Let the user place Buttons in Java

Question

I want to code a little tool that simulates a deterministic, finite automaton (like JFLAP) for myself.

My JFrame is just blank. How can I let the user place buttons on left click? And how do I assign the right values to that button (like which function to call when pressed).

I know I can place a button with

JButton button = new JButton("Press me");
frame.add(button);

But I don't know how I could dynamically code that.

Any help is welcome. Also if you think it's stupid to solve my problem with buttons, I'd like to hear suggestions for improvement.

How many buttons do you expect a user to place? What types of functions are associated with the buttons? What types of text or images would be placed on the buttons? — Gilbert Le Blanc, Dec 05 '20 at 10:06
It should be possible to place an infinite amount of buttons. Functions that are needed on a button is linkage to another button. I dont need images on my buttons. Text is irrelevant. Could be 1,2,3,4,5,... — Samuel, Dec 05 '20 at 11:09
@Samuel: there's nothing "magical" about that code: you can do it when you create your component or inside your mouse click handler (as the answer demonstrates). In fact, the word "dynamically" often means nothing in these kinds of requirements: there is no difference between "the normal way" and this way. — Joachim Sauer, Dec 05 '20 at 11:25

score 3 · Accepted Answer · answered Dec 05 '20 at 11:20

The following code will add a JButton to a "blank" JFrame every time the mouse is clicked inside the JFrame. The JButton will be placed where the mouse click occurred. The JButton text will be a number. Each JButton will display a different number.

import java.awt.Dimension;
import java.awt.EventQueue;

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;

public class AdButton extends MouseAdapter implements Runnable {
    private int  counter;
    private JFrame  frame;
    private JPanel  contentPane;

    public void mouseClicked(MouseEvent event) {
        int x = event.getX();
        int y = event.getY();
        JButton button = new JButton(String.valueOf(++counter));
        Dimension dim = button.getPreferredSize();
        button.setBounds(x, y, dim.width, dim.height);
        contentPane.add(button);
        contentPane.revalidate();
        contentPane.repaint();
    }

    @Override
    public void run() {
        showGui();
    }

    private void showGui() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        contentPane = (JPanel) frame.getContentPane();
        contentPane.setLayout(null);
        contentPane.addMouseListener(this);
        frame.setSize(400, 450);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new AdButton());
    }
}

Let the user place Buttons in Java

1 Answers1