Controlling a Fan's Speed Using JButton

Question

I was given this homework assignment by my professor to implement two buttons and control a fan. I am very new to GUI's and I have not the slightest clue how to call upon my timer in order to increment it using timer.setDelay(); Any help would be greatly appreciated. My code is below:

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


public class Fan extends JFrame implements ActionListener{

    JButton speedup;
    JButton slowdown;


 JPanel testPanel = new MyPanel();//trying to inherit properties of MyPanel
  public Fan() {
    add(testPanel);

GridLayout f = new GridLayout(1,2);
setLayout(f);

JButton speedup = new JButton("Speed Up");
speedup.addActionListener(this);
add(speedup);

JButton slowdown = new JButton("Slow Down");
slowdown.addActionListener(this);
add(slowdown);

}

/* public void actionPerformed(ActionEvent event){
    int delay;
    String cmd = event.getActionCommand();
    if(cmd == "Speed Up" ){

        delay = testPanel.getTimer().getDelay();
        delay++;
        testPanel.getTimer().setDelay(delay);
        }

    else{

         delay = testPanel.getTimer().getDelay();
        delay--;
        testPanel.getTimer().setDelay(delay);
        */ 
//My attempt at getting timer to work commented out


    }




public class MyPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    public Timer timer = new Timer(10, new TimerListener());
    private int alpha = 0; //angle

    public Timer getTimer(){
        return timer; //getter method for timer
    }

    public MyPanel() {
        timer.start();
    }


        protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        alpha = alpha + 1;
        int xc = getWidth()/2;
        int yc = getHeight()/2;
        int rad = (int)(Math.min(getWidth(), getHeight())*0.4);
        int x = xc - rad;
        int y = yc - rad;
        g.fillArc(x, y, 2*rad, 2*rad, 0+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 90+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 180+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 270+alpha, 30);
    }

    class TimerListener implements ActionListener {     

        public void actionPerformed(ActionEvent e){
            repaint();      
        }       
    }   





    public static void main(String[] args) {

        JFrame fan = new Fan();
        fan.setSize(700, 700);
        fan.setLocationRelativeTo(null);
        fan.setDefaultCloseOperation(EXIT_ON_CLOSE);
        fan.setTitle("Spinning Fan");
        fan.setVisible(true);
    }

}

For [example](http://stackoverflow.com/questions/3405799/how-to-rotate-an-image-gradually-in-swing/3420651#3420651). — trashgod, Apr 01 '14 at 00:16

Paul Samsotha · Answer 1 · 2014-04-01T02:58:45.980

JPanel testPanel = new MyPanel(); will limit testPanel to the methods of JPanel (so you can't use testPanel.getTimer()). Instead use MyPanel testPanel = new MyPanel();, then you will be able to use testTimer.getTimer();
if(cmd == "Speed Up" ){. Don't compare Strings with ==. Instead use equals. So if ("Speed Up".equals(cmd)) {}
If you want to "Speed up" an animation, you should decrease the delay, not increase it. And vice verse.

Side Notes

Run Swings apps on the Event Dispatch Thread. You can achieve this by wrapping the code in your main in a SwingUtilities.invokeLater(...). See more at Initial Threads

Here's a fixed example

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class Fan extends JFrame implements ActionListener {

    JButton speedup;
    JButton slowdown;

    MyPanel testPanel = new MyPanel();// trying to inherit properties of MyPanel

    public Fan() {
        add(testPanel);

        JButton speedup = new JButton("Speed Up");
        speedup.addActionListener(this);

        JButton slowdown = new JButton("Slow Down");
        slowdown.addActionListener(this);

        JPanel panel = new JPanel();
        panel.add(speedup);
        panel.add(slowdown);

        add(panel, BorderLayout.SOUTH);

        pack();
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("Spinning Fan");
        setVisible(true);

    }

    public void actionPerformed(ActionEvent event) {
        int delay;
        String cmd = event.getActionCommand();
        if ("Speed Up".equals(cmd)) {
            delay = testPanel.getTimer().getDelay();
            delay--;
            testPanel.getTimer().setDelay(delay);
        } else {
            delay = testPanel.getTimer().getDelay();
            delay++;
            testPanel.getTimer().setDelay(delay);
        }
    }

    // My attempt at getting timer to work commented out

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

            public void run() {
                new Fan();
            }
        });
    }
}

class MyPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    public Timer timer = new Timer(10, new TimerListener());
    private int alpha = 0; // angle

    public Timer getTimer() {
        return timer; // getter method for timer
    }

    public MyPanel() {
        timer.start();
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        alpha = alpha + 1;
        int xc = getWidth() / 2;
        int yc = getHeight() / 2;
        int rad = (int) (Math.min(getWidth(), getHeight()) * 0.4);
        int x = xc - rad;
        int y = yc - rad;
        g.fillArc(x, y, 2 * rad, 2 * rad, 0 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 90 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 180 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 270 + alpha, 30);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(600, 600);
    }

    class TimerListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            repaint();
        }
    }
}

Controlling a Fan's Speed Using JButton

1 Answers1