Java Tutorial/Swing Event/CaretListener

Caret Events and Listeners

Whenever a caret changes its position or if text is selected, a caret event is fired by a text component. The class CaretEvent supports the methods getDot() and getMark() to retrieve the current location and the end position of a text selection, respectively.

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
public class CaretEeventListener {
  public static void main(String[] a) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JTextField textField = new JTextField();
    textField.addCaretListener(new CaretListener() {
      public void caretUpdate(CaretEvent e) {
        System.out.println(e);
      }
    });
    frame.add(new JScrollPane(textField));
    frame.setSize(300, 200);
    frame.setVisible(true);
  }
}

Listen to CaretEvent with CaretListener

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
public class Main implements ActionListener {
  JTextField jtf = new JTextField(10);
  JButton jbtnGetTextUpper = new JButton("Get Text In Uppercase");
  Main() {
    JFrame jfrm = new JFrame("Demonstrate a Text Field");
    jfrm.setLayout(new FlowLayout());
    jfrm.setSize(240, 140);
    jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jtf.setActionCommand("TF");
    jtf.addActionListener(this);
    jbtnGetTextUpper.addActionListener(this);
    jtf.addCaretListener(new CaretListener() {
      public void caretUpdate(CaretEvent ce) {
        System.out.println("Text in real time: " + jtf.getText());
      }
    });
    jfrm.add(jtf);
    jfrm.add(jbtnGetTextUpper);
    jfrm.setVisible(true);
  }
  public void actionPerformed(ActionEvent ae) {
    if (ae.getActionCommand().equals("TF")) {
      System.out.println("ENTER key pressed: " + jtf.getText());
    } else {
      String str = jtf.getText().toUpperCase();
      System.out.println("Button pressed: " + str);
    }
  }
  public static void main(String args[]) {
    new Main();
  }
}