I have big problem with coding graphic part of my app, where I need to have components one on top of each other:
First I have JFrame (with fixed size)
In it I have two JPanel components. I want them to have colour background.
That's the easy part.
On one of the JPanel components I want to draw fixed shapres - rectangles, lanes, etc. Here I have problem, that I have two classes: one extends JPanel and is background for this part and second extends JComponent and represents element I draw (there is several elements). I don't know how to draw the elements in the JPanel - I tried several methods and nothing showed up. It's important to me that the JComponents should be drawn and conected only with this JPanel, not with whole frame.
On top of that I want to have moving shapes. It's easy when I have only frame and let's say rectangle, because I only change position and call repaint() method, but how to do this to make the moving shapes be connected to and be inside JPanel and to left previous layers in their place?
For my tries I created few classes with rectangles:
import javax.swing.*;
import java.awt.*;
import java.util.ArrayList;
public class Main{
public Main() {
JFrame frame = new JFrame();
frame.setSize(1200, 900);
frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
JPanel background = new JPanel();
background.setBackground(Color.lightGray);
GreenRect gr = new GreenRect();
gr.setPreferredSize(new Dimension(500,800));
background.add(gr, BorderLayout.WEST);
RedRect rr = new RedRect();
rr.setPreferredSize(new Dimension(500,800));
background.add(rr, BorderLayout.EAST);
frame.add(background);
}
public static void main(String[] args) {
new Main();
}
}
class GreenRect extends JPanel {
ArrayList<BlackRect> r = new ArrayList<>();
ArrayList<MovingRec> m = new ArrayList<>();
public GreenRect() {
setBackground(Color.green);
addRec(10,10);
addRec(50,50);
addRec(100,100);
addRec(1000,1000);
}
public void addRec(int x, int y) {
r.add(new BlackRect(x,y));
}
}
class RedRect extends JPanel {
public RedRect() {
setBackground(Color.red);
}
}
class BlackRect extends JComponent {
int x, y;
int w = 100, h = 100;
public BlackRect (int x, int y){
this.x = x;
this.y = y;
}
#Override
public void paintComponent(Graphics g) {
super.paintComponents(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.BLACK);
g2d.fillRect(x, y, w, h);
}
}
class MovingRec extends JComponent {
int x, y;
int w = 20, h = 20;
public MovingRec (int x, int y){
this.x = x;
this.y = y;
}
public void paintComponent(Graphics g) {
super.paintComponents(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.BLUE);
g2d.fillRect(x, y, w, h);
}
public void update() {
x += 5;
y += 5;
}
}
and now I have problems with points 3 and 4, because I can't place black rectangles on background and moving rectangles on the top.
I will be grateful for all help :)
You do not need to (and shouldn’t) extend BlackRect and MovingRect from JComponent.
For example, BlackRect could be a simple object, like:
class BlackRect {
int x, y;
int w = 100, h = 100;
public BlackRect(int x, int y) {
this.x = x;
this.y = y;
}
public void paint(Graphics2D g2d) {
g2d.setColor(Color.BLACK);
g2d.fillRect(x, y, w, h);
}
}
You should override GreenRect’s paint method, to paint rectangles on that panel:
public GreenRect extends JPanel {
// Existing members
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
for (BlackRect black_rect : r) {
black_rect.paint(g2d);
}
// Also paint list of moving rectangles here
}
}
When GreenRect.repaint() is called, it will paint its background, and all rectangles from the r (and m list when you add that code). If the m rectangles have had their positions updated, they will be drawn at their new positions, so they will appear to be moving. Since moving rectangles are drawn last, they would appear “on top”.
Use a Swing Timer to drive the animation. When the timer expires, it should move all of the moving rectangles slightly (ie, call MovingRec.update()), and call repaint() on GreenRect.
