Develop Reference

Painting on a class extending JFrame in Java

i'm kind of new with Java graphics, i'm trying to create a simple crossroad GUI interface with 4 traffic lights on it, when using the following classes that I have created - I get a window with a large grey rectangle on it (I assume that since I didn't allocate a traffic lights in the center it has been filled with the default grey background), how do I control the size of the center of the JFrame?
This is what i'm looking to acheive:
This is what i'm getting:
This is the JFrame class.
import java.awt.*;
import javax.swing.*;
public class CrossroadInterface extends JFrame /*implements IAppInterface*/ {
private static final int WIDTH_OF_WINDOW = 400;
private static final int HEIGHT_OF_WINDOW = 400;
//Panels
TrafficLight tLightW, tLightC, tLightE, tLightS, tLightN;
//Other
public CrossroadInterface() {
super("My Crossroad");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(WIDTH_OF_WINDOW, HEIGHT_OF_WINDOW);
this.setVisible(true);
createInterface();
}
public void createInterface () {
tLightW = new TrafficLight();
tLightE = new TrafficLight();
tLightS = new TrafficLight();
tLightN = new TrafficLight();
this.add(tLightW, BorderLayout.WEST);
this.add(tLightN, BorderLayout.NORTH);
this.add(tLightE, BorderLayout.EAST);
this.add(tLightS, BorderLayout.SOUTH);
}
}
This is the Jpanel class.
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class TrafficLight extends JPanel {
private final Color offRed = new Color(128, 0, 0);
private final Color offGreen = new Color(0, 96, 0);
private static final int CAR_DIAMETER = 50;
private static final int PERSON_HEIGHT = 100;
private static final int PERSON_WIDTH = 50;
private int status;
public TrafficLight() {
super();
this.setSize(CAR_DIAMETER, 120);
this.setBackground(Color.BLACK);
status = 0;
this.setVisible(true);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(offRed);
g.fillOval(this.getX(), this.getY(), CAR_DIAMETER, CAR_DIAMETER);
g.setColor(offGreen);
g.fillOval(this.getX(), this.getY()+CAR_DIAMETER, CAR_DIAMETER, CAR_DIAMETER);
g.setColor(offRed);
g.fillRect(this.getX(), this.getY()+CAR_DIAMETER+PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
g.setColor(offGreen);
g.fillRect(this.getX(), this.getY()+CAR_DIAMETER+2*PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
//drawIlluminatedLights(g);
System.out.println(this.getX()+" "+this.getY());
}
}
EDIT:
Following Hovercraft Full Of Eels' advise, here are my new classes:
import java.awt.*;
import javax.swing.*;
public class CrossroadInterface extends JFrame /*implements IAppInterface*/ {
private static final int WIDTH_OF_WINDOW = 900;
private static final int HEIGHT_OF_WINDOW = 900;
//Panels
TrafficLight tLightW, tLightC, tLightE, tLightS, tLightN;
//Other
public CrossroadInterface() {
super("My Crossroad");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(WIDTH_OF_WINDOW, HEIGHT_OF_WINDOW);
setLayout(new GridLayout(3,3));
createInterface();
}
public void createInterface () {
tLightW = new TrafficLight();
tLightE = new TrafficLight();
tLightS = new TrafficLight();
tLightN = new TrafficLight();
this.add(new JPanel());
this.add(tLightW);
this.add(new JPanel());
this.add(tLightN);
this.add(new JPanel());
this.add(tLightE);
this.add(new JPanel());
this.add(tLightS);
this.setVisible(true);
}
}
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JPanel;
public class TrafficLight extends JPanel {
private final Color offRed = new Color(128, 0, 0);
private final Color offGreen = new Color(0, 96, 0);
private static final int CAR_DIAMETER = 50;
private static final int PERSON_HEIGHT = 50;
private static final int PERSON_WIDTH = 50;
private int status;
public TrafficLight() {
super();
status = 0;
this.setPreferredSize(new Dimension(CAR_DIAMETER,2*CAR_DIAMETER+2*PERSON_HEIGHT));
this.setVisible(true);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(offRed);
g.fillOval(100, 50, CAR_DIAMETER, CAR_DIAMETER);
g.setColor(offGreen);
g.fillOval(100, 50+CAR_DIAMETER, CAR_DIAMETER, CAR_DIAMETER);
g.setColor(offRed);
g.fillRect(100, 50+CAR_DIAMETER+PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
g.setColor(offGreen);
g.fillRect(100, 50+CAR_DIAMETER+2*PERSON_HEIGHT, PERSON_WIDTH, PERSON_HEIGHT);
//drawIlluminatedLights(g);
}
}

