Develop Reference

Why isn't this code triggering paint()?

It runs, the buttons work, but i just can't get it to draw with the paint(). I think it has something to do with the main method on SwingDraw, but i'm not 100% sure. Thanks for any help and sorry for the long code :/
SwingDraw:
// Import Core Java packages
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.*;
import javax.swing.*;
public class SwingDraw extends JFrame implements ActionListener, ItemListener{
// Initial Frame size
static final int WIDTH = 1500; // frame width
static final int HEIGHT = 1000; // frame height
// Color choices
static final String[] COLOR_NAMES = new String[]{"None", "Red", "Blue", "Green"};
static final Color COLORS[] = {null, Color.red, Color.blue, Color.green };
// Button control
JButton circle;
JButton roundRec;
JButton threeDRec;
JButton line;
JButton square;
JButton oval;
JButton clear;
JButton delete;
// List to keep track of shapes
JList<String> shapesKeeper;
// Color choice box
JComboBox<String> colorChoice = new JComboBox<>(COLOR_NAMES);
SwingDrawCanvas betterCanvas = new SwingDrawCanvas();
/**
* Constructor
*/
public SwingDraw() {
// Create a frame
setSize(WIDTH, HEIGHT);
setLocation(130, 100);
// add window closing listener
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// create panel for controls
JPanel topPanel = new JPanel();
JPanel leftList = new JPanel();
// create button control
JPanel buttonPanel = new JPanel();
topPanel.add(buttonPanel, BorderLayout.NORTH);
circle = new JButton("Circle");
buttonPanel.add(circle);
roundRec = new JButton("Rounded Rectangle");
buttonPanel.add(roundRec);
threeDRec = new JButton("3D Rectangle");
buttonPanel.add(threeDRec);
line = new JButton("Line");
buttonPanel.add(line);
square = new JButton("Square");
buttonPanel.add(square);
oval = new JButton("Oval");
buttonPanel.add(oval);
clear = new JButton("Clear");
buttonPanel.add(clear);
JPanel listPanel = new JPanel();
leftList.add(listPanel, BorderLayout.WEST);
JList<String> shapesKeeper = new JList<>();
listPanel.add(shapesKeeper);
delete = new JButton("Delete Shape");
listPanel.add(delete);
// add button listener
circle.addActionListener(this);
roundRec.addActionListener(this);
threeDRec.addActionListener(this);
line.addActionListener(this);
square.addActionListener(this);
oval.addActionListener(this);
clear.addActionListener(this);
// create panel for color choices
JPanel colorPanel = new JPanel();
JLabel label = new JLabel("Filled Color:");
topPanel.add(colorPanel);
colorPanel.add(label);
JComboBox<String> colorChoice = new JComboBox<>(COLOR_NAMES);
colorPanel.add(colorChoice);
colorChoice.addItemListener(this);
add(topPanel, BorderLayout.NORTH);
add(leftList, BorderLayout.WEST);
setVisible(true);
} // end of constructor
/**
* Implementing ActionListener
*/
public void actionPerformed(ActionEvent event) {
if(event.getSource() == circle) { // circle button
betterCanvas.setShape(SwingDrawCanvas.CIRCLE);
}
else if(event.getSource() == roundRec) { // rounded rectangle button
betterCanvas.setShape(SwingDrawCanvas.ROUNDED_RECTANGLE);
}
else if(event.getSource() == threeDRec) { // 3D rectangle button
