单击我的JButton，但在使用ActionListener单击JFrame中的另一个按钮之前，没有得到显示的操作？

Question

I've just started my course Programming 2, and its quite a jump from the introducting course we had before. I am to make a program that has three buttons "red", "blue", "green" and when I click "red" a red square is to appear. When I click another button, there are more squares, and the color of the square depends on the button I press. My problem is, that when I press "red", I have to press another button before the red square appears. So in reality it will seem like the buttons I press are connected to a wrong action. It's really hard to describe, but it's as is there is a "delay of one action".. Can you provide a novice like me any assistance? I have tree classes in total: SquareIcon, CompositeIcon, and a tester with the frame. It should only be necessary to look at the last class I pasted here.

import javax.swing.*;
import java.awt.*;
import java.awt.geom.Rectangle2D;

/**
 * Made by   Rasmus
 * Version   13-11-2014.
 */
public class SquareIcon implements Icon{
    private int size;
    private Color color;

public SquareIcon(int size, Color color) {
    this.size = size;
    this.color = color;
}

public void paintIcon(Component c, Graphics g, int x, int y) {
    Graphics2D g2 = (Graphics2D) g;
    Rectangle2D rec = new Rectangle2D.Double(x, y, size, size);
    g2.fill(rec);
    g2.setColor(color);
}

public int getIconWidth() {
    return size;
}

public int getIconHeight() {
    return size;
}

}

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

/**
 * Made by   Rasmus
 * Version   13-11-2014.
 */
public class CompositeIcon implements Icon {
    private ArrayList<Icon> icons;

public CompositeIcon() {
    icons = new ArrayList<Icon>();
}

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

public int getIconWidth() {
    int width = 0;
    for (Icon i : icons) {
        width += i.getIconWidth();
    }
    return width;
}

public int getIconHeight() {
    int height = 0;
    for (Icon i : icons) {
        if (i.getIconHeight() > height) {
            height = i.getIconHeight();
        }
    }
    return height;
}

public void addIcon(Icon i) {
    icons.add(i);
}
}

And the last:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/**
 * Made by   Rasmus
 * Version   13-11-2014.
 */
public class FrameTest implements ActionListener {
    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setLayout(new FlowLayout());

    JButton redButton = new JButton("Rød");
    JButton greenButton = new JButton("Grøn");
    JButton blueButton = new JButton("Blå");
    frame.add(redButton);
    frame.add(greenButton);
    frame.add(blueButton);

    final CompositeIcon ci = new CompositeIcon();
    final SquareIcon red = new SquareIcon(50, Color.RED);
    final SquareIcon green = new SquareIcon(50, Color.GREEN);
    final SquareIcon blue = new SquareIcon(50, Color.BLUE);
    JLabel squareLabel = new JLabel(ci);
    frame.add(squareLabel);

    redButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            ci.addIcon(red);
            frame.pack();
            frame.repaint();
        }
    });
    greenButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            ci.addIcon(green);
            frame.pack();
            frame.repaint();
        }
    });
    blueButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            ci.addIcon(blue);
            frame.pack();
            frame.repaint();
        }
    });
    frame.setSize(250, 75);
    frame.setVisible(true);
}


public void actionPerformed(ActionEvent e) {

}
}

Answer 1

Two things I would suggest:

First, I would advise that you delete the last action performed block. That block may be causing the error.

Second, if that isn't causing the error, try inserting breakpoints or print statements to see when it enter the action performed loop, then you can work from there.