Your problem is not that the center of the JFrame is too large, but rather it's because the size of your surrounding JPanels are too small. Understand that most Swing layout managers respect a components preferred size, and use this to set the size of the component. Your other problems include
using getX() and getY() to place your drawings. These values give the location of the JPanel within its container, but that won't help you place your drawing since when you draw within the JPanel the drawing's location is placed relative to the location of the pixel within the JPanel not its container, so using these methods will mess you up.
Calling the JFrame's setVisible(true) before adding all components. This risks not displaying all components.
Making your TrafficLight class extend JPanel. You're far better off using a single JPanel to do all the drawing and have your TrafficLight class not extend from any Swing component but rather be a logical class. Give it a public void draw(Graphics2D g2) method that you can call within the drawing JPanel's paintComponent method.
For example:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import javax.swing.*;
#SuppressWarnings("serial")
public class CrossRoads2 extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = PREF_W;
private static final int TIMER_DELAY = 100;
List<TrafficLight2> lights = new ArrayList<>();
public CrossRoads2() {
// create a timer to randomly change traffic light state
// and start it
new Timer(TIMER_DELAY, new TimerListener()).start();
// create 4 TrafficLight2 objects and place them at 4
// compass locations, and add to lights ArrayList
int x = (PREF_W - TrafficLight2.getWidth()) / 2;
int y = 0;
lights.add(new TrafficLight2(x, y));
x = 0;
y = (PREF_H - TrafficLight2.getHeight()) / 2;
lights.add(new TrafficLight2(x, y));
x = (PREF_W - TrafficLight2.getWidth());
lights.add(new TrafficLight2(x, y));
x = (PREF_W - TrafficLight2.getWidth()) / 2;
y = (PREF_H - TrafficLight2.getHeight());
lights.add(new TrafficLight2(x, y));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// cast g into a Graphics2 object
Graphics2D g2 = (Graphics2D) g;
// for smooth rendering
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// iterate through the ArrayList, calling the draw method on each light
for (TrafficLight2 light : lights) {
light.draw(g2);
}
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
// give our JPanel a decent size
return new Dimension(PREF_W, PREF_H);
}
// ActionListener that randomly changes the LightState of each traffic light
private class TimerListener implements ActionListener {
private Random random = new Random();
#Override
public void actionPerformed(ActionEvent e) {
for (TrafficLight2 light : lights) {
// random number 0 to 2
int randomIndex = random.nextInt(LightState.values().length);
// get one of the LightStates using the index above
LightState lightState = LightState.values()[randomIndex];
// set our light to this state
light.setLightState(lightState);
}
repaint();
}
}
private static void createAndShowGui() {
CrossRoads2 mainPanel = new CrossRoads2();
JFrame frame = new JFrame("Cross Roads");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class TrafficLight2 {
private static final int ELLIPSE_W = 40;
private static final int GAP = 4;
private int x;
private int y;
private LightState lightState = LightState.RED; // what color is bright
// map to hold our 3 ellipses, each one corresponding to a LightState
private Map<LightState, Shape> lightMap = new EnumMap<>(LightState.class);
public TrafficLight2(int x, int y) {
// create 3 ellipses, one each for RED, YELLOW, GREEN
// place each one below the previous
// associate each one with one of our RED, YELLOW, or GREEN LightStates
// putting the Ellipse into the map with the light state as key
this.x = x;
this.y = y;
int tempX = x + GAP;
int tempY = y + GAP;
lightMap.put(LightState.RED, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W));
tempY += ELLIPSE_W + GAP;
lightMap.put(LightState.YELLOW, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W));
tempY += ELLIPSE_W + GAP;
lightMap.put(LightState.GREEN, new Ellipse2D.Double(tempX, tempY, ELLIPSE_W, ELLIPSE_W));
}
// called by JPanel's paintComponent
public void draw(Graphics2D g2) {
// iterate through the 3 LightStates
for (LightState ltSt : LightState.values()) {
// if the ltSt in the for loop is this traffic light's LightState
// then the display color should be bright
Color c = ltSt == lightState ? ltSt.getColor() :
// other wise the display color should be very dark
ltSt.getColor().darker().darker().darker();
g2.setColor(c);
g2.fill(lightMap.get(ltSt)); // fill the oval with color
g2.setColor(Color.BLACK);
g2.draw(lightMap.get(ltSt)); // draw a black border
}
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public LightState getLightState() {
return lightState;
}
public void setLightState(LightState lightState) {
this.lightState = lightState;
}
// static method for the width of our traffic lights
public static int getWidth() {
return 2 * GAP + ELLIPSE_W;
}
// static method for the height of our traffic lights
public static int getHeight() {
return 4 * GAP + 3 * ELLIPSE_W;
}
}
// enum that encapsulates the 3 possible states of the traffic light
enum LightState {
RED("Red", Color.RED), YELLOW("Yellow", Color.YELLOW), GREEN("Green", Color.GREEN);
private LightState(String text, Color color) {
this.text = text;
this.color = color;
}
private String text;
private Color color;
public String getText() {
return text;
}
public Color getColor() {
return color;
}
}