betterCanvas.setShape(SwingDrawCanvas.RECTANGLE_3D);
}
else if(event.getSource() == clear){
betterCanvas.setShape(SwingDrawCanvas.CLEAR);
}
else if(event.getSource() == line){
betterCanvas.setShape(SwingDrawCanvas.LINE);
}
else if(event.getSource() == square){
betterCanvas.setShape(SwingDrawCanvas.SQUARE);
}
else if(event.getSource() == oval){
betterCanvas.setShape(SwingDrawCanvas.OVAL);
}
}
/**
* Implementing ItemListener
*/
public void itemStateChanged(ItemEvent event) {
Color color = COLORS[colorChoice.getSelectedIndex()];
betterCanvas.setFilledColor(color);
}
/**
* the main method
*/
public static void main(String[] argv) {
new SwingDraw();
}
}
SwingDrawCanvas:
public class SwingDrawCanvas extends JPanel implements MouseListener, MouseMotionListener {
// Constants for shapes
public static final int CIRCLE = 1;
public static final int ROUNDED_RECTANGLE = 2;
public static final int RECTANGLE_3D = 3;
public static final int LINE = 4;
public static final int SQUARE = 5;
public static final int OVAL = 6;
public static final int CLEAR = 7;
// Coordinates of points to draw
private int x1, y1, x2, y2;
// shape to draw
private int shape = CIRCLE;
/**
* Method to set the shape
*/
public void setShape(int thisShape) {
System.out.println("HEY");
this.shape = thisShape;
System.out.println(shape);
}
// filled color
private Color filledColor = null;
/**
* Method to set filled color
*/
public void setFilledColor(Color color) {
filledColor = color;
}
/**
* Constructor
*/
public SwingDrawCanvas() {
addMouseListener(this);
addMouseMotionListener(this);
} // end of constructor
/**
* painting the component
*/
public void paint(Graphics g) {
System.out.println("ARHFHASJDASHDHAs");
super.paint(g);
System.out.println("AHAHAHAHAHAHAHA");
g.drawString("FUCK", 1, 1);
// the drawing area
int x, y, width, height;
// determine the upper-left corner of bounding rectangle
x = Math.min(x1, x2);
y = Math.min(y1, y2);
// determine the width and height of bounding rectangle
width = Math.abs(x1 - x2);
height = Math.abs(y1 - y2);
if(filledColor != null)
g.setColor(filledColor);
switch (shape) {
case ROUNDED_RECTANGLE :
if(filledColor == null)
g.drawRoundRect(x, y, width, height, width/4, height/4);
else
g.fillRoundRect(x, y, width, height, width/4, height/4);
break;
case CIRCLE :
int diameter = Math.max(width, height);
if(filledColor == null)
System.out.println("HRE BITCHS");
else
System.out.println("HEY FUCK YOU GUY");
break;
case RECTANGLE_3D :
if(filledColor == null)
g.draw3DRect(x, y, width, height, true);
else
g.fill3DRect(x, y, width, height, true);
break;
}
}
/**
* Implementing MouseListener
*/
public void mousePressed(MouseEvent event) {
x1 = event.getX();
y1 = event.getY();
}
public void mouseReleased(MouseEvent event) {
x2 = event.getX();
y2 = event.getY();
repaint();
}
public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
/**
* Implementing MouseMotionListener
*/
public void mouseDragged(MouseEvent event) {
x2 = event.getX();
y2 = event.getY();
repaint();
}
public void mouseMoved(MouseEvent e) {}
}
I'm not very good at this, I'm just looking for any help you guys can give me :D

