Develop Reference

Drawing Lines to JLabel Icon in Java Swing

Hi Everyone I want to draw lines to Jlabel Icon with DrawLines() class but the program isn't drawing .When I use to frame.add(m) the program is drawing lines to frame .....
DrawLine m = new DrawLine();
frame.add(m);
but when I use to label.add(m) method .The program isn't working .I need to figure out this problem Why can't I draw lines to jlabelIcon and How can I fix this ?
This is my DrawLine Class
package com.company;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.Line2D;
public class DrawLine extends JComponent {
public void paint(Graphics g) {
super.paintComponents(g);
g.drawLine(300, 152, 63, 185);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
}
g.drawLine(63, 185, 120, 198);
}
}
This is my main class
package com.company;
import com.sun.source.tree.Tree;
import jdk.swing.interop.SwingInterOpUtils;
import org.jetbrains.annotations.NotNull;
import javax.swing.*;
import java.awt.*;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;
import java.util.ArrayList;
import java.util.List;
import java.awt.geom.Line2D;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
public class Main extends JFrame {
public static void main(String[] args) {
JFrame frame = new JFrame("Display Image");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = (JPanel) frame.getContentPane();
frame.setSize(1000,560);
JLabel label = new JLabel();
label.setSize(1000,560);
label.setIcon(new ImageIcon("myimage path"));
DrawLine m = new DrawLine();
label.add(m);
panel.add(label);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}

If your goal is to draw lines and images together, then your best bet for the money is to get rid of ImageIcon and JLabel and instead is to draw them all within a single paintComponent. The images can be drawn as image sprite, and the lines as lines by calling Graphics#drawLine(...) or as Line2D objects as you have using Graphics2D#draw(...)
For example, say we had two BufferedImage objects, upImg and dnImg, and two Point objects that determined the location of these sprites, upPt and dnPt
public class Foo01 extends JPanel {
// .....
private Point upPt = new Point(300, 100);
private Point dnPt = new Point(700, 650);
private BufferedImage upImg, dnImg;
And say we wanted to draw a line that connected the two image sprites, then these could all be draw within the paintComponent method like so:
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g); // tell the JPanel to do its house-keeping painting
// make sure that neither image is null
if (upImg != null && dnImg != null) {
// draw both images at their respective locations
g.drawImage(upImg, upPt.x, upPt.y, this);
g.drawImage(dnImg, dnPt.x, dnPt.y, this);
// to get a smooth line, use rendering hiints
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// to give the line some thickness
g2.setStroke(new BasicStroke(5f));
// calculate the end-points of the line
int x1 = upPt.x + upImg.getWidth() / 2;
int y1 = upPt.y + upImg.getHeight() / 2;
int x2 = dnPt.x + dnImg.getWidth() / 2;
int y2 = dnPt.y + dnImg.getHeight() / 2;
// and then draw it
g.drawLine(x1, y1, x2, y2);
}
}
Here is an example program that does just this -- draws two images with a line connecting. I've also added a MouseAdapter to allow the user to move the first image, the green up-arrow, showing that the line will move as well, since it is calculated within the painting method:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.URL;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
public class Foo01 extends JPanel {
private static final String UP_IMG_PATH = "https://upload.wikimedia.org/wikipedia/commons/7/7d/Green_circle_icon.jpg";
private static final String DN_IMG_PATH = "https://upload.wikimedia.org/wikipedia/commons/b/bc/Red_circle_icon.jpg";
private static final int GUI_W = 1000;
private static final int GUI_H = 800;
private Point upPt = new Point(300, 100);
private Point dnPt = new Point(700, 650);
private BufferedImage upImg, dnImg;
public Foo01() {
MyMouse myMouse = new MyMouse();
addMouseListener(myMouse);
addMouseMotionListener(myMouse);
setBackground(Color.WHITE);
try {
URL url = new URL(UP_IMG_PATH);
upImg = ImageIO.read(url);
url = new URL(DN_IMG_PATH);
dnImg = ImageIO.read(url);
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(GUI_W, GUI_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (upImg != null && dnImg != null) {
g.drawImage(upImg, upPt.x, upPt.y, this);
g.drawImage(dnImg, dnPt.x, dnPt.y, this);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(5f));
int x1 = upPt.x + upImg.getWidth() / 2;
int y1 = upPt.y + upImg.getHeight() / 2;
int x2 = dnPt.x + dnImg.getWidth() / 2;
int y2 = dnPt.y + dnImg.getHeight() / 2;
g.drawLine(x1, y1, x2, y2);
}
}
private class MyMouse extends MouseAdapter {
private Point p1 = null;
#Override
public void mousePressed(MouseEvent e) {
if (e.getX() < upPt.x || e.getX() > upPt.x + upImg.getWidth()) {
return;
}
if (e.getY() < upPt.y || e.getY() > upPt.y + upImg.getHeight()) {
return;
}
p1 = new Point(e.getX(), e.getY());
}
#Override
public void mouseReleased(MouseEvent e) {
if (p1 != null) {
moveSprite(e);
p1 = null;
}
}
#Override
public void mouseDragged(MouseEvent e) {
if (p1 != null) {
moveSprite(e);
}
}
private void moveSprite(MouseEvent e) {
Point p2 = new Point(e.getX(), e.getY());
int x = upPt.x + p2.x - p1.x;
int y = upPt.y + p2.y - p1.y;
upPt = new Point(x, y);
p1 = p2;
repaint();
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(()-> {
Foo01 foo01 = new Foo01();
JFrame frame = new JFrame("Draw Sprites");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(foo01);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
});
}
}

