CODEWITHSUNDEEP
javaswing
Hamza Shahid
Hamza Shahid

Reputation: 19

Swing JTextField on text change

I am working on a Swing form. When the user changes text in a TextField, I want to get input from other fields, do some calculations and then display the results. How can I do that?

Here is what I have so far:

jTextField3.addKeyListener(

    new KeyAdapter() {
        public void keyTyped(KeyEvent e){
           char c = e.getKeyChar();
           if('0'<=c && c<='9') {
                String a = jTextField6.getText().toString();
                String l = jTextField7.getText().toString();
                int m = Integer.parseInt(a);
                int n = Integer.parseInt(l);
                jTextField13.setText("" + m*n);
          }
       }
    });

Upvotes: 0

Views: 10124

Answers (1)

MadProgrammer
MadProgrammer

Reputation: 347184

If you want to monitor for changes to one or more text fields, you should be using a DocumentListener, this will also provide you notification's of when the user pastes text into the field or the field is changed programatically (via a call to setText)

For example...

Bunnies

import java.awt.EventQueue;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class Text {

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

    public Text() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            JTextField field1 = new JTextField(10);
            JTextField field2 = new JTextField(10);
            JTextField field3 = new JTextField(10);

            DocumentListener dl = new DocumentListener() {

                @Override
                public void insertUpdate(DocumentEvent e) {
                    updateFieldState();
                }

                @Override
                public void removeUpdate(DocumentEvent e) {
                    updateFieldState();
                }

                @Override
                public void changedUpdate(DocumentEvent e) {
                    updateFieldState();
                }

                protected void updateFieldState() {
                    String text = field1.getText() + " " + field2.getText();
                    field3.setText(text);
                }
            };

            field1.getDocument().addDocumentListener(dl);
            field2.getDocument().addDocumentListener(dl);
            field3.setEditable(false);

            add(field1);
            add(field2);
            add(field3);
        }

    }

}

Now, it appear that you are trying to limit the character that can be typed into the field. You could use a JSpinner or JFormattedTextField, but these only provide post validation.

For real time validation, you should be using a DocumentFilter, which will allow you to intercept what is entered into the field before it's applied to the underlying Document.

See Implementing a DocumentFilter and DocumentFilter examples for more details

Upvotes: 4

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