date currentTime = new Date();
long deltaTInS = (currentTime.getTime()-lastEvaluation.getTime())/1000;
// s = s_0 + v*t + 0.5*a*t^2
position = new Point((int)position.getX()+ (int)(velocity.getX()*deltaTInS) + (int)(0.5*acceleration.getX()*deltaTInS*deltaTInS),
(int)position.getY()+ (int)(velocity.getY()*deltaTInS) + (int)(0.5*acceleration.getY()*deltaTInS*deltaTInS));
lastEvaluation = currentTime;
}
}
public void move(Vector vector){
velocity = velocity.add(vector);
evaluatePosition();
}
public Point getPosition(){
return position;
}
public Ellipse2D.Double getShape(){
return shape;
}
My move method does not change position but velocity. Please notice that I just changed the shape Object from Shape to Ellipse2D for testing if my code has a performance issue because of the additional code. So if you think this is more complex than it needs to be: I actually want to add some complexity so that the MovableObject can have the shape of any subclass of shape. I've seen a lot of code that seemed more complex to me and rendered fast. So I'd like to know what's wrong with this (besides the fact that it's a bit too complex for just rendering an ellipse).

Okay, so this is a simple example, based on the out-of-context code snippet you left which doesn't seem to have any problems. It has variable speed controlled by a simple slider...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.PathIterator;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class Display extends JPanel {
public static void main(String[] args) {
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 Display());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
private MovableObject object = new MovableObject(new Ellipse2D.Double(5, 5, 50, 50));
private int delay = 40;
private Timer timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
object.evaluatePosition(getSize());
repaint();
}
});
private JSlider slider = new JSlider(5, 1000);
public Display() {
object.move(50, 50);
slider = new JSlider(5, 1000);
slider.setSnapToTicks(true);
slider.setMajorTickSpacing(10);
slider.setMinorTickSpacing(5);
setLayout(new BorderLayout());
add(slider, BorderLayout.SOUTH);
// This is simply designed to put an artificate delay between the
// change listener and the time the update takes place, the intention
// is to stop it from pausing the "main" timer...
Timer delay = new Timer(250, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (timer != null) {
timer.stop();
}
timer.setDelay(slider.getValue());
timer.start();
}
});
slider.addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent e) {
delay.restart();
repaint();
}
});
slider.setValue(40);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.draw(object.getTranslatedShape());
FontMetrics fm = g2.getFontMetrics();
String text = Integer.toString(slider.getValue());
g2.drawString(text, 0, fm.getAscent());
g2.dispose();
}
public class MovableObject {
private Shape shape;
private Point location;
private int xDelta, yDelta;
public MovableObject(Shape shape) {
this.shape = shape;
location = shape.getBounds().getLocation();
Random rnd = new Random();
xDelta = rnd.nextInt(8);
yDelta = rnd.nextInt(8);
if (rnd.nextBoolean()) {
xDelta *= -1;
}
if (rnd.nextBoolean()) {
yDelta *= -1;
}
}
public void move(int x, int y) {
location.setLocation(x, y);
}
public void evaluatePosition(Dimension bounds) {
int x = location.x + xDelta;
int y = location.y + yDelta;
if (x < 0) {
x = 0;
xDelta *= -1;
} else if (x + shape.getBounds().width > bounds.width) {
x = bounds.width - shape.getBounds().width;
xDelta *= -1;
}
if (y < 0) {
y = 0;
yDelta *= -1;
} else if (y + shape.getBounds().height > bounds.height) {
y = bounds.height - shape.getBounds().height;
yDelta *= -1;
}
location.setLocation(x, y);
}
public Shape getTranslatedShape() {
PathIterator pi = shape.getPathIterator(AffineTransform.getTranslateInstance(location.x, location.y));
GeneralPath path = new GeneralPath();
path.append(pi, true);
return path;
}
}
}
You could also have a look at
Swing animation running extremely slow
Rotating multiple images causing flickering. Java Graphics2D
Java Bouncing Ball
for some more examples...