Related
I have this code in JAVA that draws a rectangle like the paint app when I drag my mouse on the panel. Every time I click and drag to make a new rectangle, the previous one disappears. I was wondering if there is a way for it to stay on the panel. And for there to be multiple rectangles, just like the paint app on windows.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class DrawRect extends JPanel {
int x, y, x2, y2;
public static void main(String[] args) {
JFrame f = new JFrame("Draw Box Mouse 2");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(new DrawRect());
f.setSize(300, 300);
f.setVisible(true);
}
DrawRect() {
x = y = x2 = y2 = 0; //
MyMouseListener listener = new MyMouseListener();
addMouseListener(listener);
addMouseMotionListener(listener);
}
public void setStartPoint(int x, int y) {
this.x = x;
this.y = y;
}
public void setEndPoint(int x, int y) {
x2 = (x);
y2 = (y);
}
public void drawPerfectRect(Graphics g, int x, int y, int x2, int y2) {
int px = Math.min(x,x2);
int py = Math.min(y,y2);
int pw=Math.abs(x-x2);
int ph=Math.abs(y-y2);
g.drawRect(px, py, pw, ph);
}
class MyMouseListener extends MouseAdapter {
public void mousePressed(MouseEvent e) {
setStartPoint(e.getX(), e.getY());
}
public void mouseDragged(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
repaint();
}
public void mouseReleased(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
repaint();
}
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.RED);
drawPerfectRect(g, x, y, x2, y2);
}
}
There are a few useful things to remember writing Swing graphics programs:
paintComponent repaints the entire component every time it is called, so you need to draw everything that you want to appear. The operations you do with the Graphics object will only persist until the next call to paintComponent.
Graphics2D is more capable than Graphics. It draws nicely antialiased shapes with floating-point co-ordinates, various line styles and so on. The Graphics parameter to paintComponent is in fact always a Graphics2D instance and you can cast it to one without worrying.
The inheritance hierarchy of components is also a painting hierarchy, so you need to call super.paintComponent(g) at the start of your paintComponent method. See this question for more details.
So I've made some changes to you program:
Added a field, List<Rectangle2D> rectangles to remember the rectangles the user has created. A rectangle is added to this list each time the mouse button is raised.
Added a call to super.paintComponent
Used Graphics2D to draw the rectangles, with a more interesting line style (Stroke)
Changed your paintComponent to draw each of the rectangles in the list, plus the 'rubber-band' rectangle the user is currently drawing.
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.List;
public class DrawRect extends JPanel {
int x, y, x2, y2;
// this is the list of all the rectangles the user has drawn so far
List<Rectangle2D> rectangles = new ArrayList<>();
public static void main(String[] args) {
JFrame f = new JFrame("Draw Box Mouse 2");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(new DrawRect());
f.setSize(300, 300);
f.setVisible(true);
}
DrawRect() {
x = y = x2 = y2 = 0; //
MyMouseListener listener = new MyMouseListener();
addMouseListener(listener);
addMouseMotionListener(listener);
}
public void setStartPoint(int x, int y) {
this.x = x;
this.y = y;
}
public void setEndPoint(int x, int y) {
x2 = (x);
y2 = (y);
}
// this creates a new rectangle object instead of drawing one
public Rectangle2D makePerfectRect(int x, int y, int x2, int y2) {
int px = Math.min(x,x2);
int py = Math.min(y,y2);
int pw=Math.abs(x-x2);
int ph=Math.abs(y-y2);
return new Rectangle2D.Float(px, py, pw, ph);
}
class MyMouseListener extends MouseAdapter {
public void mousePressed(MouseEvent e) {
setStartPoint(e.getX(), e.getY());
}
public void mouseDragged(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
repaint();
}
public void mouseReleased(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
// when the mouse is released, we add the current rectangle to our list
rectangles.add(makePerfectRect(x,y,x2,y2));
repaint();
}
}
public void paintComponent(Graphics g) {
// use Graphics2D, you can draw much nicer lines
Graphics2D g2d = (Graphics2D) g;
super.paintComponent(g);
g.setColor(Color.RED);
// draw the rectangle the user is currently drawing
g2d.draw(makePerfectRect(x,y,x2,y2));
g.setColor(Color.BLUE);
Stroke oldStroke = g2d.getStroke();
g2d.setStroke(new BasicStroke(4.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND, 0.0f));
for (Rectangle2D r : rectangles) {
g2d.draw(r);
}
g2d.setStroke(oldStroke); // restore the original Stroke
}
}
I want to draw a rectangle after pressing a button. When I press for the first time the button it draws a rectangle. I'm trying to draw more rectangles adjacent to the first one after pressing the button again, but nothing is drawn. Can anybody help me?
