如何让JComponents背景透明？

Question

There are two things that I am trying to figure out. First thing, I want to figure out how to make a Jcomponent background transparent. When placing a JPanel into another JPanel that has a color set as the background, the JPanel that is set within the other JPanel has a white background that I can't seem to get rid of. I tried using the firstpanel.setOpache function and repaint but it doesn't do anything.

And second, I noticed that putting a JPanel within another JPanel thats within another JPanel compresses it size. The images below will show what I am trying to describe. I want to know what to do to avoid compressing the JPanel size and still able to put it within two levels of other JPanels . The code below is what I am practicing with.

import javax.swing.*;
import java.awt.*;


public class LearningFrame extends JFrame {

private JLabel userLabel;

private LearningFrame(){
    JPanel backGroundPanel = new JPanel();
    JPanel mainPanel = new JPanel();
    JPanel firstPanel = new JPanel();
    JPanel secondPanel = new JPanel();

    userLabel = new JLabel("User");
    userLabel.setFont(new Font("Arial",1 ,24));

    backGroundPanel.setBackground(new Color(247,211,53));
   // backGroundPanel.setLayout(new BoxLayout(backGroundPanel,BoxLayout.Y_AXIS));

    setContentPane(backGroundPanel);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(1200,800);
    setLocationRelativeTo(null);

    //backGroundPanel.setLayout(null);
    mainPanel.setLayout(new GridLayout(1,2));

    firstPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
    secondPanel.setLayout(new BoxLayout(secondPanel,BoxLayout.Y_AXIS));

   // firstPanel.setBackground(new Color(211,43,185));
    secondPanel.setBackground(new Color(34,233,44));


    JButton button = new JButton("Click");
    JButton button2 = new JButton("Click");
    JButton button3 = new JButton("Click");
    JButton button4 = new JButton("Click");


    firstPanel.add(button);
    firstPanel.add(button2);
    firstPanel.add(userLabel);
    secondPanel.add(button3);
    secondPanel.add(button4);

    mainPanel.add(firstPanel);
    mainPanel.add(secondPanel);

    backGroundPanel.add(mainPanel);


    setVisible(true);

}

public JPanel logPanel() {

    JPanel logInPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));

    JTextField userTextField = new JTextField(14);
    JTextField passTextField = new JTextField(14);


    userLabel = new JLabel("Username: ");
    JLabel passLabel = new JLabel("Password: ");
    passLabel.setFont(new Font("Arial", Font.BOLD, 24));
    userLabel.setFont(new Font("Arial", Font.BOLD, 24));
    logInPanel.add(userLabel);
    logInPanel.add(userTextField);
    logInPanel.add(passLabel);
    logInPanel.add(passTextField);

    logInPanel.setOpaque(true);
    logInPanel.repaint();

    return logInPanel;
}

public static void main(String[] args){

    LearningFrame x = new LearningFrame();
}

}

Answer 1

Just use

firstPanel.setOpaque(false);

This is will make the background of the component invisible, but you will still be able to see any components that are positioned inside it.