GUI application in Java using eclipse

Question

So this was the example given in the notes for my current project. Usually I run the the example code and play around with it to see how everything works. However i'm not sure how to properly call the functions in the example code.

This what was given to me:

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.*; 
import java.awt.event.*;
import javax.swing.*;

public class Draw extends JPanel implements ActionListener
{
    JTextField tfInfo;
    JLabel lblColor, lblShapes;
    JCheckBox cbRed, cbBlue;
    ButtonGroup shapes;
    JRadioButton rbCircle, rbSquare;
    JButton btnSubmit; 
    public Draw() 
    {
        setLayout(new FlowLayout(FlowLayout.CENTER,5,5));
        tfInfo = new JTextField("Color & Shapes", 15);
        lblColor = new JLabel("Colors:");
        cbRed = new JCheckBox("Red");
        cbBlue = new JCheckBox("Blue");
        lblShapes = new JLabel("Shapes:");
        shapes = new ButtonGroup();
        rbCircle = new JRadioButton("Circle");
        rbSquare = new JRadioButton("Square");
        btnSubmit = new JButton("Submit"); 
        btnSubmit.addActionListener(this);
        add(tfInfo);
        add(lblColor);
        add(cbRed); 
        add(cbBlue); 
        add(lblShapes);
        add(rbCircle);
        add(rbSquare);
        add(btnSubmit);
        shapes.add(rbCircle);
        shapes.add(rbSquare); 
    }
    public static void main(String [] args)
    {
        Draw n = new Draw();
        n.setVisible(true);
    }
    public void actionPerformed(ActionEvent a)
    {
        if(a.getSource() == btnSubmit)
        { 
            if(cbRed.isSelected()&&cbBlue.isSelected())
            {
                if(rbCircle.isSelected())
                {
                    tfInfo.setText("urple Circle"); 
                }
                else if(rbSquare.isSelected())
                {
                    tfInfo.setText("Purple Square");
                } 
            }
            else if(cbRed.isSelected())
            {   
                if(rbCircle.isSelected())
                { 
                    tfInfo.setText("Red Circle");
                }
                else if(rbSquare.isSelected())
                {
                    tfInfo.setText("Red Square");
                }    
            }
            else if(cbBlue.isSelected())
            {  
                if(rbCircle.isSelected())
                {
                    tfInfo.setText("Blue Circle"); 
                } 
            }
            else if(rbSquare.isSelected())
            {
                tfInfo.setText("Blue Square");
            } 
        }
    }
    public class MApp extends JPanel implements MouseListener 
    {
        private boolean clicked; 
        private Rectangle r; 
        public MApp()
        {
            clicked = false;
            r = new Rectangle(10, 10, 50, 50); 
            addMouseListener(this);
        }
        public void paintComponent(Graphics g)
        {
            if(clicked)
            {
                g.setColor(Color.BLUE);
            }
            else
            {
                g.setColor(Color.RED);
            } 
            g.fillRect((int)r.getX(), (int)r.getY(),
            (int)r.getWidth(), (int)r.getHeight()); 
        }
        public void mouseClicked (MouseEvent e) 
        {
            Point p = new Point(e.getX(),e.getY()); 
            if(r.contains(p))
            {
                clicked = !clicked; 
            }
            repaint(); 
        }
        public void mousePressed (MouseEvent evnt) {}
        public void mouseReleased (MouseEvent evnt) {}
        public void mouseEntered (MouseEvent evnt) {}
        public void mouseExited (MouseEvent evnt) {} 
    }
}

You should by having a look a look at Creating a GUI With JFC/Swing, How to Use Buttons, Check Boxes, and Radio Buttons, How to Write an Action Listeners, Painting in AWT and Swing and Performing Custom Painting — MadProgrammer
– MadProgrammer, Commented Dec 7, 2015 at 3:44
Swing (and most GUI's) work differently from console based programs, this is because they event driven and there is a lot of "black box" code which is going on (like how does the actionPerformed method actually get called). The fact is, for the most part, you don't care. You know you can add an ActionListener to a control, like a JButton and when prescribed event occurs (like the user clicking the button) it will call your actionPerformed method — MadProgrammer
– MadProgrammer, Commented Dec 7, 2015 at 3:46

MCS · Accepted Answer · 2015-12-07 04:46:29Z

I think I would break it down into these parts:

1) put the MApp into it's own java file. Also, I changed the repaint() in the mouseClicked to: paintComponent(getGraphics()); Your new java file will look like this:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JPanel;

public class MApp extends JPanel implements MouseListener 
{
    private boolean clicked; 
    private Rectangle r; 
    public MApp()
    {
        clicked = false;
        r = new Rectangle(10, 10, 50, 50); 
        addMouseListener(this);
    }
    public void paintComponent(Graphics g)
    {
        if(clicked)
        {
            g.setColor(Color.BLUE);
        }
        else
        {
            g.setColor(Color.RED);
        } 
        g.fillRect((int)r.getX(), (int)r.getY(),
        (int)r.getWidth(), (int)r.getHeight()); 
    }
    public void mouseClicked (MouseEvent e) 
    {
        Point p = new Point(e.getX(),e.getY()); 
        if(r.contains(p))
        {
            clicked = !clicked; 
        }
        paintComponent(getGraphics()); 
    }
    public void mousePressed (MouseEvent evnt) {}
    public void mouseReleased (MouseEvent evnt) {}
    public void mouseEntered (MouseEvent evnt) {}
    public void mouseExited (MouseEvent evnt) {} 
}

Next: Create a main file like so:

import javax.swing.JFrame;

public class Tester {

    public static JFrame window = new JFrame("Graphics");

    public static void main(String[] args) {
        window.setBounds(100, 100,800, 800);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setLayout(null);

        MApp m = new MApp();
        m.setBounds(100,100,50,50);
        window.add(m);

        Draw d = new Draw();
        d.setBounds(0, 0, window.getWidth(), 80);
        window.add(d);

        window.setVisible(true);
    }

}

(Don't forget to delete the MApp class from your Draw class)

You'll be able to run your code and view what's going on... This is just a quick example with a few shortcuts but you'll get the idea

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