This is the code that I use. Thank you very much
class Coord{
int x = 0;
int y = 0;
}
public class DrawRectangle extends JPanel {
int x, y, width, height;
public DrawRectangle (int x, int y, int width, int height){
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}
public Dimension getPreferredSize()
{
return new Dimension(this.width, this.height);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.RED);
g2.fillRect(this.x, this.y, this.width, this.height);
}
public static void main(String[] args)
{
final Coord coord = new Coord();
final JPanel center = new JPanel();
center.setLayout(null);
center.setLocation(10, 10);
center.setSize(300, 300);
JButton button = new JButton("Button");
button.setBounds(350,200,75,50);
button.addActionListener( new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
DrawRectangle component = new DrawRectangle(coord.x, coord.y, 30, 30);
component.setLocation(coord.x, coord.y);
component.setSize(component.getPreferredSize());
center.add(component);
center.repaint();
coord.x += 30;
coord.y +=30;
}
});
JFrame frame = new JFrame();
frame.setLayout(null);
frame.add(center);
frame.add(button);
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
Your paintComponent() only ever draws a single rectangle. It clears the background of the panel and then draws the rectangle.
If you want multiple rectangles then you need to either:
Keep a List of Rectangle to draw and then iterate through the List each time and draw the rectangle
Draw each rectangle onto a BufferedImage and then just paint the BufferedImage.
Check out Custom Painting Approaches for working examples of both of these approaches. Try both to see which you prefer better.
I am working on a lab to practice inheritance, in which we are to create a horizontal ellipse as "Shape1" and then create a "Shape2" which extends Shape1 which draws it's superclass Shape1, and then draws a vertical ellipse over top to create a new looking shape. The shape is displaying fine in terms of inheritance and looks (color/location etc) however when running the program, the frame width is set to 1000, and the height is set to 700, but If I drag the frame by the corner to enlarge it, the shape is drawn over and over again as I keep dragging the frame larger. Ideally the shape should just stay where it is relative to the frame size. I think this is happening because while I drag the frame larger, the draw method is being called over and over again by the system, but I am not sure where this is happening or how to fix it. Any suggestions?
All classes are displayed below:
Shape1:
public class Shape1 {
private double x, y, r;
protected Color col;
private Random randGen = new Random();
public Shape1(double x, double y, double r) {
this.x = x;
this.y = y;
this.r = r;
this.col = new Color(randGen.nextFloat(), randGen.nextFloat(), randGen.nextFloat());
}
public double getX() {
return this.x;
}
public double getY() {
return this.y;
}
public double getR() {
return this.r;
}
public void draw(Graphics2D g2){
//Create a horizontal ellipse
Ellipse2D horizontalEllipse = new Ellipse2D.Double(x - 2*r, y - r, 4 * r, 2 * r);
g2.setPaint(col);
g2.fill(horizontalEllipse);
}
}
Shape2:
public class Shape2 extends Shape1 {
public Shape2(double x, double y, double r) {
super(x, y, r);
}
public void draw(Graphics2D g2) {
//Create a horizontal ellipse
Ellipse2D verticalEllipse = new Ellipse2D.Double(super.getX() - super.getR(),
super.getY() - 2*super.getR(),
2 * super.getR(), 4 * super.getR());
super.draw(g2);
g2.fill(verticalEllipse);
}
}
ShapeComponent:
public class ShapeComponent extends JComponent {
//Instance variables here
private Random coordGen = new Random();
private final int FRAME_WIDTH = 1000;
private final int FRAME_HEIGHT = 700;
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
Shape2 myShape = new Shape2(1 + coordGen.nextInt(FRAME_WIDTH), 1 + coordGen.nextInt(FRAME_HEIGHT), 20);
//Draw shape here
myShape.draw(g2);
}
}
ShapeViewer(Where the JFrame is created):
public class ShapeViewer {
public static void main(String[] args) {
final int FRAME_WIDTH = 1000;
final int FRAME_HEIGHT = 700;
//A new frame
JFrame frame = new JFrame();
frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
frame.setTitle("Lab 5");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ShapeComponent component = new ShapeComponent();
frame.add(component);
//We can see it!
frame.setVisible(true);
}
}
because while I drag the frame larger, the draw method is being called over and over again by the system,
Correct, all components are repainted when the frame is resized.