Instead of having paint(), your function should be name paintComponent(Graphics g).
When creating the paintComponent(Graphics g) functions, you need #Override so that java recognizes the function because you can not call paintComponent(Graphics g) directly.
In addition, any time you want to refresh your panel, you can call repaint() or you can resize your JFrame after the code as compiled. Both of these methods will call the paintComponent(Graphics g) function.

Swing paintComponent not working properly

I don't understand why i have to set Component.setPreferredSize() to draw and why my ovals are not placed in one place. Also i got some other questions, which are described below.
public class PaintPanel extends JPanel implements ActionListener
{
private void initStructure()
{
for (int i : new Range(MAX_AGENTS)) {
Agent agent = new Agent();
agents.add(agent);
add(agent);
}
}
//i want to override parent class 'add', to easy call 'actionPerformed' on children elements.
public Component add(Element comp)
{
elements.add(comp);
return super.add(comp);
}
#Override
public void actionPerformed(ActionEvent e)
{
for(Element element: elements){
element.actionPerformed(e);
}
repaint();
}
//ELEMENT is abstract class: 'public class Element extends JComponent implements ActionListener'
public class Agent extends Element
{
public Agent()
{
super();
// setPreferredSize(new Dimension(120,120)); !!!! a-a, i don't know the future size of the oval or triangle, i don't want and i can't set this :(
setVisible(true);
}
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
System.out.println("draw"); //called
Point p1 = new Point(1, 1);
Point p2 = new Point(101, 101);
Point p3 = new Point(10, 10);
int[] xs = { p1.x, p2.x, p3.x };
int[] ys = { p1.y, p2.y, p3.y };
Polygon triangle = new Polygon(xs, ys, xs.length);
g.setColor(new Color(255,255,255)); // !! never painted
g.fillPolygon(triangle); //!! never painted
g.drawOval(10,10,10,10); // !!!! painted only when i set preferredSize
}
#Override
public void actionPerformed(ActionEvent e)
{
System.out.println("i am alive"); //working
}
}
In case, if i set preferred size i got the picture below.
So.
Question
1) Is there any patterns to not set preferred size and draw component inside Component calling paint() on contentPanel?
2) Why g.fillPolygon not working?
3) Why my ovals are not placed in one point?

Why my ovals are not placed in one point?
I would guess you are adding your Agent components to a JPanel. By default a JPanel uses a FlowLayout. So each component is placed 120 pixels apart and flow to a new line when the row is filled.
i don't know the future size of the oval or triangle, i don't want and i can't set this
Don't use the drawOval(...) method. Instead use a Shape object that represents an oval. Then you can get the size of the Shape and use this value in the getPreferredSize() method mentioned by #hovercraft.
Check out Playing With Shapes for more info on this concept. Of course if you use this concept you would need to define the Shapes as instance variable so the Shape can be referenced by both the paintComponent() and getpreferredSize() methods.

The issue is if the JPanel doesn't have a preferred size, and if it is being added to a container that uses a layout manager that doesn't fill the container (such as FlowLayout), then how will the GUI know what size the drawing JPanel should be? I've heard that better than calling setPreferredSize(...) on your JPanel is to override its Dimension getPreferredSize() method (ask kleopatra, a Swing expert on this site).
Regarding:
Why g.fillShape not working?
Check the API -- does Graphics have a fillShape method? Nope. But Graphics2D has a fill(Shape s) method, and that's what you want.
Why my ovals are not placed in one point?
Please clarify this and provide details. What do you mean by "placed in one point"? What behavior exactly are you expecting and why?
Edit: your triangle is not being drawn because all the points are co-linear!
For example:
import java.awt.*;
import javax.swing.*;
public class MyDrawingPanel extends JPanel {
private static final int PREF_W = 100;
private static final int PREF_H = PREF_W;
// private Point p1 = new Point(1, 1);
private Point p1 = new Point(30, 1);
private Point p2 = new Point(100, 101);
// private Point p3 = new Point(10, 10);
private Point p3 = new Point(50, 10);
private int[] xs = { p1.x, p2.x, p3.x };
private int[] ys = { p1.y, p2.y, p3.y };
private Polygon triangle = new Polygon(xs, ys, xs.length);
public MyDrawingPanel() {
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(new Color(255, 255, 255)); // !! never painted
g.fillPolygon(triangle); // !! never painted
g.drawOval(10, 10, 10, 10); // !!!! painted only when i set preferredSize
}
private static void createAndShowGui() {
int rows = 4;
int cols = 4;
JPanel gridPanel = new JPanel(new GridLayout(rows, cols));
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
gridPanel.add(new MyDrawingPanel());
}
}
JFrame frame = new JFrame("PaintPanel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(gridPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

How to save current state of graphics on JPanel [duplicate]

