Trouble setting JSlider position

From:
e_matthes@hotmail.com
Newsgroups:
comp.lang.java.help
Date:
11 Sep 2006 11:45:30 -0700
Message-ID:
<1158000330.200028.34640@d34g2000cwd.googlegroups.com>
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();
   }

}

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