Drawing on top of multiple JButtons

So, I have multiple objects of the class Square, which is the subclass of JButton. I have an instance of the class Board, which contains a few instances of Square. What I want to do is when I press one of the buttons (squares), draw a shape (a circle) on top of it. For doing that, I have a boolean variable in the Square class, namely isClicked, that basically decides what has to be drawn in the paintComponent method.
The problem is that buttons start to behave in a weird way when I have a few of them. Surprisingly, if there is only one of them, there is no problem at all. At first, I had thought the problem might be related to threads, however, I put the main code into invokeLater method and that did not help at all.
I saw a solution using BufferedImage, but I would like to see if there is any possibility to solve the problem doing it my way.
Sorry for possibly not perfect English.
Square class:
public class Square extends JButton implements ActionListener {
private int number;
private boolean isClicked;
public Square(int x) {
number = x;
isClicked = false;
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
if (!isClicked) {
super.paintComponent(g);
} else {
System.out.println("EXECUTED for: " + number);
g2d.drawOval(this.getX(), this.getY(), 100, 100);
}
}
#Override
public void actionPerformed(ActionEvent e) {
isClicked = !isClicked;
System.out.println(isClicked + " " + number);
repaint();
}
}
Board class:
public class Board extends JPanel {
private static final int BOARD_WIDTH = (int) (TicTacToe.WIDTH * 0.7);
private static final int VERTICAL_LINE_LENGTH = (int) (TicTacToe.WIDTH * 0.5);
private static final int HORIZONTAL_LINE_LENGTH = (int) (TicTacToe.HEIGHT * 0.8);
private static final int STROKE_WIDTH = 5;
private Square[] squares;
public Board() {
}
public void addButtons() {
squares = new Square[9];
for (int i = 0; i < 3; i++) {
Square square = new Square(i);
square.setPreferredSize(new Dimension(30, 30));
square.addActionListener(square);
this.add(square);
squares[i] = square;
((GridLayout)this.getLayout()).setHgap(30);
((GridLayout)this.getLayout()).setVgap(30);
}
}
public Square[] getButtons() {
return squares;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setStroke(new BasicStroke(STROKE_WIDTH));
// Horiztontal lines
g2d.drawLine(0, TicTacToe.HEIGHT / 3,
BOARD_WIDTH, TicTacToe.HEIGHT / 3);
g2d.drawLine(0, 2 * TicTacToe.HEIGHT / 3,
BOARD_WIDTH, 2 * TicTacToe.HEIGHT / 3);
// Vertical lines
g2d.drawLine(BOARD_WIDTH / 3, 0, BOARD_WIDTH / 3,
TicTacToe.HEIGHT);
g2d.drawLine(2 * BOARD_WIDTH / 3, 0, 2 * BOARD_WIDTH / 3,
TicTacToe.HEIGHT);
}
}
Main method:
SwingUtilities.invokeLater(new Runnable() {
public void run() {
Board board = new Board();
board.setPreferredSize(new Dimension((int) (WIDTH * 0.7), HEIGHT));
board.setLayout(new GridLayout(3, 3));
board.addButtons();
GameOptions opt = new GameOptions();
opt.setPreferredSize(new Dimension((int) (WIDTH * 0.3), HEIGHT));
JFrame frame = new JFrame("Tic Tac Toe");
frame.setLayout(new FlowLayout());
frame.add(board);
frame.add(opt);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});

