Find the index of a Java JButton Array

Question

I am writing a Java program in which I have an array of buttons (not a calculator!) and I'm looking for an efficient way to know which JButton was clicked. From what I know of Java so far, the only way to do it is to have them all in the same ActionListener and then loop through looking for a match.

Another solution I just thought of would be to extend JButton to include a unique ID number variable in the constructor. It seems that should work when the event object is cast to JButton after an instanceof check. Kind of like using VB's Tag property which is assigned to the index number.

Is there a better/more elegant way?

You can assign a unique ID to each JButton by using the setName and getName methods. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Jul 2, 2015 at 19:38
Careful with the setName it might get nulled if set before the action. — Dima Maligin
– Dima Maligin, Commented Jul 2, 2015 at 19:40
That's a possibility. I didn't know of those methods and they are part of JComponent. That's a good thing to know. That will actually help in another program also. Thanks! — Tom K
– Tom K, Commented Jul 2, 2015 at 19:44
If you create a JButton then call setName("name") on it and after that call setAction(new AbstractAction(...)) the next call to getName will return null. Have a look at this — Dima Maligin
– Dima Maligin, Commented Jul 2, 2015 at 19:47

Community · Accepted Answer · 2017-05-23 11:58:23Z

5

Is there a better/more elegant way?

yes to use (for almost JComponents) the put/getClientProperty, there you can to set endless number of properties, can be multiplied in contrast with setName / setActionCommand / etc
getClientProperty can be used as unique identificator for Swing Action or EventHandler (rather than to use ActionListener)

Links to the Javadocs: putClientProperty(), getClientProperty()

edited May 23, 2017 at 11:58

CommunityBot

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answered Jul 2, 2015 at 19:49

mKorbel

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3 Comments

user21926 Over a year ago

Wasn't aware of these methods, very nice.

mKorbel Over a year ago

@Sean Bright please which one 1:-). ClientProperty or (my favorite) 2:-). EventHandler

user21926 Over a year ago

put/getClientProperty

andronix · Accepted Answer · 2015-07-02 20:10:34Z

Here is an example from programm I writing last few months. I have an enum called Position

public enum Position {
    BB, SB, BU, CO, MP3, MP2, MP1, EP3, EP2, EP1;
}

and have some JToggleButtons each of them holding ist own Position.

public class PositionButton extends JToggleButton {
    private final Position p;

    public PositionButton(Position p) {
        this.p = p;
        setText(p.toString());
        setActionCommand(p.toString());
    }

    public Position getPosition() {
        return p;
    }
}

This allows you to create Buttons in a Loop and get value direct from button without comparing:

ActionListener positionListener = new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        PositionButton b = (PositionButton )e.getSource();
        Position p = b.getPosition();
        //do something with Position
    }
}

for (Position p : Position.values()) {
    PositionButton b = new PositionButton (p);
    b.addActionListener(positionListener);
}

Sean Stinehour · Accepted Answer · 2015-07-03 15:46:03Z

0

The way I've done it before was using actionPerformed for different buttons. I like it more compared to some other ways I've seen.

public void actionPerformed(ActionEvent clicking)
{
    if (clicking.getSource() == button[0])
        // Do this
    if (clicking.getSource() == button[1])
        // Do something different
}

Since you built an array, you can throw the ID right where that 0 is and that's your unique ID.

edited Jul 3, 2015 at 15:46

user21926

answered Jul 2, 2015 at 19:43

Sean Stinehour

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Comments

FredK · Accepted Answer · 2015-07-02 19:35:57Z

-1

Add a separate action listener for each button.

answered Jul 2, 2015 at 19:35

FredK

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1 Comment

Tom K Over a year ago

The array I'll be using has 64 JButtons. Would there be any overhead or slowdown to have that many ActionListeners? If not for that many, would some number more? That's just for future reference.

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