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I've made a bouncing ball in Java, but now I have to add "start" and "stop" buttons to the animation, but I'm not really sure how to go about that. This is what I have so far: 

 import java.awt.Color;
 import java.awt.Graphics;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;

 import javax.swing.*;
 //import javax.swing.JFrame;
 //import javax.swing.JPanel;
 //import javax.swing.Timer;

 /**
 *
 *
 */
 public class BouncingBall extends JPanel implements ActionListener {

    Timer tm = new Timer(5,this);
    int x = 0, velX = 1;
    int y = 0, velY = 1;



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

      g.setColor(Color.yellow);

      g.fillOval(x, y, 50, 50);

      tm.start();
   }

    public void actionPerformed(ActionEvent E)
  {
     if(x < 0 || x > 550)
        velX = -velX;
     if (y < 0 || y > 280)
        velY = -velY;

     x = x + velX;
     y = y + velY;
    repaint();
  }
   public static void main(String[] args) {

      BouncingBall s = new BouncingBall();
      JFrame jf = new JFrame();
      jf.setTitle("Bouncing Ball");
      jf.setSize(600,350);
      jf.setVisible(true);
      jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      jf.add(s);
  }

}

Any ideas on how I should implement the start/stop buttons?

Thank you in advance

UPDATE: I did the following, but I'm getting an error because of this line: start.addActionListener(this); It says "non static variable this cannot be referenced from a static context"

 public void actionPerformed(ActionEvent E)
  {
    if (E.getActionCommand().equals("Start")){
      if(x < 0 || x > 550)
         velX = -velX;
      if (y < 0 || y > 280)
        velY = -velY;

     x = x + velX;
     y = y + velY;
     repaint();
    }

    else 
    {}

 }

  public static void main(String[] args) {

     BouncingBall s = new BouncingBall();
    JFrame jf = new JFrame();

    JPanel jp = new JPanel();

    JButton start = new JButton("Start");

    start.addActionListener(this);

    jp.add(start);

    jf.add(jp,BorderLayout.SOUTH);

    jf.setTitle("Bouncing Ball");
    jf.setSize(600,350);
    jf.setVisible(true);
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jf.add(s);
    }

  }

Can anyone tell me what I'm doing incorrectly? The duplicate question didn't help me a lot.

user3266259
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  • Create another panel, add your button there (yes just the one). When clicked, the Timer is running, stop it, if it's not, start it... – MadProgrammer Mar 27 '15 at 10:06
  • @MadProgrammer, where should I put the new panel, inside the main function? Sorry if my question is dumb, I'm pretty new to Java. – user3266259 Mar 27 '15 at 10:10
  • See the Java Swing tutorials for [buttons](https://docs.oracle.com/javase/tutorial/uiswing/components/button.html), [panels](https://docs.oracle.com/javase/tutorial/uiswing/components/panel.html) and [layouts](https://docs.oracle.com/javase/tutorial/uiswing/layout/using.html), for example – DNA Mar 27 '15 at 10:15
  • @user3266259 Actually; it doesn't really matter. You could add a simple border layout to your frame; place the "ball panel" in the center; and put buttons "east" and "west". See http://www.javamex.com/tutorials/swing/layouts.shtml for example. Or you use a layoutmanager within your panel itself. – GhostCat Mar 27 '15 at 10:15
  • Yes create it within the main method, and add it to the BorderLayout.SOUTH position of the frame – MadProgrammer Mar 27 '15 at 10:15

0 Answers0