Develop Reference

Drawing a triangle using mouse clicks in java graphics

this is my code. It worked for drawing a circle but I am having troubles drawing a triangle now.. A triangle should appear using mouse clicks but it is showing a triangle immediately after running the application. Please help. Thanks.
package mouse;
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.event.*;
import java.awt.geom.*;
public class triangle extends JFrame implements ActionListener, MouseListener {
int xx[]= {20, 50, 80};
int yy[]= {80, 30, 80};
public triangle () {
setSize(2000,2000);
addMouseListener(this);
}
public static void main(String[] args) {
//TODO code application logic here
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
triangle frame = new triangle();
frame.setVisible(true);
}
});
}
public void actionPerformed(ActionEvent ae) {
}
public void drawPolygon(int x, int y, int i)
{
Graphics g = this.getGraphics();
g.setColor(Color.BLACK);
g.drawPolygon(xx, yy, 3);
}
int x, y;
public void mouseClicked(MouseEvent e) {
x = e.getX();
y = e.getY();
repaint();
}
#Override
public void paint(Graphics g) {
drawPolygon(x, y, 3);
}
public void mouseExited(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
}``

The problem you have is that you override the paint method and therefore the drawPolygon method is already called in the initial painting of the JFrame.
For the effect you want to have you should avoid overriding the paint method and only use the drawPolygon method when the MouseListener is invoked.
This should look like this:
#Override
public void mouseClicked(MouseEvent e) {
x = e.getX();
y = e.getY();
drawPolygon(x,y,3);
repaint();
}
In order to paint the triangle where you click with the mouse you need to add the current position to the original triangle coordinates like this:
public void drawPolygon(int x, int y, int i)
{
Graphics g = this.getGraphics();
g.setColor(Color.BLACK);
int[] drawx = {xx[0]+x,xx[1]+x,xx[2]+x};
int[] drawy = {yy[0]+y,yy[1]+y,yy[2]+y};
g.drawPolygon(drawx, drawy, i);
}
I hope this answers you question.
Some general remarks on programming:
You should definitely include a
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
otherwise you program won't terminate on closing the frame and keep on running.
It would also help the readability of your code if you avoid having everything in one class and split your code into several classes.
The MVC model is something that is a very good general guideline for designing class structures.

Why Does Implementing an ActionListener make the applet shrink(virtually)?

I recently made a MakeDots class in java that when you drag the mouse, it makes dots(yay!). I implemented a MouseMotionListener for that. It worked fine. Then I added some buttons to change the colors of the dots. I added ActionListeners for that. Once I did that, the color-changing worked, but I could only draw in the very tiny borders of the buttons! Why does this happen? How do I fix it? If you need me to post my code just say in the comments, and I will do so.
CODE:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.applet.Applet;
import java.awt.Button;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
public class MakeDots extends Applet implements MouseMotionListener{
private Graphics graphics = null;
private Color dotColor = Color.red;
private Button setRed;
private Button setPink;
private Button setPurple;
private Button clrBtn;
public void init() {
setRed = new Button("Red");
setPink = new Button("Pink");
setPurple = new Button("Purple");
clrBtn = new Button("Clear");
this.addMouseMotionListener(this);
this.add(setRed);
this.add(setPink);
this.add(setPurple);
this.add(clrBtn);
setRed.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dotColor = Color.red;
}
});
setPink.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dotColor = Color.pink;
}
});
setPurple.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dotColor = new Color(80, 0, 80);
}
});
clrBtn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
clear();
}
});
}
public void paint(Graphics g) {
this.setSize(new Dimension(800, 600));
graphics = g.create();
clear();
}
public void drawDot(int x, int y) {
graphics.setColor(dotColor);
graphics.fillOval(x, y, 10, 10);
}
public void clear() {
Dimension d = this.getSize();
graphics.setColor(Color.WHITE);
graphics.fillRect(0, 0, d.width, d.height);
}
#Override
public void mouseDragged(MouseEvent e) {
int mouseX = e.getX();
int mouseY = e.getY();
drawDot(mouseX, mouseY);
}
#Override
public void mouseMoved(MouseEvent arg0) {
// TODO Auto-generated method stub
}
}

