Develop Reference

Why does my method inside a class only draw the first circle but if i just use filloval method inside a for loop it displays all circles?

I'm writing a program that displays a circle every time you click the Jpanel. I have it all set up and I want to be able to use the drawCircle method I created in my circle class to draw the circles in the paintComponent method. I'm storing all of the circles created in a linked list. Then I interate through each Circle in the list and try to use the method in my Circle class called drawCircle().
For some reason, if I try to use c1.drawCircle() in a for loop in the My panel class it only draws the last circle that was created. But if I just use g.fillOval(with the correct parameters grabbing the values from the Circle class) in the for loop it works properly and displays all the circles. Why is it doing this and how do I go about using the method in the Circle class properly
I'm unsure what to try right now.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.LinkedList;
public class MouseTest {
private int borderWidth = 20;
private JFrame frame;
private boolean tracking;
private boolean start;
private boolean clearBol;
private int xstart;
private int ystart;
private int xend;
private int yend;
private LinkedList<Circle> circles;
public MouseTest() {
tracking = false;
start = false;
circles = new LinkedList<Circle>();
frame = new JFrame();
frame.setBounds(250, 98, 600, 480);
frame.setTitle("Window number three");
Container cp = frame.getContentPane();
JButton clear = new JButton("Clear");
JToggleButton circleButton = new JToggleButton()("Circles");
JToggleButton drawButton = new JToggleButton("Draw");
ButtonGroup circleOrDraw = new ButtonGroup();
MyPanel pane = new MyPanel();
clear.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
clearBol = true;
frame.repaint();
}
});
JPanel top = new JPanel();
top.setLayout(new FlowLayout());
top.add(clear);
circleOrDraw.add(circleButton);
circleOrDraw.add(drawButton);
top.add(circleOrDraw);
cp.add(top, BorderLayout.NORTH);
cp.add(pane, BorderLayout.CENTER);
pane.addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
xstart = e.getX();
ystart = e.getY();
start = false;
}
public void mouseReleased(MouseEvent e) {
xend = e.getX();
yend = e.getY();
if (xend < xstart) {
int tmp = xstart;
xstart = xend;
xend = tmp;
}
if (yend < ystart) {
int tmp = ystart;
ystart = yend;
yend = tmp;
}
start = true;
frame.repaint();
}
});
pane.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseMoved(MouseEvent e) {
if (tracking) {
int x = e.getX();
int y = e.getY();
msg("(" + x + ", " + y + ")");
}
}
});
frame.setVisible(true);
} // constructor
public static void main(String[] arg) {
MouseTest first = new MouseTest();
} // main
public void msg(String s) {
System.out.println(s);
}
public void trackMouse() {
tracking = !tracking;
} // trackMouse
public class Circle extends JPanel {
Graphics g;
int x;
int y;
int r;
Color color;
public Circle(Graphics g, int x, int y, int r) {
this.g = g;
this.x = x;
this.y = y;
this.r = r;
int red = (int) (256 * Math.random());
int green = (int) (256 * Math.random());
int blue = (int) (256 * Math.random());
this.color = new Color(red, green, blue);
}
public void drawCircle() {
int x2 = x - (r / 2);
int y2 = y - (this.r / 2);
g.setColor(color);
g.fillOval(x2, y2, this.r, this.r);
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public Color getColor() {
return color;
}
public int getR() {
return r;
}
}
public class MyPanel extends JPanel {
public void paintComponent(Graphics g) {
if (start) {
circles.add(new Circle(g, xend, yend,
(int) ((250 * Math.random() + 4))));
//Area where I'm having issues
for (Circle c1 : circles) {
msg("" + c1.getX());
// this method that I created in the circle class will only draw the first circle
//c1.drawCircle();
int r = c1.getR();
int x = c1.getX();
int y = c1.getY();
g.setColor(c1.getColor());
g.fillOval((c1.getX() - (r / 2)), (c1.getY() - (r / 2)),
r, r); // this will display all the circles
}
int size = circles.size();
msg(size + " Size");
msg("" + circles.getLast().getX());
}
if (clearBol) {
super.paintComponent(g);
circles.clear();
clearBol= false;
}
Thank you!