If the need is to add custom painting to a JLabel you can override its paintComponent:
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.net.MalformedURLException;
import java.net.URL;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
public class Main extends JFrame {
private static final String BUG = "https://www.growtopiagame.com/forums/attachment.php?attachmentid=141847&d=1477126665";
public static void main(String[] args) throws MalformedURLException {
JFrame frame = new JFrame("Display Image");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DrawLine m = new DrawLine("A crossed bug", new ImageIcon(new URL(BUG)));
frame.add(m);
frame.pack();
frame.setVisible(true);
}
}
class DrawLine extends JLabel {
DrawLine(String text, Icon icon) {
super(text, icon, SwingConstants.CENTER);
setVerticalTextPosition(SwingConstants.BOTTOM);
setHorizontalTextPosition(SwingConstants.CENTER);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.YELLOW);
g2d.setStroke(new BasicStroke(10));
int w = getWidth(); int h = getHeight();
g2d.drawLine(0, 0, w, h); //draw right to left diagonal
g2d.drawLine(0, h, w, 0); //draw left to right diagonal
}
}
Swing is a single Thread library. All painting tasks are executed in the Event Dispatcher Thread (EDT).
Running long processes (such as sleep) on the EDT makes keeps this thread busy, so it does not do other things like updating the gui. The gui becomes unresponsive (freezes).
If you want to add a line after a certain delay, use swing Timer for the job:
public class Main extends JFrame {
private static final String BUG = "https://www.growtopiagame.com/forums/attachment.php?attachmentid=141847&d=1477126665";
public static void main(String[] args) throws MalformedURLException {
JFrame frame = new JFrame("Display Image");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DrawLine m = new DrawLine("A crossed bug", new ImageIcon(new URL(BUG)));
frame.add(m);
frame.pack();
frame.setVisible(true);
}
}
class DrawLine extends JLabel {
private static final int DELAY = 1500; //millies
private boolean isDrawSecondDialgonal = false;
DrawLine(String text, Icon icon) {
super(text, icon, SwingConstants.CENTER);
setVerticalTextPosition(SwingConstants.BOTTOM);
setHorizontalTextPosition(SwingConstants.CENTER);
//use timer to enable painting of a second diagonal
javax.swing.Timer timer = new javax.swing.Timer(DELAY, e-> {
isDrawSecondDialgonal = true;
repaint();
});
timer.setRepeats(false);
timer.start();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.YELLOW);
g2d.setStroke(new BasicStroke(10));
int w = getWidth(); int h = getHeight();
g2d.drawLine(0, 0, w, h); //draw right to left diagonal
if(isDrawSecondDialgonal) {
g2d.drawLine(0, h, w, 0);//draw left to right diagonal
}
}
}