Your use of getX() and getY() on the button's drawing code is completely wrong and does not belong. These methods return the location of the button relative to its container, and so while this might work for a button located at the upper left, it will fail for anything else since you'll end up drawing somewhere far away from the button itself, and so many of your drawings will never show.
You'd be much better off not extending JButton but instead simply swapping ImageIcons that display what you want drawn on the JButton. This is much simpler and much more idiot-proof. You set the button's icon by calling .setIcon(myImageIcon) on it, passing in the icon of choice.
But if you absolutely wanted to draw on the button, you'd do so without using getX() or getY(). You'd also probably want to use a JToggleButton as the parent class, since you're toggling state. For example, my MCVE:
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.image.BufferedImage;
import javax.swing.*;
#SuppressWarnings("serial")
public class DrawButtonPanel extends JPanel {
private static final int SIDE = 3;
private static final int GAP = 5;
private static final Color BG = Color.BLACK;
public DrawButtonPanel() {
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
setLayout(new GridLayout(SIDE, SIDE, GAP, GAP));
setBackground(BG);
for (int i = 0; i < SIDE * SIDE; i++) {
// add(new DrawButton1());
DrawButton2 drawButton2 = new DrawButton2(i);
AbstractButton button = drawButton2.getButton();
add(button);
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new DrawButtonPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class DrawButton2 {
private static final int PREF_W = 200;
private static final int PREF_H = PREF_W;
private static final int GAP = 20;
private static final float STROKE_WIDTH = 15f;
private static final Stroke BASIC_STROKE = new BasicStroke(STROKE_WIDTH);
private static final Color COLOR = Color.RED;
private static final Color BG = Color.LIGHT_GRAY;
private AbstractButton button = new JToggleButton();
private int index;
public DrawButton2(int index) {
this.index = index;
button.setBorderPainted(false);
button.setBorder(null);
button.setIcon(createPlainIcon());
button.setSelectedIcon(createSelectedIcon());
button.addItemListener(new ItemListener() {
#Override
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
System.out.println("Index: " + index);
}
}
});
}
public int getIndex() {
return index;
}
private Icon createPlainIcon() {
BufferedImage img = new BufferedImage(PREF_W, PREF_H, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
g2d.setColor(new Color(0, 0, 0, 0));
g2d.fillRect(0, 0, PREF_W, PREF_H);
g2d.dispose();
return new ImageIcon(img);
}
private Icon createSelectedIcon() {
BufferedImage img = new BufferedImage(PREF_W, PREF_H, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(BASIC_STROKE);
g2d.setColor(BG);
g2d.fillRect(0, 0, PREF_W, PREF_H);
g2d.setColor(COLOR);
g2d.drawOval(GAP, GAP, PREF_W - 2 * GAP, PREF_H - 2 * GAP);
g2d.dispose();
return new ImageIcon(img);
}
public AbstractButton getButton() {
return button;
}
}
#SuppressWarnings("serial")
class DrawButton1 extends JToggleButton {
private static final int PREF_W = 200;
private static final int PREF_H = PREF_W;
private static final int GAP = 20;
private static final float STROKE_WIDTH = 15f;
private static final Stroke BASIC_STROKE = new BasicStroke(STROKE_WIDTH);
private static final Color COLOR = Color.RED;
private static final Color BG = Color.LIGHT_GRAY;
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(BASIC_STROKE);
if (!isSelected()) {
super.paintComponent(g);
} else {
g2d.setColor(BG);
g2d.fillRect(0, 0, getWidth(), getHeight());
g2d.setColor(COLOR);
g2d.drawOval(GAP, GAP, getWidth() - 2 * GAP, getHeight() - 2 * GAP);
}
g2d.dispose(); // since we created a new one
}
}
Edited to show how to do this with JToggleButton and icons.