This question already has answers here:
How to serialize Java 2D Shape objects as XML?
(2 answers)
Closed 8 years ago.
I have a program that lets the user add rectangles and circles to JPanel using Graphics. What I want to be able to do is save the current state of the current JPanel (i.e. all of the shapes and their locations) into a file and be able to load that file back and restore that state. I have a Shapes class that extends JPanel and does all of the drawing and keeps track of the shapes with an ArrayList.
Will I be able to just simply save the state of the panel? Or will I have to just save the Shapes data into a file and redraw the shapes when a file is "opened"?
Can anyone guide me on how I can save the current state of my JPanel and re-open it? Thanks
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();
public UMLWindow() {
addMenus();
}
public void addMenus() {
getContentPane().add(shapeList);
JMenuBar menubar = new JMenuBar();
JMenu file = new JMenu("File");
JMenuItem openMenuItem = new JMenuItem("Open File");
openMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
// Open saved state
});
JMenuItem saveMenuItem = new JMenuItem("Save");
saveMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
// Save current state
}
});
file.add(openMenuItem);
file.add(saveMenuItem);
JMenu shapes = new JMenu("Shapes");
file.setMnemonic(KeyEvent.VK_F);
JMenuItem rectangleMenuItem = new JMenuItem("New Rectangle");
rectangleMenuItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
shapeList.addSquare(100, 100);
}
});
JMenuItem circleMenuItem = new JMenuItem("New Circle");
circleMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
shapeList.addCircle(100, 100);
}
});
shapes.add(rectangleMenuItem);
shapes.add(circleMenuItem);
menubar.add(file);
menubar.add(shapes);
setJMenuBar(menubar);
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
// 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();
}
public void addCircle(int width, int height) {
Path2D rect2 = new Path2D.Double();
rect2.append(new Ellipse2D.Double(getWidth() / 2 - width / 2,
getHeight() / 2 - height / 2, width, height), true);
shapes.add(rect2);
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
this.setOpaque(true);
this.setBackground(Color.WHITE);
Graphics2D g2 = (Graphics2D) g;
for (Path2D rect : shapes) {
g2.draw(rect);
}
}
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;
}
}
}

You could add a line of code in addCircle and addSquare that stores their H and W (or instances of the shapes themselves) in a serialized array (which could be saved to a .dat file). Then read the file and shapes.add(tehShape) for each shape entry in the dat file and repaint when needed. Used this method on an android app when i needed a persistent storage of customized ListView items. Not pretty, but it worked like a charm once properly set up. Upside of this is that you will be saving identical object instances in the dat file, downside is that they wont be human-readable.

Adding multiple MouseListeners dynamically JPanel

I am trying to add shapes onto a window using JPanel and then be able to click and drag them around the window. This works if I only have one shape; but when I add more shapes, the click and drag is very funky. It does drag but not with the mouse, it isn't proportional and doesn't drag with the mouse.
Any help is appreciated. Thanks!
public class SimpleDraw {
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);
// Display the window.
frame.setVisible(true);
}
}
class UMLWindow extends JFrame {
Squares squares = new Squares();
private static final long serialVersionUID = 1L;
public UMLWindow() {
addMenus();
}
public void addMenus() {
getContentPane().add(squares);
JMenuBar menubar = new JMenuBar();
JMenu shapes = new JMenu("Shapes");
JMenuItem rectangleMenuItem = new JMenuItem("New Rectangle");
rectangleMenuItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
squares.addSquare(10, 10, 100, 100);
}
});
shapes.add(rectangleMenuItem);
menubar.add(shapes);
setJMenuBar(menubar);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
class Squares extends JPanel {
private static final long serialVersionUID = 1L;
private List<Path2D> squares = new ArrayList<Path2D>();
// private Path2D rect = new Path2D.Double();
int currentIndex;
public void addSquare(int x, int y, int width, int height) {
Path2D rect2 = new Path2D.Double();
rect2.append(new Rectangle(getWidth() / 2 - width / 2, getHeight() / 2
- height / 2, width, height), true);
squares.add(rect2);
// rect = rect2;
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
this.setOpaque(true);
this.setBackground(Color.WHITE);
Graphics2D g2 = (Graphics2D) g;
for (Path2D rect : squares) {
g2.draw(rect);
}
repaint();
}
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 < squares.size(); i++) {
if (squares.get(i) != null
&& squares.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;
squares.get(currentIndex).transform(
AffineTransform.getTranslateInstance(deltaX, deltaY));
point = e.getPoint();
repaint();
}
}
#Override
public void mouseReleased(MouseEvent e) {
pressed = false;
}
}
}

