Java how to call a method from a child class

Question

I'm learning Swing to make GUI in java. My goal is to have 1 mainGUI class to initialize everything and another class that controls all the button.

What I'm doing now is I have a mainGUI which has:

public class mainGUI(){
.... (main and initialize things here) ....

protected JButton btnLogin;
public void initialize(){
    btnLogin = new JButton("Login");
    btnLogin.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            _buttonLogin();
        }
    });
}

protected void _buttonLogin(){};
}

Then in my buttonControl I have:

public class buttonControl extends mainGUI{
@Override
protected void _buttonLogin(){
    if (isLogin == true){
        btnLogin.setEnabled(false); 
    } else {
        // somthing else
    }
}
}

The program actually works but not as i expected. When i click on the "login" button, the login button is not set to unclickable. If i don't have the _buttonLogin method in the mainGUI class then I cannot call it from buttonControl class.

I'm just wondering is my approach right in this situation? or any other neat way to have a separated listener class?

Thank you so much

Answer 1

If you need a Single class for control all the buttons you have you can create a ButtonControl class which can register and de-register buttons to it and handle its events inside the control class. A Simple example code is given

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;


public class MainUI extends JFrame{

ButtonController buttonController;

public MainUI() {
    super();
    buttonController=new ButtonController(this);
    initialize();
}

private void initialize() {

    JTextField userName=new JTextField();
    JPasswordField passwordField=new JPasswordField();

    JButton loginButton=new JButton("Login");
    loginButton.setActionCommand(ButtonController.LOGIN_COMMAND);

    JButton cancelButton=new JButton("Cancel");
    cancelButton.setActionCommand(ButtonController.CANCEL_COMMAND);

    JPanel contentPane=new JPanel();
    contentPane.setLayout(new GridLayout(3,2));
    contentPane.add(new JLabel("Username : "));
    contentPane.add(userName);
    contentPane.add(new JLabel("Password : "));
    contentPane.add(passwordField);
    contentPane.add(loginButton);
    contentPane.add(cancelButton);

    buttonController.registerButton(loginButton);
    buttonController.registerButton(cancelButton);

    setContentPane(contentPane);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    pack();
}


/**
 * @param args
 */
public static void main(String[] args) {
    MainUI ui=new MainUI();
    ui.setVisible(true);
}


}


class ButtonController implements ActionListener
{
private MainUI mainUI;

public static String LOGIN_COMMAND="Login";
public static String CANCEL_COMMAND="Cancel";

public ButtonController(MainUI mainUi ) {
    this.mainUI=mainUi;
}

public void registerButton(JButton button)
{
    button.addActionListener(this);
}

public void deRegisterButton(Button button)
{
    button.removeActionListener(this);
}

@Override
public void actionPerformed(ActionEvent e) {
    if(e.getActionCommand().equals(LOGIN_COMMAND))
    {
        ((JButton)e.getSource()).setEnabled(false);
    }
    if(e.getActionCommand().equals(CANCEL_COMMAND))
    {
        mainUI.dispose();
    }
}

}