Question

I’m trying to program my first GUI-class in Java, using the Window Builder. Ok, the GUI is ready but has no functions yet (it contains 10 checkboxes (yes, they are all neccessary) and 2 buttons and a JTextField, so nothing special). So I just drag’n’dropped the checkboxes and button into the window, I haven’t coded anything yet.

I have two classes:
GUI.java -> only for the layout
Main.java -> should get ‘inputs’ from GUI.java

Now the user should check or uncheck the checkboxes and then finally press a button.

But how do I ‘read out’ if a checkbox is checked or not – I have two classes?

I have to add that I’m a beginner to Java and especially to GUI-programming, but I just want to learn it. I would be happy to receive some help but NOT the complete code.

Answer 1

I know you said you didn’t want the full, code but this isn’t really it, just a very basic working demo of what you want to do

Gui.java

import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Gui {
JFrame frame;
JButton button;
JCheckBox checkBox;
JLabel label;

public Gui() {
    frame = new JFrame("demo");
    button = new JButton("is it checked?");
    checkBox = new JCheckBox();
    label = new JLabel("no");
    JPanel panel = new JPanel();
    panel.add(checkBox);
    panel.add(button);
    panel.add(label);
    frame.add(panel);
    frame.pack();
    //frame.setSize(200, 60);
    frame.setResizable(false);
    frame.setLocation(400, 400);
    frame.setVisible(true);
}

// method to add an action listener to the gui's
// private button
public void setButtonActionListener(ActionListener al) {
    button.addActionListener(al);
}

// gui method to check if box is checked
public boolean isBoxChecked() {
    return checkBox.isSelected();
}

// method to set lable
public void setText(String text) {
    label.setText(text);
}

}

Main.java

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


public class Main {

public static void main(String[] args) {

    // create an instance of your gui class
    final Gui gui = new Gui();

    // add the action listener to the button
            // notice how we reference the gui here by running the methods in the
            // gui class
            // this action listener could be created in the gui
            // class but in general you don't want to do that because actions will 
            // involve multiple classes
    gui.setButtonActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent arg0) {
            gui.setText((gui.isBoxChecked() ? "yes" : "no"));
        }
    });
}

}