Add jbuttons to a GUI application

Question

1.00/5 (1 vote)

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I'm having an issue where my buttons don't show up at all.

What I have tried:

package journal.pkg7a;
/**
*
* @author stephenwessels
*/
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Journal7A extends JFrame implements ActionListener
{
Container content = new Container();
JButton btnGreen = new JButton("Green");
JButton btnBlue = new JButton("Blue");
JButton btnRed = new JButton("Red");

public Journal7A()
{
content.setLayout(new FlowLayout());
content.add(btnBlue, BorderLayout.SOUTH);
content.add(btnGreen, BorderLayout.SOUTH);
content.add(btnRed, BorderLayout.SOUTH);

this.setVisible(true);
this.setSize(300,300);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("First GUI App");

btnBlue.addActionListener(this);
btnGreen.addActionListener(this);
btnRed.addActionListener(this);
}
@Override
public void actionPerformed(ActionEvent e)
{
JButton btn = (JButton) e.getSource();
if(btn == btnBlue)
content.setBackground(Color.BLUE);
else
content.setBackground(Color.GREEN);
content.setBackground(Color.RED);
}

/**
* @param args the command line arguments
*/
public static void main(String[] args)
{
Journal7A gui = new Journal7A();
}

}

Posted 26-Feb-18 11:21am

Barais_19

Updated 26-Feb-18 17:49pm

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wseng · Answer 1 · 2018-02-26T17:49:00

There is no need for your Journal7A class to subclass JFrame. Instead, you can extends your class to JPanel, and create frame object in your main.

public class Journal7A extends JPanel implements ActionListener {

    JPanel content = new JPanel();
    JButton btnGreen = new JButton("Green");
    JButton btnBlue = new JButton("Blue");
    JButton btnRed = new JButton("Red");

    public Journal7A() {
        content.setLayout(new FlowLayout());
        content.add(btnBlue, BorderLayout.SOUTH);
        content.add(btnGreen, BorderLayout.SOUTH);
        content.add(btnRed, BorderLayout.SOUTH);
        btnBlue.addActionListener(this);
        btnGreen.addActionListener(this);
        btnRed.addActionListener(this);
        add(content);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        JButton btn = (JButton) e.getSource();
        if (btn == btnBlue) {
            content.setBackground(Color.BLUE);
        } else {
            content.setBackground(Color.GREEN);
        }
        content.setBackground(Color.RED);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Journal7A gui = new Journal7A();
        Frame frame = new JFrame();
        frame.add(gui);
        frame.pack();
        frame.setSize(300, 300);
        frame.setTitle("First GUI App");
        frame.setVisible(true);
    }

}

If you like to use your own code , add

add(content);

after line

btnRed.addActionListener(this);