Draw shapes on scrollable JPanel

I'm trying to draw rectangles on fairly large images in order to get the pixel coordinates of objects within the image. I am able to display the image and make it scrollable, or display the image and be able to draw rectangles on top of it....but not both.
It's obvious that I'm drawing the image on top of the canvas that I'm trying to draw the rectangles on, but I can't for the life of me figure out how to make it all coexist.
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
public class DrawRect extends JPanel {
int x, y, x2, y2;
private static final long serialVersionUID = 1L;
private BufferedImage image;
private JPanel canvas;
public static void main(String[] args) {
JPanel p = new DrawRect();
JFrame f = new JFrame();
f.setContentPane(p);
f.setSize(400, 300);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
DrawRect() {
x = y = x2 = y2 = 0; //
MyMouseListener listener = new MyMouseListener();
addMouseListener(listener);
addMouseMotionListener(listener);
try {
this.image = ImageIO.read(new URL("https://previews.123rf.com/images/victoroancea/victoroancea1201/victoroancea120100059/12055848-tv-color-test-pattern-test-card-for-pal-and-ntsc.jpg"));
}catch(IOException ex) {
Logger.getLogger(DrawRect.class.getName()).log(Level.SEVERE, null, ex);
}
this.canvas = new JPanel() {
private static final long serialVersionUID = 1L;
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(image, 0, 0, null);
}
};
canvas.setPreferredSize(new Dimension(image.getWidth(), image.getHeight()));
JScrollPane sp = new JScrollPane(canvas);
setLayout(new BorderLayout());
add(sp, BorderLayout.CENTER);
}
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 drawRect(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);
drawRect(g, x, y, x2, y2);
}
}

Your image-drawing JPanel must be the same JPanel that draws the rectangle and that has the MouseAdapter added to it. For instance:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Image;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
#SuppressWarnings("serial")
public class DrawRect2 extends JPanel {
public static final String IMG_PATH = "https://previews.123rf.com/images/victoroancea"
+ "/victoroancea1201/victoroancea120100059"
+ "/12055848-tv-color-test-pattern-test-card-for-pal-and-ntsc.jpg";
private static final int PREF_W = 600;
private static final int PREF_H = PREF_W;
private DrawingPanel drawingPanel;
public DrawRect2(Image img) {
drawingPanel = new DrawingPanel(img);
JScrollPane scrollPane = new JScrollPane(drawingPanel);
MyMouse myMouse = new MyMouse();
drawingPanel.addMouseListener(myMouse);
drawingPanel.addMouseMotionListener(myMouse);
setLayout(new BorderLayout());
add(scrollPane);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private static void createAndShowGui() {
Image img = null;
try {
URL url = new URL(IMG_PATH);
img = ImageIO.read(url);
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
DrawRect2 mainPanel = new DrawRect2(img);
JFrame frame = new JFrame("DrawRect2");
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());
}
}
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class DrawingPanel extends JPanel {
private Image img;
private Rectangle rectangle;
public DrawingPanel(Image img) {
this.img = img;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, this);
}
if (rectangle != null) {
Graphics2D g2 = (Graphics2D) g.create();
g2.setXORMode(Color.WHITE);
g2.draw(rectangle);
g2.dispose(); // since we created this object
}
}
#Override
public Dimension getPreferredSize() {
Dimension superSize = super.getPreferredSize();
if (img == null) {
return super.getPreferredSize();
} else {
int w = img.getWidth(this);
int h = img.getHeight(this);
return new Dimension(w, h);
}
}
public void setRectangle(Rectangle rectangle) {
this.rectangle = rectangle;
}
}
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
public class MyMouse extends MouseAdapter {
private Point p1;
#Override
public void mousePressed(MouseEvent e) {
p1 = e.getPoint();
}
#Override
public void mouseDragged(MouseEvent e) {
if (p1 != null) {
createRect(e);
}
}
private void createRect(MouseEvent e) {
Point p2 = e.getPoint();
int x = Math.min(p1.x, p2.x);
int y = Math.min(p1.y, p2.y);
int width = Math.abs(p1.x - p2.x);
int height = Math.abs(p1.y - p2.y);
Rectangle r = new Rectangle(x, y, width, height);
((DrawingPanel) e.getSource()).setRectangle(r);
((DrawingPanel) e.getSource()).repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
if (p1 != null) {
createRect(e);
}
p1 = null;
}
}
So in this paintComponent method, I draw both the image and the Rectangle, using Graphics2D XOR mode to help show the lines regardless of the background color:
#SuppressWarnings("serial")
public class DrawingPanel extends JPanel {
private Image img;
private Rectangle rectangle;
public DrawingPanel(Image img) {
this.img = img;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, this);
}
if (rectangle != null) {
Graphics2D g2 = (Graphics2D) g.create();
g2.setXORMode(Color.WHITE);
g2.draw(rectangle);
g2.dispose(); // since we created this object
}
}
I also have this method:
public void setRectangle(Rectangle rectangle) {
this.rectangle = rectangle;
}
To allow the MouseListener/Adapter to pass in the Rectangle into this JPanel.
Rectangle r = new Rectangle(x, y, width, height);
((DrawingPanel) e.getSource()).setRectangle(r);
((DrawingPanel) e.getSource()).repaint();

How to draw a continuous curve of repeated ovals on speedy mouse cursor dragging?

