Adding Interior Bounds to a Slider

Question

I am attempting to create a version of JSlider which has interior bounds that its value must respect. Included in the default Bounded Range model, employed by JSlider, is a value called extent, whose function is similar to the end product I am working towards. The Default Bound Range Model has the following constraints for its values:
min <= value <= value + extent <= max
where min is the minimum value, max is the maximum value, value is its current value and extent is a sort of buffer that limits how close value can get to max. When this model is employed by JSlider, it usually has extent set to zero, but if extent takes on a non zero value, then the slider will prevent the thumb from being dragged all the way max value, with extent being the closest to max it can get. I would like to have this effect on both the left and right sides of the slider, effectively decreasing the sliders range by a total of 2*extent.
In order to do this, I have extended the default bounded range model so that it now obeys the following constraint:
min <= value - extent <= value <= value + extent <= max
where extent can only take on values between zero and (max - min)/2. If value is found to be too large or small to obey the constraints involving extent, then value is adjusted so that extent is maintained and value is found within the inner bounds.
So as it is now, the Model seems to be working, enforcing an inner boundary defined by extent, but the visual representation (the slider) does not reflect this. Below is a simple class that displays the problem. The window includes a label to the right of the slider which displays the slider's current value. As you can see, you cannot pull the thumb past 80 (because extent = 20), but you can pull the thumb all the way to zero, though value will not go below 20. If you resize the window, forcing it to repaint the component, then the thumb moves up to 20, where it should be. Also, only drag events cause this problem, simply clicking or using the arrow keys will not take the thumb below 20. How do I fix this? I have tried extending JSlider and rewriting the setValue() method so that it calls repaint() or revalidate(), but that does not work. Please help!!! Thank you so much! (sorry for the long explanation)
Here is the code:
/*BoundedSliderTest.java */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.DefaultBoundedRangeModel;
public class BoundedSliderTest extends JPanel
implements ChangeListener {
private JSlider slider;
private JLabel label;
private int extent;
private int min;
private int max;
private int initValue;
public BoundedSliderTest() {
     min = 0;
     max = 100;
     initValue = 50;
     extent = 20;
public void init() {
     setLayout(new BorderLayout(5,5));
     DoubleBoundedRangeModel myModel = new DoubleBoundedRangeModel();
     slider = new JSlider();
     slider.setModel(myModel);
     slider.setMinimum(min);
     slider.setMaximum(max);
     slider.setExtent(extent);
     slider.setValue(initValue);
     slider.setMajorTickSpacing(20);
     slider.setMinorTickSpacing(2);
     slider.setPaintLabels(true);
     slider.setPaintTicks(true);
     slider.addChangeListener(this);
     Dimension size = new Dimension(3slider.getMinimumSize().width,
                    slider.getMinimumSize().height);
     slider.setMinimumSize(size);
     slider.setPreferredSize(size);
     slider.setMaximumSize(size);
     label = new JLabel(String.valueOf(slider.getValue()));
     add(slider, BorderLayout.CENTER);
     add(label, BorderLayout.EAST);
public void stateChanged(ChangeEvent e) {
     JSlider source = (JSlider)e.getSource();
     int value = (int)source.getValue();
     label.setText(String.valueOf(value));
public static void main(String [] args) {
     JFrame frame = new JFrame("Bounded Slider Test ...");
     frame.getContentPane().setLayout(new BorderLayout());
     MyWindowListener l = new MyWindowListener();
     frame.addWindowListener(l);
     BoundedSliderTest test = new BoundedSliderTest();
     test.init();
     test.setOpaque(true);
     frame.getContentPane().add(test,BorderLayout.CENTER);
     frame.pack();
     frame.setVisible(true);
     frame.show();
class MyWindowListener extends WindowAdapter {
public void windowClosing(WindowEvent e) {
     System.exit(0);
class DoubleBoundedRangeModel extends DefaultBoundedRangeModel{
public DoubleBoundedRangeModel() {
public int getValueRules(int tryValue) {
     int extent = super.getExtent();
     int min = super.getMinimum();
     int max = super.getMaximum();
     if((tryValue-extent) < min){
     tryValue = min + extent;
     if((tryValue+extent) > max) {
     tryValue = max - extent;
     return tryValue;
public void setValue(int newValue) {
     //System.out.println("Try setting value of " + newValue);
     int value = super.getValue();
     int extent = super.getExtent();
     int min = super.getMinimum();
     int max = super.getMaximum();
     //Now must ensure compliance with inner bounds;
     if((newValue-extent) < min){
     newValue = min + extent;
     if((newValue+extent) > max) {
     newValue = max - extent;
     if( newValue != value)
     super.setValue(newValue);
public void setExtent(int newExtent) {
     int value = super.getValue();
     int extent = super.getExtent();
     int min = super.getMinimum();
     int max = super.getMaximum();
     if (newExtent < 0)
     newExtent = 0;
     else if (newExtent > (int)Math.floor((max - min)/2.))
     newExtent = (int)Math.floor((max - min)/2.);
     if( newExtent != extent)
     super.setExtent(newExtent);
public void setRangeProperties(int newValue,
                    int newExtent,
                    int newMin,
int newMax,
boolean newAdjusting) {
     //System.out.println("setRangeProps");
     int value = super.getValue();
     int extent = super.getExtent();
     int min = super.getMinimum();
     int max = super.getMaximum();
     boolean isAdjusting = super.getValueIsAdjusting();
if (newMax < newMin) {
if(max >= newMin)
          newMax = max;
     else if(min <= newMax)
          newMin = min;
     else {
          newMin = min;
          newMax = max;
     if (newExtent < 0)
     newExtent = 0;
     else if (newExtent > (int)Math.floor((newMax - newMin)/2.))
     newExtent = (int)Math.floor((newMax - newMin)/2.);
     if (!bounded(newMin,newMax,newValue)) {
     if (newMin == newMax)
          newValue = newMin;
     else if (bounded(newMin,newMax,value))
          newValue = value;
     else
          newValue = (int)Math.round((newMax+newMin)/2.);
     //Now must ensure compliance with inner bounds;
     if((newValue-newExtent) < newMin){
     newValue = newMin + newExtent;
     if((newValue+newExtent) > newMax) {
     newValue = newMax - newExtent;
boolean changeOccurred = false;
if (newValue != value) {
value = newValue;
changeOccurred = true;
if (newMax != max) {
max = newMax;
changeOccurred = true;
if (newMin != min) {
min = newMin;
changeOccurred = true;
if (newExtent != extent) {
     extent = newExtent;
changeOccurred = true;
if (newAdjusting != isAdjusting) {
isAdjusting = newAdjusting;
changeOccurred = true;
if (changeOccurred)
super.setRangeProperties(newValue, newExtent, newMin, newMax,
                    newAdjusting);
private static boolean bounded(int lowBound, int highBound,
                    int num) {
     boolean bounded = false;
     if(num >= lowBound && num <= highBound) bounded = true;
     return bounded;

Answer 1

perrymanp-
I tried employing your suggestion by including the following code in my stateChanged listener for the slider, but it had no effect... maybe I am missing something? Thanks.
     BoundedRangeModel brm = source.getModel();
     source.setModel(new DoubleBoundedRangeModel(value,brm.getExtent(),
                              brm.getMinimum(),
                              brm.getMaximum()));
-kheldar83
PS any more suggestions or clarifications are greatly appreciated!