simply print a component in java with a diagonal line

I'm a beginner trying to print a basic window with a line 0,0,500,500.
I've tried validate, doLayout, printAll. I am unsure about the g in the printAll. I can't find anywhere that says what it is. ??
package helloprogram;
import java.awt.Graphics.*;
/**
*
* #author jglvn
*/
class Component{
void setSize(int width, int height){ }
void setBounds(int x, int y){ }
void drawLine(int x1, int y1, int x2, int y2){ }
void setBackground(int r, int g, int b){ }
void validate(){ }
void doLayout(){ }
void printAll(Graphics g){ }
}
public class HelloProgram {
public static void main(String[] args) {
Component canvas = new Component();
canvas.setSize(500, 500);
canvas.setBounds(300, 300);
canvas.setBackground(153,153,153);
canvas.drawLine(0, 0, 500, 500);
canvas.doLayout();
canvas.validate();
canvas.printAll(g);
}
}

It seams you want to draw a line in a frame. If this is the case, you should go for some container like a JPanel. You want to paint something on the panel, you should override the paint method:
Here is a sample code:
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class DrawLinePanel extends JPanel{
private static final int FRAME_HEIGHT = 600;
private static final int FRAME_WIDTH = 600;
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(FRAME_WIDTH, FRAME_HEIGHT);
f.add(new DrawLinePanel(new Point(100, 100), new Point(500, 500)));
f.setVisible(true);
}
private Point pointA;
private Point pointB;
public DrawLinePanel(Point pointA, Point pointB) {
this.pointA = pointA;
this.pointB = pointB;
}
#Override
public void paint(Graphics g) {
super.paintComponents(g);
//
Graphics2D g2 = (Graphics2D) g;
g2.drawLine(pointA.x, pointA.y, pointB.x, pointB.y);
}
}
Some advice:
Don't make the frame visible before you do all your graphics.
Don't mix the Component sub classes like Frame or Panel with JComponent sub classes like JFrame or JPanel.
Hope this would be helpful.

Best to handle 2 overlaying live updated panels?

In very basic terms I have a panel that is drawing a line pixel by pixel and is being updated in real time. On top of this I want another panel that draws a box around the current pixel but clears itself later. Both are in real time
My current situation is a wrapper JPanel that has an OverlayLayout. The bottom panel has the line that is drawn with the Graphics2D object fetched from its JPanel. The top panel the box that follows around that is also drawn with the Graphics2D object fetched from its JPanel.
The issues in this system are many. Since I'm just drawing on the Graphics2D object separately and not overriding the JPanel's paint() not only is all the lines lost when the panel needs to repaint, I think I'm going against Swing's threading model by only having a single thread update the screen. I have also not gotten the top panel to work correctly, it just keeps clearing the screen and won't let the bottom panel draw a line.
What would be the best way to approach this situation? I have little experience with image processing and the low-level displaying of images in Swing, I just know the basics. I've heard of BufferedImage, but not knowing where to put that image, if it will be updated when changed later, the efficiency of doing that, and the fact that its buffered scare me off. I'm not sure what to use
Can someone point me in the right direction of what I need to use to accomplish this?

