尝试从另一个类更改JFrame的背景

Question

Im trying to get this program running for my Spanish teacher, and I want to change the background of the first JFrame. Here it is.

package com.jaketherey;

import java.awt.Color;
import java.awt.Image;
import java.awt.Toolkit;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class Inglés {

public static void main(String[] args) {

    SwingUtilities.invokeLater(new Runnable() {
        public void run() {

        JFrame frame = new switcherContent();

        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(950, 850);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setTitle("Inglés");
        frame.getContentPane().setBackground(Color.GREEN);
        }

    });

}

}

Here is the class I want to change it from, in the Action Listener for the button at the bottom.

package com.jaketherey;

import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingConstants;

public class switcherContent extends JFrame {

public switcherContent(){

    //Constrains

    GridBagConstraints constr = new GridBagConstraints();

    //Layout

    GridBagLayout gBL = new GridBagLayout();

    //Buttons

    final JButton buttonSwitch = new JButton("Switch");

    //JLabel

    final JLabel phrase1 = new JLabel("Inglés");
    phrase1.setHorizontalAlignment(SwingConstants.CENTER);
    phrase1.setForeground(Color.red);
    phrase1.setFont (phrase1.getFont ().deriveFont (150.0f));

    final JLabel phrase2 = new JLabel("Permitido");
    phrase2.setHorizontalAlignment(SwingConstants.CENTER);
    phrase2.setForeground(Color.red);
    phrase2.setFont (phrase2.getFont ().deriveFont (150.0f));

    //Set Layout//
    setLayout(gBL);

    //Constraints & Adding//

    constr.gridx=0;
    constr.gridy=1;
    constr.gridheight=1;
    constr.gridwidth=1;
    constr.weightx=1.0;
    constr.weighty=1.0;
    constr.weightx=1.0;
    constr.weighty=1.0;
    gBL.setConstraints(buttonSwitch, constr);
    add(buttonSwitch);

    constr.gridx=0;
    constr.gridy=0;
    constr.gridheight=1;
    constr.gridwidth=1;
    constr.weightx=1.0;
    constr.weighty=1.0;
    constr.weightx=1.0;
    constr.weighty=1.0;
    constr.fill=constr.BOTH;
    gBL.setConstraints(phrase1, constr);
    add(phrase1);

    constr.gridx=0;
    constr.gridy=2;
    constr.gridheight=1;
    constr.gridwidth=1;
    constr.weightx=1.0;
    constr.weighty=1.0;
    constr.weightx=1.0;
    constr.weighty=1.0;
    constr.fill=constr.BOTH;
    gBL.setConstraints(phrase2, constr);
    add(phrase2);

    buttonSwitch.addActionListener(new ActionListener() {

        @Override

        public void actionPerformed(ActionEvent e) {
            String check = phrase2.getText();

            if(check.equals("Permitido")){
            phrase2.setText("Prohibido");

            phrase1.setForeground(Color.green);
            phrase2.setForeground(Color.green);

            //Set Background to RED

            }
            else if(check.equals("Prohibido")){
            phrase2.setText("Permitido");

            phrase1.setForeground(Color.red);
            phrase2.setForeground(Color.red);

            //Set Background to GREEN

            };

        }

    });

}

}

Thanks for any and all help!

Answer 1

Sorry, I misread your question. All you have to do is call getContentPane() from within your ActionListener

        public void actionPerformed(ActionEvent e) {
            String check = phrase2.getText();

            if (check.equals("Permitido")) {
                phrase2.setText("Prohibido");

                phrase1.setForeground(Color.green);
                phrase2.setForeground(Color.green);

                getContentPane().setBackground(Color.RED);// !!

Answer 2

I found a way to do what you're asking. I added the following class variable in switcherContent :

Container contentPane;

In the constructor, I added the following line:

contentPane = this.getContentPane();

Then in your action listener, I added the following line:

contentPane.setBackground(Color.red);

Answer 3

simply add this.getContentPane().setBackground(Color.GREEN) inside button action listener;

'this' refers to your Jframe:switcherContent itself inside its class. You can call this method to change background color from any place inside your switcherContent class. Not only in the actionListener() method.