Java Swing -- Key Input with JPanel added to JOptionpane

When I run the code, the added Example1 class to the JOptionPane (in Frame) should get keyInput and then change the y value of the player instance (in example1), but it doesn't work. Also, how would I be able to rotate the ship on its axis and then move in the direction its facing? Currently it moves in the direction its rotated towards, but it rotates on what seems the coordinates 0,0.
Frame
import javax.swing.*;
import java.awt.*;
/**
* Created by griffin on 12/7/2015.
*/
public class Frame extends JFrame {
public Frame() {
initUI();
}
private void initUI() {
JTabbedPane jtp = new JTabbedPane();
Example1 e1 = new Example1();
Example2 e2 = new Example2();
getContentPane().add(jtp);
jtp.add(e1);
jtp.add(e2);
jtp.addTab("Example 1", e1);
jtp.addTab("Example 2", e2);
setResizable(false);
pack();
setTitle("NLTP");
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new Frame();
frame.setVisible(true);
}
});
}
}
Example1
import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.AffineTransform;
/**
* Created by griffin on 12/7/2015.
*/
public class Example1 extends JPanel implements Runnable {
private final int B_WIDTH = 640;
private final int B_HEIGHT = 480;
private int DELAY = 25;
private Thread thread;
Ship player = new Ship(320, 240);
public Example1() {
initScreen();
}
private void initScreen() {
JButton explanation = new JButton("Explanation");
explanation.setBounds(0, 0, 150, 30);
this.setLayout(null);
add(explanation);
addKeyListener(new keyInput());
setFocusable(true);
setBackground(Color.BLACK);
setPreferredSize(new Dimension(B_WIDTH, B_HEIGHT));
setDoubleBuffered(true);
}
#Override
public void addNotify() {
super.addNotify();
thread = new Thread(this);
thread.start();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
draw(g);
}
public void draw(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
AffineTransform old = g2d.getTransform();
g2d.rotate(Math.toRadians(player.angle));
g2d.drawImage(player.ship, player.x, player.y, null);
g2d.setTransform(old);
Toolkit.getDefaultToolkit().sync();
}
public void cycle() {
player.y += player.vY;
}
#Override
public void run() {
long beforeTime, timeDiff, sleep;
beforeTime = System.currentTimeMillis();
while (true) {
cycle();
repaint();
timeDiff = System.currentTimeMillis() - beforeTime;
sleep = DELAY - timeDiff;
if (sleep < 0) {
sleep = 2;
}
try {
Thread.sleep(sleep);
} catch (InterruptedException e) {
System.out.println("Interrupted: " + e.getMessage());
}
beforeTime = System.currentTimeMillis();
}
}
public class keyInput extends KeyAdapter {
#Override
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
if(key == KeyEvent.VK_W) {
}
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if (key == KeyEvent.VK_W) {
player.vY -= 1;
}
if(key == KeyEvent.VK_A) {
player.angle++;
}
if(key == KeyEvent.VK_D) {
player.angle--;
}
}
}
}

