We Keep Coding

java Swing button action

I am new in java and i wanted to work on a simple paint program using java swing.
my simple paint program should draw a shape like triangle, circle and square whenever i clicked on buttons.
i managed to draw these shapes and print it without buttons but i can not do it using ActionListener?
As you see i have a single button at the moment, i want to draw the oval whenever this button is clicked.
This is the code that i am working on it so far:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class PaintProject extends JComponent implements ActionListener{
public static void main(String[] args) {
JFrame frame=new JFrame("NEW PAINT PROGRAME!");
JButton button1=new JButton("ADD");
PaintProject paint=new PaintProject();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLayout(new FlowLayout());
frame.add(paint);
frame.add(button1);
frame.pack();
frame.setVisible(true);
}
#Override
public Dimension getPreferredSize(){
return new Dimension(500,500);
}
#Override
protected void paintComponent(Graphics g){
super.paintComponent(g);
g.setColor(Color.red);
g.fillOval(0,0, 100, 100);
}
#Override
public void actionPerformed(ActionEvent e) {
}
}

Could you please take following steps:
Step 1:
Insert button1.addActionListener(paint); just after PaintProject paint=new PaintProject(); in the main method of PaintProject.java
Step 2:
Remove the method named protected void paintComponent(Graphics g). Instead create following method:
private void drawOval(){
Graphics g = this.getGraphics();
g.setColor(Color.red);
g.fillOval(0,0, 100, 100);
}
Step 3:
Call the above method as follows:
#Override
public void actionPerformed(ActionEvent e) {
drawOval();
}
EDIT:
Following example demonstrates how to draw two shapes when respective buttons are clicked:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
public class PaintProject extends JComponent implements ActionListener {
public static void main(String[] args) {
JFrame frame = new JFrame("NEW PAINT PROGRAME!");
JButton ovalButton = new JButton("Oval");
ovalButton.setActionCommand("Oval");
JButton rectangleButton = new JButton("Rectangle");
rectangleButton.setActionCommand("Rectangle");
PaintProject paint = new PaintProject();
ovalButton.addActionListener(paint);
rectangleButton.addActionListener(paint);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLayout(new FlowLayout());
frame.add(paint);
frame.add(ovalButton);
frame.add(rectangleButton);
frame.pack();
frame.setVisible(true);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
private void drawOval() {
Graphics g = this.getGraphics();
g.setColor(Color.red);
g.fillOval(0, 0, 100, 100);
}
private void drawRectangle() {
Graphics g = this.getGraphics();
g.setColor(Color.green);
g.fillRect(150, 150, 100, 100);
}
#Override
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (command.equals("Oval")) {
drawOval();
} else if (command.equals("Rectangle")) {
drawRectangle();
}
}
}

What will be the Main of this program in java |How do i call the line method in main?

package drawinglinebymethods;
import java.awt.*;
import javax.swing.JFrame;
public class DrawingLineByMethods extends Frame {
public JFrame f=new JFrame();
void fra_size()
{
f.setSize(450, 300);
}
void fra_visible()
{
f.setVisible(true);
}
void fra_title()
{
f.setTitle(" java frame");
}
void exit()
{
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void line(Graphics g) {
g.drawLine(10, 10, 20, 300);
}
public static void main(String[] args) {
DrawingLineByMethods obj = new DrawingLineByMethods();
obj.fra_size();
obj.fra_title();
obj.fra_visible();
obj.fra_exit();
obj.line(g); // <-- error here
}
}

