JSlider不会更改值并保持不变

Question

I have just made a java program with eclipse to change a Jprogress bar with a jslider but the sliders value doesn't change It keeps constant, here is the code:

First class:

package pro;

import java.awt.Color;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;

public class pro1 {

int value;

public static void main(String[] args) {
    // TODO Auto-generated method stub

    //setting the objects
    final pro1 p = new pro1();
    final pro2 p2 = new pro2();


    //adding the JFrame.
    JFrame fr = new JFrame();
    fr.setVisible(true);
    fr.setSize(380, 80);
    fr.setLayout(new FlowLayout(FlowLayout.LEFT));
    fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    //adding the JProgressBar.
    JProgressBar pb = new JProgressBar(0,100);
    pb.setOpaque(false);
    Color c = new Color (0,200,0);
    pb.setForeground(c);        
    pb.setValue(p.value);


    //adding the JPanel
    JPanel panel = new JPanel();
    panel.add(pb);
    panel.add(p2.slider());

    //adding the panel to the frame.
    fr.add(panel);
    fr.revalidate();

}
}

Second Class:

package pro;

import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class pro2 {

//setting the object
        pro1 p = new pro1();

public JSlider slider(){


//adding the slider.
        final JSlider s = new JSlider ();
        s.setMinimum(0);
        s.setMaximum(100);
        s.setValue(0);
        s.setMajorTickSpacing(10);
        s.setPaintTicks(true);
        s.addChangeListener(new ChangeListener(){

            @Override
            public void stateChanged(ChangeEvent e) {
                // TODO Auto-generated method stub
                p.value = s.getValue();
            }

        });

        return s;
}

I have also tried to assign the value of a slider to a value and print it out but it keeped at the default value I set it to which was 0......

anything wrong thing in the code??

Answer 1

In your main method, you are creating an instance of pro1 . In pro2 you are creating a new instance of pro1 . Each of these instances has its own value .

Additionally, when you change the value , then the progress bar will not notice this. You have to call JProgressBar#setValue explicitly.

There have been some additional issues with the code, here is a slightly modified version that shows ONE possible way of doing it...

import java.awt.Color;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JSlider;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class SliderProgressTest
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                createAndShowGUI();
            }
        });
    }

    private static void createAndShowGUI()
    {
        //adding the JFrame.
        JFrame fr = new JFrame();
        fr.setSize(380, 80);
        fr.setLayout(new FlowLayout(FlowLayout.LEFT));
        fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //adding the JProgressBar.
        JProgressBar pb = new JProgressBar(0,100);
        pb.setOpaque(false);
        Color c = new Color (0,200,0);
        pb.setForeground(c);        

        //adding the JPanel
        JPanel panel = new JPanel();
        panel.add(pb);
        panel.add(createSlider(pb));

        //adding the panel to the frame.
        fr.add(panel);
        fr.setVisible(true);
    }

    private static JSlider createSlider(final JProgressBar pb)
    {
        //adding the slider.
        final JSlider s = new JSlider ();
        s.setMinimum(0);
        s.setMaximum(100);
        s.setValue(0);
        s.setMajorTickSpacing(10);
        s.setPaintTicks(true);
        s.addChangeListener(new ChangeListener(){

            @Override
            public void stateChanged(ChangeEvent e) {
                pb.setValue(s.getValue());
            }

        });

        return s;
    }
}