KeyListener is well known for having focus related issues. Not only does the component need to be focusable, but it has to have keyboard focus before it will register key events. This is an issue as it's all to easy for your component to lose focus for any number of reasons.
The solution is to use the key bindings API which was designed to help solve this issue. See How to Use Key Bindings for more details.
Swing uses a passive rendering approach. That is, updates occur when ever the API decides something needs to be updated. See Painting in AWT and Swing for more details
What you really need is some kind of active rendering approach, where updates are made on a regular bases. This can be accomplished in a verity of ways, the simplest would be to use a Swing Timer, as it's safe to update the UI (or values that the UI relies on) without the risk of introducing race conditions. See How to use Swing Timers for more details
So, this example basically abstracts the input into four basic movements, rotate left/right and up/down. The code doesn't care how those inputs are generated, only that they can be.
It then uses the key bindings API to register actions for the inputs. This is all done with a single Action class, which just adds the Input to a Set, which the Timer uses to determine what actions should be applied before requesting the UI be repainted.
The rotation is accomplished through the use of a AffineTransform. First we translate the origin to the sprites current x/y position, then rotate it around the center of the sprite. This reduces a lot of the complexity/issues related to rotating things (me simple)
AffineTransform at = AffineTransform.getTranslateInstance(xPos, yPos);
at.rotate(Math.toRadians(angle), sprite.getWidth() / 2, sprite.getHeight() / 2);
g2d.setTransform(at);
g2d.drawImage(sprite, 0, 0, this);
Just beware, a Graphics context is a shared resource, before making these type of changes, you need to make a copy of it (and dispose of it when you are finished)
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class FlyingPoniesWithGuns {
public static void main(String[] args) {
new FlyingPoniesWithGuns();
}
public FlyingPoniesWithGuns() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
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);
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
}
public enum Input {
ROTATE_LEFT,
ROTATE_RIGHT,
UP,
DOWN
}
public class TestPane extends JPanel {
private BufferedImage sprite;
private double angle;
private int xPos, yPos;
private double xDelta, yDelta;
private Set<Input> inputs;
public TestPane() throws IOException {
inputs = new HashSet<>(25);
sprite = ImageIO.read(getClass().getResource("/Pony.png"));
xPos = (400 - sprite.getWidth()) / 2;
yPos = (400 - sprite.getHeight()) / 2;
addKeyBinding("rotate-left", KeyEvent.VK_A, Input.ROTATE_LEFT);
addKeyBinding("rotate-right", KeyEvent.VK_D, Input.ROTATE_RIGHT);
Timer timer = new Timer(40, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (inputs.contains(Input.ROTATE_LEFT)) {
angle -= 5;
} else if (inputs.contains(Input.ROTATE_RIGHT)) {
angle += 5;
}
repaint();
}
});
timer.start();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
AffineTransform at = AffineTransform.getTranslateInstance(xPos, yPos);
at.rotate(Math.toRadians(angle), sprite.getWidth() / 2, sprite.getHeight() / 2);
g2d.setTransform(at);
g2d.drawImage(sprite, 0, 0, this);
g2d.dispose();
}
protected void addKeyBinding(String name, int keyCode, Input input) {
InputMap inputMap = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap actionMap = getActionMap();
inputMap.put(KeyStroke.getKeyStroke(keyCode, 0, false), name + ".pressed");
actionMap.put(name + ".pressed", new InputAction(input, true));
inputMap.put(KeyStroke.getKeyStroke(keyCode, 0, true), name + ".released");
actionMap.put(name + ".released", new InputAction(input, false));
}
protected class InputAction extends AbstractAction {
private Input input;
private boolean pressed;
public InputAction(Input input, boolean pressed) {
this.input = input;
this.pressed = pressed;
}
#Override
public void actionPerformed(ActionEvent e) {
if (pressed) {
inputs.add(input);
} else {
inputs.remove(input);
}
}
}
}
}
Okay, what about movement? You could have a look at How do I make an entity move in a direction? and How can I move a sprite in the direction it is facing? for more ideas on how you might be able to achieve that

Resizing a Path2D shape when user clicks and drags

So, I have a program that adds a square to a JPanel and lets the user drag the shape around the panel. What I want to do is be able to click on the bottom-right corner of the shape and resize it as the user drags it. I'm kind of stuck on how to do this. I know that as the user drags it will need to recalculate the rectangle's length and width to make the bottom right corner match where the mouse is. But how can I detect a click on the bottom right edge of the rectangle? Thanks for any help.
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Panel;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Path2D;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class UMLEditor {
public static void main(String[] args) {
JFrame frame = new UMLWindow();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(30, 30, 1000, 700);
frame.getContentPane().setBackground(Color.white);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
class UMLWindow extends JFrame {
Shapes shapeList = new Shapes();
Panel panel;
private static final long serialVersionUID = 1L;
public UMLWindow() {
addMenus();
panel = new Panel();
}
public void addMenus() {
getContentPane().add(shapeList);
setTitle("UML Editior");
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
shapeList.addSquare(100, 100);
}
public void loadFile() {
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
int r = chooser.showOpenDialog(this);
if (r == JFileChooser.APPROVE_OPTION) {
}
}
}
// Shapes class, used to draw the shapes on the panel
// as well as implements the MouseListener for dragging
class Shapes extends JPanel {
private static final long serialVersionUID = 1L;
private List<Path2D> shapes = new ArrayList<Path2D>();
int currentIndex;
public Shapes() {
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
}
public void addSquare(int width, int height) {
Path2D rect2 = new Path2D.Double();
rect2.append(new Rectangle(getWidth() / 2 - width / 2, getHeight() / 2
- height / 2, width, height), true);
shapes.add(rect2);
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setStroke(new BasicStroke(2));
for (Path2D shape : shapes) {
g2.draw(shape);
}
}
class MyMouseAdapter extends MouseAdapter {
private boolean pressed = false;
private Point point;
#Override
public void mousePressed(MouseEvent e) {
if (e.getButton() != MouseEvent.BUTTON1) {
return;
}
for (int i = 0; i < shapes.size(); i++) {
if (shapes.get(i) != null
&& shapes.get(i).contains(e.getPoint())) {
currentIndex = i;
pressed = true;
this.point = e.getPoint();
}
}
}
#Override
public void mouseDragged(MouseEvent e) {
if (pressed) {
int deltaX = e.getX() - point.x;
int deltaY = e.getY() - point.y;
shapes.get(currentIndex).transform(
AffineTransform.getTranslateInstance(deltaX, deltaY));
point = e.getPoint();
repaint();
}
}
#Override
public void mouseReleased(MouseEvent e) {
pressed = false;
}
}
}