Your question suggests that you are not yet clear on how graphics and drawing works in Swing GUI's. Some suggestions for you:
Don't have your class extend java.awt.Frame as this makes no sense. You're not creating an AWT Frame window and have no need of this.
Create a class that extends JPanel and draw in its paintComponent method as the Swing painting tutorials (link now added) show you.
You never call drawing code directly but rather it is indirectly called by the JVM.
If you want to draw from outside of the GUI itself, then draw to a BufferedImage, one that is then displayed within the GUI.
Don't use a Graphics object obtained by calling getGraphics() on a GUI component as the object thus obtained will not persist, and this risks you creating unstable graphics or worse -- throwing a NullPointerException.
For example:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.*;
#SuppressWarnings("serial")
public class LineDraw extends JPanel {
private static final int PREF_W = 450;
private static final int PREF_H = 300;
public LineDraw() {
}
#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);
// use rendering hints to draw smooth lines
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// do drawing here
g.drawLine(10, 10, 20, 300);
}
private static void createAndShowGui() {
LineDraw mainPanel = new LineDraw();
JFrame frame = new JFrame("Line Draw");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}
If you want to add lines as the program runs, again, use a BufferedImage that is drawn within the JPanel's paintComponent method. When you need to add a new line to the GUI, extract the Graphics or Graphics2D object from the BufferedImage using getGraphics() or createGraphics() respectively (it's OK to do this), draw with this Graphics object, dispose of the Graphics object, and repaint the GUI. For example in the code below, I draw a new line when the button is pressed by adding code within the JButton's ActionListener (actually its AbstractAction which is similar to an ActionListener but more powerful):
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;
#SuppressWarnings("serial")
public class LineDraw extends JPanel {
private static final int PREF_W = 450;
private static final int PREF_H = 300;
private BufferedImage img;
private int yDistance = 20;
private int deltaY = 10;
public LineDraw() {
img = new BufferedImage(PREF_W, PREF_H, BufferedImage.TYPE_INT_ARGB);
add(new JButton(new DrawLineAction("Draw Line", KeyEvent.VK_D)));
}
#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);
// draw the buffered image here
if (img != null) {
g.drawImage(img, 0, 0, this);
}
// use rendering hints to draw smooth lines
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// do drawing here
g.drawLine(10, 10, 20, 300);
}
public void drawNewLines() {
Graphics2D g2 = img.createGraphics();
g2.setColor(Color.BLACK);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
yDistance += deltaY;
g2.drawLine(10, 10, yDistance, PREF_H);
g2.dispose();
repaint();
}
private class DrawLineAction extends AbstractAction {
public DrawLineAction(String name, int mnemonic) {
super(name); // give button its text
putValue(MNEMONIC_KEY, mnemonic); // alt-hot key for button
}
#Override
public void actionPerformed(ActionEvent e) {
drawNewLines();
}
}
private static void createAndShowGui() {
LineDraw mainPanel = new LineDraw();
JFrame frame = new JFrame("Line Draw");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}

Line is a non-static method, the only way to call it from a static method (main here) is to have an instance of the class.

Request focus for keylistener, not sure if i have focus or not?

I'm not sure why when I press w my rectangle doesn't adjust accordingly. Do I have my focus set up right, or do I need to request it from a separate class? Should I be doing this in my drawingComponent class or in my "core" class?
package scratch;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.util.*;
public class drawingComponent extends JComponent implements KeyListener {
Rectangle hello = new Rectangle(300, 100, 50, 50);
public void paintComponent(Graphics g){
Graphics2D g2 = (Graphics2D) g;
g2.setColor(new Color(255,25,0));
g2.setFont(new Font("monospace", Font.BOLD+Font.ITALIC, 30));
g2.drawString("nothing yet",300,320);
g2.fill(hello);
}
#Override
public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_W){
hello.setLocation(hello.x-50, hello.y);
repaint();
}
}
#Override
public void keyReleased(KeyEvent e) {
}
#Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}
I have solved the problem by adding the following to my drawingComponent class.
setFocusable(true);
requestFocus();
addKeyListener(this);

You want to use Key Bindings, not a KeyListener for several reasons, but one being that you don't have to worry so much about focus with Key Bindings. Also, you'll want to in the future post a minimal example program that we can test, run and modify, something like this:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;
public class DrawingComponent extends JPanel {
private static final int PREF_W = 800;
private static final int PREF_H = 600;
private static final Color RECT_COLOR = new Color(255,25,0);
private Rectangle rect = new Rectangle(300, 100, 50, 50);
public DrawingComponent() {
setUpKeyBindings();
}
private void setUpKeyBindings() {
int condition = WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
KeyStroke wStroke = KeyStroke.getKeyStroke(KeyEvent.VK_W, 0);
inputMap.put(wStroke, wStroke.toString());
actionMap.put(wStroke.toString(), new WAction());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(RECT_COLOR);
g2.fill(rect);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class WAction extends AbstractAction {
#Override
public void actionPerformed(ActionEvent e) {
rect.setLocation(rect.x-50, rect.y);
repaint();
}
}
private static void createAndShowGui() {
DrawingComponent mainPanel = new DrawingComponent();
JFrame frame = new JFrame("DrawingComponent");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Also, call the super's paintComponent method in your override, else your JPanel won't erase the old images.

paint method draws outside jFrame if first coord 0,0

First coord in this case should be 0,0 and not 8,30. What am i doing wrong(i am using NetBeans)
import java.awt.Color;
import java.awt.Graphics;
public class TEST extends javax.swing.JFrame {
#Override
public void paint(Graphics g){
super.paint(g);
g.setColor(Color.blue);
g.drawRect(8, 30, 200, 200);
repaint();
}}

Add a JPanel to the frame and paint in that. The frame's coordinates include the decorations (title bar, borders, etc.). It would look something like this:
public class Test extends JFrame {
public static void main(String[] args) {
new Test();
}
private Test() {
add(new MyPanel());
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(600, 600);
setVisible(true);
}
private class MyPanel extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.blue);
g.drawRect(8, 30, 200, 200);
}
}
}
Also, don't call repaint(); in paint();. That will cause an infinite loop and will freeze the entire program.