Most of the structure of your class needs to be changed
Your MyPanel should have a better name to give its functionality, maybe something like DrawingPanel.
The DrawingPanel is then responsible for managing the Circles to be painted. So typically you would just use an ArrayList to hold the Circle information.
Then you would add a method to the class, like addCircle(...) to add the Circle information to the ArrayList and then invoke repaint().
Then in your paintComponent(...) method the first thing you do is invoke super.paintComponent(...) to clear the panel. Then you iterate through the ArrayList and paint all the Circles. There will be no need for the Boolean values to check the state of the class. The ArrayList will either have circles or it won't.
You would also need a method like clearCircles(). This would simply remove all the Circles from the ArrayList and invoke repaint() on itself.
Your Circle class should NOT extend JPanel. It should just be a class that contains the information need to paint the circle: x/y location, size of circle and color of circle.
Now your frame is responsible of displaying your DrawingPanel and the buttons.
When you click the "Clear" button you simply invoke the clearCircles() method of the DrawingPanel.
For your MouseListener you simply invoke the addCircle(...) method of your DrawingPanel once you have all the information needed to create a Circle instance.
For a complete working example that incorporates all these suggestions check out the DrawOnComponent example found in Custom Painting Approaches

Java 2D game: repaint

I am creating a very simple game for my homework and right now I am solving the following problem:
in this game when you click on the shape (for now it is just a circle) it should dissapear and render a new one somewhere else (you are collecting points when you hit that shapes, that´s the point) and my problem is in the mouseClicked method, i think. I put some control System.out.println() there and everytime when the program reach this method it displays as many prints as there was circles. I mean, if you click on the first circle it displays one print, if you click on the second circle it diplays two prints and so on. Can you help me pls? I just started with the swing and awt and I don´t have much time for thorough study. Thank you so much.
public class Shape extends JPanel implements ActionListener{
Graphics2D g2;
Ellipse2D circle;
Timer t = new Timer(2000, this);
int x, y, count;
JLabel counting;
public Shape(JLabel counting){
this.counting = counting;
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g2 = (Graphics2D)g;
ListenForMouse lForMouse = new ListenForMouse();
addMouseListener(lForMouse);
Random ran = new Random();
int green = ran.nextInt(256);
int red = ran.nextInt(256);
int blue = ran.nextInt(256);
Color randomColor = new Color(green, red, blue);
int wid = ran.nextInt(101) + 50;
x = ran.nextInt(650);
if(x > wid)
x = x - wid;
y = ran.nextInt(600);
if(y > wid)
y = y - wid;
circle = new Ellipse2D.Double(x,y,wid,wid);
t.start();
g2.setColor(randomColor);
g2.fill(circle);
}
#Override
public void actionPerformed(ActionEvent arg0) {
repaint();
}
private class ListenForMouse implements MouseListener{
#Override
public void mouseClicked(MouseEvent e) {
System.out.println("Control before");
if(circle.contains(e.getPoint())){
count++;
counting.setText(Integer.toString(count));
t.stop();
repaint();
System.out.println("Control in");
}
System.out.println("Control out");
}
}
}

This happens, because you add a new mouse listener every time paintComponent is called. You should do this once, inside the constructor.

Having trouble with pen transparency in paint program

I'm relatively new to Java, but I've made a simple paint program that allows the user to draw, change the color and size of the pen, and clear the drawing area.
The user selects a color from the JColorChooser object 'c' and this is handed off to the Color variable 'selected' through c.getColor(). I want to be able to change the transparency of the selected color, but I don't know if there is a way to convert from Color to RGB so that I can use the setColor(r, g, b, a) method. My code is below. I really appreciate any help!
Color selected;
public class ColorTool extends JPanel {
public ColorTool() {
super(new BorderLayout());
b = new JLabel("Pen Color", JLabel.CENTER);
b.setForeground(Color.black);
c = new JColorChooser(b.getForeground());
c.getSelectionModel().addChangeListener(new ColorListener());
add(c, BorderLayout.PAGE_END);
}
}
public DrawPanel() {
setDoubleBuffered(false);
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
for (int i = 0; i <= 100; i++) {
if (PS == i) {
oldX = (int)(e.getX() - Math.ceil(PS/2));
oldY = (int)(e.getY() - Math.ceil(PS/2));
if (graphics != null) {
graphics.setColor(selected);
graphics.fillOval(oldX, oldY, PS, PS);
}
repaint();
oldX = e.getX();
oldY = e.getY();
}
}
}
});
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
BasicStroke size = new BasicStroke(PS,
BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
currentX = e.getX();
currentY = e.getY();
if (graphics != null) {
graphics.setColor(selected);
graphics.setStroke(size);
graphics.drawLine(oldX, oldY, currentX, currentY);
}
repaint();
oldX = currentX;
oldY = currentY;
}
});
}
public class ColorListener implements ChangeListener {
public void stateChanged(ChangeEvent e) {
selected = c.getColor();
}
}