This code is for drawing on a JPanel. In the paintComponent(Graphics) I am trying to draw curves via repeated Graphics2D#fillOval(x, y, with, height).
The app is working OK, and when I drag the mouse cursor slowly; it draws a continuous curve as I need. But when I speed up dragging the mouse cursor, the result is separated dots and not a continuous curve.
So how to make it draw a continuous curve even if I speed up dragging?
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class Painter extends JPanel {
int x, y;
ArrayList<Point> points;
public Painter() {
setBackground(Color.white);
points = new ArrayList<>();
MouseHandler listener = new MouseHandler();
this.addMouseMotionListener(listener);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(600, 600);
}
private class MouseHandler extends MouseAdapter implements MouseMotionListener {
#Override
public void mouseDragged(MouseEvent e) {
Point point = new Point(e.getX(), e.getY());
points.add(point);
repaint();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
for (Point point : points) {
g2d.fillOval(point.x, point.y, 15, 15);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame();
f.setContentPane(new Painter());
f.pack();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
});
}
}

As mentioned in comment to your previous similar question:
Don't draw discrete ovals in your paintComponent method.
Instead connect the points hold in the List in the paintComponent by drawing lines between adjacent points.
If you need to make the line thicker, change the Stroke property of the Graphics2D object, using one that has a wider thickness.
Be careful with Strokes however since often you don't want the property change to propagate down the paint chain. This means that sometimes you will want to copy the Graphics object and set the Stroke on the new Graphics object and paint with that, then dispose of it.
The simplest way to create a Stroke is to use the BasicStroke class, e.g., new BasicStroke(6f) will get you a nice thick curve.
For example:
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class Painter2 extends JPanel {
private static final float STROKE_WIDTH = 15f;
private static final Stroke STROKE = new BasicStroke(STROKE_WIDTH, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
int x, y;
ArrayList<Point> points;
public Painter2() {
setBackground(Color.white);
points = new ArrayList<>();
MouseHandler listener = new MouseHandler();
this.addMouseMotionListener(listener);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(600, 600);
}
private class MouseHandler extends MouseAdapter implements MouseMotionListener {
#Override
public void mouseDragged(MouseEvent e) {
Point point = new Point(e.getX(), e.getY());
points.add(point);
repaint();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setStroke(STROKE);
for (int i = 1; i < points.size(); i++) {
int x1 = points.get(i - 1).x;
int y1 = points.get(i - 1).y;
int x2 = points.get(i).x;
int y2 = points.get(i).y;
g2d.drawLine(x1, y1, x2, y2);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame();
f.setContentPane(new Painter2());
f.pack();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
});
}
}
Or better still:
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
#SuppressWarnings("serial")
public class Painter2 extends JPanel {
private static final float STROKE_WIDTH = 15f;
private static final Stroke STROKE = new BasicStroke(STROKE_WIDTH, BasicStroke.CAP_ROUND,
BasicStroke.JOIN_ROUND);
private static final Color CURVES_COLOR = Color.BLUE;
private static final Color TEMP_CURVE_COLOR = Color.PINK;
private List<List<Point>> curvesList = new ArrayList<>();
private List<Point> tempCurve = null;
public Painter2() {
setBackground(Color.white);
MouseHandler listener = new MouseHandler();
addMouseListener(listener);
addMouseMotionListener(listener);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(600, 600);
}
private class MouseHandler extends MouseAdapter implements MouseMotionListener {
#Override
public void mousePressed(MouseEvent e) {
tempCurve = new ArrayList<>();
tempCurve.add(e.getPoint());
repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
tempCurve.add(e.getPoint());
repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
tempCurve.add(e.getPoint());
curvesList.add(tempCurve);
tempCurve = null;
repaint();
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setStroke(STROKE);
g2.setColor(CURVES_COLOR);
for (List<Point> curve : curvesList) {
drawCurve(g2, curve);
}
if (tempCurve != null) {
g2.setColor(TEMP_CURVE_COLOR);
drawCurve(g2, tempCurve);
}
g2.dispose();
}
private void drawCurve(Graphics2D g2, List<Point> ptList) {
for (int i = 1; i < ptList.size(); i++) {
int x1 = ptList.get(i - 1).x;
int y1 = ptList.get(i - 1).y;
int x2 = ptList.get(i).x;
int y2 = ptList.get(i).y;
g2.drawLine(x1, y1, x2, y2);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame();
f.setContentPane(new Painter2());
f.pack();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
});
}
}

