Handle JButton click event in another class

Question

I'm new to java coming from C# so I'm not familiar with java best practices.

I have a main class that opens a JFrame to get several input strings from a user. When the user clicks submit the GUI should close and the main class continue processing using the input.

This is the main class:

public class Main {
    FInput fInput;

    public void main(String[] args) {
        if(args.length==0)
        {
            fInput = new FInput();
            fInput.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            fInput.pack();
            fInput.setVisible(true);
        }
    else
        startProcess(args);
    }

    public void startProcess(String[] args) {
// Do stuff
}

The main class will use this frame to get input from the user:

public class FInput extends JFrame{
    private JTextField txtSourceDirectory;
    private JTextField txtTargetDirectory;
    private JTextField txtDefectNumber;
    private JTextField txtSliceTokens;
    private JButton btnStart;

    public FInput() {
        // Initialize text fields and button
        JButton.addActionListener(something);
    }
}

In all the examples I could find, the listener would be a FMain itself. However in this case I want Main to listen and use the input in method startProcess.

Would having Main implement ActionListener, and passing it to FMain constructor is the way to go?

Answer 1

Yes, that is the right idea. You must do two things in order to be able to do that, though:

1. Put this at the beginning of the FInput class:

   Main m = new Main(this);
   

2. Then, put these lines somewhere in the Main class...

   FInput gui;
   
   public Main(FInput in) { gui = in; }
   

Now you can refer to any component in the FInput class from the Main class by doing something like this.

gui.someComponent ...

To set up listeners just write someComponent.addItemListener(m); or something of the sort.

Hope this helps!

---

@Yoav In response to your latest comment...

You don't have to separate the listening class from the GUI class; you can combine the two into one class...

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Main extends JFrame implements ActionListener {

    private JTextField txtSourceDirectory;
    private JTextField txtTargetDirectory;
    private JTextField txtDefectNumber;
    private JTextField txtSliceTokens;
    private JButton btnStart;

    public Main() {
        txtSourceDirectory = new JTextField(40); //change this to the amount of characters you need
        txtTargetDirectory = new JTextField(40);
        txtDefectNumber = new JTextField(40);
        txtSliceTokens = new JTextField(40);
        btnStart = new JButton("Start");
        add(txtSourceDirectory);
        add(txtTargetDirectory);
        add(txtDefectNumber);
        add(txtSliceTokens);
        add(btnStart);
        btnStart.addActionListener(this);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }

    public void actionPerformed(ActionEvent event) {
        //do stuff
    }

    static void startProcess(String[] ARGS) {
        //do stuff
    }

    public static void main(String[] args) {
        if (args.length == 0) {
            Main frame = new Main();
        } else {
            startProcess(args);
        }
    }
}

Answer 2

Also consider using JOptionPane, shown here, in your Main class. You can customize the appearance, including button text, as shown in How to Make Dialogs.