There are few things you might want to do. Lose the practice of writing actionPerformed(...) everytime you add an actionListener(). Just use getActionCommand() to check which button triggered the event. Also,create a global object of Color() and update it in actionPerformed()

mouse location and graphics painting

this program is suppose to shift the two rectangles by 10 points to the right each time I click on the screen at the x coordinate 300 or greater, but it doesn't, whats the problem?
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.io.IOException;
/**
* Created with IntelliJ IDEA.
* To change this template use File | Settings | File Templates.
*/
public class MasterMind extends JComponent implements ActionListener,MouseListener {
//private MouseEvent me;
private int screenX=0;
private int screenY=0;
private ActionEvent e;
private int xX=10;
public MasterMind() throws IOException {
}
public static void main(String [] args) throws IOException {
JFrame window = new JFrame("Master Mind");
MasterMind game= new MasterMind();
window.add(game);
window.pack();
window.setLocationRelativeTo(null);
window.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
window.setVisible(true);
Timer t = new Timer(30, game);
t.start();
window.addMouseListener(game);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(800,600);
}
#Override
protected void paintComponent(Graphics g) {
g.setColor(Color.red);
g.drawRect(xX,30,200,200);
g.setColor(Color.red);
g.drawString("x,y coordinates: "+screenX+" , "+screenY,400,100);
g.setColor(Color.blue);
g.drawRect(xX+3, 33, 194, 194);
}
#Override
public void mousePressed(MouseEvent me) {
}
#Override
public void mouseReleased(MouseEvent me) {
repaint();
}
#Override
public void mouseEntered(MouseEvent me) {
}
#Override
public void mouseExited(MouseEvent me) {
}
#Override
public void mouseClicked(MouseEvent e) {
MouseEvent mouseIvent = (MouseEvent) e;
int screenX = mouseIvent.getX();
int screenY = mouseIvent.getY();
System.out.println("screen(X,Y) = " + screenX + "\t" + screenY);
repaint();
}
#Override
public void actionPerformed(ActionEvent e) {
//To change body of implemented methods use File | Settings | File Templates.
if (screenX>300) {
xX=xX+10; }
//timer animation
repaint();
}
}
I am very new to Java. so please answer in details if I may ask. thank you all.

These lines should be in the mouseClicked method rather than in actionPerformed.
if (screenX > 300) {
xX = xX + 10;
}
immediately before the existing repaint method there. They ensure that X coordinate variable xX is updated for use later in the paintComponent method.
Unrelated but make sure to invoke super.paintComponent(g) as the first statement of paintComponent

Put this ,In your MouseClicked or MousePressed or MouseReleased Method
if(me.getX()>300)
xX=xX+10;
repaint();

JFrame repaint() issues - Java

I want to be able to draw using Java's paint() on a JFrame. When I click the JFrame (anywhere for now) I want the JFrame to be repainted with the co-ordinates of the click - similar to this Java applet http://www.realapplets.com/tutorial/MouseClickExample.html
Currently Working:
Everything is drawn initially and the JFrame is properly displayed
Not Working:
JFrame does not repaint and update even when repaint() is declared
Here is my code - Please be as stringent as possible with it - I would like to improve my Java programming technique so (if you have time that is) point out every aspect I could improve on.
Any help would be very much appreciated.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class AreaForText extends JPanel implements MouseListener {
int xpos;
int ypos;
JFrame myJFrame = new JFrame();
public void setJFrame() {
myJFrame.setSize(300, 150);
myJFrame.setTitle("Bigger Text!");
myJFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
myJFrame.setVisible(true);
myJFrame.getContentPane().add(new AreaForText());
myJFrame.addMouseListener(new AreaForText());
}
public void mouseClicked(MouseEvent me) {
//Save the coordinates of the click lke this.
xpos = MouseInfo.getPointerInfo().getLocation().x;
ypos = MouseInfo.getPointerInfo().getLocation().y;
System.out.print("Click" + " x: " + xpos + " y: " + ypos);
myJFrame.invalidate();
repaint();
revalidate();
}
public void mouseEntered(MouseEvent e){
}
public void mouseReleased(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void paint(Graphics g) {
System.out.print("hello");
g.drawString("Hello World", 30, 80);
g.fillRect(20,20,20,20);
g.drawString("("+xpos+","+ypos+")",xpos,ypos);
}
}
class EnlargeText {
public static void main(String args[]) {
AreaForText test = new AreaForText();
test.setJFrame();
}
}