I wrote a couple of things back in the day that might be helpful to you
To start, AreaManager (http://sourceforge.net/p/tus/code/HEAD/tree/tjacobs/ui/shape/) This is kind of what you want, in that it's dealing with Shapes (Area's, actually). There's a dragger class which uses mouse drag, and a resizer class that uses the mouse wheel. But this isn't exactly the user interface you've described.
That user interface for doing changing the cursor and resizing based on the type of cursor and the mouse drag is in Draggable in http://sourceforge.net/p/tus/code/HEAD/tree/tjacobs/ui/drag/. Draggable works with Components that are contained in Containers with the layoutmanager turned off. But it should be not so complicated to adapt to your purposes

Java Swing - How to create custom components with auto size adjustment to the parent

I'm trying to build a custom triangle component that has the same features as a JComponent (like a JButton per say).
The porpoise of the program will be to add triangle on a mouse click exactly where the mouse is and to handle a mouseover event by highlighting the bg of the shape.
I let the default layouts(or null), because while using others, the applications just doesn't place the triangles where I want...
Right now my major issue is how to adjust the size of the triangles with direct proportionality relative to the form size? So that if I reduce the frame size 50% all the components are down that value as well.
One other issue is that the JComponent requires a rectangular area to handle events, for what I've seen there's no way countering this, so if I try to click on the affected area it will just ignore it instead of creating a new triangle there.
And yet another problem is that sometimes while moving out of the triangle from the bottom it is still green.
Thanks!
Here is the SSCCE:
// TriangleCustom.java
package TriangleCustom;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.GeneralPath;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TriangleCustom {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
createAndShowGUI();
}
});
}
private static void createAndShowGUI() {
JFrame f = new JFrame("Triangle");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(1200, 800);
Panel p = new Panel();
f.add(p);
f.setVisible(true);
}
}
class Panel extends JPanel {
// the offsets are the area (rect border) to contain the triangle shape
private final int xOFFSET = 25;
private final int yOFFSET = 50;
ArrayList<TriangleShape> triangleAL = new ArrayList<TriangleShape>();
public Panel() {
setBounds(0, 0, 800, 400);
// setBorder(BorderFactory.createLineBorder(Color.black,2));
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
addTriangle(new Point(e.getX(), e.getY()), new Point(e.getX()
- xOFFSET, e.getY() + yOFFSET), new Point(e.getX()
+ xOFFSET, e.getY() + yOFFSET));
}
});
}
private void addTriangle(Point topCorner, Point leftCorner,
Point rightCorner) {
final TriangleDTO tdto = new TriangleDTO(new Point(25, 0), new Point(0,
50), new Point(50, 50));
TriangleShape ts = new TriangleShape(tdto);
ts.setBorderColor(Color.BLACK);
ts.setFillColor(Color.RED);
ts.setBounds((int) (topCorner.getX() - 25), (int) topCorner.getY(), 51,
51);
triangleAL.add(ts);
this.add(ts);
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.draw(new Rectangle2D.Double(0, 0, 799, 399));
}
}
// the custom component in a shape of a triangle
class TriangleShape extends JComponent {
private GeneralPath triangle = new GeneralPath();
private TriangleDTO tdto = new TriangleDTO();
private Color borderColor = new Color(0);
private Color fillColor = new Color(0);
// Constructor
public TriangleShape(TriangleDTO tdto) {
this.tdto = tdto;
triangle.moveTo(tdto.getTopCorner().getX(), tdto.getTopCorner().getY());
triangle.lineTo(tdto.getLeftCorner().getX(), tdto.getLeftCorner()
.getY());
triangle.lineTo(tdto.getRightCorner().getX(), tdto.getRightCorner()
.getY());
triangle.closePath();
addMouseMotionListener(new MouseAdapter() {
public void mouseMoved(MouseEvent e) {
// there are some issues when going out of the triangle from
// bottom
if (triangle.contains((Point2D) e.getPoint())) {
setFillColor(Color.GREEN);
repaint();
} else {
setFillColor(Color.RED);
repaint();
}
}
});
}
public void setBorderColor(Color borderColor) {
this.borderColor = borderColor;
}
public void setFillColor(Color fillColor) {
this.fillColor = fillColor;
}
#Override
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setPaint(fillColor);
g2d.fill(triangle);
g2d.setPaint(borderColor);
g2d.draw(triangle);
}
}
// just a plain DTO for the triangle points
class TriangleDTO {
private Point topCorner = new Point();
private Point leftCorner = new Point();
private Point rightCorner = new Point();
// Constructors
public TriangleDTO() {
}
public TriangleDTO(Point topCorner, Point leftCorner, Point rightCorner) {
super();
this.topCorner = topCorner;
this.leftCorner = leftCorner;
this.rightCorner = rightCorner;
}
// Getters and Setters
public Point getTopCorner() {
return topCorner;
}
public void setTopCorner(Point topCorner) {
this.topCorner = topCorner;
}
public Point getLeftCorner() {
return leftCorner;
}
public void setLeftCorner(Point leftCorner) {
this.leftCorner = leftCorner;
}
public Point getRightCorner() {
return rightCorner;
}
public void setRightCorner(Point rightCorner) {
this.rightCorner = rightCorner;
}
}

