Java Frame duplicated without applying change

Question

I have 2 frames from different class, one is the main frame containing just a jbutton and jtextfield, and the other one contains a the setting to change the background color of the first frame, so i've a problem because when i clicked the the button OK button the color changed but it created a new main frame with new change instead of applying the change in the active main frame.

here is the main frame code

package com.srccodes.example;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Cheb extends JFrame implements ActionListener {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Cheb cheb = new Cheb();

}

JTextArea about = new JTextArea(3,30);

JButton callB = new JButton("Settings");
Cheb(){
    setLayout(new FlowLayout(FlowLayout.CENTER, 20,25));
    setSize(400,400);
    setTitle("Check Box");
    

    add(new Label("About you"));
    JScrollPane aboutScroll= new JScrollPane(about);
    add(aboutScroll);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    add(callB);
    setVisible(true);
    callB.addActionListener(this);
    
    
}


public void actionPerformed(ActionEvent e)
{
    
     
    //Countinent selection with Check Box
     if(e.getSource() == callB)
     {
         CollorClass cl =new CollorClass();
     }
    
    
}

}

here is the code to change the color of the main frame

package com.srccodes.example;

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

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class CollorClass extends JFrame implements ActionListener {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    CollorClass cc = new CollorClass();

}
 JLabel bg = new JLabel("Background Color"); 
 String colorName[] = {"None","RED","GREEN","BLACK","BLUE","YELLOW","WHITE"};
 JComboBox bgColor = new JComboBox(colorName);
 JButton ok = new JButton("OK");
CollorClass()
{
    setLayout(new FlowLayout(FlowLayout.CENTER, 20,25));
    setSize(400,400);
    setTitle("Check Box");
    add(bg);
    add(bgColor);
    add(ok);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
    ok.addActionListener(this);
    
}
@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    
    if(e.getSource() == ok)
    {
        Cheb cheb = new Cheb();
        String SelectedValue = bgColor.getSelectedItem().toString();
        switch (SelectedValue){
            case "RED" :
                cheb.about.setBackground(Color.red);
                System.out.print(SelectedValue);
                break;
            case "YELLOW" :
                cheb.about.setBackground(Color.yellow);
                System.out.print(SelectedValue);
                break;
            case "BLUE" :
                cheb.about.setBackground(Color.blue);
                System.out.print(SelectedValue);
                break;
        
            case "GREEN" :
                cheb.about.setBackground(Color.green);
                System.out.print(SelectedValue);
                break;
            case "BLACK" :
                cheb.about.setBackground(Color.black);
                System.out.print(SelectedValue);
                break;
            case "WHITE" :
                cheb.about.setBackground(Color.white);
                System.out.print(SelectedValue);
                break;
        
        
            default:
                
                System.out.print(SelectedValue);
        }
    }
    
}

}

Troley · Accepted Answer · 2022-04-28 17:07:12Z

1

The issue here is, you are invoking a new instance of the Cheb class when you select a color. So you are not changing the color of the initial window, but of the new window.

It is specifically this line in the CollorClass's actionPerformed method that is causing the issue:

Cheb cheb = new Cheb();

What you instead might want to do is inject the Cheb class as a dependency into the CollorClass. This way, you can invoke methods and get to properties of the initial Cheb class.

One way of doing that could be as follows (the ellipsis '...' dots are used to hide unnecessary code):

CollorClass:

public class CollorClass extends JFrame implements ActionListener {

    private final Cheb cheb;

    ...

    CollorClass(Cheb cheb) // important addition
    {
        this.cheb = cheb; // important addition

        setLayout(new FlowLayout(FlowLayout.CENTER, 20,25));
        setSize(400,400);
        setTitle("Check Box");
        add(bg);
        add(bgColor);
        add(ok);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        ok.addActionListener(this);

    }

    ...
    
    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == ok)
        {
            // No instantiation of new Cheb here anymore.
            // Using the dependency instead.

            String SelectedValue = bgColor.getSelectedItem().toString();
            switch (SelectedValue){
                case "RED" :
                    cheb.about.setBackground(Color.red);
                    System.out.print(SelectedValue);
                    break;
                case "YELLOW" :

                ...
        }

Cheb:

public class Cheb extends JFrame implements ActionListener {

    ...

    public void actionPerformed(ActionEvent e)
    {


        //Countinent selection with Check Box
        if(e.getSource() == callB)
        {
            CollorClass cl = new CollorClass(this); // Pass this Cheb instance as argument
        }


    }

Hope that it's clear. It still could use improvements (e.g. closing one window will close both windows), but that might be a next challenge to figure out!

answered Apr 28, 2022 at 17:07

Troley

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3 Comments

Andrew Thompson Over a year ago

Good answer. :) "It still could use improvements (e.g. closing one window will close both windows), but that might be a next challenge to figure out!" Use a modal JDialog or a JOptionPane instead of one of the frames would be how I'd approach it.

jonathan pascal Over a year ago

I find a way(closing one window will close both windows), by changing the from setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) to setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE) in CollorClass;

Troley Over a year ago

Thank you! Glad it helped OP :) those are indeed both great options to tackle the closing-every-window issue.

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