You can access that by calling the method getComponents on the instance of Color.
From the documentation:
public float[] getComponents(float[] compArray)
Returns a float array containing the color and alpha components of the Color, in the ColorSpace of the Color. If compArray is null, an array with length equal to the number of components in the associated ColorSpace plus one is created for the return value. Otherwise, compArray must have at least this length and it is filled in with the components and returned.
Parameters: compArray - an array that this method fills with the color and alpha components of this Color in its ColorSpace and returns
Returns:
the color and alpha components in a float array.

Java SWT Drawing Shapes on canvas with mouse events

I want to make an application in order to draw forms (rectangle, line, square, arrow) like in paint using Java SWT Canvas. I'm using mouse events (Up, Down and move) to get the canvas Y and X position. And i have a button for each form types that get canvas mouse position and draw the selected form using the mouse events. My problem is, when i draw the first form (Circle, square, line) everything works, but when draw the second, the first erase. How can I make the first form stay on drawn after redraw the canvas?
Variables:
private static boolean drag = false;
private Canvas compCanvas;
private Button btnSend, btnAdd,btnFreeHand,btnArrow,btnCircle,btnSquare,btnLine;
private Composite mainPanel;
compCanvas = new Canvas(mainPanel, SWT.NONE);
mouseEvents():
private void mouseEvents(){
compCanvas.addListener(SWT.MouseDown, new Listener(){
public void handleEvent(Event e){
System.out.println("Mouse event on canvas DOWN: X VALUE:"+e.x+"Y VALUE:"+e.y);
startY = e.y;
startX = e.x;
drag = true;
}
});
compCanvas.addListener(SWT.MouseUp, new Listener(){
public void handleEvent(Event e){
System.out.println("Mouse event on canvas UP: X VALUE:"+e.x+"Y VALUE:"+e.y);
endY = e.y;
endX = e.x;
drag = false;
//compCanvas.redraw();
}
});
compCanvas.addListener(SWT.MouseMove, new Listener(){
public void handleEvent(Event e){
System.out.println("Mouse event on canvas MOVE: X VALUE:"+e.x+"Y VALUE:"+e.y);
if(drag){
endY = e.y;
endX = e.x;
compCanvas.redraw();
}
}
});
};
btnSquare.selectionListener() and Declaration:
btnSquare = new Button(compSendAdd, SWT.NONE);
btnSquare.setLayoutData(new RowData(25, 25));
btnSquare.setImage(squareIcon);
btnSquare.addSelectionListener(new SelectionListener(){
private void btnSquare(){
mouseEvents();
//LightweightSystem lws = new LightweightSystem(compCanvas);
compCanvas.addListener(SWT.Paint, new Listener(){
public void handleEvent(Event e){
if(drag){
GC gc = e.gc;
//gc.setAlpha(128);
int minX = Math.min(startX,endX);
int minY = Math.min(startY,endY);
int maxX = Math.max(startX, endX);
int maxY = Math.max(startY, endY);
int width = maxX - minX;
int height = maxY - minY;
gc.fillRectangle(minX, minY,width,height);
}
}
});
}
public void widgetSelected(SelectionEvent event) {
btnSquare();
}
public void widgetDefaultSelected(SelectionEvent event) {
btnSquare();
}
});

By default controls are filled with current background color each time the SWT.Paint listener is called. You need to turn this off.
Do this by specifying the SWT.NO_BACKGROUND style on the Canvas
compCanvas = new Canvas(mainPanel, SWT.NO_BACKGROUND);
You will also need to fill the background the first time the canvas is drawn.

