如何使用 JComboBox 更改背景颜色

Question

So, basically, the main idea for this project is that I wanted to change the background color by using the jcombobox method. and the background will change with the option chosen when the button(proceed) is clicked. The background color chosen will then be implemented to the next page when the button is clicked. The background that im talking about is the background for all the JPanel(including the other page's JPanel). If (getsource() == f2.btenter2), it will go to f2(2nd file) btenter2(button)'s when clicked.

public class MainPage extends JFrame implements ActionListener {

    JLabel lbTitle, lbWelcome, lbSelect;
    JComboBox cbColor;
    public Color color[] = {RED, GREEN, BLUE, YELLOW, GRAY};
    public String clr[] ={"RED","GREEN","BLUE","YELLOW","GRAY"};
    public int index;
    JButton btProceed;

    public static void main(String[] args) {
        MainPage f1 = new MainPage();
        f1.setSize(800, 500);
        f1.setTitle("Java Assignment");
        f1.setVisible(true);
        f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public MainPage() {
        lbTitle = new JLabel("Rock-Paper-Scissors-Lizard-Spock");
        lbWelcome = new JLabel("Welcome!");
        lbSelect = new JLabel("Please select the background color before you proceed:");

        lbWelcome.setFont(new Font("Courier", Font.PLAIN, 18));lbSelect.setFont(new Font("Courier", Font.PLAIN, 15)); cbColor = new JComboBox(color);btProceed = new JButton("Proceed");

        //1st panel on the north side to set the title
        JPanel p1 = new JPanel();
        p1.add(lbTitle);
        p1.setBackground(new Color(255, 106, 0));

        //2nd panel on the center position

        JPanel p2 = new JPanel();
        p2.setLayout(new GridLayout(14, 1));JPanel a1 = new JPanel();
        JPanel a2 = new JPanel();
        JPanel a3 = new JPanel();
        JPanel e1 = new JPanel();
        a1.add(lbWelcome);
        a2.add(lbSelect);
        a3.add(cbColor);
        p2.add(e1);
        p2.add(a1);
        p2.add(a2);
        p2.add(a3);

        JPanel p3 = new JPanel();
        p3.add(btProceed);

        setLayout(new BorderLayout());
        add(p1, BorderLayout.NORTH);
        add(p2, BorderLayout.CENTER);
        add(p3, BorderLayout.SOUTH);

        btProceed.addActionListener(this);
        cbColor.addActionListener(this);
        color().addActionListener(this);
    }

      @Override
    public void actionPerformed(ActionEvent e) {
        index = cbColor.getSelectedIndex();  //to get the index

        if (e.getSource()==cbColor) {
            index = cbColor.getSelectedIndex();
            p2.setBackground(color[index]);
            a1.setBackground(color[index]);
            a2.setBackground(color[index]);
            a3.setBackground(color[index]);
            e1.setBackground(color[index]);
            e1.setBackground(color[index]);
            p3.setBackground(color[index]);

        }

        Team f2 = new Team();
        GamePage f3 = new GamePage();
        GamePage2 f4 = new GamePage2();
        Result f5 = new Result();

        if (e.getSource()==btProceed) {
            this.setVisible(false);
            f2.setVisible(true);
            f2.setSize(800, 500);
            f2.p2.setBackground(color[index]);
            f2.p3.setBackground(color[index]);
            f2.p4.setBackground(color[index]);
            // btenter2 is located in the second file under the same package
if (e.getSource()==f2.btenter2){
            this.setVisible(false);
            f3.setVisible(true);
            f3.setSize(800,500);
            f3.p2.setBackground(color[index]);
            f3.p3.setBackground(color[index]);
            f3.p4.setBackground(color[index]);
            f3.p5.setBackground(color[index]);}
if (e.getSource()==f3.btNext){this.setVisible(false);
            f4.setVisible(true);
            f4.setSize(800,500);
            f4.p2.setBackground(color[index]);
            f4.p3.setBackground(color[index]);
            f4.p4.setBackground(color[index]);
            f4.p5.setBackground(color[index]); }
        if (e.getSource() == f4.btResult)
        {
            this.setVisible(false);
            f5.setVisible(true);
            f5.setSize(800,500);
            f5.p2.setBackground(color[index]);
            f5.p3.setBackground(color[index]);
            f5.p4.setBackground(color[index]);
            f5.p5.setBackground(color[index]);}}

Answer 1

The background assigned by the renderer is overriden by the selection background color of the JList that is used in the popup for the combo box.

JComboBox cbColor = new JComboBox(...);
Object child = cbColor.getAccessibleContext().getAccessibleChild(0);
BasicComboPopup popup = (BasicComboPopup)child;
JList list = popup.getList();
list.setSelectionBackground(Color.RED);

Credits to this answer

Answer 2

Introduction

I started working on this before I saw the OP's latest edit.

Here's the GUI I came up with.

Here's the GUI when you pick red.

Here's the GUI when you pick yellow.

The red GUI uses white text for better contrast. Some background colors work better with black text.

I didn't create an ActionListener for the button. I wanted to demonstrate two things.

1. A JComboBox can hold any class, not just the String class.

2. An ActionListener that changes the background and foreground color of a JPanel .

Explanation

When creating a Swing GUI, or almost any Java application, I use the model / view / controller pattern. This pattern allows me to focus on one part of the application at a time and helps me separate my concerns.

So, the first thing I did was create a ColorPair class. The ColorPair class holds a background color, a foreground color, and a String name of the background color. When passing class instances to a JComboBox , the class toString method is used to display the combo box options.

Next, I created a Pallete class. The Pallete class holds a List of ColorPair instances.

