Creating GUI components dynamically in java

Question

So, we can create for example a button dynamically:

panel.add(new JButton("Button"));
validate();

But the question is, how do we make calls to those elements later? For example, how do I add an event listener to this button created above, like, 100 lines of code later?

You would need a variable for the button, just like you have for panel. — Mick Mnemonic
– Mick Mnemonic, Commented Sep 13, 2017 at 20:57
Store the JButton away somewhere (e.g. field variable) to access it later — Steve Kuo
– Steve Kuo, Commented Sep 13, 2017 at 20:58

Awais Syed · Accepted Answer · 2017-09-13 21:10:49Z

1

Create a variable for your JButton:

JButton jButton = new JButton("Button");
panel.add(jButton);
validate();
/*
 *
 *
100 lines of code 
 *
 */

// add an event listener
jButton.addActionListener((ActionEvent) -> {
            // do something
        });

answered Sep 13, 2017 at 21:10

Awais Syed

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Comments

SleevelessJoe · Accepted Answer · 2017-09-13 21:07:07Z

1

I've always created my buttons before adding to the panel like so

   private JPanel buttonPanel() { //button panel method containting 
        JPanel panel = new JPanel();
        JButton addButton = new JButton("Add");
        addButton.setToolTipText("Add Customer Data");
        JButton editButton = new JButton("Edit");
        editButton.setToolTipText("Edit selected Customer");
        JButton deleteButton = new JButton ("Delete");
        deleteButton.setToolTipText("Delete selected Customer");

        addButton.addActionListener((ActionEvent) -> {
            doAddButton();
        });
        editButton.addActionListener((ActionEvent) -> {
            doEditButton();
        });
        deleteButton.addActionListener((ActionEvent) -> {
            doDeleteButton();
        });

        panel.add(addButton);
        panel.add(editButton);
        panel.add(deleteButton);

        return panel;
    }

Allows you do something like this later on.

    private void doAddButton() { //provides action for add button
    CustomerForm customerForm = new CustomerForm(this, "Add Customer", true);
    customerForm.setLocationRelativeTo(this);
    customerForm.setVisible(true);
}

answered Sep 13, 2017 at 21:07

SleevelessJoe

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2 Comments

oksuzlerOmer Over a year ago

Ok, the problem is, I don't know how many rows will be returned from the database query. Say, 23 results come from the query which means I need 23 buttons. Can I use array with size of 23 to store 23 separate buttons?

SleevelessJoe Over a year ago

Arraylist maybe the way to go in that case. I'm not all that familiar with setting an array for to create buttons with each increment though. Sorry.

Mick Mnemonic · Accepted Answer · 2017-09-13 21:07:36Z

0

In order to bind event listeners or other functionality into the button, you'd need to store a reference to it in a variable. So, instead of

panel.add(new JButton("Button"));

You could initialize the button with

JButton myButton = new JButton("Button");
panel.add(myButton);

and then later in your code

myButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
         // do something
     } 
});

answered Sep 13, 2017 at 21:07

Mick Mnemonic

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1 Comment

Hovercraft Full Of Eels Over a year ago

If you use an AbstractAction, then the first would be perfectly fine: panel.add(new JButton(new ButtonAction()));

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