How can I have a group of JSpinner objects with a maximum total value?

Question

I am designing a program where I have a set of JSpinner objects and I need to make sure that the total of all objects never exceeds a specified value. Is there a built-in way of doing this, or do I need to roll my own?

By way of example, here's the current interface:

I want to make sure that changing a JSpinner updates the remaining at the top, but doesn't allow it to go below 0.

From what I can see, ChangeListener only notifies after the change, with no way of stopping it.

Answer 1

I'm sure there is a better way to do this but here is something really basic to give you some ideas.

You can only increase the spinners to a total value of 10:

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

public class GroupSpinner
{
    private int groupMaximum;

    private List<GroupSpinnerNumberModel> models = new ArrayList<GroupSpinnerNumberModel>();

    public GroupSpinner(int maximum)
    {
        this.groupMaximum = maximum;
    }

    public SpinnerNumberModel createGroupModel(int value, int minimum, int maximum, int step)
    {
        GroupSpinnerNumberModel model = new GroupSpinnerNumberModel(value, minimum, maximum, step, this);
        models.add( model );

        return model;
    }

    public Object getNextValue(int currentValue, int step)
    {
        int maximum = getGroupValue() + step;

        if (maximum > groupMaximum)
        {
            return currentValue;
        }
        else
        {
            groupValueUpdated(maximum);
            int nextValue = currentValue + step;
            return nextValue;
        }
    }

    public int getGroupValue()
    {
        int maximum = 0;

        for (GroupSpinnerNumberModel model: models)
        {
            maximum += model.getNumber().intValue();
        }

        return maximum;
    }

    private void groupValueUpdated(int value)
    {
        System.out.println(value);
    }

    public class GroupSpinnerNumberModel extends SpinnerNumberModel
    {
        private GroupSpinner model;

        public GroupSpinnerNumberModel(int value, int minimum, int maximum, int step, GroupSpinner model)
        {
            super(value, minimum, maximum, step);

            this.model = model;
        }

        public Object getNextValue()
        {
            int currentValue = super.getNumber().intValue();
            int step = super.getStepSize().intValue();

            return model.getNextValue(currentValue, step);
        }
    }

    private static void createAndShowGUI()
    {
        JPanel panel = new JPanel( new GridLayout(0, 1) );

        GroupSpinner group = new GroupSpinner(10);

        JSpinner number1 = new JSpinner( group.createGroupModel(0, 0, 10, 1) );
        panel.add(number1);
        panel.add( new JSpinner( group.createGroupModel(0, 0, 10, 1) ) );
        panel.add( new JSpinner( group.createGroupModel(0, 0, 10, 1) ) );
        panel.add( new JSpinner( group.createGroupModel(0, 0, 10, 1) ) );

        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater( () -> createAndShowGUI() );
/*
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
*/
    }

}

Basically the code is overriding the getNextValue() method of the SpinnerModel to determine if you are at the maximum or not. The value is only updated when you are below the group maximum.