Swing displaying some JLabels but not others

Question

I am working on designing a simple GUI for a simple battlships clone. I had previously done something similar using painted squares but decided to try it with JPanels. Everything here works as I intended except the labels across top (1-14). It has displayed anywhere between 1 and 4, but never all 14, and it seems to be somewhat random how many show up. This code should run so that the problem is easy to see. The print statements are there simply to confirm that the values are correct. Thanks for the help!

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Foo {
    private JFrame frame;
    private JPanel[][] opponentBoard;
    private JLabel[] coordLabels;
    private final int FRAME_HEIGHT = 800;
    private final int FRAME_WIDTH = 600;
    private final int SQ_SIZE = 30;
    public Foo() {
        frame = new JFrame();
        frame.setBounds(new Rectangle(FRAME_WIDTH, FRAME_HEIGHT));
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBackground(Color.RED); // for debugging porpoises
        frame.setLayout(null);

        Container container = frame.getContentPane();
        container.setBackground(Color.BLACK);
        container.setVisible(true);

        opponentBoard = new JPanel[15][11];

        coordLabels = new JLabel[24];

        for (int i = 0; i < 15; i++) {
            for (int j = 0; j < 11; j++) {
                opponentBoard[i][j] = new JPanel();
                container.add(opponentBoard[i][j]);
                opponentBoard[i][j].setLocation(i + i * SQ_SIZE, j + j * SQ_SIZE);
                opponentBoard[i][j].setSize(new Dimension(SQ_SIZE, SQ_SIZE));
                opponentBoard[i][j].setVisible(true);
                if ((i == 0) ^ (j == 0)) {
                    opponentBoard[i][j].setBackground(Color.GRAY);
                    if (i == 0) {
                        coordLabels[j - 1] = new JLabel((char) (j + 64) + "");
                        opponentBoard[i][j].add(coordLabels[j - 1]);
                        System.out.println(j-1);
                    }
                    if (j == 0) {
                        coordLabels[i + 9] = new JLabel(i + "");
                        System.out.println(i + 9 + "    " + i + " " + coordLabels[i + 9].getText());
                        opponentBoard[i][j].add(coordLabels[i + 9]);
                    }
                    opponentBoard[i][j].repaint();
                } else {
                    opponentBoard[i][j].setBackground(Color.DARK_GRAY);
                }
            }
        }
        opponentBoard[0][0].setBackground(Color.BLACK);
    }

    public static void main(String[] args){
        new Foo();
    }
}

Answer 1

You need to call container.validate() after all of the panels have been added to the container. Additionally I would remove the call to repaint() within the inner for loop.

Alternatively, you could not set the frame to visible until after the panels have been added; this performs better.

A working version of your code can be found here:

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Foo {
    private JFrame frame;
    private JPanel[][] opponentBoard;
    private JLabel[] coordLabels;
    private final int FRAME_HEIGHT = 800;
    private final int FRAME_WIDTH = 600;
    private final int SQ_SIZE = 30;
    public Foo() {
        frame = new JFrame();
        frame.setBounds(new Rectangle(FRAME_WIDTH, FRAME_HEIGHT));
        //frame.setVisible(true); Build the UI before making it visible
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBackground(Color.RED); // for debugging porpoises
        frame.setLayout(null);

        Container container = frame.getContentPane();
        container.setBackground(Color.BLACK);
        container.setVisible(true);

        opponentBoard = new JPanel[15][11];

        coordLabels = new JLabel[24];

        for (int i = 0; i < 15; i++) {
            for (int j = 0; j < 11; j++) {
                opponentBoard[i][j] = new JPanel();
                container.add(opponentBoard[i][j]);
                opponentBoard[i][j].setLocation(i + i * SQ_SIZE, j + j * SQ_SIZE);
                opponentBoard[i][j].setSize(new Dimension(SQ_SIZE, SQ_SIZE));
                opponentBoard[i][j].setVisible(true);
                if ((i == 0) ^ (j == 0)) {
                    opponentBoard[i][j].setBackground(Color.GRAY);
                    if (i == 0) {
                        coordLabels[j - 1] = new JLabel((char) (j + 64) + "");
                        opponentBoard[i][j].add(coordLabels[j - 1]);
                        System.out.println(j-1);
                    }
                    if (j == 0) {
                        coordLabels[i + 9] = new JLabel(i + "");
                        System.out.println(i + 9 + "    " + i + " " + coordLabels[i + 9].getText());
                        opponentBoard[i][j].add(coordLabels[i + 9]);
                    }
                    //opponentBoard[i][j].repaint();
                } else {
                    opponentBoard[i][j].setBackground(Color.DARK_GRAY);
                }
            }
        }
        opponentBoard[0][0].setBackground(Color.BLACK);

        // If the UI is already visible call validate
        // I've chose to not make the frame visible until all of the children
        // have been added so the call to validate isn't really needed.
        //container.validate();
        frame.setVisible(true);
    }

    public static void main(String[] args){
        new Foo();
    }
}