ChangeListener未觸發

Question

我正在學習有關更改偵聽器的信息，並且想知道爲什麼我的代碼的一部分在用戶移動滑塊時未觸發更改偵聽器。

這是聽衆。一切都是在同一個方法：

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下面是一些代碼，增加了聽衆：

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); 

這個代碼是基於上面的代碼塊，但是當用戶移動滑塊什麼也沒有發生：

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

好像有什麼不對您的代碼中的一部分，如在你的showDate()方法評論中指出，這件事情完美的作品在此代碼：

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(); 
      } 
     }); 
    } 
}