Generating specific shapes with random dimensions using a JComboBox to select shapes

Question

I am trying to create a program that uses a JComboBox containing specific shapes (Circle, Square, Oval, Rectangle). After the user clicks on a specified shape, the Panel will display 20 of that shape in random dimensions and locations.

I am having trouble on how to make the shapes have random dimensions and locations. Here is my code so far. Any advice or sources to look at would be appreciated.

Thank you.

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

public class HW1b extends JFrame 
{


public HW1b()
{

    super("Shapes"); 

    final ComboPanel comboPanel = new ComboPanel();
    String[] shapeItems = {"Circle", "Square", "Oval", "Rectangle"}; 

    JComboBox shapeBox = new JComboBox<String>(shapeItems); 
    shapeBox.addItemListener(new ItemListener()
    {

        public void itemStateChanged(ItemEvent ie)
        {

            if (ie.getStateChange() == ItemEvent.SELECTED)
            {
                String item = (String)ie.getItem(); 

                if(shapeBox.getSelectedItem().equals("Circle"))
                    comboPanel.makeCircles(); 

                if(shapeBox.getSelectedItem().equals("Square"))
                    comboPanel.makeSquares(); 

                if(shapeBox.getSelectedItem().equals("Oval"))
                    comboPanel.makeOvals(); 

                if(shapeBox.getSelectedItem().equals("Rectangle"))
                    comboPanel.makeRectangles();
            }

        }

    });


    JPanel southPanel = new JPanel(); 
    southPanel.add(shapeBox);   
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    getContentPane().add(comboPanel, "Center");
    getContentPane().add(southPanel, "South"); 

    setSize( 400, 400 );
        setLocation( 200, 200 );
        setVisible( true );

}


private class ComboPanel extends JPanel
{
    int w, h;
    Random rand; 

    static final int OVAL = 0; 
    static final int RECTANGLE = 1; 
    int shapeType = -1; 

    public ComboPanel()
    {
        rand = new Random(); 
        setBackground(Color.white); 

    }

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g); 

        Graphics2D g2d = (Graphics2D) g; 
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                     RenderingHints.VALUE_ANTIALIAS_ON);

        int width = getWidth(); 
        int height = getHeight(); 
        int x, y; 

        Shape s = null;


        for (int i = 0; i < 20; i++)
        {
            x = rand.nextInt(width - w); 
            y = rand.nextInt(width - h); 

            switch(shapeType)
            {

                case OVAL: s = new Ellipse2D.Double(x,y,w,h); 
                    break; 

                case RECTANGLE: s = new Rectangle2D.Double(x,y,w,h); 
                    break;
            }

            if (shapeType > -1) 
                g2d.draw(s); 
        }

    }

    public void makeCircles()
    {
        shapeType = OVAL; 
        w = 75; 
        h = 75; 
        repaint(); 
    }

    public void makeSquares()
    {
        shapeType = RECTANGLE; 
        w = 50; 
        h = 50; 
        repaint(); 
    }

    public void makeOvals()
    {
        shapeType = OVAL; 
        w = 80; 
        h = 60; 
        repaint(); 
    }

    public void makeRectangles()
    {
        shapeType = RECTANGLE; 
        w = 80; 
        h = 40; 
        repaint(); 
    }

}


public static void main(String[] args)
    {
        new HW1b();

    }

}

Answer 1

You're hard-coding w and h in your code, and so there's no way for this to vary among your shapes. Instead of doing this, use your Random variable, rand, to select random w and h values that are within some desired range. Myself, I wouldn't create my shapes within the paintComponent method since painting is not fully under my control and can occur when I don't want it to. For instance, in your code, your shapes will vary tremendously if the GUI is resized. Instead I'd create a collection such as an ArrayList<Shape> and fill it with created Shape objects (i.e., Ellipse2D for my circles) when desired, and then iterate through that collection within your paintComponent method, drawing your shapes.

for example...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.swing.*;

public class SomeShapes extends JPanel {
    private ShapePanel shapePanel = new ShapePanel();
    private JComboBox<MyShape> myShapeCombo = new JComboBox<>(MyShape.values());

    public SomeShapes() {
        myShapeCombo.setSelectedIndex(-1);
        myShapeCombo.addItemListener(new ComboListener());

        JPanel bottomPanel = new JPanel();
        bottomPanel.add(myShapeCombo);

        setLayout(new BorderLayout());
        add(shapePanel, BorderLayout.CENTER);
        add(bottomPanel, BorderLayout.PAGE_END);
    }

    private class ComboListener implements ItemListener {
        @Override
        public void itemStateChanged(ItemEvent e) {
            MyShape myShape = (MyShape) e.getItem();
            shapePanel.drawShapes(myShape);
        }
    }

    private static void createAndShowGui() {
        JFrame frame = new JFrame("SomeShapes");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new SomeShapes());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}

enum MyShape {
    OVAL("Oval"), RECTANGLE("Rectangle"), SQUARE("Square"), CIRCLE("Circle");
    private String name;

    private MyShape(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return getName();
    }

}

class ShapePanel extends JPanel {
    private static final int PREF_W = 600;
    private static final int PREF_H = PREF_W;
    private static final Color SHAPE_COLOR = Color.BLUE;
    private static final int SHAPE_COUNT = 20;
    private static int MIN = 5;
    private static int MAX = 200;
    private List<Shape> shapeList = new ArrayList<>();
    private Random random = new Random();

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    public void drawShapes(MyShape myShape) {
        shapeList.clear();  // empty the shapeList
        switch (myShape) {
        case OVAL:
            drawOval();
            break;
        case RECTANGLE:
            drawRectangle();
            break;
            // etc...

        default:
            break;
        }
        repaint();
    }

    private void drawOval() {
        // for loop to do this times SHAPE_COUNT(20) times.
        for (int i = 0; i < SHAPE_COUNT; i++) {
            // first create random width and height
            int w = random.nextInt(MAX - MIN) + MIN;
            int h = random.nextInt(MAX - MIN) + MIN;

            // then random location, but taking care so that it 
            // fully fits into our JPanel
            int x = random.nextInt(getWidth() - w);
            int y = random.nextInt(getHeight() - h);

            // then create new Shape and place in our shapeList.
            shapeList.add(new Ellipse2D.Double(x, y, w, h));
        }
    }

    private void drawRectangle() {
        // .... etc
    }

    //.. .. etc

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;

        // set rendering hints for smooth ovals
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        g2d.setColor(SHAPE_COLOR);
        // iterate through the shapeList ArrayList
        for (Shape shape : shapeList) {
            g2d.draw(shape);  // and draw each Shape it holds
        }            
    }
}