ChangeListener未触发

Question

我正在学习有关更改侦听器的信息，并且想知道为什么我的代码的一部分在用户移动滑块时未触发更改侦听器。

这是听众。一切都是在同一个方法：

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下面是一些代码，增加了听众：

m_slDay = new JSlider(JSlider.HORIZONTAL, 1, maxDays, 
    m_calendar.get(Calendar.DAY_OF_MONTH)); 
m_slDay.setPaintLabels(true); 
m_slDay.setMajorTickSpacing(5); 
m_slDay.setMinorTickSpacing(1); 
m_slDay.setPaintTicks(true); 

// This line of code seems to work. 
m_slDay.addChangeListener(lst); 

p = new JPanel(); 
p.setBorder(new TitledBorder(new EtchedBorder(), "Day")); 
p.setLayout(new BoxLayout(p, BoxLayout.Y_AXIS)); 
p.add(Box.createRigidArea(RIGID_DIMENSION)); 
p.add(m_slDay); 
p.add(Box.createRigidArea(RIGID_DIMENSION)); 
p1.add(p); 

这个代码是基于上面的代码块，但是当用户移动滑块什么也没有发生：

m_slDayOfWeek = new JSlider(JSlider.HORIZONTAL, 1, maxDaysOfTheWeek, 
    m_calendar.get(Calendar.DAY_OF_WEEK)); 
m_slDayOfWeek.setPaintLabels(true); 
m_slDayOfWeek.setMajorTickSpacing(1); 
m_slDayOfWeek.setMinorTickSpacing(1); 
m_slDayOfWeek.setPaintTicks(true); 

// This one is not working and I'm not sure why it's happening. 
m_slDayOfWeek.addChangeListener(lst); 

p = new JPanel(); 
p.setBorder(new TitledBorder(new EtchedBorder(), "Day of Week")); 
p.setLayout(new BoxLayout(p, BoxLayout.Y_AXIS)); 
p.add(Box.createRigidArea(RIGID_DIMENSION)); 
p.add(m_slDayOfWeek); 
p.add(Box.createRigidArea(RIGID_DIMENSION)); 
p1.add(p); 

Answer 1

好像有什么不对您的代码中的一部分，如在你的showDate()方法评论中指出，这件事情完美的作品在此代码：

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

public class SliderChangeEffect extends JFrame 
{ 
    private JSlider slider; 
    private int count = 0; 
    private ChangeListener changeListener = new ChangeListener() 
    { 
     public void stateChanged(ChangeEvent ce) 
     { 
      System.out.println(count++); 
     } 
    }; 

    private void createAndDisplayGUI() 
    { 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     setLocationByPlatform(true); 

     JPanel contentPane = new JPanel(); 
     contentPane.setOpaque(true); 

     slider = new JSlider(0, 10, 5); 
     slider.setMajorTickSpacing(2); 
     slider.setMinorTickSpacing(1); 
     slider.addChangeListener(changeListener); 

     contentPane.add(slider); 

     getContentPane().add(contentPane); 
     pack(); 
     setVisible(true); 
    } 

    public static void main(String... args) 
    { 
     SwingUtilities.invokeLater(new Runnable() 
     { 
      public void run() 
      { 
       new SliderChangeEffect().createAndDisplayGUI(); 
      } 
     }); 
    } 
}