Create class shape with x, y, width, height fields
class Shape {
public int x; // coordiates
public int y;
public int width;
public int heigth;
String type; // "rect" for example
public Shape(int x, int y, int width, int height, String type) {
this.x = x;
this.y = y;
this.width = width;
this.heigth = height;
this.type = type;
}
}
After mouse up store your shape in list according to which button is selected
List<Shape> shapes = new ArrayList<Shape>();
shapes.add(new Shape(x, y, width, height, getType()));
In PainListener You MUST redraw all shapes from your list
for(Shape s: shapes) {
//draw shape s
}

how to draw rectangle on java applet using mouse drag event

i am using java.
i want to draw rectangle based on mousedrag event. if user dragging the mouse, then the rectangle on the applet should increase or decrease basing on current mouse coordinates.
i have the following code.
in the following code i am using [b]SelectionArea[/b] class which extends a canvas on which i am performing drawing operation. i am using [b]image[/b] variable in this class for double buffering to reduce flickering and to save the applet's previous state(i.e drawing content of applet)
but the code is working fine if i draw first rectangle. if i start to draw second rectangle the previously drawn rectangle is disappearing. i want the previously drawn rectangle to be on the screen
can any one tell me how to solve this.
import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;
/*
* This displays a framed area. When the user drags within
* the area, this program displays a rectangle extending from
* where the user first pressed the mouse button to the current
* cursor location.
*/
public class RectangleDemo extends Applet {
SelectionArea drawingPanel;
Label label;
public void init() {
GridBagLayout gridBag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
setLayout(gridBag);
drawingPanel = new SelectionArea(this);
c.fill = GridBagConstraints.BOTH;
c.weighty = 1.0;
c.gridwidth = GridBagConstraints.REMAINDER; //end row
gridBag.setConstraints(drawingPanel, c);
add(drawingPanel);
label = new Label("Drag within the framed area.");
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 1.0;
c.weighty = 0.0;
gridBag.setConstraints(label, c);
add(label);
drawingPanel.setVisible(true);
validate();
}
public void paint(Graphics g){
drawingPanel.repaint();
}
public void update(Graphics g){
paint(g);
}
}
class SelectionArea extends Canvas implements ActionListener, MouseListener, MouseMotionListener{
Rectangle currentRect;
RectangleDemo controller;
//for double buffering
Image image;
Graphics offscreen;
public SelectionArea(RectangleDemo controller) {
super();
this.controller = controller;
addMouseListener(this);
addMouseMotionListener(this);
}
public void actionPerformed(ActionEvent ae){
repaintoffscreen();
}
public void repaintoffscreen(){
image = createImage(this.getWidth(), this.getHeight());
offscreen = image.getGraphics();
Dimension d = getSize();
if(currentRect != null){
Rectangle box = getDrawableRect(currentRect, d);
//Draw the box outline.
offscreen.drawRect(box.x, box.y, box.width - 1, box.height - 1);
//repaint();
}
}
public void mouseEntered(MouseEvent me) {}
public void mouseExited(MouseEvent me){ }
public void mouseClicked(MouseEvent me){}
public void mouseMoved(MouseEvent me){}
public void mousePressed(MouseEvent me) {
currentRect = new Rectangle(me.getX(), me.getY(), 0, 0);
repaintoffscreen();
}
public void mouseDragged(MouseEvent me) {
System.out.println("here in dragged()");
currentRect.setSize(me.getX() - currentRect.x, me.getY() - currentRect.y);
repaintoffscreen();
repaint();
}
public void mouseReleased(MouseEvent me) {
currentRect.setSize(me.getX() - currentRect.x, me.getY() - currentRect.y);
repaintoffscreen();
repaint();
}
public void update(Graphics g){
paint(g);
}
public void paint(Graphics g) {
g.drawImage(image, 0, 0, this);
}
Rectangle getDrawableRect(Rectangle originalRect, Dimension drawingArea) {
int x = originalRect.x;
int y = originalRect.y;
int width = originalRect.width;
int height = originalRect.height;
//Make sure rectangle width and height are positive.
if (width < 0) {
width = 0 - width;
x = x - width + 1;
if (x < 0) {
width += x;
x = 0;
}
}
if (height < 0) {
height = 0 - height;
y = y - height + 1;
if (y < 0) {
height += y;
y = 0;
}
}
//The rectangle shouldn't extend past the drawing area.
if ((x + width) > drawingArea.width) {
width = drawingArea.width - x;
}
if ((y + height) > drawingArea.height) {
height = drawingArea.height - y;
}
return new Rectangle(x, y, width, height);
}
}
also if i run this code on full screen mode then i am seeing that the rectangle is appering on screen only after i released the mouse. but i want the rectangle to be on the screen while dragging the mouse and it should change it's dimension according to the current mouse coordinates.
can any one help me pls.

