We make the buttons work using Listeners.

In this tutorial we are going to make the buttons of our window work, adding Listeners to the buttons of our example.

To do so we have two different examples:

In the first one we will use the LoginView1 class code. The code is very similar to the example of the last tutorial but for the last two lines in which we have added a Listener to the loginButton. When the button is clicked, a call is made to the actionPerformed() method defined in the class of the listener object. An ActionEvent object is passed as a parameter to the actionPerformed() method, which will show a message reporting that the login button has been pressed.

package com.edu4java.swing.tutrial4;

import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class LoginView1 {

	public static void main(String[] args) {
		JFrame frame = new JFrame("Demo application");
		frame.setSize(300, 150);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		placeComponents(frame);
		frame.setVisible(true);
	}

	private static void placeComponents(JFrame frame) {
		frame.setLayout(null);

		JLabel userLabel = new JLabel("User");
		userLabel.setBounds(10, 10, 80, 25);
		frame.add(userLabel);

		JTextField userText = new JTextField(20);
		userText.setBounds(100, 10, 160, 25);
		frame.add(userText);

		JLabel passwordLabel = new JLabel("Password");
		passwordLabel.setBounds(10, 40, 80, 25);
		frame.add(passwordLabel);

		JPasswordField passwordText = new JPasswordField(20);
		passwordText.setBounds(100, 40, 160, 25);
		frame.add(passwordText);

		JButton loginButton = new JButton("login");
		loginButton.setBounds(10, 80, 80, 25);
		frame.add(loginButton);

		JButton registerButton = new JButton("register");
		registerButton.setBounds(180, 80, 80, 25);
		frame.add(registerButton);

		ActionListener loginButtonListener = new LoginButtonListener();
		loginButton.addActionListener(loginButtonListener);
	}
}

package com.edu4java.swing.tutrial4;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JOptionPane;

public class LoginButtonListener implements ActionListener {
	@Override
	public void actionPerformed(ActionEvent e) {
		JOptionPane.showMessageDialog(null, "login button has been pressed");
	}
}

In the case of the LoginView2 class, the code is similar to LoginView1 but for the creation of a Listener object "myButtonListener", which we add to the loginButton as well as to the registerButton. The ActionEvent parameter of the actionPerformed method gives us information about the event. In this example we ask the ActionEvent parameter to tell us which is the button pressed with the instruction; "e.getSource()" and to display it with a message.

package com.edu4java.swing.tutrial4;

import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class LoginView2 {

	public static void main(String[] args) {
		JFrame frame = new JFrame("Demo application");
		frame.setSize(300, 150);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		placeComponents(frame);
		frame.setVisible(true);
	}

	private static void placeComponents(JFrame frame) {
		frame.setLayout(null);

		JLabel userLabel = new JLabel("User");
		userLabel.setBounds(10, 10, 80, 25);
		frame.add(userLabel);

		JTextField userText = new JTextField(20);
		userText.setBounds(100, 10, 160, 25);
		frame.add(userText);

		JLabel passwordLabel = new JLabel("Password");
		passwordLabel.setBounds(10, 40, 80, 25);
		frame.add(passwordLabel);

		JPasswordField passwordText = new JPasswordField(20);
		passwordText.setBounds(100, 40, 160, 25);
		frame.add(passwordText);

		JButton loginButton = new JButton("login");
		loginButton.setBounds(10, 80, 80, 25);
		frame.add(loginButton);

		JButton registerButton = new JButton("register");
		registerButton.setBounds(180, 80, 80, 25);
		frame.add(registerButton);

		ActionListener myButtonListener = new MyButtonListener();
		loginButton.addActionListener(myButtonListener);
		registerButton.addActionListener(myButtonListener);
	}
}

package com.edu4java.swing.tutrial4;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JOptionPane;

public class MyButtonListener implements ActionListener {
	@Override
	public void actionPerformed(ActionEvent e) {
		JButton source = (JButton) e.getSource();
		JOptionPane.showMessageDialog(source, source.getText() + " button has been pressed");
	}
}

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