Drawing the Quadratic formula with sliders on a JPanel

Question

So, I'm trying to make a program where you can input the quadratic formula (ax^2+bx+c) via sliders. Then it draws a graph as you adjust for A, B, and C.

Issues:

I want the stuff I wrote in super paint and the sliders to be in one place. The sliders are in place when I run it. There's space with the correct background where I want my graph in the panel but no actual graph.

Here's my driver class:

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

public class quadraticslider
{

     public static void main (String[] args)
   {
      JFrame frame = new JFrame ("Quadratic Slider");
      frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

      frame.getContentPane().add(new pp109quadraticpanel());

      frame.pack();
      frame.setVisible(true);
   }
}

Here's the panel class:

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

public class quadraticpanel extends JPanel
{
   private JPanel controls, graphPanel;
   private JSlider ASlider, BSlider, CSlider;
   private JLabel ALabel, BLabel, CLabel;
   double A, B, C, x,Y;

  //
  //SLIDERS YO
  //
   public quadraticpanel()
   {
      ASlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      ASlider.setMajorTickSpacing (50);
      ASlider.setMinorTickSpacing (10);
      ASlider.setPaintTicks (true);
      ASlider.setPaintLabels (true);
      ASlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      BSlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      BSlider.setMajorTickSpacing (50);
      BSlider.setMinorTickSpacing (10);
      BSlider.setPaintTicks (true);
      BSlider.setPaintLabels (true);
      BSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      CSlider = new JSlider (JSlider.HORIZONTAL, 0, 255, 0);
      CSlider.setMajorTickSpacing (50);
      CSlider.setMinorTickSpacing (10);
      CSlider.setPaintTicks (true);
      CSlider.setPaintLabels (true);
      CSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      SliderListener listener = new SliderListener();
      ASlider.addChangeListener (listener);
      BSlider.addChangeListener (listener);
      CSlider.addChangeListener (listener);


      ALabel = new JLabel ("a: 0");
      ALabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      BLabel = new JLabel ("b: 0");
      BLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      CLabel = new JLabel ("c: 0");
      CLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      controls = new JPanel();
      BoxLayout layout = new BoxLayout (controls, BoxLayout.Y_AXIS);
      controls.setLayout (layout);
      controls.add (ALabel);
      controls.add (ASlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (BLabel);
      controls.add (BSlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (CLabel);
      controls.add (CSlider);



      graphPanel = new JPanel();
      graphPanel.setPreferredSize (new Dimension (500, 500));
      graphPanel.setBackground (Color.white);

      add (controls); 
      add (graphPanel);




   }   

    //Here I'm taking the equation, running it through -10 to 10
    //It takes the doubles from the equation, converts
    //it to int then draws the quadratic formula in dots.

     public void paintComponent(Graphics page)
   {  

     super.paintComponent (page);

     for ( x=-10; x <= 10; x++)
     {
         Y = (A*(Math.pow(x,2)))+(B*x)+(C);
         int g = (int)Math.round(x);
         int h = (int)Math.round(Y);
         page.setColor (Color.black);
          page.fillOval (g, h, 1, 1);
      }


    }


   public class SliderListener implements ChangeListener
   {
///
///Reads the user input via slider.
///

      public void stateChanged (ChangeEvent event)
      {
         A = ASlider.getValue();
         B = BSlider.getValue();
         C = CSlider.getValue();

         ALabel.setText ("a: " + A);
         BLabel.setText ("b: " + B);
         CLabel.setText ("c: " + C);

      }
   }
}

Right, but an [sscce](http://sscce.org/) is always a good start. It shows effort and allows one to focus on particular problems. — trashgod, Dec 13 '13 at 12:52
Thanks! I've been beating my head into a wall trying to get this program to work lol. — munchschair, Dec 13 '13 at 12:55
[sscce](http://sscce.org/), the number one programming headache remedy! — trashgod, Dec 13 '13 at 13:20
I love this program. It's been a real headache but I love the result. — munchschair, Dec 13 '13 at 15:58

score 6 · Accepted Answer · edited May 23 '17 at 12:11

These examples using JFreeChart may be of interest. As shown here, you can animate the rendering using SwingWorker, and this example updates a chart using a JSlider.

Addendum: This variation of your code may guide you going forward. Note,

Override relevant methods in your graphPanel.
Scale and invert coordinates, as shown here.
Consider JSpinner for fractional values.
Use constants for consistency.
Use common naming conventions for clarity.
See also Initial Threads.