The problem is your paint(..) method is not taking into account the JFrame Insets by calling getInsets which as docs state:
If a border has been set on this component, returns the border's
insets.
this code works fine:
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
createAndShowGui();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
private void createAndShowGui() {
JFrame frame = new JFrame() {
#Override
public void paint(Graphics g) {
super.paint(g);
g.setColor(Color.blue);
g.drawRect(0 + getInsets().left, 0 + getInsets().top, 200, 200);
}
};
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}
however this is not best practice.
Rather add JPanel to JFrame and override paintComponent(Graphics g) of JPanel dont forget call to super.paintComponent(g) as first call in the overridden method and than draw there (dont forget to override getPreferredSize() and return correct Dimensions so the JPanel will fit its drawing/graphic content) this problem will no longer persist as JPanel is added at correct co-ordinates on contentPane like so:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
createAndShowGui();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
private void createAndShowGui() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY));
g2d.setColor(Color.blue);
g2d.drawRect(0, 0, 200, 200);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
};
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
}
The above includes Graphics2D and RenderingHints i.e anti-aliasing. Just for some better looking drawings :)

How to update java canvas dynamically?

Problem: I am trying to update the canvas with new painting objects based on user action. The canvas dosent get updated.
What i have done: The user interacts with the DnD action,The transferrable object reaches the canvas, Calls an update graphics method created by me. And the method simply uses the aldready created graphics 2d object and draws images using it.I have checkd the DnD action,the object is properly recived at canvas class and i was able to print them out using System.out.println.
A sample code,that has a similar function to that of mine,
Paint class:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;
public class PaintPanel extends JPanel{
private Graphics2D drawImage;
public PaintPanel()
{
}
#Override
public void paint(Graphics g) {
drawImage = (Graphics2D) g;
drawImage.setColor(Color.WHITE);
drawImage.fillRect(0, 0, getWidth(), getHeight());
}
public void updateGraphics(int length,int width)
{
drawImage.setColor(Color.black);
drawImage.drawRect(100, 150, length, width);
repaint();
}
}
mainframe class:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
public class MainPaint extends JFrame{
public MainPaint()
{
setTitle("test paint");
setSize(400,400);
setLayout(new BorderLayout());
final PaintPanel paintPan = new PaintPanel();
JButton testButon = new JButton("Display shape");
add(paintPan,BorderLayout.CENTER);
add(testButon,BorderLayout.PAGE_END);
testButon.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
paintPan.updateGraphics(50,50);
repaint();
}
});
setVisible(true);
}
public static void main(String[] args)
{
new MainPaint();
}
}

Graphics2D drawImage; //source of the problem!
Don't attempt to cache a Graphics (or Graphics2D) instance! Instead:
Add the new objects to a list
Call repaint().
In paintComponent(Graphics) draw the list of objects.
An alternative to that is to use a BufferedImage as the drawing object. See this answer for an example.
Update - SSCCE based on latest code.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MainPaint extends JFrame {
public MainPaint() {
setTitle("test paint");
setSize(400, 400);
setLayout(new BorderLayout());
final PaintPanel paintPan = new PaintPanel();
JButton testButon = new JButton("Display shape");
add(paintPan, BorderLayout.CENTER);
add(testButon, BorderLayout.PAGE_END);
testButon.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
paintPan.updateGraphics(50, 50);
repaint();
}
});
setVisible(true);
}
public static void main(String[] args) {
new MainPaint();
}
}
class PaintPanel extends JPanel {
private int x, y;
private Color color = null;
public PaintPanel() {
setBackground(Color.ORANGE);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D drawImage = (Graphics2D) g;
if (color != null) {
drawImage.setColor(color);
drawImage.drawRect(100, 150, x, y);
}
}
public void updateGraphics(int length, int width) {
color = Color.RED;
x = length;
y = width;
repaint();
}
}
Note
There are still a number of things about that code that need changing. I decided to stop at the earliest variant that worked to display the rectangle on button click.

I think you need to call the validate() method.