homework?
basically what you need to do is:
on mouse down keep the mouse-down coordinates and repaint
on mouse move keep current mouse coordinates and repaint
on mouse up, nullify the mouse-down coordinates to indicate there is no rect, and repaint.
on paint, draw background and then rect between mousedown and cur-mouse coordinates.
if you don't want to keep a background image, you can do a trick with the Graphics xor function, drawing the same rect twice will erase the old rect, so you can use it to restore the old image straight on the graphics object.
Edit: code xor usage sample:
public void paint(Graphics g)
{
g.setXORMode(Color.black);
// draw old rect if there is one. this will erase it
// draw new rect, this will draw xored
g.setDrawMode(); // restore normal draw mode
}
Xor has the an interesting property:
xor(xor(x)) = x
so xoring the same pixel twice restores it's original color.

There are a couple issues that need to be addressed.
First, regarding only one rectangle can be drawn, this is due to the design of your program. In your code, whenever the repaintoffscreen method is called, the currectRect field is used to draw a rectangle. However, there is no provision to keep holding onto rectangles which were made in the past.
One way to keep a hold of past rectangles would be perhaps to make another field which is, for example, a List<Rectangle> which is used to store past rectangles. Then, when the mouse is released, add the current rectangle to that list.
Then, in order for all rectangles, currentRect and past rectangles to appear, repaintoffscreen will need to not only perform getDrawableRect and offscreen.drawRect using the currentRect but also with the past rectangles which are stored in the List<Rectangle>. (Hint, use a for loop to iterate through the list.)
Second, regarding the rectangle not appearing until after releasing the mouse button, rather than using the mouseDragged method, maybe using the mouseMoved method along with a check to see that the mouse button is depressed may be a workaround. (I think I've also had trouble dealing with the mouseDragged method in the past.)
The MouseEvent passed into the mouseMoved method can be used to check if a button is depressed by the getButton method:
public void mouseMoved(MouseEvent e)
{
// Check if button1 is pressed.
if (e.getButton() == MouseEvent.BUTTON1)
{
// Perform sizing of rectangle and off-screen drawing, and repaint.
}
}

My question was about create a select rectangle invert mouse click position, but, in the end I got make this with this method:
... //to set the selection area
private int iniSelX;
private int iniSelY;
private int endSelX;
private int endSelY;
private JPanel myJPanel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.WHITE);
g.fillRect(0, 0, this.getWidth(), this.getHeight());
g.setColor(Color.red);
g.drawLine(260, 5, 260, 260);
g.setColor(Color.BLUE);
//verify if go draw the rectangle
if (iniSelX != 0 || endSelX != 0) {
boolean revertX = iniSelX < endSelX;
boolean revertY = iniSelY < endSelY;
//Simple way
//g.drawRect(iniSelX, iniSelY, endSelX - iniSelX, endSelY - iniSelY);
//reverse way
g.drawRect(revertX ? iniSelX : endSelX, revertY ? iniSelY : endSelY,
revertX ? endSelX - iniSelX : iniSelX - endSelX, revertY ? endSelY - iniSelY : iniSelY - endSelY);
}
}
}; ...
addMouseMotionListener(new MouseMotionListener() {
#Override
public void mouseDragged(MouseEvent m) {
//update selection area
endSelX = m.getX();
endSelY = m.getY();
repaint();
}
#Override
public void mouseMoved(MouseEvent m) {
repaint();
}
});
addMouseListener(new MouseListener() {
...
#Override
public void mousePressed(MouseEvent e) {
//start drawing the selection
iniSelX = e.getX() - 15;
iniSelY = e.getY() - 20;
}
#Override
public void mouseReleased(MouseEvent e) {
//start drawing the selection
iniSelX = 0;
iniSelY = 0;
endSelX = 0;
endSelY = 0;
}
...
});
}
public void log() {
System.out.println("iniSelX" + iniSelX);
System.out.println("iniSelY" + iniSelY);
System.out.println("endSelX" + endSelX);
System.out.println("endSelY" + endSelY);
} ...
I hope this is useful.