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

/** @see https://stackoverflow.com/a/20556929/230513 */
public class QuadraticSlider {

    private static final int N = 500;
    private static final int A = 1;
    private static final int B = 0;
    private static final int C = 0;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame("Quadratic Slider");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new QuadraticPanel());
                frame.pack();
                frame.setVisible(true);
            }
        });
    }

    private static class QuadraticPanel extends JPanel {

        private Box controls;
        private JPanel graphPanel;
        private JSlider aSlider, bSlider, cSlider;
        private JLabel aLabel, bLabel, cLabel;
        double a, b, c, x, y;

        public QuadraticPanel() {
            aSlider = new JSlider(JSlider.HORIZONTAL, -25, 25, A);
            aSlider.setMajorTickSpacing(10);
            aSlider.setMinorTickSpacing(5);
            aSlider.setPaintTicks(true);
            aSlider.setPaintLabels(true);
            aSlider.setAlignmentX(Component.LEFT_ALIGNMENT);

            bSlider = new JSlider(JSlider.HORIZONTAL, -10, 10, B);
            bSlider.setMajorTickSpacing(5);
            bSlider.setMinorTickSpacing(1);
            bSlider.setPaintTicks(true);
            bSlider.setPaintLabels(true);
            bSlider.setAlignmentX(Component.LEFT_ALIGNMENT);

            cSlider = new JSlider(JSlider.HORIZONTAL, -100, 100, C);
            cSlider.setMajorTickSpacing(50);
            cSlider.setMinorTickSpacing(10);
            cSlider.setPaintTicks(true);
            cSlider.setPaintLabels(true);
            cSlider.setAlignmentX(Component.LEFT_ALIGNMENT);

            SliderListener listener = new SliderListener();
            aSlider.addChangeListener(listener);
            bSlider.addChangeListener(listener);
            cSlider.addChangeListener(listener);

            aLabel = new JLabel("a: 0");
            bLabel = new JLabel("b: 0");
            cLabel = new JLabel("c: 0");
            controls = new Box(BoxLayout.Y_AXIS);
            controls.add(aLabel);
            controls.add(aSlider);
            controls.add(Box.createRigidArea(new Dimension(0, 20)));
            controls.add(bLabel);
            controls.add(bSlider);
            controls.add(Box.createRigidArea(new Dimension(0, 20)));
            controls.add(cLabel);
            controls.add(cSlider);

            graphPanel = new JPanel() {
                private static final int SCALE = 5;
                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(N, N);
                }

                @Override
                public void paintComponent(Graphics g) {
                    super.paintComponent(g);
                    for (x = -10; x <= 10; x++) {
                        y = a * x * x + b * x + c;
                        g.setColor(Color.black);
                        int w = (int) (x * SCALE) + N / 2;
                        int h = (int) (-y * SCALE) + N / 2;
                        g.fillOval(w, h, 5, 5);
                    }
                }
            };
            graphPanel.setBackground(Color.white);

            add(controls);
            add(graphPanel);
            listener.stateChanged(null);
        }

        class SliderListener implements ChangeListener {

            @Override
            public void stateChanged(ChangeEvent event) {
                a = aSlider.getValue() / 5d;
                b = bSlider.getValue();
                c = cSlider.getValue();

                aLabel.setText("a: " + a);
                bLabel.setText("b: " + b);
                cLabel.setText("c: " + c);

                repaint();
            }
        }
    }
}

I've been working hard at this and I'm close to finishing it. Now I have some sort of compiler error. — munchschair, Dec 13 '13 at 01:09
Cool, I ran the code and this is exactly what I wanted it to do. Now to see what you changed. What is "EventQueue.invokeLater(new Runnable()" and what are the "@Override" supposed to mean? — munchschair, Dec 13 '13 at 13:25
@munchschair: Oh, that's a `double` literal; `5.0` would do, too. — trashgod, Dec 14 '13 at 01:38
See also [*JLS §3.10.2. Floating-Point Literals*](http://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html#jls-3.10.2). — trashgod, Dec 14 '13 at 04:24

score 1 · Answer 2 · answered Dec 13 '13 at 01:27

1

_"error: possible loss of precision Y = (A*(Math.pow(x,2)))+(B*x)+(C); ^ required: int found: double"_

All your int variables int A, B, C, x,Y;. Make them doubles. double A, B, C, x,Y;

answered Dec 13 '13 at 01:27

Paul Samsotha

205,037
37
486
720

I beat you to that a minute ago and then rounded the variables, so it makes it easier to draw? Do I have to do that, or can I draw doubles? Anyway, I run it from my driver class, it compiles, but nothing comes when I run it. – munchschair Dec 13 '13 at 01:28
1

