Multiple JSliders activating and deactivating - Sh

Context

Im writing a piece of code that has 1+ Sliders. These sliders form a group. The sum of the slider values of this group must always be 100. However, as a NEEDED feature, the user can disable and enable (add/remove) sliders from this group. Therefore, this requires that the sliders values get adjusted properly.

After attempting to code my own group, I decided to look for a better/tested and implemented code. It improved from mine, however, some issues appeared.

Primary Issue

Adding or removing sliders by selection or deselection the checkbox causes errors and the sliders stop working. Notice that adding, in this scenario, just means enabling a previously disabled slider (by deselecting the checkbox).

Preliminary Solution

The code below was found in stackoverflow. I did implement in my code but since I cant post it, I decided to adjust the code found in the stackoverflow example to represent my scenario.

How to?

Any help is greatly appreciated. Im not sure how to approach the fix for this problem without causing more errors. I did try re-adjusting the calculus done on the update method but it just caused more nonsense. I dont find productive posting all my attempts here because stackoverflow would say its too much code and because im not sure it would help with finding an answer.

References

https://stackoverflow.com/a/21391448/2280645

import java.awt.GridLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class ConnectedSliders {

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

    private static void createAndShowGUI() {
        JSlider s0 = new JSlider(0, 100, 30);
        JSlider s1 = new JSlider(0, 100, 40);
        JSlider s2 = new JSlider(0, 100, 30);

        SliderGroup sliderGroup = new SliderGroup();
        //sliderGroup.add(s0);
        //sliderGroup.add(s1);
        //sliderGroup.add(s2);

        JPanel panel = new JPanel(new GridLayout(0, 3));
        panel.add(s0);
        panel.add(createListeningLabel(s0));
        panel.add(createCheckBox(s0, sliderGroup));

        panel.add(s1);
        panel.add(createListeningLabel(s1));
        panel.add(createCheckBox(s1, sliderGroup));

        panel.add(s2);
        panel.add(createListeningLabel(s2));
        panel.add(createCheckBox(s2, sliderGroup));

        panel.add(createListeningLabel(s0, s1, s2));

        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(panel);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static JLabel createListeningLabel(final JSlider... sliders) {
        final JLabel label = new JLabel("");
        for (JSlider slider : sliders) {
            slider.addChangeListener(new ChangeListener() {
                @Override
                public void stateChanged(ChangeEvent e) {
                    int sum = 0;
                    for (JSlider slider : sliders) {
                        sum += slider.getValue();
                    }
                    label.setText("Sum: " + sum);
                }
            });
        }
        return label;
    }

    private static JLabel createListeningLabel(final JSlider slider) {
        final JLabel label = new JLabel("");
        slider.addChangeListener(new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                label.setText(String.valueOf(slider.getValue()));
            }
        });
        return label;
    }

    private static JCheckBox createCheckBox(final JSlider slider, SliderGroup group) {
        final JCheckBox checkBox = new JCheckBox();
        checkBox.setSelected(true);

        checkBox.addItemListener(new ItemListener() {
            @Override
            public void itemStateChanged(ItemEvent e) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    group.add(slider);
                    slider.setEnabled(true);
                } else if(e.getStateChange() == ItemEvent.DESELECTED) {
                    group.remove(slider);
                    slider.setEnabled(false);
                }
            }
        });

        return checkBox;

    }

}

class SliderGroup {

    private final Map<JSlider, Integer> values;
    private final LinkedList<JSlider> candidates;

    private final ChangeListener changeListener;
    private boolean updating = false;

    SliderGroup() {
        this.values = new HashMap<JSlider, Integer>();
        this.candidates = new LinkedList<JSlider>();

        changeListener = new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                JSlider source = (JSlider) e.getSource();
                update(source);
            }
        };
    }

    private void update(JSlider source) {
        if (updating) {
            return;
        }
        updating = true;

        int delta = source.getValue() - values.get(source);
        if (delta > 0) {
            distributeRemove(delta, source);
        } else {
            distributeAdd(delta, source);
        }

        for (JSlider slider : candidates) {
            values.put(slider, slider.getValue());
        }

        updating = false;
    }

    private void distributeRemove(int delta, JSlider source) {
        int counter = 0;
        int remaining = delta;
        while (remaining > 0) {
            JSlider slider = candidates.removeFirst();
            counter++;

