Search code examples
javatextjframecenterjlabel

JLabel, FlowLayout. Centering the JLabel?

So I'm creating this "Lottery" and I've tried some various things to Center the text my JLabel but it just goes from the right on the middle of the screen. Here is my code and a picture of what I mean.

This is my first time posting on this form so feel free to correct me if I missed something.

The Lottery

The code:

import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.HeadlessException;
import javax.swing.JLabel;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
/**
 * Author Samy
 */
public class Game extends JFrame {
    public Game() throws HeadlessException{

        int width = 720;
        int height = width/16*9;

        setSize(width,height);
        setTitle("The Lottery - V1.0");
        setResizable(false);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        setLayout(new FlowLayout());

        String winnings;
        double lotteryChance = Math.random()*100;

        if (lotteryChance > 50) {
            winnings = ("You've won $100!");
        } else if (lotteryChance < 50 && lotteryChance > 20) {
            winnings = ("You've won $500!");
        } else if (lotteryChance < 20 && lotteryChance > 5) {
            winnings = ("You've won $2,000!");
        } else if (lotteryChance < 5 && lotteryChance > 1) {
            winnings = ("You've won $5,000!");
        } else if (lotteryChance < 1 && lotteryChance > 0.1) {
            winnings = ("You've won $25,000!");
        } else if (lotteryChance < 0.1 && lotteryChance > 0.01) {
            winnings = ("You've won $50,000!");
        } else if (lotteryChance < 0.01 && lotteryChance > 0.001) {
            winnings = ("You've won $250,000!");
        } else if (lotteryChance < 0.001 && lotteryChance > 0) {
            winnings = ("YOU'VE WON THE JACKPOT! $1,000,000!!!");
        } else winnings = ("Something went wrong, no winnings this round.");

        int number = 74;
        JLabel label = new JLabel("<HTML>The Lottery<BR>Authored by: Samy<BR><BR>-=Prize Board=-<BR><BR>100  - 50:     $100<BR>50   - 20:     $500<BR>20   - 5:      $2,000<BR>5    - 1:      $5,000<BR>1    - 0.1:    $25,000<BR>0.1  - 0.01:   $50,000<BR>0.01 - 0.001:  $250,000<BR>0.001 - 0.0001: $1,000,000<BR><BR>Your number is: "+lotteryChance+"<BR><BR>"+winnings+"</HTML>");


        getContentPane().add(label);


    }
    public static void main(String args[]){
        new Game().setVisible(true);
    }
}
Solution

  • This is a version of the lottery game where I've used Swing components, in order to show how a Java Swing application might look.

    enter image description here

    I put all the Java classes together to make it easier to copy and paste. These classes should be in separate files.

    Here are the changes I made to the code.

    1. In the main method, I put the start code inside a SwingUtilities invokeLater method call. I did this to put the Swing components definition and execution on the Event Dispatch thread.

    2. In the Game class, I used a JFrame, rather than extending a JFrame. The only time you should extend a Swing component is when you're overriding one of the component methods.

    3. I created two JPanels to put in the JFrame. The top JPanel, WinningsPanel, contains the lottery prize table. I used a JTable for this to space the values out. The bottom JPanel, ButtonPanel, contains a JButton to let the application generate a number and display the lottery prize.

    4. I created two model classes. The first model class, LotteryLine, holds the values for one line of the lottery table. The second model class, GameModel, holds the entire lottery table and generates the random number.

    5. I created a lottery table model for the JTable. This allows me to control the display of the values in the lottery table.

    6. ButtonPanel contains a controller, PickNumberActionListener, which generates a random lottery number and displays the number and the winnings.

    Here's the code:

    package com.ggl.testing;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;
import javax.swing.table.AbstractTableModel;
/**
 * Author Samy
 */
public class Game {

    private GameModel model;

    private JFrame frame;

    public Game() throws HeadlessException {

        model = new GameModel();

        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("The Lottery - Version 1.0");
        frame.setLocationByPlatform(true);
        frame.setLayout(new BorderLayout());

        WinningsPanel wPanel = new WinningsPanel(model);
        frame.add(wPanel.getPanel(), BorderLayout.NORTH);

        ButtonPanel bPanel = new ButtonPanel(model);
        frame.add(bPanel.getPanel(), BorderLayout.SOUTH);

        frame.pack();
    }

    public JFrame getFrame() {
        return frame;
    }

    public static void main(String args[]){
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Game().getFrame().setVisible(true);
            }
        });
    }

    public class LotteryLine {

        private double lowValue;
        private double highValue;

        private int prize;

        private NumberFormat nf = NumberFormat.getCurrencyInstance();

        public LotteryLine(double highValue, double lowValue, 
                int prize) {
            this.highValue = highValue;
            this.lowValue = lowValue;
            this.prize = prize;
        }

        public double getLowValue() {
            return lowValue;
        }

        public double getHighValue() {
            return highValue;
        }

        public int getPrize() {
            return prize;
        }

        public String getFormattedPrize() {
            return nf.format(prize);
        }

        public String getLeftPaddedPrize() {
            StringBuilder builder = new StringBuilder();
            String s = getFormattedPrize();

            for (int i = s.length(); i < 16; i++) {
                builder.append(' ');
            }
            builder.append(s);

            return builder.toString();
        }

    }

    public class GameModel {

        private double randomNumber;

        private List<LotteryLine> lotteryList;