Boolean not keeping value

I have an application where the user draws lines. There is a JButton btnClear which, when the user clicks, must clear the drawings, so that the user can draw anew. I use an ActionListener on btnClear to know when it is clicked. I set a boolean Clear so that the correct IF statement is executed in paintComponent(). However, the boolean Clear keeps a False value in paintComponent() although I set it to True just before repaint(). Why is it so?
Note: I tried setting the frame's background to red just for to test the boolean in paintComponent().
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Line2D;
import javax.swing.*;
public class Clipping extends JPanel implements MouseListener, ActionListener
{
static JFrame frame;
static JComboBox cboDraw;
static JButton btnClear;
static JButton btnClip;
double x1, y1, x2, y2;
boolean FirstPoint;
boolean Clear = false;
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable() {
public void run()
{
CreateFrame();
}
});
}
private static void CreateFrame()
{
frame = new JFrame("Clipping");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Clipping());
frame.setSize(500,500);
frame.setVisible(true);
}
public Clipping()
{
setLayout(new BorderLayout());
JToolBar toolbar = new JToolBar(JToolBar.VERTICAL);
PopulateToolBar(toolbar);
add(toolbar, BorderLayout.WEST);
addMouseListener(this);
cboDraw.addMouseListener(this);
btnClip.addActionListener(this);
btnClear.addActionListener(this);
}
private static void PopulateToolBar(JToolBar toolbar)
{
String[] cboList = {"Line", "Polygon"};
cboDraw = new JComboBox(cboList);
cboDraw.setMaximumSize(new Dimension(70,30));
btnClip = new JButton("Set clip area");
btnClear = new JButton("Clear");
toolbar.add(cboDraw);
toolbar.addSeparator();
toolbar.add(btnClip);
toolbar.addSeparator();
toolbar.add(btnClear);
cboDraw.setAlignmentX(Component.CENTER_ALIGNMENT);
btnClip.setAlignmentX(Component.CENTER_ALIGNMENT);
btnClear.setAlignmentX(Component.CENTER_ALIGNMENT);
toolbar.setMargin(new Insets(10,10,10,10));
toolbar.setFloatable(false);
toolbar.setBackground(Color.black);
}
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
if (cboDraw.getSelectedIndex() == 0) //draw line
{
g2.draw(new Line2D.Double(x1, y1, x2, y2));
}
else if (Clear == true)
{
frame.setBackground(Color.red); //ONLY FOR TESTING PURPOSE
}
}
public void mousePressed(MouseEvent e)
{
if (e.getSource() != cboDraw) //to prevent line coordinates from being saved when selecting from combobox
{
if (cboDraw.getSelectedIndex() == 0) //user wants to draw line
{
if (FirstPoint == false) //first coordinates
{
x1 = e.getX();
y1 = e.getY();
FirstPoint = true;
}
else //second coordinates
{
x2 = e.getX();
y2 = e.getY();
repaint();
FirstPoint = false;
}
}
}
}
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == btnClear)
{
Clear = true;
repaint();
Clear = false;
}
}
public void mouseClicked(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
}

You should just do setBackground(Color.red); to call it on your JPanel instead of the JFrame

I think your actionPerformed and mousePressed are both executed at the same time. In mousePressed your if condition inside mousePressed is satisfied also if btnClear() is the source. So repaint method is called anyway, and you see no changes.

