如何使用Java使两个GUI滑块彼此独立工作？

Question

Here's the code I have been working on below:

package ASG2;

import javax.swing.*;
import java.awt.*;
import javax.swing.event.*;

public class GUI extends JFrame
{
    JSlider slider;
    JLabel label;

    public GUI()
    {
        setLayout(new FlowLayout());
        slider = new JSlider(JSlider.HORIZONTAL, 0, 5, 0);
        slider.setMajorTickSpacing(1);
        slider.setPaintTicks(true);
        add(slider);

        label = new JLabel("Current value: 0");
        add(label);

        event b = new event();
        slider.addChangeListener(b);

        setLayout(new FlowLayout());
        slider = new JSlider(JSlider.HORIZONTAL, 0, 5, 0);
        slider.setMajorTickSpacing(1);
        slider.setPaintTicks(true);
        add(slider);

        label = new JLabel("Current value: 0");
        add(label);

        event c = new event();
        slider.addChangeListener(c);
    }

    public class event implements ChangeListener
    {
        public void stateChanged(ChangeEvent a)
        {
            int value = slider.getValue();

            label.setText("Current value: " + value);
        }
    }

    public static void main(String args[])
    {
        GUI asg2 = new GUI();
        asg2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        asg2.setSize(500,500);
        asg2.setVisible(true);
        asg2.setTitle("Slider program");
    }
}

I got two sliders and only the bottom one is retrieving the current value. The top one is sliding correctly, but the current value won't change. Is there any way I can make both work independently from one another?

Answer 1

only the bottom one is retrieving the current value.

slider = new JSlider(JSlider.HORIZONTAL, 0, 5, 0);
add(slider);
...
slider = new JSlider(JSlider.HORIZONTAL, 0, 5, 0);

That is because the "slider" variable is set to the last JSlider created.

Get rid of the slider variable.

Instead your listener code should be something like:

public void stateChanged(ChangeEvent a)
{
    JSlider slider = (JSlider)e.getSource(); // added
    int value = slider.getValue();

    label.setText("Current value: " + value);
}

So now you have access to the component that generated the event.