Buttons and Icons Within a Label - SquareIcon

问题

I am trying to create a program with three buttons and a label with a CompositeIcon that at the start is empty. When you click one of the buttons there will be added a square at the screen (with the described color), when another button is pressed there is gonna be added another square and so on. That means, when i press a button five times, there will be created five squres at the given colors. If any one will read my code i will be thankful.

/*
    This program creates a window with three buttons - red, green and blue - and a label with an icon.
    This icon is a CompositeIcon that at the start is empty. When we press one of the three buttons, there will
    be added a square at the specified color.
*/

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

public class ResponsiveFrame extends JFrame {
    static SquareIcon icon;
    static int number; // this
    static Color awtColor; // this

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        final JLabel label = new JLabel();

        JButton redButton = new JButton("RED");
        JButton greenButton = new JButton("GREEN");
        JButton blueButton = new JButton("BLUE");

        /*
            this is the part that i am not sure about!
            not sure about the parameters.
        */      
        icon = new SquareIcon(number, awtColor);

        redButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                icon.addIcon(new SquareIcon(20, Color.RED));
                label.setIcon(icon);
                frame.repaint();
                frame.pack();
            }
        });

        greenButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                icon.addIcon(new SquareIcon(20, Color.GREEN));
                label.setIcon(icon);
                frame.repaint();
                frame.pack();
            }
        });

        blueButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                icon.addIcon(new SquareIcon(20, Color.BLUE));
                label.setIcon(icon);
                frame.repaint();
                frame.pack();
            }
        });

        frame.setLayout(new FlowLayout());

        frame.add(redButton);
        frame.add(greenButton);
        frame.add(blueButton);
        frame.add(label);

        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

And here is the part with the SquareIcon.

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

public class SquareIcon implements Icon {
        private ArrayList<Icon> icons;
        private int width;
        private int height;

    public SquareIcon(int number, Color awtColor) {
        icons = new ArrayList<Icon>();
        number = number;
        awtColor = awtColor;
    }

    public void addIcon(Icon icon) {
        icons.add(icon);
        width += icon.getIconWidth();
        int iconHeight = icon.getIconHeight();
        if (height < iconHeight)
            height = iconHeight;
    }

    public int getIconHeight() {
        return height;
    }

    public int getIconWidth() {
        return width;
    }

    public void paintIcon(Component c, Graphics g, int x, int y) {
        for (Icon icon : icons) {
            icon.paintIcon(c, g, x, y);
            x += icon.getIconWidth();
        }
    }
} 

The program does compile, but when i press the buttons, nothing happens!

回答1:

You create a JLabel but add it to nothing.

I suggest that you create a new JLabel each time you need one, and be sure to add it to the GUI after creating it. You will want to add it to a JPanel that is displayed in the JFrame/GUI, and will want to call revalidate() and repaint() on the JPanel after adding the label so that the panel knows to re-layout all its components, including the new one, and to re-draw itself and its children.

来源：https://stackoverflow.com/questions/19881700/buttons-and-icons-within-a-label-squareicon