You can accumulate your points in a suitable Shape, such as GeneralPath, as shown in LissajousPanel. Use a javax.swing.Timer to cause periodic updates, and highlight the most recently added point with a surrounding rectangle.

I suggest
that you do not get your JPanel's Graphics or Graphics2D object via getGraphics as this object is not meant to be stable and will not work once the component has been repainted for any reason.
that you instead do all your drawing in a single JPanel's paintComponent method, but first in that method call the super's method.
that you again draw in only one JPanel, not two,
that you draw your line in a BufferedImage, since that is a more permanent part of your image.
That you get the BufferedImage's Graphics2D object via its createGraphics method
That you properly dispose of the BufferedImage's Graphics object when done using it so as to conserve resources.
that you display your BufferedImage in the paintComponent method of your JPanel (after calling the super method first)
that you draw your box, the more fleeting portion of the image, directly in the paintComponent using int class variables to tell paintComponent where to draw and perhaps a class boolean variable to tell if to draw.
and that most important, you review the tutorials on Swing graphics as to do this properly, you'll have to throw all old assumptions out and learn the correct way from the ground up (as we all had to do).
For example:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
#SuppressWarnings("serial")
public class BufferedImageEg extends JPanel {
private static final int BI_WIDTH = 700;
private static final int BI_HEIGHT = 500;
private static final Color BACKGROUND = new Color(255, 255, 240);
private static final int THIS_PT_WIDTH = 12;
private static final int THIS_PT_HEIGHT = THIS_PT_WIDTH;
private static final float THIS_PT_STROKE_WIDTH = 2f;
private static final Color THIS_PT_BORDER_COLOR = Color.red;
private static final Color THIS_PT_FILL_COLOR = new Color(250, 250, 0, 125);
private static final int TIMER_DELAY = 30;
private static final int X_MIN = 0;
private static final int X_MAX = 100;
private static final double X_STEP = 0.1;
private static final double X_SCALE = (double) BI_WIDTH
/ ((double) X_MAX - X_MIN);
private static final double Y_SCALE = 8;
private static final float LINE_WIDTH = 4;
private static final Color LINE_COLOR = Color.blue;
private Point lastPoint = null;
private Point thisPoint = null;
private BufferedImage bImage = new BufferedImage(BI_WIDTH, BI_HEIGHT,
BufferedImage.TYPE_INT_RGB);
private double xValue = X_MIN;
public BufferedImageEg() {
Graphics biG = bImage.getGraphics();
biG.setColor(BACKGROUND);
biG.fillRect(0, 0, BI_WIDTH, BI_HEIGHT);
setBackground(BACKGROUND);
new Timer(TIMER_DELAY, new ActionListener() {
public void actionPerformed(ActionEvent e) {
timerActionPerformed(e);
}
}).start();
}
private void timerActionPerformed(ActionEvent e) {
if (xValue <= X_MAX) {
lastPoint = thisPoint;
double tempX = xValue;
double yValue = function(xValue);
tempX *= X_SCALE;
yValue *= Y_SCALE;
yValue = BI_HEIGHT / 2.0 - yValue;
thisPoint = new Point((int) tempX, (int) yValue);
if (lastPoint != null) {
drawInBufferedImage();
}
xValue += X_STEP;
} else {
((Timer) e.getSource()).stop();
thisPoint = null;
}
repaint();
}
private void drawInBufferedImage() {
Graphics2D g2 = bImage.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(LINE_WIDTH, BasicStroke.CAP_ROUND,
BasicStroke.JOIN_ROUND));
g2.setColor(LINE_COLOR);
int x1 = lastPoint.x;
int y1 = lastPoint.y;
int x2 = thisPoint.x;
int y2 = thisPoint.y;
g2.drawLine(x1, y1, x2, y2);
g2.dispose();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(BI_WIDTH, BI_HEIGHT);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(bImage, 0, 0, null);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
if (thisPoint != null) {
drawThisPoint(g2);
}
}
private void drawThisPoint(Graphics2D g2) {
int x = thisPoint.x - THIS_PT_WIDTH / 2;
int y = thisPoint.y - THIS_PT_HEIGHT / 2;
Graphics2D g2b = (Graphics2D) g2.create();
g2b.setStroke(new BasicStroke(THIS_PT_STROKE_WIDTH));
g2b.setColor(THIS_PT_FILL_COLOR);
g2b.fillOval(x, y, THIS_PT_WIDTH, THIS_PT_HEIGHT);
g2b.setColor(THIS_PT_BORDER_COLOR);
g2b.drawOval(x, y, THIS_PT_WIDTH, THIS_PT_HEIGHT);
g2b.dispose();
}
private double function(double x) {
return 24 * Math.sin(x / 12.0) * Math.sin(x);
}
private static void createAndShowGui() {
JFrame frame = new JFrame("BufferedImage Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new BufferedImageEg());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