You're not calling the super.paintComponent(g) method within your paintComponent method override. Call this first, else, clear won't work.
Note that in your current code, this will not work for you since you're painting incorrectly in that you're not specifying, iterating through and drawing all the lines that need to be drawn within your paintComponent method. The way to solve this is via one of two ways:
Either create a List<Line2D> such as an ArrayList<Line2D>, fill it in your MouseListener/MouseMotionListener code, and then iterate through this List in your paintComponent method, drawing each line. If you do this, then your clear button's action would be to simply clear the List via clear() and call repaint(). No need for a boolean.
Or you could draw your lines onto a BufferedImage, and then draw the BufferedImage in your paintComponent method via the g.drawImage(...) method. If you do this, always check that the image is not null before drawing. Then in your mouse listening code, you'd draw to this image. In your clear button action, you'd create a new BufferedImage, or clear the current BufferedImage.
Also get rid of setBackground(...) calls from within paintComponent as they really shouldn't be in there.
For example of use of an ArrayList of lines:
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.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
#SuppressWarnings("serial")
public class DrawPanelViaArrayList extends JPanel {
private static final int PREF_W = 500;
private static final int PREF_H = PREF_W;
private static final Color LINES_COLOR = Color.black;
private static final Color DRAW_LINE_COLOR = Color.pink;
private static final Stroke STROKE = new BasicStroke(3f);
private List<Line2D> lineList = new ArrayList<>();
private int x1 = 0;
private int y1 = 0;
private int x2 = 0;
private int y2 = 0;
public DrawPanelViaArrayList() {
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
add(new JButton(new ClearAction("Clear")));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
// for smooth graphics
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// first draw the temporary line to show the user
// where he's drawing
if (x1 != x2 && y1 != y2) {
g2.setColor(DRAW_LINE_COLOR);
g2.drawLine(x1, y1, x2, y2);
}
// then draw all the lines held in the linesList.
Stroke oldStroke = g2.getStroke();
g2.setColor(LINES_COLOR);
g2.setStroke(STROKE); // draw thicker lines
for (Line2D line2d : lineList) {
g2.draw(line2d);
}
g2.setStroke(oldStroke); // reset stroke
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class MyMouseAdapter extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
x1 = e.getPoint().x;
y1 = e.getPoint().y;
}
#Override
public void mouseReleased(MouseEvent e) {
x2 = e.getPoint().x;
y2 = e.getPoint().y;
Line2D line = new Line2D.Double(x1, y1, x2, y2);
// add line to ArrayList
lineList.add(line);
x1 = x2 = y1 = y2 = 0;
repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
x2 = e.getPoint().x;
y2 = e.getPoint().y;
// draw temporary line
repaint();
}
}
private class ClearAction extends AbstractAction {
public ClearAction(String name) {
super(name);
}
#Override
public void actionPerformed(ActionEvent e) {
lineList.clear();
repaint();
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Foo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new DrawPanelViaArrayList());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
And what the heck, a BufferedImage version
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.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import javax.swing.*;
#SuppressWarnings("serial")
public class DrawPanelViaBufferedImage extends JPanel {
private static final int PREF_W = 500;
private static final int PREF_H = PREF_W;
private static final Color LINES_COLOR = Color.black;
private static final Color DRAW_LINE_COLOR = Color.pink;
public static final Color CLEAR_COLOR = new Color(0, 0, 0, 0);
public static final Stroke STROKE = new BasicStroke(3f);
private int x1 = 0;
private int y1 = 0;
private int x2 = 0;
private int y2 = 0;
private BufferedImage img = new BufferedImage(PREF_W, PREF_W, BufferedImage.TYPE_INT_ARGB);
public DrawPanelViaBufferedImage() {
MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
addMouseListener(myMouseAdapter);
addMouseMotionListener(myMouseAdapter);
add(new JButton(new ClearAction("Clear")));
// if the GUI is to be re-sizeable, then consider adding a
// ComponentListener here, and resizing the BufferedImage in it
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
// for smooth graphics
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// first draw the temporary line to show the user
// where he's drawing
if (x1 != x2 && y1 != y2) {
g2.setColor(DRAW_LINE_COLOR);
g2.drawLine(x1, y1, x2, y2);
}
// then draw the BufferedImage if not null
if (img != null) {
g2.drawImage(img, 0, 0, null);
}
}
// size of our GUI
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class MyMouseAdapter extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
x1 = e.getPoint().x;
y1 = e.getPoint().y;
}
#Override
public void mouseReleased(MouseEvent e) {
x2 = e.getPoint().x;
y2 = e.getPoint().y;
Line2D line = new Line2D.Double(x1, y1, x2, y2);
// draw to the BufferedImage
Graphics2D g2 = img.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(STROKE);
g2.setColor(LINES_COLOR);
g2.draw(line);
g2.dispose();
x1 = x2 = y1 = y2 = 0;
repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
x2 = e.getPoint().x;
y2 = e.getPoint().y;
repaint();
}
}
private class ClearAction extends AbstractAction {
public ClearAction(String name) {
super(name);
}
#Override
public void actionPerformed(ActionEvent e) {
Graphics2D g2 = img.createGraphics();
g2.setBackground(CLEAR_COLOR);
g2.clearRect(0, 0, getWidth(), getHeight());
g2.dispose();
repaint();
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Foo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new DrawPanelViaBufferedImage());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

