Question

using Java Your mission in this exercise is to implement a very simple Java painting application.

Rapid Prototyping The JFrame is an example that can support the following functions:

1. Draw curves, specified by a mouse drag.

2. Draw filled rectangles or ovals, specified by a mouse drag (don't worry about dynamically drawing the shape during the drag - just draw the final shape indicated).

3. Shape selection (line, rectangle or oval) selected by a combo box OR menu.

4. Color selection using radio buttons OR menu.

5. Line thickness using a combo box OR menu.

6. A CLEAR button.

some tips are:-

>> Put import java.awt.*; and import java.awt.event.*; at the top of your java source.

>> To find the mouse coordinates of a mouse event (e.g., a click), use the int getX() and int getY() methods on the MouseEvent object.

>> Remember that getGraphics() returns a Graphics object that represents one set of drawing parameter settings for the JFrame (there is no global Graphics object!).

>> Heres a code snippet to draw a blue dot at X=10, Y=100 on the JFrame:

Graphics G=getGraphics();

G.setColor(Color.BLUE);

G.drawRect(10,100,1,1);

>> Here's the mouse dragged handler we wrote in class for a (lame) painting function on the JFrame:

private void myMouseDragged(java.awt.event.MouseEvent evt) {

int x=evt.getX();

int y=evt.getY();

java.awt.Graphics G=getGraphics();

G.drawRect(x, y, 1, 1); }

>> And another snippet to find out which item was selected from a combo box:

public void actionPerformed(ActionEvent e) {

JComboBox cb=(JComboBox)e.getSource();

String itemName=(String)cb.getSelectedItem(); }

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class paintGUI extends JComponent {

// Image in which we're going to draw
        private Image image;
// Graphics2D object ==> used to draw on
        private Graphics2D g2;
// Mouse coordinates
        private int currentX, currentY, oldX, oldY;

        public paintGUI() {
                setDoubleBuffered(false);
                addMouseListener(new MouseAdapter() {
                        public void mousePressed(MouseEvent e) {
                                // save coord x,y when mouse is pressed
                                oldX = e.getX();
                                oldY = e.getY();
                                System.out.println("Mouse pressed");
                        }
                });

                addMouseMotionListener(new MouseMotionAdapter() {
                        public void mouseDragged(MouseEvent e) {
                                System.out.println("Mouse dragged");
                                
                                // coord x,y when drag mouse
                                currentX = e.getX();
                                currentY = e.getY();
                        }
                });
        }

        protected void paintComponent(Graphics g) {
                if (image == null) {
                        // image to draw null ==> we create
                        image = createImage(getSize().width, getSize().height);
                        g2 = (Graphics2D) image.getGraphics();

                        // clear draw area
                        clear();
                }

                g.drawImage(image, 0, 0, null);
                repaint();
        }

        // now we create exposed methods
        public void clear() {
                g2.clearRect(0, 0, getSize().width, getSize().height);
                repaint();
        }

        public void thin() {
                g2.setStroke(new BasicStroke(3));
        }

        public void thick() {
                g2.setStroke(new BasicStroke(10));
        }

        public void red() {
                // apply red color on g2 context
                g2.setPaint(Color.red);
        }

        public void black() {
                g2.setPaint(Color.black);
        }

        public void magenta() {
                g2.setPaint(Color.magenta);
        }

        public void drawLine() {
                System.out.println("Drawing line");
                g2.drawLine(oldX, oldY, currentX, currentY);
                repaint();
        }

        public void drawRectangle() {
                System.out.println("Drawing rectangle");
                g2.drawRect(oldX, oldY, Math.abs(currentX - oldX), Math.abs(currentY - oldY));
                g2.fillRect(oldX, oldY, Math.abs(currentX - oldX), Math.abs(currentY - oldY));
                repaint();
        }

}

public class GUIPaint {

        JButton clearBtn, blackBtn, redBtn, magentaBtn, filledRectangleBtn, lineBtn, thinBtn, thickBtn;
        paintGUI paintGUI;
        ActionListener actionListener = new ActionListener() {

                public void actionPerformed(ActionEvent e) {
                        if (e.getSource() == clearBtn) {
                                paintGUI.clear();
                        } else if (e.getSource() == thinBtn) {
                                paintGUI.thin();
                        } else if (e.getSource() == thickBtn) {
                                paintGUI.thick();
                        } else if (e.getSource() == blackBtn) {
                                paintGUI.black();
                        } else if (e.getSource() == redBtn) {
                                paintGUI.red();
                        } else if (e.getSource() == magentaBtn) {
                                paintGUI.magenta();
                        } else if (e.getSource() == filledRectangleBtn) {
                                paintGUI.drawRectangle();
                        } else if (e.getSource() == lineBtn) {
                                paintGUI.drawLine();
                        }
                }
        };

        public static void main(String[] args) {
                new GUIPaint().show();
        }

        public void show() {
                // create main frame
                JFrame frame = new JFrame("Swing Paint");
                Container content = frame.getContentPane();
                // set layout on content pane
                content.setLayout(new BorderLayout());
                // create draw area
                paintGUI = new paintGUI();

                // add to content pane
                content.add(paintGUI, BorderLayout.CENTER);

                // create controls to apply colors and call clear feature
                JPanel controls = new JPanel();

                clearBtn = new JButton("Clear");
                clearBtn.addActionListener(actionListener);
                blackBtn = new JButton("Black");
                blackBtn.addActionListener(actionListener);
                redBtn = new JButton("Red");
                redBtn.addActionListener(actionListener);
                magentaBtn = new JButton("Magenta");
                magentaBtn.addActionListener(actionListener);

                lineBtn = new JButton("Line");
                lineBtn.addActionListener(actionListener);
                filledRectangleBtn = new JButton("Filled Rectangle");
                filledRectangleBtn.addActionListener(actionListener);

                thickBtn = new JButton("Thick Line");
                thickBtn.addActionListener(actionListener);
                thinBtn = new JButton("Thin Line");
                thinBtn.addActionListener(actionListener);

                controls.add(lineBtn);
                controls.add(filledRectangleBtn);
                controls.add(thinBtn);
                controls.add(thickBtn);
                controls.add(blackBtn);
                controls.add(redBtn);
                controls.add(magentaBtn);
                controls.add(clearBtn);

                // add to content pane
                content.add(controls, BorderLayout.NORTH);

                frame.setSize(800, 800);
                // can close frame
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                // show the swing paint result
                frame.setVisible(true);

        }

}

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