Question

  

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
//Class that paints according to the user wish.
public class RapidPrototyping extends JFrame implements MouseListener,ItemListener,ActionListener,MouseMotionListener {
  
   //panel to hold color,shapes and thickness components
   JPanel panel;
   //shapes combobox
   JComboBox shapes;
   //color radio buttons
   JRadioButton red, green, blue;
   //thickness combobox
   JComboBox thicknesses;
   //clear button.
   JButton clear;
   JPanel center;
  
   /*values of each selection*/
   Color color;
   int thickness;
   String shape;

   //start and end positions of mouse start and end positions of drag.
   int startX, startY;
   int endX, endY;
   boolean startSet;

   final String shapesList[] = { "RECTANGLE", "OVAL", "LINE" };

   final String thicknessesList[] = { "3", "6", "9", "12", "15" };

   RapidPrototyping() {
       //initialize values.
       setSize(600, 400);
       setLayout(new BorderLayout());

       panel = new JPanel(new FlowLayout());

       JLabel shapeLabel = new JLabel("Shape :");
       shapes = new JComboBox(shapesList);

       JLabel colorLabel = new JLabel("Color :");
       red = new JRadioButton("Red");
       green = new JRadioButton("Green");
       blue = new JRadioButton("Blue");
       ButtonGroup g = new ButtonGroup();
       g.add(red);
       g.add(blue);
       g.add(green);

       JLabel thicknessLabel = new JLabel("thickness :");
       thicknesses = new JComboBox(thicknessesList);

       clear = new JButton("Clear");
      
       center = new JPanel();
      
       //add elements to panel
       panel.add(shapeLabel);
       panel.add(shapes);
  
  
  
       panel.add(colorLabel);
       panel.add(red);
       panel.add(green);
       panel.add(blue);

       panel.add(thicknessLabel);
       panel.add(thicknesses);

       panel.add(clear);
       add(panel, BorderLayout.NORTH);
       add(center,BorderLayout.CENTER);
      
       /*Listeners*/
       addMouseListener(this);
       //adding mouse motionlistener is good but there is a drawback in that.
       //code will draw a shape without dragging.
       //it takes the previous point location and the curred dragged position.
       red.addItemListener(this);
       blue.addItemListener(this);
       green.addItemListener(this);
      
       shapes.addActionListener(this);
      
       clear.addActionListener(this);
      
       thicknesses.addActionListener(this);

       /* Default Values Setting */
       color = Color.RED;
       red.setSelected(true);
      
       thickness = 3;
       shape = "RECTANGLE";
       startSet = false;
      
      
   }
   //action listener
   public void actionPerformed(ActionEvent ae)
   {
       //set shape value on shapes selection changed.
       if(ae.getSource() == shapes)
       {
           shape = ""+shapes.getItemAt(shapes.getSelectedIndex());
       }
       //repaint the frame if clear button clicked.
       else if(ae.getSource() == clear)
       {
           repaint();
       }
       //change the thickness value.
       else if(ae.getSource() == thicknesses)
       {
           try
           {
               thickness = Integer.parseInt(""+thicknesses.getItemAt(thicknesses.getSelectedIndex()));
           }
           catch(Exception e)
           {
               thickness = 3;
           }
       }
   }
   //set color value according to the selection in color selectin of radio buttons.
   public void itemStateChanged(ItemEvent ie)
   {
       if(ie.getSource() == red)
       {
           color = Color.RED;
       }
       else if(ie.getSource() == blue)
       {
           color = Color.BLUE;
       }
       else if(ie.getSource() == green)
       {
           color = Color.GREEN;
       }
   }
   //mouse pressed is the first step in clicking mouse.
   //when a button is presesd this will invoke
   public void mousePressed(MouseEvent e)
   {
       //if the start point is not set
       if(startSet == false)
       {
           //then set start point as current mouse location
           startX = e.getX();
           startY = e.getY();
           startSet = true;
          
       }
   }

   // this function is invoked when the mouse is released
   public void mouseReleased(MouseEvent e)
   {
       //when mouse click is released .set end point.
       if(startSet)
       {
           endX = e.getX();
           endY = e.getY();
           startSet = false;
           //call drawShape() to draw current shape.
           drawShape();
          
       }
   }
   //when mouse is dragged in right to left or bottom to up
   //we have to change the start and end points for drawing rectangel and oval
   //because they take start position and width,height(not end position like line).
   public void checkAndSwap()
   {
       //swap value of x and y
       if(startX > endX)
       {
           int temp = startX;
           startX = endX;
           endX = temp;
       }
       if(startY > endY)
       {
           int temp = startY;
           startY = endY;
           endY = temp;
       }
   }
   //method drawShape() that draws current selected properties of paint
   //and draws them .
   public void drawShape()
   {
      
       //Graphics2D will be more useful than Graphics class.
       Graphics2D g2 = (Graphics2D) getGraphics();
       g2.setStroke(new BasicStroke(thickness));
       g2.setColor(color);
       //cal width and height
       int width = Math.abs(endX-startX);
       int height = Math.abs(endY-startY);
       System.out.println("\nThickness: "+thickness);
      
       //if shape is rectangle draw shape
       if(shape.equals(("RECTANGLE")))
       {
           //check and swap call only for rectangle and oval
           checkAndSwap();
           System.out.printf("Drawing %s : at -> %d %d with width and height %d,%d end point: %d %d\n",shape,startX,startY,width,height,endX,endY);
           //fillRect with following fields.
           g2.fillRect(startX,startY,width,height);
          
       }
       else if(shape.equals("OVAL"))
       {
           checkAndSwap();
           System.out.printf("Drawing %s : at -> %d %d with width and height %d,%d end point: %d %d\n",shape,startX,startY,width,height,endX,endY);
           g2.fillOval(startX,startY,width,height);
       }
       else
       {
           System.out.printf("Drawing %s : at -> %d %d end point: %d %d\n",shape,startX,startY,width,height,endX,endY);
           g2.drawLine(startX, startY, endX, endY);
       }
              
   }
   // this function is invoked when the mouse exits the component
   public void mouseExited(MouseEvent e)
   {

   }

   // this function is invoked when the mouse enters the component
   public void mouseEntered(MouseEvent e)
   {

   }

   // this function is invoked when the mouse is pressed or released
   public void mouseClicked(MouseEvent e)
   {
      
         
   }
   //MouseMotionListener methods are not used.
   public void mouseDragged(MouseEvent e)
   {
   }
   public void mouseMoved(MouseEvent e)
   {
   }
   //create jframe object and set its properties.
   public static void main(String[] args) {
       RapidPrototyping frame = new RapidPrototyping();
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setVisible(true);
       frame.setResizable(false);
       frame.setTitle("Rapid Prototyping");
   }
}

NEED a two paragraph report on this GUI painting app.

Answer 1

The GUI Panel contains a set of options to draw the different shapes.. We can select the shape of drawing using the dropdown, While the color of the shape is choosen using the radio buttons..
GUI also contains a clear button, which is use to remove all the drawings on the canvas. We also can change the thickness of lines using a dropdown.
We keep the current color as the class attributes, which is updated everytime a different radio button is selected using the itemStateChanged method of ComboBox. Similarly, Using the MousePressed and MouseReleased method, we capture the start and end position of the mouse drag and on basis of that, the shape is drawn.