We Keep Coding

How to add a shape on button click?

I have the following code, I am trying to add a circle to my frame when the button is clicked, I tried calling circle class from my main function, but do not know how to add a circle after that. please help me!
public static void main(String[] args) {
// Create a frame and put a scribble pane in it
JFrame frame = new JFrame("FrameFormula");
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
final FrameFormula scribblePane = new FrameFormula();
JPanel shapePanel = new JPanel();
JButton horGap = new JButton("Add a circle");
horGap.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
int[] circleValues = generateRandomValues(300, 300, 50, 150);
int x = circleValues[0];
int y = circleValues[1];
int width = circleValues[2];
int height = width;
Circle circle = new Circle(x, y, width, height);
//scribblePane.addCircle(circle);
}
});
shapePanel.add(horGap);
frame.add(shapePanel, BorderLayout.SOUTH);
frame.getContentPane().add(scribblePane, BorderLayout.CENTER);
}
I have created separate classes for creating circle with x and y points.
private static int[] generateRandomValues(int maxX, int maxY,
int minSize, int maxSize) {
Random random = new Random();
int[] values = new int[3];
values[0] = random.nextInt(maxX);
values[1] = random.nextInt(maxY);
values[2] = Math.min(random.nextInt(maxSize) + minSize, maxSize);
return values;
}
static class Circle {
int x, y, width, height;
public Circle(int x, int y, int width, int height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}
public void draw(Graphics g) {
g.drawOval(x, y, width, height);
}
}

it remains for a second and gets removed if something else we do on the panel
Check out Custom Painting Approaches for the two common ways to do custom painting:
Add objects to an ArrayList and then paint all the objects in the list
Paint the objects to a BufferedImage and then paint the BufferedImage
The demo code shows how to randomly add Rectangles using the mouse. Your code would obviously be slightly different because you would add the Rectangles with a button.
So start with the working code to get it working with a button. Then change the code to work for circles instead of rectangles.

What you do is creating a circle but not calling the draw-Method. You would use something like:
Circle circle = new Circle(x, y, width, height);
Graphics g = shapepanel.getGraphics();
circle.draw(g);
But that leads to problems so I would suggest you take a look at this thread: Drawing an object using getGraphics() without extending JFrame
There is explained why and how to draw something consistently in a JPanel.

Java - I want to draw multiple 2D Ellipses using a timer, but it's not working

Already tried searching, but couldn't find anything.
I'm trying to draw multiple 2D Ellipses using an array, and a for loop, I'm repainting the frame every second. The thing is, I only get one Ellipse everytime I repaint, can somebody tell me what's wrong with me code, please?
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class MovingDot extends JFrame{
static int posX = (int)Math.round(Math.random()*780);
static int posY = (int)Math.round(Math.random()*780);
static int width = (int)Math.round(Math.random()*780);
static int height = (int)Math.round(Math.random()*780);
static int dots = 0;
public static Timer timer;
public MovingDot(){
super("Moving Dot");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(800, 800);
Dot2 dot = new Dot2();
add(dot);
setVisible(true);
timer = new Timer((int)Math.round((1000)), timerAction);
timer.start();
}
private ActionListener timerAction = new ActionListener(){
#Override
public void actionPerformed(ActionEvent ae){
posX = (int)Math.round(Math.random()*780);
posY = (int)Math.round(Math.random()*780);
width = (int)Math.round(Math.random()*780);
height = (int)Math.round(Math.random()*780);
float r = (float)Math.random();
float g = (float)Math.random();
float b = (float)Math.random();
Color col = new Color(r,g,b);
setBackground(col);
dots++;
repaint();
}
};
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run()
{
new MovingDot();
}
});
}
}
class Dot2 extends JPanel{
#Override
public void paintComponent(Graphics c2){
int x = MovingDot.posX;
int y = MovingDot.posY;
int w = MovingDot.width;
int h = MovingDot.height;
float r,g,b;
Color col;
Graphics2D c = (Graphics2D) c2;
c.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Ellipse2D.Float[] e = new Ellipse2D.Float[10];
for (int i = 0; i < 10; i++) {
if (i == 0)
r = (float)Math.random();
else
r = 0.163F;
g = (float)Math.random();
b = (float)Math.random();
col = new Color(r,g,b);
c.setColor(col);
e[i] = new Ellipse2D.Float(x, y, w, h);
c.fill(e[i]);
}
}
}
Found out what was wrong myself, I had to make x, y, w and h random in my paintComponent. And no, this is not for a school assignment, I'm trying to teach myself Java using a book.
And about making my methods static, I was planning on using them in my JPanel, but I realised I don't need them, so I'm going to delete them. Thanks for your advice!

