的Java Swing的JPanel不會更新

Question

這是我的代碼：

private class ValueReporter implements ListSelectionListener { 

    public void valueChanged(ListSelectionEvent event) { 
     if (!event.getValueIsAdjusting()) { 
      jTextField9.setText(jList2.getSelectedValue().toString()); 
      JLabel someLabel = new JLabel("Some new Label"); 
      jPanel7.add(someLabel); 
      jPanel7.revalidate(); 
     } 
    } 
} 

的「jTextField9」得與文本，但面板「jPanel7」不更新 已分配給它的新標籤更新。

Answer 1

下面的代碼片段我趕緊扔在一起，這增加了標籤的JPanel和repaint小號

import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.Timer; 
import java.awt.EventQueue; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

public class UpdatingJPanel extends JPanel{ 

    public UpdatingJPanel() { 
    Timer timer = new Timer(1500, new ActionListener() { 
     @Override 
     public void actionPerformed(ActionEvent e) { 
     UpdatingJPanel.this.add(new JLabel("A label")); 
     UpdatingJPanel.this.revalidate(); 
     UpdatingJPanel.this.repaint(); 

     if(UpdatingJPanel.this.getComponentCount() == 0){ 
      ((Timer) e.getSource()).stop(); 
     } 
     } 
    }); 
    timer.setRepeats(true); 
    timer.start(); 
    } 

    public static void main(String[] args) { 
    EventQueue.invokeLater(new Runnable() { 
     @Override 
     public void run() { 
     JFrame testFrame = new JFrame(); 
     testFrame.getContentPane().add(new UpdatingJPanel()); 
     //not using pack() as the panel is still empty and I want avoid 
     //resizing when adding labels as that triggers a repaint 
     testFrame.setSize(200,200); 
     testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     testFrame.setVisible(true); 
     } 
    }); 

    } 
}