            if (slider == source) {
                candidates.addLast(slider);
            } else {
                if (slider.getValue() > 0) {
                    slider.setValue(slider.getValue() - 1);
                    remaining--;
                    counter = 0;
                }
                candidates.addLast(slider);
                if (remaining == 0) {
                    break;
                }
            }
            if (counter > candidates.size()) {
                String message = "Can not distribute " + delta + " among " + candidates;
                //System.out.println(message);
                //return;
                throw new IllegalArgumentException(message);
            }
        }
    }

    private void distributeAdd(int delta, JSlider source) {
        int counter = 0;
        int remaining = -delta;
        while (remaining > 0) {
            JSlider slider = candidates.removeLast();
            counter++;

            if (slider == source) {
                candidates.addFirst(slider);
            } else {
                if (slider.getValue() < slider.getMaximum()) {
                    slider.setValue(slider.getValue() + 1);
                    remaining--;
                    counter = 0;
                }
                candidates.addFirst(slider);
                if (remaining == 0) {
                    break;
                }
            }
            if (counter > candidates.size()) {
                String message = "Can not distribute " + delta + " among " + candidates;
                //System.out.println(message);
                //return;
                throw new IllegalArgumentException(message);
            }
        }
    }

    void add(JSlider slider) {
        candidates.add(slider);
        values.put(slider, slider.getValue());
        slider.addChangeListener(changeListener);
    }

    void remove(JSlider slider) {
        candidates.remove(slider);
        values.remove(slider);
        slider.removeChangeListener(changeListener);
    }

}

With a minor adjustment of the example that you linked to, this should be doable.

The basic idea is to not only have the SliderGroup#add and remove methods that are used for constructing the group initially, but also addAndAdjust and removeAndAdjust methods that (in addition to adding/removing the slider) distribute the value of the slider that was added or removed, using the same methods that adjusted the sliders originally only when the value of one slider changed.

I also added a keepOneSelected method for the check boxes: If all sliders could be disabled, then there is none to have the remaining value. So the method makes sure that at least one of the check boxes remains always checked.

_{(Edited based on the discussion in the comments:)}

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.LinkedList;

import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class ConnectedSlidersExt
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(() -> createAndShowGUI());
    }

    private static void createAndShowGUI()
    {
        JSlider s0 = new JSlider(0, 100, 33);
        JSlider s1 = new JSlider(0, 100, 33);
        JSlider s2 = new JSlider(0, 100, 34);

        int expectedSum = 100;
        SliderGroup sliderGroup = new SliderGroup(expectedSum);
        sliderGroup.add(s0);
        sliderGroup.add(s1);
        sliderGroup.add(s2);

        JPanel panel =new JPanel(new GridLayout(0,3));
        panel.add(s0);
        panel.add(createListeningLabel(s0));
        JCheckBox checkBox0 = createCheckBox(s0, sliderGroup);
        panel.add(checkBox0);
        panel.add(s1);
        panel.add(createListeningLabel(s1));
        JCheckBox checkBox1 = createCheckBox(s1, sliderGroup);
        panel.add(checkBox1);
        panel.add(s2);
        panel.add(createListeningLabel(s2));
        JCheckBox checkBox2 = createCheckBox(s2, sliderGroup);
        panel.add(checkBox2);

        keepOneSelected(checkBox0, checkBox1, checkBox2);

        panel.add(createListeningLabel(s0, s1, s2));

        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(panel);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static void keepOneSelected(JCheckBox ...checkBoxes)
    {
        ActionListener actionListener = new ActionListener()
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
                int numSelected = 0;
                for (JCheckBox checkBox : checkBoxes)
                {
                    if (checkBox.isSelected())
                    {
                        numSelected++;
                    }
                }
                if (numSelected == 1)
                {
                    for (int i = 0; i < checkBoxes.length; i++)
                    {
                        JCheckBox checkBox = checkBoxes[i];
                        if (checkBox.isSelected())
                        {
                            checkBox.setEnabled(false);
                        }
                    }
                }
                else
                {
                    for (int i = 0; i < checkBoxes.length; i++)
                    {
                        JCheckBox checkBox = checkBoxes[i];
                        checkBox.setEnabled(true);
                    }
                }
            }
        };
        for (JCheckBox checkBox : checkBoxes)
        {
            checkBox.addActionListener(actionListener);
        }
    }

    private static JCheckBox createCheckBox(
        JSlider slider, SliderGroup group)
    {
        JCheckBox checkBox = new JCheckBox();
        checkBox.setSelected(true);
        checkBox.addActionListener(new ActionListener()
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
                if (checkBox.isSelected())
                {
                    slider.setEnabled(true);
                    group.addAndAdjust(slider);
                }
                else
                {
                    slider.setEnabled(false);
                    group.removeAndAdjust(slider);
                }
            }
        });

        return checkBox;