You shouldn't be creating your Ellipse array inside of paintComponent, makes no sense.
Instead create the array in the class.
Your JPanel's paintComponent method should not have any program logic in it. It should only have code that paints the ellipses. That is, it should iterate through your array with a for loop, and if the item in the array is not null draw it.
You'd be even better off using an ArrayList<Ellipse2D> and not an array. That way you wouldn't have to check for nulls.
In the Timer's ActionListener, if your counter is < 10, you'd add an Ellipse2D to the array and call repaint.
If the counter >= 10 you'd stop the Timer
Also, none of your static variables should be static, and having them as static suggests that the program design is off. If this is for a school assignment, that could lead to deduction of your grade.

Java Applet adding thread makes while loop infinite

I am trying to make a program that generates 25 random ovals then draw a ball and make it bounce, I got it somewhat done, I generated the ovals and I got the ball to move but when I added the thread it kept repeating the draw oval loop, I get somewhat why this is happening but I have no idea how to fix it.
Basically my program should:
draw 25 random sized ovals on random locations within the border - completed
draw a ball and make it move - completed
make the ball bounce - not done but I know how to do it
but it keeps repeating step one.
this is my code that I have written, oh and I have to use applets right now its part of the course please don't suggest I use swing or something else:
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
public class As4B extends Applet implements Runnable
{
public int x, y;
public int width = 854;
public int height = 480;
public int border = 20;
public Image offscreen;
public Graphics d;
public void init()
{
setSize(width,height);
Thread th = new Thread(this);
th.start();
offscreen = createImage(width,height);
d = offscreen.getGraphics();
}
public void run()
{
x = 100;
y = 100;
while(true)
{
x ++;
y ++;
repaint();
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void paint(Graphics gfx)
{
d.setColor(java.awt.Color.black);
d.fillRect(0, 0, width, height);
d.setColor(java.awt.Color.green);
d.fillRect(0 + border, 0 + border, (width - (border * 2)), (height - (border* 2)));
genOval(25, d);
d.setColor(Color.gray);
d.fillOval(x, y, 50, 50);
gfx.drawImage(offscreen, 0, 0, this);
}
public int random(int low, int high)
{
int answer =(int)((Math.random()*(high-low))+ low);
return answer;
}
public void genOval(int amount, Graphics f)
{
int ranWidth, ranHeight, ranX, ranY, red, blue, green;
int i = 0;
while(i < 25)
{
green = random(0,255);
blue = random(0,255);
red = random(0,255);
f.setColor(new Color(red,green,blue));
ranWidth = random(30,400);
ranHeight = random(30,200);
ranX = random(0 + border, ((width - border)- (ranWidth)));
ranY = random(0 + border , ((height - border)- (ranHeight)));
f.fillOval(ranX, ranY, ranWidth, ranHeight);
i++;
}
}
public void update(Graphics gfx) {
paint(gfx);
}
}