Changing JPanel Graphics g color drawing line

i have a program similar to paint. and that i am trying to implement a change pen color however when i change the color, everything currently drawn is changed to the color RED for example in my program,how can i make it such that it will not repaint everything currently drawn to the currently changed color?Below code will compile and run
Class for the JPanel drawing area
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
//refer to http://jkost.ergoway.gr/jnkjavaconnection/freedraw.html for the algorithm.
public class STDrawingArea extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;
ArrayList<Rectangle> dPoint = new ArrayList<Rectangle>();
Point point = new Point(-1,-1);
private Color currentColor;
public STDrawingArea()
{
setBorder(BorderFactory.createLineBorder(Color.black));
setBackground(Color.WHITE);
addMouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent e)
{
dPoint.add(new Rectangle(point.x,point.y,e.getX(),e.getY()));
point.x = e.getX();
point.y = e.getY();
repaint();
}
});
addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e)
{
System.out.println("mousePressed X: "+e.getX()+"mousePressed Y: "+e.getY());
dPoint.add(new Rectangle(e.getX(),e.getY(),-1,-1));
point.x = e.getX();
point.y = e.getY();
}
});
addMouseListener(new MouseAdapter(){
public void mouseReleased(MouseEvent e)
{
System.out.println("mouseReleased X: "+e.getX()+"mouseReleased Y: "+e.getY());
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(700,500);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getCurrentColor());
for (int i=0; i < dPoint.size(); i++) {
Rectangle r = dPoint.get(i);
if (r.width != -1)
{
g.drawLine(r.x, r.y, r.width, r.height);
}
}
/* Draw current point.*/
g.drawLine(point.x, point.y, point.x, point.y);
}
//set current drawing color
public void changePenColor(Color color)
{
if (color == null)
setCurrentColor(Color.BLACK);
else
setCurrentColor(color);
}
//clear drawings method
public void clearDrawings()
{
if(!(dPoint==null))
{
dPoint.clear();
repaint();
}
}
private void setCurrentColor(Color currentColor) {
this.currentColor = currentColor;
}
private Color getCurrentColor() {
return currentColor;
}
}
Test main class.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class STTestMain extends JFrame {
STDrawingArea drawingArea = new STDrawingArea();
public STTestMain()
{
//JFrame settings
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Spelling Trainer");
setResizable(false);
setVisible(true);
//Panel of buttons
JPanel buttonContainer = new JPanel();
JButton btnPenColor = new JButton("Red Pen");
buttonContainer.add(btnPenColor);
//Drawing Area instantiation
//Adding things to JFrame
getContentPane().add(drawingArea);
getContentPane().add(buttonContainer,BorderLayout.PAGE_END);
pack();
//button listener
btnPenColor.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
drawingArea.changePenColor(Color.RED);
}
});
}
public static void main(String args[])
{
STTestMain test = new STTestMain();
}
}

