Creating special classes

[indienick]

I have a question about creating my own custom classes. I want my own class - NButton. The idea of this class was to quickly make JButtons, by adding my own custom argument sets. Here's my prototype for this:

import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
/**
 * NButton - Nick's JButton.
 * 
 * @author (Nick Saika) 
 * @version (1.0 - 2006)
 */
public class NButton
{
    /**
     * Constructor for objects of class Btn
     */
    public NButton(String s) 
    {
        JButton button = new JButton();
        button.setText(s);
    }
    public NButton(String s, ActionListener al)
    {
        JButton button = new JButton();
        button.setText(s);
        button.addActionListener(al);
    }
    
}

On it's own, the code compiles fine. But I get the following error when I try to implement it with the following code in the main runtime class with the line npanel.add(new NButton("Exit", new ActionExit(0))); .

(NOTE: ActionExit is another class I wrote which exits the program - I'm referencing it the same way as I am the NButton class, and it doesn't complain.

[MattEvans]

well, you need to make the button extend JButton (or Component) to be able to add it to a form; try with JButton because otherwise you'll have to write your own graphic routines and action notifiers; try this code:

[LEFT]import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
/**
 * NButton - Nick's JButton.
 * 
 * @author (Nick Saika) 
 * @version (1.0 - 2006)
 */
public class NButton [B]extends JButton
[/B]{
    /**
     * Constructor for objects of class Btn
     */
    public NButton(String s) 
    {
      [B]  this.setText(s);[/B]
    }
    public NButton(String s, ActionListener al)
    {
        [B]this.[/B]setText(s);
        [B]this.[/B]addActionListener(al);
    }
    
}[/LEFT]

as you can see, your class is now acting alot more like a button (it's writing its own label and adding its own actionlistener as apposed to adding changing them on another object). Now, your JFrame will accept it as if it were a button/component aswell.

Matt

[hooknc]

I'm a fan of Making a button a listener of itself.

public class ExtendJButton implements ActionListener
{
  public ExtendJButton(String label)
  {
    super(label);
    addActionListener(this);
  }

  public void actionPerformed(ActionEvent e)
  {
    System.out.println("Override this action event please.");
  }
}

Then create an anonymous inner class' with these buttons...

JButton jButton = new ExtendedJButton("Test Button")
{
  public void actionPerformed(ActionEvent e)
  {
    System.out.println("Your code for what ever the button should do goes here.");
  }
};

And then you're good. You never have to write an if statement to determine which button is being pressed. The button itself knows what it needs to do.

[MattEvans]

Then create an anonymous inner class' with these buttons...

you learn something new everyday. knowing that would have saved me alot of extension/workarounds in previous work.

Matt

[indienick]

Thanks for the help guys (and quite possibly girls).

The method which you proposed, hooknc, is the same model that's used in a Java book I have. What I've done is created a separate class that's the ActionListener, and then if I need to use it, I use it with the special button class that MattEvans helped me get working.

:cheesy:

EDIT: And with my method, you can just do the shorthand creating of the button - ie. without needing an if statement to figure out which button is being pressed.