Any suggestions?
Painting code should be based on properties of your class. If you want the painting to be a fixed size then you define the properties that control the painting and set these properties outside the painting method.
For example, you would never invoke Random.nextInt(...) in the painting method. This means the value will change every time the component is repainted.
So the Shape should be created in the constructor of your class and its size would be defined there, not each time you paint it.
I am trying to learn the paint method and get a ball to move across the frame. here is my code so far. w=.
I currently have two classes One is the main and one for the ball.
this is the main class
import java.awt.;
import javax.swing.;
public class PaintTest extends JPanel {
int x = 0;
int y = 0;
public void moveBall(){
x = x + 1;
y = y + 1;
}
public static void main(String[] args){
JFrame frame = new JFrame();
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
Ball ball = new Ball(x,y);
while(true){
ball.moveBall();
repaint();
}
}
protected void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g.setColor(Color.magenta);
g.drawLine(0,100,500,100);
g.drawLine(0,101,500,101);
g.drawLine(0,102,500,102);
g.drawLine(0,103,500,103);
g2.fillOval(x,y,35,35);
}
}
and here is the ball class
public class Ball {
int x,y;
public Ball(int x, int y){
this.x = x;
this.y = y;
}
}
now when i compile I get an error saying cannot find symbol ball in class PaintTest even though I am calling it from the class Ball. I am aware of the repaint error as i do not know what to put in front of it.
Draw in a JPanel
In its paintComponent method not in its paint method -- this gives you double buffering.
Call the super's paintComponent method in your override. This allows the JPanel to do housekeeping drawing including erasing the oval image at its old position.
Don't use a while (true) loop as this can cause serious Swing threading issues. Use a Swing Timer instead.
In the Swing Timer, increment your animation variables and then call repaint(). This will tell Swing to repaint the component which will re-draw the oval in the new location.
Don't guess at this stuff as that leads to frustration since Swing graphics coding is a different beast. Instead check the tutorials. You can find links to the Swing tutorials and to other Swing resources here: Swing Info. Also check out Performing Custom Painting with Swing.
Graphics2D goodies: RenderingHints can be used to smooth out your image jaggies.
More Graphics2D goodies: Stroke can be used to draw thicker lines when needed.
For example:
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
#SuppressWarnings("serial")
public class PaintTest extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = PREF_W;
private static final int TIMER_DELAY = 20;
private static final Stroke STROKE = new BasicStroke(5f);
private int x;
private int y;
public PaintTest() {
new Timer(TIMER_DELAY, new TimerListener()).start();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
// to smooth graphics
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.magenta);
Stroke initialStroke = g2.getStroke();
g2.setStroke(STROKE);
g.drawLine(0, 100, 500, 100);
g2.setStroke(initialStroke);
g2.fillOval(x, y, 35, 35);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
x++;
y++;
repaint();
}
}
private static void createAndShowGui() {
PaintTest mainPanel = new PaintTest();
JFrame frame = new JFrame("PaintTest");
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();
}
});
}
}
You have to put the paintComponent method in a JPanel. You can do it by using something like this.
JPanel panel = new JPanel(){
#Overide
public void paintComponent(Graphics g){
super.paint();
// Draw Stuff Here
}
};
The reason you are not getting the ball to move across the frame is that you are not calling the repaint method. You should do so on a thread.
Thread th = new Thread(new Runnable(){
#Overide
public void run(){
while(frame.isVisible()){
ball.moveBall();
panel.repaint();
try{Thread.sleep(5);}catch(Exception e){e.printStackTrace();}
}
}
});
Also, why are you making ball a instance of the PaintTest class? To get only one frame and ball you would want to add a class named Ball and use that to make an instance:
public class Ball{
int x, y;
public Ball(int x, int y){
this.x = x;
this.y = y;
}
}
That is why you were getting 2 frames.
Then you would want to get rid of the x and y variables in the main class. To make an instance using this class you would do:
Ball ball = new Ball(x, y);
Then to paint the ball in the paintComponent method you would do:
g.fillOval(ball.x, ball.y, 35, 35);
You didn't call the repaint(); method.