Your genOval() method has no persistent backing. Every time repaint() is called (by your thread), the paint() method is called, and this generates new locations for the random ovals. You need to create a persistent source for that information, like so:
List<Rectangle> rectangles = new ArrayList<Rectangle>();
List<Color> colors = new ArrayList<Color>();
public void init() {
...
for (int i = 0; i < 25; i++) {
int green = random(0,255);
int blue = random(0,255);
int red = random(0,255);
colors.add(new Color(red,green,blue));
ranWidth = random(30,400);
ranHeight = random(30,200);
ranX = random(0 + border, ((width - border)- (ranWidth)));
ranY = random(0 + border , ((height - border)- (ranHeight)));
rectangles.add(new Rectangle(ranX, ranY, ranWidth, ranHeight));
}
}
public void genOval(Graphics g) {
for (int i = 0; i < 25; i++) {
Color color = colors.get(i);
Rectangle rectangle = rectangle.get(i);
// Draw using color & rectangle
}
}

Cutting part of an image out and keeping the original image

So I have a black image that acts as darkness (In my game). I want to show a small portion around the character only. Like so
The red square is the player.
The green bit is the ground in the game (grass).
The black is the shadow/darkness.
What I want to do is cut a Ellipse/hole out of the blank, black image. I want this Ellipse to be centered around the players (The red square) x and y position.
Currently I am using this to get the effect:
for(int x = 0; x < width; x++) {
for(int y = 0; y < height; y++) {
//draw mask
g.setColor(Color.black);
if(!nearPlayer(x, y)) {
g.drawLine(x, y, x, y);
}
}
}
But, this processes extremely slow and laggs the players movement drastically.
Is this possible?

..the Player is the red square. Basically what i want to do is cut a circle out of the blank, black image around the coordinates of the player relative to said black image.
What DYM by 'black image' - exactly? To me that just looks like the BG is painted black, which would make more sense for any solid color. In that case, just create the red thing using an Area, fill it, then for the border set a stroke & the color to black, and draw it. This example shows how.
The relevant part of that short code is..
public void paintDaisyPart(Graphics2D g, Area daisyArea) {
g.setClip(daisyArea);
g.setColor(Color.YELLOW);
g.fillRect(0, 0, 200, 200);
g.setColor(Color.YELLOW.darker());
g.setClip(null);
g.setStroke(new BasicStroke(3));
g.draw(daisyArea);
}
I must be bored. This is an animated SSCCE version of the code that drew the image above. It is typically showing >130 FPS. And that is on a clunky machine for which I told the guy my spec. was 'cheap' & reminded him twice that I don't play (heavy rendering) games.
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class DaisyDisplay {
DaisyDisplay() {
JPanel gui = new JPanel(new BorderLayout(2,2));
final BufferedImage daisy = new BufferedImage(
200,200,BufferedImage.TYPE_INT_RGB);
final JLabel daisyLabel = new JLabel(new ImageIcon(daisy));
gui.add(daisyLabel,BorderLayout.CENTER);
final Daisy daisyPainter = new Daisy();
daisyPainter.setSize(200);
final JLabel fps = new JLabel("FPS: ");
gui.add(fps,BorderLayout.SOUTH);
ActionListener animator = new ActionListener() {
int counter = 0;
long timeLast = 0;
long timeNow = 0;
public void actionPerformed(ActionEvent ae) {
Graphics2D g = daisy.createGraphics();
g.setColor(Color.GREEN.darker());
g.fillRect(0, 0, 200, 200);
daisyPainter.paint(g);
g.dispose();
daisyLabel.repaint();
counter++;
timeNow = System.currentTimeMillis();
if (timeLast<timeNow-1000) {
fps.setText("FPS: " + counter);
counter = 0;
timeLast = timeNow;
}
}
};
Timer timer = new Timer(1,animator);
timer.start();
JOptionPane.showMessageDialog(null, gui);
timer.stop();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new DaisyDisplay();
}
});
}
}
class Daisy {
double size = 200;
Point location;
double offset = 0.0;
public void paint(Graphics2D g) {
Area daisyArea = getDaisyShape();
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
offset += .02d;
AffineTransform plain = g.getTransform();
g.setTransform(AffineTransform.getRotateInstance(
offset + (Math.PI*1/8),
100,100));
paintDaisyPart(g,daisyArea);
g.setTransform(AffineTransform.getRotateInstance(
offset + (Math.PI*3/8),
100,100));
paintDaisyPart(g,daisyArea);
g.setTransform(AffineTransform.getRotateInstance(
offset,
100,100));
paintDaisyPart(g,daisyArea);
g.setTransform(AffineTransform.getRotateInstance(
offset + (Math.PI*2/8),
100,100));
paintDaisyPart(g,daisyArea);
g.setTransform(plain);
}
public void setLocation(Point location) {
this.location = location;
}
public void paintDaisyPart(Graphics2D g, Area daisyArea) {
g.setClip(daisyArea);
g.setColor(Color.YELLOW);
g.fillRect(0, 0, 200, 200);
g.setColor(Color.YELLOW.darker());
g.setClip(null);
g.setStroke(new BasicStroke(3));
g.draw(daisyArea);
}
public void setSize(double size) {
this.size = size;
}
public Area getDaisyShape() {
int diameter = (int)size*6/20;
Ellipse2D.Double core = new Ellipse2D.Double(
(size-diameter)/2,(size-diameter)/2,diameter,diameter);
int pad = 10;
int petalWidth = 50;
int petalLength = 75;
Area area = new Area(core);
// left petal
area.add(new Area(new Ellipse2D.Double(
pad,(size-petalWidth)/2,petalLength,petalWidth)));
// right petal
area.add(new Area(new Ellipse2D.Double(
(size-petalLength-pad),(size-petalWidth)/2,petalLength,petalWidth)));
// top petal
area.add(new Area(new Ellipse2D.Double(
(size-petalWidth)/2,pad,petalWidth,petalLength)));
// bottom petal
area.add(new Area(new Ellipse2D.Double(
(size-petalWidth)/2,(size-petalLength-pad),petalWidth,petalLength)));
return area;
}
}