You can cast (int) to the variable when you draw. – Paul Samsotha Dec 13 '13 at 01:30
I have my doubles being converted into ints. – munchschair Dec 13 '13 at 01:33
"_I run it from my driver class, it compiles, but nothing comes when I run it._". It's probab;y something else wrong in your code. – Paul Samsotha Dec 13 '13 at 01:35
Look at this. `page.fillOval (g, h, 1, 1);`. You do realize the parameters are `(xCoordinate, yCoordinate, width, height)`. Your making a circe with 1 height and width. – Paul Samsotha Dec 13 '13 at 01:38
Yes, I want to draw dots to graph the lines of the quadratic formula. I figured that'd be the simplest way to draw it. – munchschair Dec 13 '13 at 03:07
1

@trashgod I actually just downloaded `JFreeChart` today. Never used it before, but I'm excited to get started. Thanks for your "promotion" of it throughout this site! :) – Paul Samsotha Dec 13 '13 at 12:31

Lou44 · Answer 3 · 2013-12-13T17:58:15.590

I modified the code so that it solves for x given a b and c. Then plugs x back in and solves for y. I'm still not getting it to draw though. I also took out the loop since the sliders are setting the a b and c values which lead to x. Anyone know why it won't draw?

package quadraticslider;

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

public class quadraticslider
{

     public static void main (String[] args)
   {
      JFrame frame = new JFrame ("Quadratic Slider");
      frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

      frame.getContentPane().add(new quadraticpanel());

      frame.pack();
      frame.setVisible(true);
   }
}

package quadraticslider;

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

public class quadraticpanel extends JPanel
{
   private JPanel controls, graphPanel;
   private JSlider ASlider, BSlider, CSlider;
   private JLabel ALabel, BLabel, CLabel;
   double A, B, C, x,Y;


   public quadraticpanel()
   {
      ASlider = new JSlider (JSlider.HORIZONTAL, -25, 25, 0);
      ASlider.setMajorTickSpacing (50);
      ASlider.setMinorTickSpacing (10);
      ASlider.setPaintTicks (true);
      ASlider.setPaintLabels (true);
      ASlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      BSlider = new JSlider (JSlider.HORIZONTAL, -25, 25, 0);
      BSlider.setMajorTickSpacing (50);
      BSlider.setMinorTickSpacing (10);
      BSlider.setPaintTicks (true);
      BSlider.setPaintLabels (true);
      BSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      CSlider = new JSlider (JSlider.HORIZONTAL, -25, 25, 0);
      CSlider.setMajorTickSpacing (50);
      CSlider.setMinorTickSpacing (10);
      CSlider.setPaintTicks (true);
      CSlider.setPaintLabels (true);
      CSlider.setAlignmentX (Component.LEFT_ALIGNMENT);

      SliderListener listener = new SliderListener();
      ASlider.addChangeListener (listener);
      BSlider.addChangeListener (listener);
      CSlider.addChangeListener (listener);


      ALabel = new JLabel ("a: 0");
      ALabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      BLabel = new JLabel ("b: 0");
      BLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      CLabel = new JLabel ("c: 0");
      CLabel.setAlignmentX (Component.LEFT_ALIGNMENT);
      controls = new JPanel();
      BoxLayout layout = new BoxLayout (controls, BoxLayout.Y_AXIS);
      controls.setLayout (layout);
      controls.add (ALabel);
      controls.add (ASlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (BLabel);
      controls.add (BSlider);
      controls.add (Box.createRigidArea (new Dimension (0, 20)));
      controls.add (CLabel);
      controls.add (CSlider);



      graphPanel = new JPanel();
      graphPanel.setPreferredSize (new Dimension (500, 500));
      graphPanel.setBackground (Color.white);

      add (controls); 
      add (graphPanel);




   }   



     public void paintComponent(Graphics page)
   {  

     super.paintComponent (page);




         x = (-B + (Math.sqrt((B*B - ((4 * A * C))))))/ (2 * A);
         Y = (A*(Math.pow(x,2)))+(B*x)+(C);
         int g = (int)Math.round(x);
         int h = (int)Math.round(Y);
         page.setColor (Color.black);
         page.drawOval (g, h, 1, 1);



    }


   public class SliderListener implements ChangeListener
   {
///
///Reads the user input via slider.
///

      public void stateChanged (ChangeEvent event)
      {
         A = ASlider.getValue();
         B = BSlider.getValue();
         C = CSlider.getValue();

         ALabel.setText ("a: " + A);
         BLabel.setText ("b: " + B);
         CLabel.setText ("c: " + C);

      }

} }

I edited it to that. It's giving a loss of precision error pointing to the last plus sign in this: Y = (A*(Math.pow(x,2)))+(B*x)+(C) I tried rounding the numbers after the equation, but it has no effect. It points TO the equation. — munchschair, Dec 13 '13 at 01:23
_Anyone know why it won't draw?_ See this [answer](http://stackoverflow.com/a/20556929/230513). — trashgod, Dec 14 '13 at 05:01

Drawing the Quadratic formula with sliders on a JPanel

3 Answers3

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