You don't need the y + 1 part.
Instead of using the while(true) loop, you should use a for loop.
You didn't call the super.paint() method.
You didn't use any Thread.sleep(), which made the ball move across instantaneously.
Here is the code:
import java.awt.*;
import javax.swing.*;
public class PaintTest extends JFrame {
int x = 8;
int y = 30;
public void moveBall(){
x = x + 1;
//y = y + 1;
try{
Thread.sleep(500);
} catch(InterruptedException e){
}
repaint();
}
public static void main(String[] args){
PaintTest frame1 = new PaintTest();
PaintTest ball = new PaintTest();
for(int i = 0; i<100; i++){
//while(true){
ball.moveBall();
}
}
public PaintTest() {
super("Paint Test");
setSize(500,500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
public void paint(Graphics g){
Graphics2D g2 = (Graphics2D) g;
super.paint(g);
super.paint(g2);
g.setColor(Color.magenta);
g.drawLine(0,100,500,100);
g.drawLine(0,101,500,101);
g.drawLine(0,102,500,102);
g.drawLine(0,103,500,103);
g.fillOval(x,y,35,35);
}
}
This code will make the ball move across the screen VERY slowly. If you want to speed it up, change the number of miliseconds in the Thread.sleep(miliseconds) part to a smaller number of miliseconds.
I have this simple application in which a command like RECT 10 20 100 150 draws a rectangle with specified arguments on a DrawPanel(extends JPanel).
Also, after drawing the primitive, it adds it to List<String> cmdList;, so that in
paintComponent(Graphics g) of DrawPanel I iterate through the list, process each command, and draw each of them.
The problem I am facing is that after drawing few shapes, and resizing (or maximizing) the panel becomes empty. And on resizing again several times, all the shpaes get drawn correctly.
This is the screenshot after drawing few primitives.
After stretching window slightly to left, the primitives are gone.
The code for DrawPanel
public class DrawPanel extends JPanel {
private List<String> cmdList;
public final Map<String,Shape> shapes;
public DrawPanel()
{
shapes = new HashMap<String,Shape>();
shapes.put("CIRC", new Circ());
shapes.put("circ", new Circ());
shapes.put("RECT", new Rect());
shapes.put("rect", new Rect());
shapes.put("LINE", new Line());
//... and so on
cmdList = new ArrayList<String>();
}
public void addCmd(String s)
{
cmdList.add(s);
}
public void removeCmd()
{
cmdList.remove(cmdList.size());
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
setBackground(Color.BLACK);
for (int i = 0; i < cmdList.size(); ++i){
StringTokenizer cmdToken = new StringTokenizer(cmdList.get(i));
String cmdShape = cmdToken.nextToken();
int []args = new int[cmdToken.countTokens()];
for(int i1 = 0; cmdToken.hasMoreTokens(); i1++){
args[i1] = Integer.valueOf(cmdToken.nextToken());
}
shapes.get(cmdShape).draw(this, args);
}
}
public void getAndDraw(String cmdShape, int[] args)
{
shapes.get(cmdShape).draw(this, args);
}
public void rect(int x1, int y1, int width, int height)
{
Graphics g = getGraphics();
g.setColor(Color.BLUE);
g.drawRect(x1, y1, width, height);
}
public void circ(int cx, int cy, int radius)
{
Graphics g = getGraphics();
g.setColor(Color.CYAN);
g.drawOval(cx - radius, cy - radius, radius*2, radius*2);
}
}
The partial code for Shape (Interface)
public interface Shape {
void draw(DrawPanel dp, int[] data);
}
class Rect implements Shape {
public void draw(DrawPanel dp, int[] data) {
dp.rect(data[0], data[1], data[2], data[3]);
}
}
Lines used in MainFrame (extends JFrame) to draw after each command is entered.
drawPanel.getAndDraw(cmdShape, args);
drawPanel.addCmd(cmd);
Why is Drawing panel, sometimes painting and other time not, on window resize?
How can I get stable output?
Note : If I have missed anything, please ask.
It's because your using getGraphics() when you should be using the Graphics object passed as an argument to paintComponent.
Oh, and btw, setBackground(Color.BLACK) should be in the constructor, not in the paintComponent method.