JButton Array ActionListener Issue

Question

I'm writing a program and I've run into an issue...

I create 1 JLabel array and 1 JButton array. The JLabel array holds a string, a Club Name. The JButton array holds a string that just says "Edit".

A For loop then fills each array based on the length of the clubs array, as well as add an action listener for each button.

When the user clicks the JButton corresponding to the JLabel it initiates an Event. In this event I need to find out the value stored in the JLabel that matches the JButton.

Since the event listener doesn't know it's inside a loop, I can't use it.

How do I achieve the goal I want?

See the bellow code.

JLabel clubs[]      = new JLabel[99];
JButton editAClub[] = new JButton[99];

for(int i=0; i <= (allClubs.length - 1);i++)
{
    clubs[i]        =   new JLabel("Club " + i);
    editAClub[i]    =   new JButton("Edit");
    editAClub[i].addActionListener(new ActionListener()
    {
        public void actionPerformed(ActionEvent e)
        {
            selectedClub = clubs[i].getText().toString();
            System.out.println(selectedClub);
        }
    });
}

what's wrong with the current code?

Adel Boutros
– Adel Boutros

2013-04-06 18:24:13 +00:00
Commented Apr 6, 2013 at 18:24 — Adel Boutros
– Adel Boutros, Commented Apr 6, 2013 at 18:24
You can't use i inside the actionListener.

Ricky Rodrigues
– Ricky Rodrigues

2013-04-06 18:55:33 +00:00
Commented Apr 6, 2013 at 18:55 — Ricky Rodrigues
– Ricky Rodrigues, Commented Apr 6, 2013 at 18:55

ApproachingDarknessFish · Accepted Answer · 2013-04-07 20:29:04Z

1

I would create a map of Buttons and JLabels and pass the source of the action in the actionListener:

JLabel clubs[]      = new JLabel[99];
JButton editAClub[] = new JButton[99];

//create a map to store the values
final HashMap<JButton,JLabel> labelMap = new HashMap<>(); //in JDK 1.7

for(int i=0; i <= (allClubs.length - 1); i++)
{
    clubs[i]        =   new JLabel("Club " + i);
    editAClub[i]    =   new JButton("Edit");

    //add the pair to the map
    labelMap.put(editAClub[i],clubs[i]);

    editAClub[i].addActionListener(new ActionListener()
    {
        public void actionPerformed(ActionEvent e)
        {
            //get the label associated with this button from the map
            selectedClub = labelMap.get(e.getSource()).getText(); // the toString() is redundant
            System.out.println(selectedClub);
        }
    });
}

This way the Buttons and Labels are associated with each other via a separate data structure rather than just by their indices in their respective arrays.

edited Apr 7, 2013 at 20:29

answered Apr 6, 2013 at 18:25

ApproachingDarknessFish

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8 Comments

Ricky Rodrigues Over a year ago

Valek, that throws NullPointerException's... I Also had to make the labelMap final. Either way though doesn't work..

Ricky Rodrigues Over a year ago

Issue resolved, I used Valek's idea... However, rather then use "this" I used e.getSource().

ApproachingDarknessFish Over a year ago

@RickyRodrigues Fixed. Sorry, I get confused about the different levels of this within anonymous class declarations. feel free to accept if it solved your problem.

MadProgrammer Over a year ago

So why not use ((JButton)e.getSource())?

ApproachingDarknessFish Over a year ago

@MadProgrammer Why bother? get takes an Object as its parameter.

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