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Java issues with all my color changing and the drawing not starting when I click

I am having an issue figuring out why my code isn't working for when I click to turn the drawing on/off. It should start as off initially but it doesn't. I also have an issue with my arraylist where I am not sure how to make it so that all the colors don't change when I click on a new color. This is my code so far, any help would be much appreciated.
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.util.ArrayList;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import java.awt.event.MouseMotionAdapter;
public class Draw extends JPanel {
private Point startPoint, endPoint;
private ArrayList<Point> pointList;
private JButton clear;
private JRadioButton red, yellow, blue, eraser;
private boolean clicked;
private final static int SIZE = 30;
public Draw() {
// set the background color
setBackground(Color.WHITE);
// set starting point and end point of mouse click
startPoint = null;
endPoint = null;
this.addMouseListener(new MyMouseListener());
this.addMouseMotionListener(new MyMouseListener());
clicked = false;
pointList = new ArrayList<Point>();
this.addMouseMotionListener(new MyMouseListener());
clear = new JButton("Clear Drawing");
this.add(clear);
clear.addActionListener(new ButtonListener());
red = new JRadioButton("Red", true);
this.add(red);
red.addActionListener(new OptionListener());
yellow = new JRadioButton("Yellow", false);
this.add(yellow);
yellow.addActionListener(new OptionListener());
blue = new JRadioButton("Blue", false);
this.add(blue);
blue.addActionListener(new OptionListener());
eraser = new JRadioButton("Eraser",false);
this.add(eraser);
eraser.addActionListener(new OptionListener());
ButtonGroup group = new ButtonGroup();
group.add(red);
group.add(yellow);
group.add(blue);
group.add(eraser);
}
private class OptionListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
repaint();
}
}
private class ButtonListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
if (event.getSource() == clear) {
pointList.clear();
repaint();
} else {
repaint();
}
}
}
private class MyMouseListener extends MouseAdapter {
#Override
public void mouseClicked(MouseEvent event) {
if (clicked) {
pointList = new ArrayList<Point>();
pointList.add(event.getPoint());
endPoint = null;
} else {
endPoint = event.getPoint();
startPoint = null;
}
clicked = !clicked;
repaint();
}
#Override
public void mouseMoved(MouseEvent event) {
pointList.add(event.getPoint());
repaint();
}
}
#Override
public void paintComponent(Graphics pen) {
super.paintComponent(pen);
Graphics2D g2 = (Graphics2D) pen;
for (Point p : pointList) {
if (red.isSelected()) {
g2.setColor(Color.RED);
g2.fill(new Ellipse2D.Double(p.getX(), p.getY(), SIZE, SIZE));
} else if (yellow.isSelected()) {
g2.setColor(Color.YELLOW);
g2.fill(new Ellipse2D.Double(p.getX(), p.getY(), SIZE, SIZE));
} else if (blue.isSelected()) {
g2.setColor(Color.BLUE);
g2.fill(new Ellipse2D.Double(p.getX(), p.getY(), SIZE, SIZE));
} else {
}
}
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Drawing Time");
frame.setSize(500, 500);
// create an object of your class
Draw panel = new Draw();
frame.getContentPane().add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}

I also have an issue with my arraylist where I am not sure how to make it so that all the colors dont change when I click on a new color
There are two ways to do custom painting:
paint to a BufferedImage. Using this approach the object is painted and the currently selected color will be used to paint the object
(the approach you are using) - store the object you want to paint in an ArrayList. The problem is you are only storing the Point objects in the list so all Points get repainted with the same color. If you want each Point to have a different Color, then you need to store a custom Object that contains both the Color and the Point.
Check out Custom Painting Approaches for working examples of both of these approaches.
You need to associate the Color with each individual object that you paint.

Java - Access datas of a MouseListener from another Component

I'm currently working on a level editor for a game. Currently, to create an Entity, you have to click on a creation JButton, then a form appears, where you enter its coordinate and its size.
I would like to implement a mouse fonction. The user click on the creation JButton, then have to press the mouseButton somewhere on the JPanel where the level is previewed, then drag to set the size of the object, and finally release the button. The object is then created where the button was pressed.
I add a MouseListener to the previewPanel (to get the correct coordinates).
My problem is : what should I do when I click on the button ?Inside the actionPerformed method ?
bascially, the procedure would be :
1) Wait the button to be pressed
2) get coordinates
3) Wait the button to be released
4) Get new coordinates to make the size of the object
5) Create object
How should I proceed to do it properly ?
Thanks in advance

My problem is : what should I do when I click on the button ?
Inside the actionPerformed method ?
Activate the MouseListener. This can be by adding the MouseListener and MouseMotionListener (a MouseAdapater can do both) to the drawing JPanel on button click, or by changing the state of an already added MouseAdapater (my preference), again one that has already been added to the JPanel. This could be as simple as switching a boolean variable to true, and then have the mousePressed, mouseDragged, mouseReleased methods check the state of this boolean before doing any of their actions.
Note that if you go the first route -- by adding a MouseListener/MouseMotionListener on button press, you risk adding multiple listeners if you don't take care to remove them when you're through. That is why I prefer the 2nd approach.
e.g.,
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
public class ActivateMouse extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = PREF_W;
private static final Color DRAW_RECT_COLOR = Color.pink.brighter();
private static final Color DRAW_ALL_RECTS_COLOR = Color.red;
private boolean mouseActive = false;
private Shape drawRect = null;
private List<Shape> shapeList = new ArrayList<>();
private ButtonAction buttonAction = new ButtonAction("Create New Rectangle", KeyEvent.VK_C);
public ActivateMouse() {
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
add(new JButton(buttonAction));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
if (drawRect != null) {
g2.setColor(DRAW_RECT_COLOR);
g2.draw(drawRect);
}
g2.setColor(DRAW_ALL_RECTS_COLOR);
for (Shape shape : shapeList) {
g2.draw(shape);
}
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class MyMouseAdapter extends MouseAdapter {
private Point firstPt;
#Override
public void mousePressed(MouseEvent e) {
if (mouseActive && e.getButton() == MouseEvent.BUTTON1) {
firstPt = e.getPoint();
}
}
#Override
public void mouseDragged(MouseEvent e) {
if (!mouseActive || firstPt == null) {
return;
}
drawRect = createRect(e.getPoint());
repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
if (!mouseActive || firstPt == null) {
return;
}
shapeList.add(createRect(e.getPoint()));
repaint();
mouseActive = false;
}
private Shape createRect(Point p) {
int x = Math.min(firstPt.x, p.x);
int y = Math.min(firstPt.y, p.y);
int width = Math.abs(firstPt.x - p.x);
int height = Math.abs(firstPt.y - p.y);
return new Rectangle(x, y, width, height);
}
}
private class ButtonAction extends AbstractAction {
public ButtonAction(String name, int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
mouseActive = true;
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("ActivateMouse");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ActivateMouse());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

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();
}
}