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Question

I am making an emulator for a seven segment display calculator with up to 10 digits. I have the logic down where I have an array of size 10 of objects. These objects take in a number and "turn on" the segments necessary to display the correct number on the canvas. I am trying to have 10 separate canvas' next to each other and have a draw function that draws the correct number in each digit based on what segments are "turned on". Anyways, I can figure that part out. The part I can't seem to figure out is how to get 10 separate canvas' next to each other on a single JFrame. I have tried using 10 panels, but the formatting is not working and I'm having issues. Any suggestions on how to make this?

Answer 1

This is a really basic example of 7 segment display set up using nothing more then custom JPanel s...

Each element in the display is just a JPanel with some additional "properties", which are then laid out on another JPanel which acts as the primary display. You can effect which segements are turned on and off through the use of a boolean array, where position;

• 0 is the top
• 1 & 2 are the left and right, top half
• 3 is the middle
• 4 * 5 are the left and right, bottom half
• 6 is the bottom

---

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class TestSegmentDisplay {

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

    private SegmentDisplay segmentDisplay;
    private int count = 0;

    public TestSegmentDisplay() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                segmentDisplay = new SegmentDisplay();

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(segmentDisplay);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

                final Timer timer = new Timer(1000, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        setSegmentValue(segmentDisplay, count);
                        count++;
                        if (count > 9) {
                            count = 0;
                        }
                    }
                });
                timer.start();

            }
        });
    }

    public static void setSegmentValue(SegmentDisplay display, int value) {

        boolean[] states = new boolean[]{
            false,
            false, false,
            false,
            false, false,
            false
        };
        switch (value) {
            case 0:
                states = new boolean[]{
                    true,
                    true, true,
                    false,
                    true, true,
                    true};
                break;
            case 1:
                states = new boolean[]{
                    false,
                    false, true,
                    false,
                    false, true,
                    false};
                break;
            case 2:
                states = new boolean[]{
                    true,
                    false, true,
                    true,
                    true, false,
                    true};
                break;
            case 3:
                states = new boolean[]{
                    true,
                    false, true,
                    true,
                    false, true,
                    true};
                break;
            case 4:
                states = new boolean[]{
                    false,
                    true, true,
                    true,
                    false, true,
                    false};
                break;
            case 5:
                states = new boolean[]{
                    true,
                    true, false,
                    true,
                    false, true,
                    true};
                break;
            case 6:
                states = new boolean[]{
                    true,
                    true, false,
                    true,
                    true, true,
                    true};
                break;
            case 7:
                states = new boolean[]{
                    true,
                    false, true,
                    false,
                    false, true,
                    false};
                break;
            case 8:
                states = new boolean[]{
                    true,
                    true, true,
                    true,
                    true, true,
                    true};
                break;
            case 9:
                states = new boolean[]{
                    true,
                    true, true,
                    true,
                    false, true,
                    true};
                break;
        }

        display.setSegments(states);

    }

    public static class SegmentDisplay extends JPanel {

        private Segement[] segemnts;

        public SegmentDisplay() {
            segemnts = new Segement[7];
            segemnts[0] = new Segement(Segement.Direction.HORIZONTAL);
            segemnts[1] = new Segement(Segement.Direction.VERTICAL);
            segemnts[2] = new Segement(Segement.Direction.VERTICAL);
            segemnts[3] = new Segement(Segement.Direction.HORIZONTAL);
            segemnts[4] = new Segement(Segement.Direction.VERTICAL);
            segemnts[5] = new Segement(Segement.Direction.VERTICAL);
            segemnts[6] = new Segement(Segement.Direction.HORIZONTAL);

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 1;
            gbc.gridy = 0;
            add(segemnts[0], gbc);

            gbc.gridx = 0;
            gbc.gridy = 1;
            add(segemnts[1], gbc);
            gbc.gridx = 2;
            add(segemnts[2], gbc);

            gbc.gridx = 1;
            gbc.gridy++;
            add(segemnts[3], gbc);

            gbc.gridx = 0;
            gbc.gridy++;
            add(segemnts[4], gbc);
            gbc.gridx = 2;
            add(segemnts[5], gbc);

            gbc.gridx = 1;
            gbc.gridy++;
            add(segemnts[6], gbc);
        }

        public void setSegments(boolean[] states) {

            if (states != null && states.length > 0 && states.length == segemnts.length) {

                for (int index = 0; index < segemnts.length; index++) {
                    segemnts[index].setOn(states[index]);
                }

            }

        }

    }

    public static class Segement extends JPanel {

        public enum Direction {

            VERTICAL,
            HORIZONTAL;
        }

        public static final int SMALL_SIZE = 10;
        public static final int LARGE_SIZE = SMALL_SIZE * 4;

        protected static final Color OUT_LINE = new Color(128, 0, 0);
        protected static final Color ON_COLOR = Color.RED;
        protected static final Color OFF_COLOR = new Color(64, 0, 0);

        private final Direction direction;
        private boolean on;

        public Segement(Direction direction) {
            this.direction = direction;
            setBorder(new LineBorder(OUT_LINE));
            setOn(true);
            setOn(false);
        }

        public void setOn(boolean value) {
            if (on != value) {
                on = value;
                if (on) {
                    setBackground(ON_COLOR);
                } else {
                    setBackground(OFF_COLOR);
                }
            }
        }

        public boolean isOn() {
            return on;
        }

        public Direction getDirection() {
            return direction;
        }

        @Override
        public Dimension getPreferredSize() {
            return getDirection() == Direction.VERTICAL ? new Dimension(SMALL_SIZE, LARGE_SIZE) : new Dimension(LARGE_SIZE, SMALL_SIZE);
        }

    }

}

There's probably a really clever way to set up the switch statement, but I can't really be bothered right now...

What I would then do, is add each SegmentDisplay to a JPanel using something like GridBagLayout or FlowLayout ...