Lot of problems...
Most important, no you don't want to add a bunch of MouseListeners/MouseMotionListeners to your JPanel. You only want to add one, and have it control any and all squares that the JPanel holds.
Don't put a repaint() in your paintComponent method as that's a poor way to try to create an animation loop, a loop that you have absolutely no control over. Plus there's no need. The MouseAdapter should drive all the animation by itself.
class Squares extends JPanel {
private static final long serialVersionUID = 1L;
public Squares() {
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
}
private List<Path2D> squares = new ArrayList<Path2D>();
// private Path2D rect = new Path2D.Double();
int currentIndex;
public void addSquare(int x, int y, int width, int height) {
Path2D rect2 = new Path2D.Double();
rect2.append(new Rectangle(getWidth() / 2 - width / 2, getHeight() / 2
- height / 2, width, height), true);
squares.add(rect2);
repaint(); // !!
// rect = rect2;
// !! MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
// addMouseListener(myMouseAdapter);
// addMouseMotionListener(myMouseAdapter);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
this.setOpaque(true);
this.setBackground(Color.WHITE);
Graphics2D g2 = (Graphics2D) g;
for (Path2D rect : squares) {
g2.draw(rect);
}
// !! repaint();
}

Change stroke-size while program is running

I know it's a stupid question for the Java cracks out there.
At the moment I'm writing a little paintingprogramm.
So my problem is, that i want to set the stroke size in a little dropdownmenu.
The code for the dropdown is here:
DefaultComboBoxModel model = new DefaultComboBoxModel();
model.addElement("1");
model.addElement("5");
model.addElement("10");
JComboBox comboBox = new JComboBox(model);
panel.add(comboBox);
And the Code of the stroke size is here:
public void mouseDragged(MouseEvent e) {
currentX = e.getX();
currentY = e.getY();
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Stroke stroke = new BasicStroke(10);
graphics2D.setStroke(stroke);
graphics2D.drawLine(oldX, oldY, currentX, currentY);
repaint();
oldX = currentX;
oldY = currentY;
}
The 10 in the BasicStroke is just some random number. I wanted to realize it, that it reads from the dropdown (standart 1), saves it in a variable and the variable get used in the BasicStroke function.
Here is the whole code (Netbeans project):
package paint;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Paint {
public static void main(String[] args) {
PaintWindow frame = new PaintWindow();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.setVisible(true);
}
}
class PaintWindow extends JFrame {
public PaintWindow() {
setTitle("Paint it");
setSize(700, 600);
panel = new JPanel();
panel.setPreferredSize(new Dimension(64, 64));
drawPad = new PadDraw();
//Creates a new container
Container content = this.getContentPane();
content.setLayout(new BorderLayout());
//sets the panel to the left, padDraw in the center
content.add(panel, BorderLayout.NORTH);
content.add(drawPad, BorderLayout.CENTER);
//add the color buttons:
makeColorButton(Color.BLACK);
makeColorButton(Color.BLUE);
makeColorButton(Color.MAGENTA);
makeColorButton(Color.RED);
makeColorButton(Color.ORANGE);
makeColorButton(Color.YELLOW);
makeColorButton(Color.GREEN);
makeColorButton(Color.CYAN);
DefaultComboBoxModel model = new DefaultComboBoxModel();
model.addElement("1");
model.addElement("5");
model.addElement("10");
JComboBox comboBox = new JComboBox(model);
panel.add(comboBox);
//creates the clear button
JButton clearButton = new JButton("Clear");
clearButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
drawPad.clear();
}
});
panel.add(clearButton);
panel = new JPanel();
JLabel jlabel = new JLabel("Copyright© by Jan Büttiker");
panel.setPreferredSize(new Dimension(0, 20));
panel.add(jlabel);
content.add(panel, BorderLayout.SOUTH);
}
/*
* makes a button that changes the color
* #param color the color used for the button
*/
public void makeColorButton(final Color color) {
JButton tempButton = new JButton();
tempButton.setBackground(color);
tempButton.setPreferredSize(new Dimension(56, 56));
panel.add(tempButton);
tempButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
drawPad.changeColor(color);
}
});
}
private JPanel panel;
private PadDraw drawPad;
}
class PadDraw extends JComponent {
//this is gonna be the image that you draw on
Image image;
//this is what we'll be using to draw on
Graphics2D graphics2D;
//these are gonna hold the mouse coordinates
int currentX, currentY, oldX, oldY;
public PadDraw() {
setDoubleBuffered(false);
addMouseListener(new MouseAdapter() {
//if the mouse is pressed it sets the oldX & oldY
//coordinates as the mouses x & y coordinates
public void mousePressed(MouseEvent e) {
oldX = e.getX();
oldY = e.getY();
}
});
addMouseMotionListener(new MouseMotionAdapter() {
//while the mouse is dragged it sets currentX & currentY as the mouses x and y
//then it draws a line at the coordinates
//it repaints it and sets oldX and oldY as currentX and currentY
public void mouseDragged(MouseEvent e) {
currentX = e.getX();
currentY = e.getY();
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
Stroke stroke = new BasicStroke(10);
graphics2D.setStroke(stroke);
graphics2D.drawLine(oldX, oldY, currentX, currentY);
repaint();
oldX = currentX;
oldY = currentY;
}
});
}
//this is the painting bit
//if it has nothing on it then
//it creates an image the size of the window
//sets the value of Graphics as the image
//sets the rendering
//runs the clear() method
//then it draws the image
public void paintComponent(Graphics g) {
if (image == null) {
image = createImage(getSize().width, getSize().height);
graphics2D = (Graphics2D) image.getGraphics();
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
clear();
}
g.drawImage(image, 0, 0, null);
}
//this is the clear
//it sets the colors as white
//then it fills the window with white
//thin it sets the color back to black
public void clear() {
graphics2D.setPaint(Color.white);
graphics2D.fillRect(0, 0, getSize().width, getSize().height);
graphics2D.setPaint(Color.black);
repaint();
}
public void changeColor(Color theColor) {
graphics2D.setPaint(theColor);
repaint();
}
}
It's my first post, so please be kind, I'm still in the learning phase ^^.
Thanks for the help and have a nice day

For that purposes you need to use ItemListener on your JComboBox. read more about ComboBox in tutorial.
1) add instance variable public float strokeSize = 10.0f; to your PadDraw as default value.
2) use Stroke stroke = new BasicStroke(strokeSize); instead of Stroke stroke = new BasicStroke(10);
3) Create your ComboBox in next way, it will change strokeSize value if you change value in JComboBox:
DefaultComboBoxModel<Float> model = new DefaultComboBoxModel<Float>();
model.addElement(1f);
model.addElement(5f);
model.addElement(10f);
final JComboBox<Float> comboBox = new JComboBox<Float>(model);
comboBox.addItemListener(new ItemListener() {
#Override
public void itemStateChanged(ItemEvent arg0) {
Float selectedItem = (Float) comboBox.getSelectedItem();
if(selectedItem != null){
drawPad.strokeSize = selectedItem;
}
}
});