Find selected item of a JList and display it in real time

Question

I have a JList, where i am displaying some ID's. I want to capture the ID the user clicked and dis play it on a JLabel.

String selected = jlist.getSelectedItem().toString();

The above code gives me the selected JList value. But this code has to be placed inside a button event, where when i click the button it will get the JList value an assign it to the JLabel.

But, what i want to do is, as soon as the user clicks an item of the JList to update the JLabel in real time. (without having to click buttons to fire an action)

Answer 1

A simple example would be like below using listselectionlistener

import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public class JListDemo extends JFrame {

    public JListDemo() {

        setSize(new Dimension(300, 300));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new FlowLayout());
        final JLabel label = new JLabel("Update");
        String[] data = { "one", "two", "three", "four" };
        final JList dataList = new JList(data);

        dataList.addListSelectionListener(new ListSelectionListener() {

            @Override
            public void valueChanged(ListSelectionEvent arg0) {
                if (!arg0.getValueIsAdjusting()) {
                  label.setText(dataList.getSelectedValue().toString());
                }
            }
        });
        add(dataList);
        add(label);

        setVisible(true);

    }

    public static void main(String args[]) {
        new JListDemo();
    }

}

Answer 2

Why don't you put a ListSelectionListener on your JList, and add your above code in to it.

I'm assuming you already know how to create listeners on JButtons, based on your question, so you just need to tweak it to create a ListSelectionListener instead, then assign the listener to your JList using jlist.addListSelectionListener(myListener);

There is a nice tutorial here that should get you started, or refer to the documentation

You should be aiming for something like this...

jlist.addListSelectionListener(new ListSelectionListener() {
    public void valueChanged(ListSelectionEvent event) {
        if (!event.getValueIsAdjusting()){
            JList source = (JList)event.getSource();
            String selected = source.getSelectedValue().toString();
        }
    }
});

Answer 3

Use a ListSelectionListener:

JList list = new JList(...);
list.addListSelectionListener(new ListSelectionListener() {
  public void valueChanged(ListSelectionEvent evt) {
    if (!evt.getValueIsAdjusting()) {
      // code here
    }
  }
});