You are creating 2 instances of AreaForText which is not what you want to do. One is added to the JFrame, and one is added to the listener. So the one that actually gets the mouse events and is calling repaint is not the same object that is being displayed.
Some of your code organization is not the best. You have a JPanel subclass that builds its own JFrame and puts itself into the panel. You should just pass in the JFrame if you really need it. I've made a few changes below.
EDIT. I fixed up some of the mouse listener stuff, you were getting the wrong X/Y co-ordinates, and also, you should just add the listener to the panel directly, not the JFrame, that way you don't have to translate the co-ordinates.
EDIT I changed the paint method to paintComponent, which is the preferred method to override here. Have a look at the Swing Paint Tutorial for more information.
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.MouseInfo;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
class AreaForText extends JPanel implements MouseListener {
private int xpos;
private int ypos;
public AreaForText() {
super();
this.addMouseListener(this);
}
public void mouseClicked(MouseEvent me) {
// Save the coordinates of the click lke this.
xpos = me.getX();
ypos = me.getY();
System.out.print("Click" + " x: " + xpos + " y: " + ypos);
repaint();
}
public void mouseEntered(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.print("hello");
g.drawString("Hello World", 30, 80);
g.fillRect(20, 20, 20, 20);
g.drawString("(" + xpos + "," + ypos + ")", xpos, ypos);
}
}
class EnlargeText {
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
JFrame myJFrame = new JFrame("Bigger Text!");
myJFrame.setSize(300, 150);
myJFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
myJFrame.getContentPane().add(new AreaForText());
myJFrame.setVisible(true);
}
});
}
}

Your not calling the JFrames repaint() you are calling the JPanel repaint method ( the class you are in)
Try:
myJFrame.repaint();

Clear painted screen at each click of the mouse?

Can't seem to figure out how to only show one circle. Was trying to //g.clearRect(0, 0, 400, 400); but that clears the background too. Was also trying to just fill the background with yellow again but couldn't get that working either. Any suggestions?
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JMouseFrame extends JFrame
implements MouseListener {
Container con = null;
int x, y;
int size;
public JMouseFrame() {
setTitle("JMouseFrame");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
con = this.getContentPane();
addMouseListener(this);
}
public void mousePressed(MouseEvent e) {
x = e.getX();
y = e.getY();
}
public void mouseClicked(MouseEvent e) {
int whichButton = e.getButton();
if (whichButton == MouseEvent.BUTTON1) {
size = 15;
} else if (whichButton == MouseEvent.BUTTON3) {
size = 4;
}
repaint();
}
public void mouseEntered(MouseEvent e) {
con.setBackground(Color.yellow);
}
public void mouseExited(MouseEvent e) {
con.setBackground(Color.black);
}
public void paint(Graphics g) {
//g.clearRect(0, 0, 400, 400);
g.drawOval(x - size, y - size, size * 3, size * 3);
}
public static void main(String[] args) {
JMouseFrame mFrame = new JMouseFrame();
mFrame.setSize(400, 400);
mFrame.setVisible(true);
}
public void mouseReleased(MouseEvent e) {
}
}

It looks like you're mixing AWT and Swing painting. Instead, override paintComponent(), as suggested in the example below. See Painting in AWT and Swing for details.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** #see http://stackoverflow.com/questions/3898775 */
public class MousePanel extends JPanel {
private static final int SIZE = 20;
Point p = new Point(Short.MAX_VALUE, Short.MAX_VALUE);
public MousePanel() {
this.setPreferredSize(new Dimension(400, 400));
this.setBackground(Color.yellow);
this.addMouseListener(new MouseHandler());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.black);
g.drawOval(p.x - SIZE, p.y - SIZE, SIZE * 2, SIZE * 2);
}
private final class MouseHandler extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
p = e.getPoint();
repaint();
}
}
private void display() {
JFrame f = new JFrame("MousePanel");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(this);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new MousePanel().display();
}
});
}
}
Addendum:
I can't figure out how to make the code you posted work with what I have...
You can restore your mouse methods to the MouseHandler almost verbatim. The only difference is the need to qualify this, e.g.
#Override
public void mouseClicked(MouseEvent e) {
int whichButton = e.getButton();
if (whichButton == MouseEvent.BUTTON1) {
MousePanel.this.size = 15;
} else if (whichButton == MouseEvent.BUTTON3) {
MousePanel.this.size = 4;
}
repaint();
}
#Override
public void mouseEntered(MouseEvent e) {
MousePanel.this.setBackground(Color.yellow);
}
#Override
public void mouseExited(MouseEvent e) {
MousePanel.this.setBackground(Color.black);
}