One way:
Use your ArrayList to draw the current curve as it is being drawn, but
Use a BufferedImage to draw your completed curves
You would do this on mouseReleased and would draw the current curve to the BufferedImage using the current color.
You'll also need to re-initialize your ArrayList of points after drawing to the BufferedImage.
Don't forget to dispose of the BufferedImage's Graphics object after you're done using it.
Draw the BufferedImage in your paintComponent method after super.paintComponent but before drawing your current curve.
This way when you change the color of your drawing, only the current curve is effected.
EDIT
You've mentioned in a comment that you're not familiar with BufferedImage, and are looking for another way. I suppose you could create a class that holds an ArrayList of Points together with a Color, and then on each mouseReleased create an object of this class and add it to an ArrayList in your drawing panel. Then your paintComponent method could iterate through that ArrayList, drawing the list of Points with their associated color, but my gut tells me that you're an intelligent guy and that you'd pick up on how to use a BufferedImage in no time. I really think it's the best solution. And if you try it and it flops, show us your code, and we'll likely be able to help you.
EDIT 2
The BufferedImage constructor will need the image width, height and an image type -- something I'm not 100% familiar with. I usually use BufferedImage.TYPE_INT_RGB for general purpose drawing, and BufferedImage.TYPE_INT_ARGB for general purpose that needs an alpha too. Then you'll extract a Graphics object out of the BufferedImage, say getGraphics() if all you need is a Graphics object and not a Graphics2D object. Then when you initialize the BufferedImage in your constructor, fill it with a Color.white, just as you for your JPanel. Then dispose the Graphics object. Then each time you want to draw, you getGraphics, draw with it, just like you do in the paintComponent method, dispose of the Graphics when done, and finally draw the BufferedImage in the paintComponent via the drawImage method.
EDIT 3
Example program that doesn't do quite what you are trying to do but does illustrate use of a BufferedImage with drawing. This program changes the color each time a new path or curve is drawn.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import javax.swing.*;
public class STTestSimple {
private static void createAndShowUI() {
STDrawPanel drawPanel = new STDrawPanel();
STMouseAdapter mAdapter = new STMouseAdapter(drawPanel);
drawPanel.addMouseListener(mAdapter);
drawPanel.addMouseMotionListener(mAdapter);
JFrame frame = new JFrame("Drawing");
frame.getContentPane().add(drawPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
#SuppressWarnings("serial")
class STDrawPanel extends JPanel {
private static final int ST_WIDTH = 700;
private static final int ST_HEIGHT = 500;
private static final Color BACKGROUND_COLOR = Color.white;
private static final float STROKE_WIDTH = 6f;
private static final Stroke STROKE = new BasicStroke(STROKE_WIDTH,
BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
private static final Color[] colors = {Color.black, Color.blue, Color.red,
Color.green, Color.orange, Color.MAGENTA};
private BufferedImage bImage = new BufferedImage(ST_WIDTH, ST_HEIGHT,
BufferedImage.TYPE_INT_RGB);
private Color color = Color.black;
private ArrayList<Point> points = new ArrayList<Point>();
private int colorIndex = 0;
public STDrawPanel() {
Graphics g = bImage.getGraphics();
g.setColor(BACKGROUND_COLOR);
g.fillRect(0, 0, ST_WIDTH, ST_HEIGHT);
g.dispose();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(bImage, 0, 0, null);
Graphics2D g2 = (Graphics2D) g;
drawCurve(g2);
}
private void addCurveToBufferedImage() {
Graphics2D g2 = bImage.createGraphics();
drawCurve(g2);
g2.dispose();
}
private void drawCurve(Graphics2D g2) {
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(STROKE);
g2.setColor(color);
if (points != null && points.size() > 1) {
for (int i = 0; i < points.size() - 1; i++) {
int x1 = points.get(i).x;
int y1 = points.get(i).y;
int x2 = points.get(i + 1).x;
int y2 = points.get(i + 1).y;
g2.drawLine(x1, y1, x2, y2);
}
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(ST_WIDTH, ST_HEIGHT);
}
public void curveStart(Point point) {
points.clear();
points.add(point);
}
public void curveEnd(Point point) {
points.add(point);
addCurveToBufferedImage();
points.clear();
repaint();
colorIndex++;
colorIndex %= colors.length;
setColor(colors[colorIndex]);
}
public void curveAdd(Point point) {
points.add(point);
repaint();
}
public void setColor(Color color) {
this.color = color;
}
}
class STMouseAdapter extends MouseAdapter {
private STDrawPanel drawPanel;
public STMouseAdapter(STDrawPanel drawPanel) {
this.drawPanel = drawPanel;
}
#Override
public void mousePressed(MouseEvent e) {
drawPanel.curveStart(e.getPoint());
}
#Override
public void mouseReleased(MouseEvent e) {
drawPanel.curveEnd(e.getPoint());
}
#Override
public void mouseDragged(MouseEvent e) {
drawPanel.curveAdd(e.getPoint());
}
}