Once I created the model, I started on the view. I reorganized the OP's view code so it was easier to read. Generally, I keep all the methods for each Swing component together, and create the Swing components in the order they appear on the JPanel .

I separated the JFrame and JPanel creation into separate methods.

After I was satisfied with the view, I wrote the ActionListener for the JComboBox . I didn't need to pass all the components to the ActionListener class since I could get the children components of the JPanel .

The propagateColors method of the ActionListener is recursive. This is one of those rare instances where a recursive method makes sense in the real world since you can have JPanels as children of a JPanel .

Here's the complete runnable code. I hope it's helpful.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class BackgroundColorGUI implements Runnable {
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new BackgroundColorGUI());
    }
    
    private ColorPair colorPair;
    
    private JPanel mainPanel;
    private JPanel buttonPanel;
    
    private Pallete pallete;
    
    public BackgroundColorGUI() {
        this.pallete = new Pallete();
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Java Assignment");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(createTitlePanel(), BorderLayout.BEFORE_FIRST_LINE);
        this.mainPanel = createMainPanel();
        frame.add(mainPanel, BorderLayout.CENTER);
        this.buttonPanel = createButtonPanel();
        frame.add(buttonPanel, BorderLayout.AFTER_LAST_LINE);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }    
     
    private JPanel createTitlePanel() {
        //1st panel on the north side to set the title
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        JLabel lbTitle = new JLabel("Rock-Paper-Scissors-Lizard-Spock");
        lbTitle.setFont(panel.getFont().deriveFont(Font.BOLD, 24f));
        panel.add(lbTitle);
        panel.setBackground(new Color(255, 106, 0));
        return panel;
    }
       
    private JPanel createMainPanel() {
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        panel.setLayout(new GridLayout(0, 1, 5, 5));
        
        JPanel e1 = new JPanel();
        JLabel dummy = new JLabel(" ");
        e1.add(dummy);
        panel.add(e1);

        JPanel a1 = new JPanel();
        JLabel lbWelcome = new JLabel("Welcome!");
        lbWelcome.setFont(new Font("Courier", Font.PLAIN, 18));
        a1.add(lbWelcome);
        panel.add(a1);
        
        JPanel a2 = new JPanel();
        JLabel lbSelect = new JLabel("Please select the background "
                + "color before you proceed:");
        lbSelect.setFont(new Font("Courier", Font.PLAIN, 15));
        a2.add(lbSelect);
        panel.add(a2);
 
        JPanel a3 = new JPanel();
        JComboBox<ColorPair> cbColor = new JComboBox<ColorPair>();
        List<ColorPair> colors = pallete.getColors();
        for (ColorPair colorPair : colors) {
            cbColor.addItem(colorPair);
        }
        cbColor.addActionListener(new ColorListener(this));
        a3.add(cbColor);
        panel.add(a3);
        
        return panel;
    }
        
    private JPanel createButtonPanel() {
         JPanel panel = new JPanel();
         JButton btProceed = new JButton("Proceed");
         panel.add(btProceed);
         
         return panel;
    }
    
    public JPanel getMainPanel() {
        return mainPanel;
    }

    public JPanel getButtonPanel() {
        return buttonPanel;
    }

    public class ColorListener implements ActionListener {
        
        private BackgroundColorGUI frame;

        public ColorListener(BackgroundColorGUI frame) {
            this.frame = frame;
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            JComboBox<?> comboBox = (JComboBox<?>) event.getSource();
            colorPair = (ColorPair) comboBox.getSelectedItem();
            propagateColors(frame.getMainPanel(), colorPair);
            propagateColors(frame.getButtonPanel(), colorPair);
        }

        private void propagateColors(JPanel panel, ColorPair colorPair) {
            panel.setBackground(colorPair.getBackgroundColor());
            panel.setForeground(colorPair.getForegroundColor());
            Component[] components = panel.getComponents();
            for (Component component : components) {
                if (component instanceof JPanel) {
                    JPanel childPanel = (JPanel) component;
                    propagateColors(childPanel, colorPair);
                }
                component.setBackground(colorPair.getBackgroundColor());
                component.setForeground(colorPair.getForegroundColor());
            }
        }
        
    }
    
    public class Pallete {
        
        private final List<ColorPair> colors;
        
        public Pallete() {
            this.colors = generatePalleteFactory();
        }
        
        private List<ColorPair> generatePalleteFactory() {
            List<ColorPair> colors = new ArrayList<>();
            colors.add(new ColorPair("Light Grey", 
                    new Color(238, 239, 238), Color.BLACK));
            colors.add(new ColorPair("Red", Color.RED, Color.WHITE));
            colors.add(new ColorPair("Green", Color.GREEN, Color.BLACK));
            colors.add(new ColorPair("Blue", Color.BLUE, Color.WHITE));
            colors.add(new ColorPair("Yellow", Color.YELLOW, Color.BLACK));
            colors.add(new ColorPair("Grey", 
                    new Color(153, 153, 153), Color.WHITE));
            
            return colors;
        }

        public List<ColorPair> getColors() {
            return colors;
        }
        
    }
    
    public class ColorPair {
        
        private final Color backgroundColor;
        private final Color foregroundColor;
        
        private final String backgroundColorName;
        
        public ColorPair(String backgroundColorName, 
                Color backgroundColor, Color foregroundColor) {
            this.backgroundColorName = backgroundColorName;
            this.backgroundColor = backgroundColor;
            this.foregroundColor = foregroundColor;
        }

        public Color getBackgroundColor() {
            return backgroundColor;
        }

        public Color getForegroundColor() {
            return foregroundColor;
        }

        public String getBackgroundColorName() {
            return backgroundColorName;
        }
        
        @Override
        public String toString() {
            return getBackgroundColorName();
        }

    }
       
}