    }

    private static JLabel createListeningLabel(final JSlider ... sliders)
    {
        final JLabel label = new JLabel("");
        for (JSlider slider : sliders)
        {
            slider.addChangeListener(new ChangeListener()
            {
                @Override
                public void stateChanged(ChangeEvent e)
                {
                    int sum = 0;
                    for (JSlider slider : sliders)
                    {
                        if (slider.isEnabled())
                        {
                            sum += slider.getValue();
                        }
                    }
                    label.setText("Sum: "+sum);
                }
            });
        }
        return label;
    }

    private static JLabel createListeningLabel(final JSlider slider)
    {
        final JLabel label = new JLabel("");
        slider.addChangeListener(new ChangeListener()
        {
            @Override
            public void stateChanged(ChangeEvent e)
            {
                label.setText(String.valueOf(slider.getValue()));
            }
        });
        return label;
    }


}


class SliderGroup
{
    private final int expectedSum;
    private final LinkedList<JSlider> candidates;

    private final ChangeListener changeListener;
    private boolean updating = false;

    SliderGroup(int expectedSum)
    {
        this.expectedSum = expectedSum;
        this.candidates = new LinkedList<JSlider>();

        changeListener = new ChangeListener()
        {
            @Override
            public void stateChanged(ChangeEvent e)
            {
                JSlider source = (JSlider)e.getSource();
                update(source);
            }
        };
    }

    private void update(JSlider source)
    {
        if (updating)
        {
            return;
        }
        updating = true;

        for (JSlider slider : candidates)
        {
            slider.setValueIsAdjusting(true);
        }

        if (candidates.size() > 1)
        {
            int delta = computeSum() - expectedSum;
            if (delta > 0)
            {
                distributeRemove(delta, source);
            }
            else
            {
                distributeAdd(delta, source);
            }
        }

        for (JSlider slider : candidates)
        {
            slider.setValueIsAdjusting(false);
        }

        updating = false;
    }


    private void distributeRemove(int delta, JSlider source)
    {
        int counter = 0;
        int remaining = delta;
        while (remaining > 0)
        {
            //System.out.println("remove "+remaining);

            JSlider slider = candidates.removeFirst();
            counter++;

            if (slider == source)
            {
                candidates.addLast(slider);
            }
            else
            {
                if (slider.getValue() > 0)
                {
                    slider.setValue(slider.getValue()-1);
                    remaining--;
                    counter = 0;
                }
                candidates.addLast(slider);
                if (remaining == 0)
                {
                    break;
                }
            }
            if (counter > candidates.size())
            {
                String message =
                    "Can not distribute " + delta + " among " + candidates;
                // System.out.println(message);
                // return;
                throw new IllegalArgumentException(message);
            }
        }
    }

    private void distributeAdd(int delta, JSlider source)
    {
        int counter = 0;
        int remaining = -delta;
        while (remaining > 0)
        {
            //System.out.println("add "+remaining);

            JSlider slider = candidates.removeLast();
            counter++;

            if (slider == source)
            {
                candidates.addFirst(slider);
            }
            else
            {
                if (slider.getValue() < slider.getMaximum())
                {
                    slider.setValue(slider.getValue()+1);
                    remaining--;
                    counter = 0;
                }
                candidates.addFirst(slider);
                if (remaining == 0)
                {
                    break;
                }
            }
            if (counter > candidates.size())
            {
                String message =
                    "Can not distribute " + delta + " among " + candidates;
                // System.out.println(message);
                // return;
                throw new IllegalArgumentException(message);
            }
        }
    }

    private int computeSum()
    {
        int sum = 0;
        for (JSlider slider : candidates)
        {
            sum += slider.getValue();
        }
        return sum;
    }

    void add(JSlider slider)
    {
        candidates.add(slider);
        slider.addChangeListener(changeListener);
    }

    void remove(JSlider slider)
    {
        candidates.remove(slider);
        slider.removeChangeListener(changeListener);
    }

    void addAndAdjust(JSlider slider)
    {
        add(slider);
        if (candidates.size() == 2)
        {
            update(candidates.get(0));
        }
        else
        {
            update(slider);
        }
    }

    void removeAndAdjust(JSlider slider)
    {
        remove(slider);
        update(slider);
        if (candidates.size() == 1)
        {
            JSlider candidate = candidates.get(0);
            int max = candidate.getMaximum();
            candidate.setValue(Math.min(max, expectedSum));
        }
    }


}