Help with simple frame and graphics

For homework, I'm trying to create a "CustomButton" that has a frame and in that frame, I draw two triangles, and a square over it. It's supposed to give the user the effect of a button press once it is depressed. So for starters, I am trying to set up the beginning graphics, drawing two triangles, and a square. The problem I have is although I set my frame to 200, 200, and the triangles I have drawn I think to the correct ends of my frame size, when I run the program, I have to extend my window to make the whole artwork, my "CustomButton," viewable. Is that normal? Thanks.
Code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class CustomButton
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
CustomButtonFrame frame = new CustomButtonFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
class CustomButtonFrame extends JFrame
{
// constructor for CustomButtonFrame
public CustomButtonFrame()
{
setTitle("Custom Button");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
CustomButtonSetup buttonSetup = new CustomButtonSetup();
this.add(buttonSetup);
}
private static final int DEFAULT_WIDTH = 200;
private static final int DEFAULT_HEIGHT = 200;
}
class CustomButtonSetup extends JComponent
{
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
// first triangle coords
int x[] = new int[TRIANGLE_SIDES];
int y[] = new int[TRIANGLE_SIDES];
x[0] = 0; y[0] = 0;
x[1] = 200; y[1] = 0;
x[2] = 0; y[2] = 200;
Polygon firstTriangle = new Polygon(x, y, TRIANGLE_SIDES);
// second triangle coords
x[0] = 0; y[0] = 200;
x[1] = 200; y[1] = 200;
x[2] = 200; y[2] = 0;
Polygon secondTriangle = new Polygon(x, y, TRIANGLE_SIDES);
g2.drawPolygon(firstTriangle);
g2.setColor(Color.WHITE);
g2.fillPolygon(firstTriangle);
g2.drawPolygon(secondTriangle);
g2.setColor(Color.GRAY);
g2.fillPolygon(secondTriangle);
// draw rectangle 10 pixels off border
g2.drawRect(10, 10, 180, 180);
}
public static final int TRIANGLE_SIDES = 3;
}

Try adding
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
to your CustomButtonSetup class.
And then do
setTitle("Custom Button");
//setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
CustomButtonSetup buttonSetup = new CustomButtonSetup();
this.add(buttonSetup);
pack();
(From the api-docs on pack():)
Causes this Window to be sized to fit the preferred size and layouts of its subcomponents.
You should get something like:

The DEFAULT_WIDTH and DEFAULT_HEIGHT that you set is for the entire frame, including borders, window titles, icons, etc. It's not the size of the drawing canvas itself. Thus, it is expected that if you draw something in a 200x200 canvas, it would not necessarily fit in a 200x200 window containing that canvas.