Java: Waiting for input and transferring information between JFrames

Question

I've read a couple of similar questions on here but none have addressed, specifically, the problem I've been having. As an idea this seems like it should be remarkably simple, in practice I have found it to be utterly impossible.

What I want to do is have a form, let's call it form A, create another form, let's call it form B, and wait for input on form B before continuing. So, you'd have your main window, press a button and another window comes up prompting you for some value, the main window then waits for the input to be entered and processed and for the input window to close, then it uses that entered value to do something else.

I know this can be accomplished because JOptionPane does exactly that, but I'm going to be using mostly numerical values and I don't want to go through the extra step of converting it. Also, it just seems like a good idea to know how to do something like this since it sounds so basic yet is proving quite difficult.

Edit: It was suggested that this may be similar to some sort of "modal" something, but I read through that and it didn't even seem at all related to what I'm asking.

Edit 2: There is a response with code that does exactly what I need, but whenever I attempt to modify it in almost any way, it ceases to function, this is what my class looks like, or at least this is the part that I'm testing, the rest of it is mostly empty methods that aren't being called yet:

public Gather(GraphWindow parent, int type)
{
    super(parent);
    parentWindow=parent;
    this.info=new String[0];
    constructType(type);
}
private void constructType(int type)
{
    msgLab=new JLabel();
    if(type==TEXT)
    {
        goText();
    }       
}

private void goText()
{
    final JTextField jtf = new JTextField();
    JButton done = new JButton("Done");

    if(info.length==0)
    {
        setTitle(TEXT_T);
        msgLab.setText(TEXT_M);
    }
    else
    {
        if(info[0].length()==0)
        {
            setTitle(TEXT_T);
            msgLab.setText(info[1]);
        }
        else if(info[1].length()==0)
        {
            setTitle(info[1]);
            msgLab.setText(TEXT_M);
        }
        else
        {
            setTitle(info[0]);
            msgLab.setText(info[1]);
        }
    }
    done.addActionListener(new ActionListener()
    {
        @Override public void actionPerformed(ActionEvent e) 
        {
            parentWindow.setText(jtf.getText());
            Gather.this.dispose();
        }

    });
    this.setLayout(new GridLayout(3,1));
    this.setSize(250, 150);

    this.add(msgLab);
    this.add(jtf);
    this.add(done);

    this.setVisible(true);
}

Answer 1

It's JDialog you need!

When you create an instance of JDialog, and make it visible, the execution of the MainWindow thread will be paused there til you close the dialog. See and run the sample code below:

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class Test {
    public static void main(String[] args) {
        MainWindow mainWindow = new MainWindow();
        mainWindow.setVisible(true);
    }
}

class MainWindow extends JFrame{

    private static final long serialVersionUID = 679207429168581441L;
    //
    private static final int FRAME_WIDTH = 800;
    private static final int FRAME_HEIGHT = 600;
    private String nameFromModal;
    //
    private ModalDialog dialog;

    public MainWindow() {
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        setBounds(dim.width/2-FRAME_WIDTH/2, dim.height/2-FRAME_HEIGHT/2, FRAME_WIDTH, FRAME_HEIGHT);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //
        JButton clickMe = new JButton("Open Modal Dialog!");
        clickMe.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                dialog = new ModalDialog(MainWindow.this);
                dialog.setVisible(true);
                JOptionPane.showMessageDialog(MainWindow.this, "Name From Modal Dialog: "+MainWindow.this.getNameFromModal());
            }
        });
        //
        JPanel p = new JPanel(new FlowLayout());
        p.add(clickMe);
        MainWindow.this.add(p, BorderLayout.NORTH);
    }

    public void setValuesOfModalDialog(String name){
        this.nameFromModal = name;
    }

    public String getNameFromModal() {
        return nameFromModal;
    }
}

class ModalDialog extends JDialog{
    private static final int FRAME_WIDTH = 300;
    private static final int FRAME_HEIGHT = 300;
    private MainWindow parentWindow;
    private JTextField nameField;

    public ModalDialog(MainWindow parentWindow) {
        super(parentWindow);
        this.parentWindow = parentWindow;
        //
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        setBounds(dim.width/2-FRAME_WIDTH/2, dim.height/2-FRAME_HEIGHT/2, FRAME_WIDTH, FRAME_HEIGHT);
        setModal(true);
        //
        setLayout(new FlowLayout());
        //
        JLabel nameLabel = new JLabel("Name: ");
        add(nameLabel);
        nameField = new JTextField();
        nameField.setPreferredSize(new Dimension(100, 25));
        add(nameField);
        //
        JButton submit = new JButton("Submit!");
        submit.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                parentWindow.setValuesOfModalDialog(nameField.getText());
                ModalDialog.this.dispose();
            }
        });
        //
        add(submit);
    }
}

Good Luck.