Painting pixels images in Java

Which method is the best way to create a pixel image with java.
Say, I want to create a pixel image with the dimensions 200x200 which are 40.000 pixels in total. How can I create a pixel from a random color and render it at a given position on a JFrame.
I tried to create a own component which just creates pixel but it seems that this is not very performant if I create such a pixel a 250.000 times with a for-loop and add each instance to a JPanels layout.
class Pixel extends JComponent {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getRandomColor());
g.fillRect(0, 0, 1, 1);
}
}

You do not need to create a class for this. Java already has the excellent BufferedImage class that does exactly what you need. Here is some pseudo-code:
int w = 10;
int h = 10;
int type = BufferedImage.TYPE_INT_ARGB;
BufferedImage image = new BufferedImage(w, h, type);
int color = 255; // RGBA value, each component in a byte
for(int x = 0; x < w; x++) {
for(int y = 0; y < h; y++) {
image.setRGB(x, y, color);
}
}
// Do something with image

The key here is the Canvas class. It is the standard Component that allows arbitrary draw operations. In order to use it, you must subclass the Canvas class and override the paint(Graphics g) method, then loop through each pixel and draw your random color. The following code should work:
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;
import javax.swing.JFrame;
public class PixelCanvas extends Canvas {
private static final int WIDTH = 400;
private static final int HEIGHT = 400;
private static final Random random = new Random();
#Override
public void paint(Graphics g) {
super.paint(g);
for(int x = 0; x < WIDTH; x++) {
for(int y = 0; y < HEIGHT; y++) {
g.setColor(randomColor());
g.drawLine(x, y, x, y);
}
}
}
private Color randomColor() {
return new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(WIDTH, HEIGHT);
frame.add(new PixelCanvas());
frame.setVisible(true);
}
}
The generated image looks like this:

You'll probably want to create a BufferedImage of the size you want, and use img.setRGB(x, y, getRandomColor()) to create a bunch of random pixels. Then you could render the whole image wherever you want it.