How do I format JTextField text to uppercase?

By I Wayan Saryada in Swing 0 Comment

To change JTextField text to upper case can be easily done by adding a DocumentFilter to the JTextField component using the setDocumentFilter() method. The DocumentFilter allow us to filter action for changes in the document such as insert, replace and remove.

The code snippet below show us how to do it.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;

public class DocumentFilterExample extends JFrame {
    public DocumentFilterExample() throws HeadlessException {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new DocumentFilterExample().setVisible(true));
    }

    protected void initComponents() {
        setSize(500, 500);
        setTitle("DocumentFilter Example");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));

        JTextField firstName = new JTextField();
        firstName.setPreferredSize(new Dimension(150, 20));
        JTextField lastName = new JTextField();
        lastName.setPreferredSize(new Dimension(150, 20));

        DocumentFilter filter = new UppercaseDocumentFilter();
        AbstractDocument firstNameDoc = (AbstractDocument) firstName.getDocument();
        firstNameDoc.setDocumentFilter(filter);

        AbstractDocument lastNameDoc = (AbstractDocument) lastName.getDocument();
        lastNameDoc.setDocumentFilter(filter);

        getContentPane().add(new JLabel("First Name: "));
        getContentPane().add(firstName);
        getContentPane().add(new JLabel("Last Name: "));
        getContentPane().add(lastName);
    }

    static class UppercaseDocumentFilter extends DocumentFilter {
        @Override
        public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr)
            throws BadLocationException {
            fb.insertString(offset, text.toUpperCase(), attr);
        }

        @Override
        public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
            throws BadLocationException {
            fb.replace(offset, length, text.toUpperCase(), attrs);
        }
    }
}
JTextField Uppercase Text

JTextField Uppercase Text

How do I add key listener event handler to JTextField?

By I Wayan Saryada in Swing 3 Comments

In this small Swing code snippet we demonstrate how to use java.awt.event.KeyAdapter abstract class to handle keyboard event for the JTextField component. The snippet will change the characters typed in the JTextField component to uppercase.

A better approach for this use case is to use the DocumentFilter class. See the following code snippet How do I format JTextField text to uppercase?.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

public class UppercaseTextFieldDemo extends JFrame {
    public UppercaseTextFieldDemo() throws HeadlessException {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new UppercaseTextFieldDemo().setVisible(true));
    }

    protected void initComponents() {
        // Set default form size, closing event and layout manager
        setSize(500, 500);
        setTitle("JTextField Key Listener");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));

        // Create a label and text field for our demo application and add the
        // component to the frame content pane object.
        JLabel usernameLabel = new JLabel("Username: ");
        JTextField usernameTextField = new JTextField();
        usernameTextField.setPreferredSize(new Dimension(150, 20));
        getContentPane().add(usernameLabel);
        getContentPane().add(usernameTextField);

        // Register a KeyListener for the text field. Using the KeyAdapter class
        // allow us implement the only key listener event that we want to listen,
        // in this example we use the keyReleased event.
        usernameTextField.addKeyListener(new KeyAdapter() {
            public void keyReleased(KeyEvent e) {
                JTextField textField = (JTextField) e.getSource();
                String text = textField.getText();
                textField.setText(text.toUpperCase());
            }
        });
    }
}
JTextField Key Listener

JTextField Key Listener

How do I change JFrame image icon?

By I Wayan Saryada in Swing 0 Comment

This code snippet demonstrates how to change a JFrame image icon using the setIconImage() method.

package org.kodejava.swing;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
import java.awt.Dimension;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

public class FrameIconExample extends JFrame {
    public static void main(String[] args) {
        FrameIconExample frame = new FrameIconExample();
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        // Set the window size and its title
        frame.setSize(new Dimension(500, 500));
        frame.setTitle("Frame Icon Example");

        // Read the image that will be used as the application icon.
        // Using "/" in front of the image file name will locate the
        // image at the root folder of our application. If you don't
        // use a "/" then the image file should be on the same folder
        // with your class file.
        try {
            URL resource = frame.getClass().getResource("/logo.png");
            BufferedImage image = ImageIO.read(resource);
            frame.setIconImage(image);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // Display the form
        frame.setVisible(true);
    }
}
Change JFrame Image Icon

Change JFrame Image Icon

How do I handle a window closing event in Swing?

By I Wayan Saryada in Swing 1 Comment

Here you will see how to handle the window closing event of a JFrame. What you need to do is to implement a java.awt.event.WindowListener interface and call the frame addWindowListener() method to add the listener to the frame instance. To handle the closing event implements the windowClosing() method of the interface.

Instead of implementing the java.awt.event.WindowListener interface which require us to implement the entire methods defined in the interface, we can create an instance of WindowAdapter object and override only the method we need, which is the windowsClosing() method. Let’s see the code snippet below.

package org.kodejava.swing;

import javax.swing.JFrame;
import java.awt.Button;
import java.awt.Dimension;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class WindowClosingDemo extends JFrame {
    public static void main(String[] args) {
        WindowClosingDemo frame = new WindowClosingDemo();
        frame.setSize(new Dimension(500, 500));
        frame.add(new Button("Hello World"));

        // Add window listener by implementing WindowAdapter class to
        // the frame instance. To handle the close event we just need
        // to implement the windowClosing() method.
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.out.println("WindowClosingDemo.windowClosing");
                System.exit(0);
            }
        });

        // Show the frame
        frame.setVisible(true);
    }
}

How do I close a JFrame application?

By I Wayan Saryada in Swing 0 Comment

Closing a JFrame application can be done by setting the default close operation of the frame. There are some defined constants for the default operation. These constants defined in the javax.swing.WindowConstants interface include EXIT_ON_CLOSE, HIDE_ON_CLOSE, DO_NOTHING_ON_CLOSE and DISPOSE_ON_CLOSE.

To exit an application we can set the default close operation to EXIT_ON_CLOSE, this option will call the System.exit() method when user initiate a close operation on the frame.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.WindowConstants;

public class MainFrameClose extends JFrame {
    public static void main(String[] args) {
        MainFrameClose frame = new MainFrameClose();
        frame.setSize(500, 500);

        // Be defining the default close operation of a JFrame to
        // EXIT_ON_CLOSE the application will be exited by calling
        // System.exit() when user initiate a close event on the
        // frame.
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}