Drawing Shapes with Mouse Events

 

1. Set up the main frame and panel:

   • Create a JFrame for the main window.
   • Add a custom JPanel to handle drawing.

2. Handle mouse events:

   • Implement MouseListener and MouseMotionListener to track the starting and ending points for drawing.

3. Implement drawing logic:

   • Allow the user to choose between drawing lines, rectangles, and ovals.
   • Draw shapes based on user interactions.

Here's a complete Java program to accomplish this:

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.util.ArrayList;

public class DrawingApp extends JFrame {

    private DrawArea drawArea;

    private String currentShape = "Line";

    public DrawingApp() {

        drawArea = new DrawArea();

        add(drawArea, BorderLayout.CENTER);

        JPanel controls = new JPanel();

        String[] shapes = {"Line", "Rectangle", "Oval"};

        JComboBox<String> shapeSelector = new JComboBox<>(shapes);

        shapeSelector.addActionListener(e -> currentShape = (String) shapeSelector.getSelectedItem());

        controls.add(new JLabel("Shape:"));

        controls.add(shapeSelector);

        add(controls, BorderLayout.NORTH);

        setSize(800, 600);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setTitle("Drawing App");

        setVisible(true);

    }

    private class DrawArea extends JPanel implements MouseListener, MouseMotionListener {

        private ArrayList<Shape> shapes = new ArrayList<>();

        private Point start, end;

        public DrawArea() {

            setBackground(Color.WHITE);

            addMouseListener(this);

            addMouseMotionListener(this);

        }

        @Override

        protected void paintComponent(Graphics g) {

            super.paintComponent(g);

            for (Shape shape : shapes) {

                shape.draw(g);

            }

        }

        @Override

        public void mousePressed(MouseEvent e) {

            start = e.getPoint();

        }

        @Override

        public void mouseReleased(MouseEvent e) {

            end = e.getPoint();

            Shape shape = null;

            switch (currentShape) {

                case "Line":

                    shape = new Line(start, end);

                    break;

                case "Rectangle":

                    shape = new Rect(start, end);

                    break;

                case "Oval":

                    shape = new Oval(start, end);

                    break;

            }

            if (shape != null) {

                shapes.add(shape);

            }

            repaint();

        }

        @Override

        public void mouseDragged(MouseEvent e) {

            end = e.getPoint();

            repaint();

        }

        @Override

        public void mouseMoved(MouseEvent e) {}

        @Override

        public void mouseClicked(MouseEvent e) {}

        @Override

        public void mouseEntered(MouseEvent e) {}

        @Override

        public void mouseExited(MouseEvent e) {}

    }

    abstract class Shape {

        Point start, end;

        Shape(Point start, Point end) {

            this.start = start;

            this.end = end;

        }

        abstract void draw(Graphics g);

    }

    class Line extends Shape {

        Line(Point start, Point end) {

            super(start, end);

        }

        @Override

        void draw(Graphics g) {

            g.drawLine(start.x, start.y, end.x, end.y);

        }

    }

    class Rect extends Shape {

        Rect(Point start, Point end) {

            super(start, end);

        }

        @Override

        void draw(Graphics g) {

            int x = Math.min(start.x, end.x);

            int y = Math.min(start.y, end.y);

            int width = Math.abs(start.x - end.x);

            int height = Math.abs(start.y - end.y);

            g.drawRect(x, y, width, height);

        }

    }

    class Oval extends Shape {

        Oval(Point start, Point end) {

            super(start, end);

        }

        @Override

        void draw(Graphics g) {

            int x = Math.min(start.x, end.x);

            int y = Math.min(start.y, end.y);

            int width = Math.abs(start.x - end.x);

            int height = Math.abs(start.y - end.y);

            g.drawOval(x, y, width, height);

        }

    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(DrawingApp::new);

    }

}

Explanation:

1. Main Frame (DrawingApp):

   • Contains the DrawArea panel for drawing and a control panel with a shape selector.
   • Uses JComboBox to allow the user to choose the shape type.

2. DrawArea (DrawArea extends JPanel):

   • Manages the drawing logic.
   • Implements MouseListener and MouseMotionListener to handle mouse events.
   • Maintains a list of shapes (ArrayList<Shape>) and redraws them in paintComponent.

3. Shape Classes:

   • Abstract Shape class and its subclasses (Line, Rect, Oval) handle the drawing of different shapes.