Custom Painting Approaches gives two ideas on how you might do this.

Thanks hovercraft, i've done it looking at your code and fiddling around lol.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
public class STDrawingArea extends JPanel {
/**
*
*/
private static final int DA_WIDTH = 700;
private static final int DA_HEIGHT = 500;
private static final Color DA_BGCOLOR = Color.WHITE;
private static final long serialVersionUID = 1L;
ArrayList<Point> points = new ArrayList<Point>();
private Color currentColor;
BufferedImage bImage = new BufferedImage(DA_WIDTH, DA_HEIGHT, BufferedImage.TYPE_INT_RGB);
public STDrawingArea()
{
setBorder(BorderFactory.createLineBorder(Color.black));
//Basic Settings for bImage
Graphics g2d = bImage.getGraphics();
g2d.setColor(DA_BGCOLOR);
g2d.fillRect(0, 0, DA_WIDTH, DA_HEIGHT);
g2d.dispose();
addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e)
{
points.clear();
points.add(e.getPoint());
}
});
addMouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent e)
{
points.add(e.getPoint());
repaint();
}
});
addMouseListener(new MouseAdapter(){
public void mouseReleased(MouseEvent e)
{
points.add(e.getPoint());
points.clear();
System.out.println("mouseReleased X: "+e.getX()+"mouseReleased Y: "+e.getY());
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(DA_WIDTH,DA_HEIGHT);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
drawIntoBufferedImage();
g.drawImage(bImage,0,0,null);
freehandLines(g);
}
public void drawIntoBufferedImage()
{
Graphics g = bImage.getGraphics();
freehandLines(g);
g.dispose();
}
public void freehandLines(Graphics g)
{
if(points != null && points.size() > 1)
{
g.setColor(getCurrentColor());
for(int i = 0; i < points.size()-1;i++)
{
int x1 = points.get(i).x;
int y1 = points.get(i).y;
int x2 = points.get(i+1).x;
int y2 = points.get(i+1).y;
g.drawLine(x1, y1, x2, y2);
}
}
}
//clear drawings method
public void clearDrawings()
{
if(points!=null)
{
points.clear();
Graphics g = bImage.getGraphics();
g.setColor(DA_BGCOLOR);
g.fillRect(0, 0, DA_WIDTH, DA_WIDTH);
g.dispose();
repaint();
}
}
public void setCurrentColor(Color currentColor) {
if(currentColor == null)
{
currentColor = Color.BLACK;
}else{
this.currentColor = currentColor;
}
}
public Color getCurrentColor() {
if (currentColor == null)
return Color.BLACK;
else
return currentColor;
}
}
main class
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class STTestMain extends JFrame {
STDrawingArea drawingArea = new STDrawingArea();
public STTestMain()
{
//JFrame settings
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Spelling Trainer");
setResizable(false);
setVisible(true);
//Panel of buttons
JPanel buttonContainer = new JPanel();
JButton btnRedPen = new JButton("Red Pen");
JButton btnGreenPen = new JButton("Green Pen");
JButton btnClear = new JButton("Clear");
buttonContainer.add(btnRedPen);
buttonContainer.add(btnGreenPen);
buttonContainer.add(btnClear);
//Drawing Area instantiation
//Adding things to JFrame
getContentPane().add(drawingArea);
getContentPane().add(buttonContainer,BorderLayout.PAGE_END);
pack();
//button listener
btnRedPen.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
drawingArea.setCurrentColor(Color.RED);
}
});
btnGreenPen.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
drawingArea.setCurrentColor(Color.GREEN);
}
});
btnClear.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
drawingArea.clearDrawings();
}
});
}
public static void main(String args[])
{
STTestMain test = new STTestMain();
}
}