        public GameModel() {
            this.lotteryList = new ArrayList<LotteryLine>();
            createLotteryList();
        }

        private void createLotteryList() {
            lotteryList.add(new LotteryLine(100D, 50D, 100));
            lotteryList.add(new LotteryLine(50D, 20D, 500));
            lotteryList.add(new LotteryLine(20D, 5D, 2000));
            lotteryList.add(new LotteryLine(5D, 1D, 5000));
            lotteryList.add(new LotteryLine(1D, 0.1D, 25000));
            lotteryList.add(new LotteryLine(0.1D, 0.01D, 50000));
            lotteryList.add(new LotteryLine(0.01D, 0.001D, 250000));
            lotteryList.add(new LotteryLine(0.001D, 0.0001D, 1000000));
        }

        public double generateRandomNumber() {
            this.randomNumber = Math.random() * 100D;
            return randomNumber;
        }

        public List<LotteryLine> getLotteryList() {
            return lotteryList;
        }

        public LotteryLine getLotteryLine(double randomNumber) {
            for (LotteryLine lotteryLine : lotteryList) {
                if (randomNumber > lotteryLine.getLowValue()) {
                    return lotteryLine;
                }
            }
            throw new IllegalArgumentException();
        }
    }

    public class WinningsPanel {

        private GameModel model;

        private JPanel panel;

        public WinningsPanel(GameModel model) {
            this.model = model;
            createPartControl();
        }

        private void createPartControl() {
            panel = new JPanel();
            panel.setLayout(new BorderLayout());

            JPanel labelPanel = new JPanel();
            labelPanel.setLayout(new BoxLayout(
                    labelPanel, BoxLayout.PAGE_AXIS));

            JLabel writtenLabel = new JLabel("Written by: Samy");
            writtenLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);
            labelPanel.add(writtenLabel);

            labelPanel.add(Box.createVerticalStrut(20));

            JLabel prizeLabel = new JLabel("Prize Table");
            prizeLabel.setFont(new Font("default", Font.BOLD, 32));
            prizeLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);
            labelPanel.add(prizeLabel);

            panel.add(labelPanel, BorderLayout.NORTH);

            LotteryTableModel tableModel = new LotteryTableModel(model);

            JTable lotteryTable = new JTable(tableModel);
            int height = tableModel.getRowCount() * 
                    lotteryTable.getRowHeight();
            lotteryTable.setPreferredScrollableViewportSize(
                    new Dimension(300, height));
            JScrollPane scrollPane = new JScrollPane(lotteryTable);
            panel.add(scrollPane, BorderLayout.CENTER);
        }

        public JPanel getPanel() {
            return panel;
        }

    }

    public class LotteryTableModel extends AbstractTableModel {

        private static final long   serialVersionUID    = 
                7330112393676204265L;

        private GameModel model;

        private String[] columns = {"High Value", "Low Value", "Prize"};

        public LotteryTableModel(GameModel model) {
            this.model = model;
        }

        @Override
        public int getRowCount() {
            return model.getLotteryList().size();
        }

        @Override
        public int getColumnCount() {
            return columns.length;
        }

        @Override
        public String getColumnName(int columnIndex) {
            return columns[columnIndex];
        }

        @Override
        public Class<?> getColumnClass(int column) {
            switch (column) {
                case 0:
                case 1:
                    return Double.class;
                case 2:
                    return String.class;
                default:
                    return String.class;
            }
        }

        @Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            LotteryLine lotteryLine = 
                    model.getLotteryList().get(rowIndex);
            switch (columnIndex) {
            case 0: return lotteryLine.getHighValue();
            case 1: return lotteryLine.getLowValue();
            case 2: return lotteryLine.getLeftPaddedPrize();
            default: return "";
            }
        }

    }

    public class ButtonPanel {

        private GameModel model;

        private JLabel numberLabel;
        private JLabel prizeLabel;

        private JPanel panel;

        public ButtonPanel(GameModel model) {
            this.model = model;
            createPartControl();
        }

        private void createPartControl() {
            panel = new JPanel();
            panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));

            panel.add(Box.createVerticalStrut(10));

            JButton playButton = new JButton("Pick Number");
            playButton.addActionListener(new PickNumberActionListener());
            playButton.setAlignmentX(JButton.CENTER_ALIGNMENT);
            panel.add(playButton);

            panel.add(Box.createVerticalStrut(20));

            numberLabel = new JLabel(" ");
            numberLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);
            panel.add(numberLabel);

            prizeLabel = new JLabel(" ");
            prizeLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);
            panel.add(prizeLabel);
        }

        public void updateNumberLabel(double number) {
            StringBuilder builder = new StringBuilder();
            builder.append("Your number is ");
            builder.append(String.format("%.4f", number));
            numberLabel.setText(builder.toString());
        }

        public void updatePrizeLabel(String prize) {
            StringBuilder builder = new StringBuilder();
            builder.append("You've won ");
            builder.append(prize);
            prizeLabel.setText(builder.toString());
        }

        public JPanel getPanel() {
            return panel;
        }

        public class PickNumberActionListener implements ActionListener {

            @Override
            public void actionPerformed(ActionEvent e) {
                double number = model.generateRandomNumber();
                LotteryLine lotteryLine = model.getLotteryLine(number);
                updateNumberLabel(number);
                updatePrizeLabel(lotteryLine.getFormattedPrize());
            }

        }

    }
}