Re: Trouble setting JSlider position

Hello everyone,

I have been playing with jsliders for a while now, and have never had
any trouble positioning sliders where I want in response to particular
events. I am running into trouble right now though, where I want to
prevent one slider from passing below the value of another slider.

I have written a simple program which demonstrates this problem. The
program displays two sliders (only listens to second slider). If I
move the second slider below the first slider and release it,
- it shows the proper portion of code has been reached;
- it shows the lower bound has been read correctly;
- it shows that the value of the slider has been reset properly;
- problem: as soon as the slider value is adjusted by the program, it
goes right back to where the user had set it.

I am guessing the problem is in the checkSliderBounds method, but maybe
it's in the stateChanged method. Any thoughts?

import javax.swing.*;
import javax.swing.event.*;

public class SliderSnapTester extends JFrame implements ChangeListener
{

JSlider sliderOne;
JSlider sliderTwo;
JTextField sliderOneDisplay = new JTextField(3);
JTextField sliderTwoDisplay = new JTextField(3);

public SliderSnapTester() {

  super("Slider Snap Tester");
  setSize(500, 200);
   setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   setVisible(true);

   // Container panel for whole frame.
   JPanel wholePanel = new JPanel();
   BoxLayout wholePanelLayout = new BoxLayout(wholePanel,
BoxLayout.Y_AXIS);
   wholePanel.setLayout(wholePanelLayout);

   // Build Sliders
   buildSliders();

  // Build panels for each row.
  JPanel sliderOnePanel = new JPanel();
  BoxLayout sliderOnePanelLayout = new BoxLayout(sliderOnePanel,
BoxLayout.X_AXIS);
  sliderOnePanel.setLayout(sliderOnePanelLayout);

sliderOnePanel.add(sliderOne);
sliderOnePanel.add(sliderOneDisplay);

JPanel sliderTwoPanel = new JPanel();
  BoxLayout sliderTwoPanelLayout = new BoxLayout(sliderTwoPanel,
BoxLayout.X_AXIS);
  sliderTwoPanel.setLayout(sliderTwoPanelLayout);

sliderTwoPanel.add(sliderTwo);
sliderTwoPanel.add(sliderTwoDisplay);

// Build whole panel.
wholePanel.add(sliderOnePanel);
wholePanel.add(sliderTwoPanel);

// Initialize displays.
sliderOneDisplay.setText("" + sliderOne.getValue() );
sliderTwoDisplay.setText("" + sliderTwo.getValue() );

add(wholePanel);
  setVisible(true);

} // END SliderSnapTester()

public void stateChanged(ChangeEvent evt) {

JSlider sliderChanged = (JSlider)evt.getSource();

if ( sliderChanged == sliderTwo &&
!sliderChanged.getValueIsAdjusting() ) {
checkSliderBounds();
}

} // END stateChanged(ChangeEvent evt)

private void checkSliderBounds() {

int sliderTwoValue = sliderTwo.getValue();
int lowerBound = sliderOne.getValue() + 1; // Lowest allowed value
for slider two.

if (sliderTwoValue < lowerBound) {
sliderTwo.setValue(lowerBound);
JOptionPane.showMessageDialog(null, "lowerBound: " + lowerBound);
}

sliderTwoDisplay.setText("" + sliderTwoValue);

} // END checkSliderBounds()

private void buildSliders() {
sliderOne = new JSlider(JSlider.HORIZONTAL, 0, 100, 50);
   sliderTwo = new JSlider(JSlider.HORIZONTAL, 0, 100, 75);

   sliderOne.setMajorTickSpacing(25);
sliderOne.setMinorTickSpacing(5);
sliderOne.setPaintTicks(true);
sliderOne.setPaintLabels(true);

sliderTwo.setMajorTickSpacing(25);
sliderTwo.setMinorTickSpacing(5);
sliderTwo.setPaintTicks(true);
sliderTwo.setPaintLabels(true);

  sliderOne.addChangeListener(this);
  sliderTwo.addChangeListener(this);

} // END buildSliders()

public static void main(String[] arguments) {
  SliderSnapTester sliderSnapTester = new SliderSnapTester();
  }

}