I have an applet which selects an audio file from a JFileChooser. Two JSliders are created or updated to match the length of the clip and titled "point A" and "point B". A JButton is pressed, and then the file plays up until point A. When it reaches point A, the clip begins looping audio from point A to point B with a crossfade.
The problem is that I have to make sure that point A is never beyond point B for obvious reasons, but my method isn't working for that.
Adding a changelistener that updates when the source JSlider is or is not updating are the two things I have tried. For !source.getValueIsAdjusting(), it works for using the arrow keys, but not the mouse, and for source.getValueIsAdjusting(), it works in a delayed way: It seems that it's either comparing or resetting the values an event late.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.BorderFactory;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.Timer;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class SliderExample extends JApplet{
private MyPanel panel;
private final Random rand = new Random();
public SliderExample() {
panel = new MyPanel();
add(panel);
}
private class MyPanel extends JPanel implements
ActionListener{
private JSlider sliderA, sliderB;
private final Timer t = new Timer(20, this);
public MyPanel()
{
super(false);
sliderA = new JSlider(JSlider.HORIZONTAL, 0, 20, 5);
sliderB = new JSlider(JSlider.HORIZONTAL, 0, 20, 15);
sliderA.setBorder(BorderFactory.createTitledBorder("Point A"));
sliderB.setBorder(BorderFactory.createTitledBorder("Point B"));
sliderA.setMajorTickSpacing(5);
sliderB.setMajorTickSpacing(5);
sliderA.setMinorTickSpacing(1);
sliderB.setMinorTickSpacing(1);
sliderA.setPaintTicks(true);
sliderB.setPaintTicks(true);
sliderA.setPaintLabels(true);
sliderB.setPaintLabels(true);
sliderA.addChangeListener(new SliderHandler());
sliderB.addChangeListener(new SliderHandler());
add(sliderA);
add(sliderB);
t.start();
}
@Override
public void actionPerformed(ActionEvent e) {
// uncomment these to see that the slider set value does work
// sliderA.setValue(rand.nextInt(sliderA.getMaximum()));
// sliderB.setValue(rand.nextInt(sliderB.getMaximum()));
int A = sliderA.getValue();
int B = sliderB.getValue();
if (A > B)
{
System.out.println("ERROR: slider A is: " + A + " and slider B is : " + B);
sliderA.setValue(B);
}
}
private class SliderHandler implements ChangeListener
{
private SliderHandler()
{
}
public void stateChanged(ChangeEvent e)
{
JSlider source = (JSlider)e.getSource();
if (!source.getValueIsAdjusting())
{
if (source == sliderA)
{
if (source.getValue() > sliderB.getValue())
{
source.setValue(sliderB.getValue());
}
}
else if (source == sliderB)
{
if (source.getValue() < sliderA.getValue())
{
source.setValue(sliderA.getValue());
}
}
}
}
}
}
}
It seems to work OK for me. I've changed my sliders to + 1 or - 1 form the value I'm trying to move away from. For example:
import javax.swing.*;
import javax.swing.event.*;
@SuppressWarnings("serial")
public class SliderExample2 extends JPanel {
private JSlider sliderA = new JSlider(JSlider.HORIZONTAL, 0, 20, 5);
private JSlider sliderB = new JSlider(JSlider.HORIZONTAL, 0, 20, 15);
private JSlider[] sliders = {sliderA, sliderB};
private String[] titles = {"Point A", "Point B"};
private ChangeListener[] changeListeners = {new ChangeListenerA(),
new ChangeListenerB()};
public SliderExample2() {
for (int i = 0; i < sliders.length; i++) {
sliders[i].setBorder(BorderFactory.createTitledBorder(titles[i]));
sliders[i].setMajorTickSpacing(5);
sliders[i].setMinorTickSpacing(1);
sliders[i].setPaintTicks(true);
sliders[i].setPaintLabels(true);
sliders[i].addChangeListener(changeListeners[i]);
add(sliders[i]);
}
}
private class ChangeListenerA implements ChangeListener {
@Override
public void stateChanged(ChangeEvent cEvt) {
if (sliderA.getValue() >= sliderB.getValue()) {
sliderB.setValue(sliderA.getValue() + 1);
}
}
}
private class ChangeListenerB implements ChangeListener {
@Override
public void stateChanged(ChangeEvent cEvt) {
if (sliderA.getValue() >= sliderB.getValue()) {
sliderA.setValue(sliderB.getValue() - 1);
}
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("SliderExample2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new SliderExample2());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Edit
Oh, I see your goal and problem -- you want to limit the range of the moved slider. You're forgetting to set setSnapToTicks(true):
import javax.swing.*;
import javax.swing.event.*;
@SuppressWarnings("serial")
public class SliderExample3 extends JPanel {
private JSlider sliderA = new JSlider(JSlider.HORIZONTAL, 0, 20, 5);
private JSlider sliderB = new JSlider(JSlider.HORIZONTAL, 0, 20, 15);
private JSlider[] sliders = {sliderA, sliderB};
private String[] titles = {"Point A", "Point B"};
private ChangeListener[] changeListeners = {new ChangeListenerA(),
new ChangeListenerB()};
public SliderExample3() {
for (int i = 0; i < sliders.length; i++) {
sliders[i].setBorder(BorderFactory.createTitledBorder(titles[i]));
sliders[i].setMajorTickSpacing(5);
sliders[i].setMinorTickSpacing(1);
sliders[i].setPaintTicks(true);
sliders[i].setPaintLabels(true);
sliders[i].setSnapToTicks(true);
sliders[i].addChangeListener(changeListeners[i]);
add(sliders[i]);
}
}
private class ChangeListenerA implements ChangeListener {
@Override
public void stateChanged(ChangeEvent cEvt) {
if (sliderA.getValue() >= sliderB.getValue()) {
sliderA.setValue(sliderB.getValue());
}
}
}
private class ChangeListenerB implements ChangeListener {
@Override
public void stateChanged(ChangeEvent cEvt) {
if (sliderA.getValue() >= sliderB.getValue()) {
sliderB.setValue(sliderA.getValue());
}
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("SliderExample3");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new SliderExample3());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}