JLabel goes out of alignment (aka funky) when overlaying a rectangle on it

I have a GUI I am making for the popular software ImageMagick in Java SWING.
Now, I am implementing the Crop feature into it and was trying to implement a drawable box to denote the region to be cropped.
The issue is that although I have gotten the rectangle to draw on the JLabel, the JLabel itself starts to move around once I finish painting the graphics on it.
As an example, here is a screenshot of the app before and after the selection is made.
Here is the code for the MouseReleased() event listener
private void input_showerMouseReleased(java.awt.event.MouseEvent evt) {
end_x = evt.getX();
end_y = evt.getY();
paint(input_shower.getGraphics());
input_shower.revalidate();
}
Here is the code for the paint() method
public void paint(Graphics g) {
super.paintComponents(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.red);
g2.setStroke(new BasicStroke(5));
Rectangle2D.Double rectangle = new Rectangle2D.Double(start_x, start_y, (end_x - start_x), (end_y - start_y));
g2.draw(rectangle);
}
Are there any ideas as to why this is happening and any possible solutions?

This is dangerous code:
private void input_showerMouseReleased(java.awt.event.MouseEvent evt) {
end_x = evt.getX();
end_y = evt.getY();
paint(input_shower.getGraphics());
input_shower.revalidate();
}
since you're painting directly to a component with a Graphics object that was not given to you by the JVM. Just don't do this, and instead paint passively.
Instead use end_x and end_y in your listened to jcomponent's paintComponent method and draw with that.
e.g.,
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
#SuppressWarnings("serial")
public class PaintComponentCorrect extends JPanel {
public static final String BULL_FIGHT = "https://duke.kenai.com/misc/Bullfight.jpg";
private static final Color RECT_COLOR = new Color(150, 150, 255);
private int startX;
private int startY;
private int endX;
private int endY;
private BufferedImage img;
public PaintComponentCorrect() throws IOException {
URL url = new URL(BULL_FIGHT);
img = ImageIO.read(url);
MyMouseAdapt myMouseAdapt = new MyMouseAdapt();
addMouseListener(myMouseAdapt);
addMouseMotionListener(myMouseAdapt);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, null);
}
g.setColor(RECT_COLOR);
int x = Math.min(startX, endX);
int y = Math.min(startY, endY);
int width = Math.abs(startX - endX);
int height = Math.abs(startY - endY);
g.drawRect(x, y, width, height);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet() || img == null) {
return super.getPreferredSize();
}
return new Dimension(img.getWidth(), img.getHeight());
}
private class MyMouseAdapt extends MouseAdapter {
private BufferedImage subImg;
#Override
public void mousePressed(MouseEvent e) {
if (e.getButton() != MouseEvent.BUTTON1) {
return;
}
startX = e.getX();
startY = e.getY();
endX = startX;
endY = startY;
repaint();
}
#Override
public void mouseReleased(MouseEvent e) {
if (e.getButton() != MouseEvent.BUTTON1) {
return;
}
endX = e.getX();
endY = e.getY();
repaint();
int x = Math.min(startX, endX);
int y = Math.min(startY, endY);
int w = Math.abs(startX - endX);
int h = Math.abs(startY - endY);
subImg = img.getSubimage(x, y, w, h);
ImageIcon icon = new ImageIcon(subImg);
JOptionPane.showMessageDialog(PaintComponentCorrect.this, icon);
}
#Override
public void mouseDragged(MouseEvent e) {
endX = e.getX();
endY = e.getY();
repaint();
}
}
private static void createAndShowGui() {
PaintComponentCorrect mainPanel = null;
try {
mainPanel = new PaintComponentCorrect();
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
JFrame frame = new JFrame("PaintComponent Correct");
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();
}
});
}
}

public void paint(Graphics g) {
super.paintComponents(g);
Custom painting is done by overriding the paintComponent() method.
You then invoke super.paintComponent(), not "paintComponents" with an "s"
For example check out Custom Painting Approaches. The code isn't designed to do what you want, but it does show how to draw a Rectangle on a component using the above suggestion.