Java JList模型addElement（）打破列表的可視化表示

Question

只有向JList模型添加元素纔會有奇怪的行爲。在調用addElement（）方法時，列表變爲空白，添加巨大的空元素或將新元素向下移動幾行。對於這些方法的另一個要求是在問題出現之前和之後使用所有元素，包括通過「unstable」調用添加的項目。 首先它似乎是繪畫問題，只是重繪調用不起作用，只有添加新元素才能糾正問題。

這個問題發生，然後添加一部分元素，不同的啓動涉及相同的索引。從來沒有見過它在第一個索引很快失敗。

package r; 

import java.io.IOException; 
import java.net.InetAddress; 
import java.net.ServerSocket; 
import java.net.Socket; 
import javax.swing.DefaultListModel; 
import javax.swing.JOptionPane; 


public class R extends javax.swing.JFrame { 

    ServerSocket serverport; 

    /** 
    * Creates new form R 
    */ 
    public R() { 
     initComponents(); 
    } 

    /** 
    * This method is called from within the constructor to initialize the form. 
    * WARNING: Do NOT modify this code. The content of this method is always 
    * regenerated by the Form Editor. 
    */ 
    @SuppressWarnings("unchecked") 
    // <editor-fold defaultstate="collapsed" desc="Generated Code">       
    private void initComponents() { 

     scrollDebug = new javax.swing.JScrollPane(); 
     debugList = new javax.swing.JList(); 

     setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 
     setTitle("Debug"); 
     addWindowListener(new java.awt.event.WindowAdapter() { 
      public void windowOpened(java.awt.event.WindowEvent evt) { 
       formWindowOpened(evt); 
      } 
     }); 

     scrollDebug.setAutoscrolls(true); 

     debugList.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION); 
     scrollDebug.setViewportView(debugList); 

     javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); 
     getContentPane().setLayout(layout); 
     layout.setHorizontalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addComponent(scrollDebug, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, 682, Short.MAX_VALUE) 
     ); 
     layout.setVerticalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addComponent(scrollDebug, javax.swing.GroupLayout.DEFAULT_SIZE, 383, Short.MAX_VALUE) 
     ); 

     pack(); 
     setLocationRelativeTo(null); 
    }// </editor-fold>       

    private void formWindowOpened(java.awt.event.WindowEvent evt) {         
     new Thread() { 

      @Override 
      public void run() { 

       try { 
        serverport = new ServerSocket(33002, 0, InetAddress.getLoopbackAddress()); 

        debugList.setModel(new DefaultListModel()); 

        while (R.this.isVisible()) { 
         new ClientConnection(serverport.accept()).start(); 

        } 

       } catch (IOException ex) { 
        JOptionPane.showMessageDialog(null, "Error opening server port", "Debug", JOptionPane.ERROR_MESSAGE); 
       } 
      } 

     }.start(); 


    }         

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String args[]) { 
     /* Set the Nimbus look and feel */ 
     //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) "> 
     /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel. 
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */ 
     try { 
      for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) { 
       if ("Nimbus".equals(info.getName())) { 
        javax.swing.UIManager.setLookAndFeel(info.getClassName()); 
        break; 
       } 
      } 
     } catch (ClassNotFoundException ex) { 
      java.util.logging.Logger.getLogger(R.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (InstantiationException ex) { 
      java.util.logging.Logger.getLogger(R.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (IllegalAccessException ex) { 
      java.util.logging.Logger.getLogger(R.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (javax.swing.UnsupportedLookAndFeelException ex) { 
      java.util.logging.Logger.getLogger(R.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } 
     //</editor-fold> 

     /* Create and display the form */ 
     java.awt.EventQueue.invokeLater(new Runnable() { 
      public void run() { 
       new R().setVisible(true); 
      } 
     }); 
    } 

    class ClientConnection extends Thread { 
     Socket connection; 
     public ClientConnection(Socket connection){ 
      this.connection=connection; 
     } 


     @Override 
     public void run() { 
      try { 


       connection.getOutputStream().write(String.format("debug>").getBytes()); 
       connection.getOutputStream().flush(); 

       String response = ""; 
       do { 
        response += (char) connection.getInputStream().read(); 
       } while (!response.endsWith(System.lineSeparator())); 
       response = response.replace(System.lineSeparator(), ""); 

       ((DefaultListModel) debugList.getModel()).addElement(response); 

       if (((DefaultListModel) debugList.getModel()).getSize() > 0) { 
        //debugList.ensureIndexIsVisible(((DefaultListModel) debugList.getModel()).getSize() - 1); 
        debugList.setSelectedIndex(((DefaultListModel) debugList.getModel()).getSize() - 1); 
        scrollDebug.getVerticalScrollBar().setValue(scrollDebug.getVerticalScrollBar().getMaximum()); 

       } 

       connection.close(); 
      } catch (IOException ex) { 
       JOptionPane.showMessageDialog(null, "Error receiving connection", "Debug", JOptionPane.ERROR_MESSAGE); 
      } 
     } 

    } 
    // Variables declaration - do not modify      
    private javax.swing.JList debugList; 
    private javax.swing.JScrollPane scrollDebug; 
    // End of variables declaration     
} 

現在添加完整的示例代碼。對造成的不便表示歉意！

Answer 1

這是用於創建接收數據和向JList添加字符串的新線程的框架的內部類。

Swing組件需要在事件派發線程上更新，因此您無法直接在線程中更新組件。

所以你可以用代碼更新模型在SwingUtilities.invokeLater(...)

或代替使用一個單獨的線程，你可以使用一個SwingWorker和「發佈」的結果，因爲他們成爲可用。

閱讀關於Concurrency的Swing教程的部分，以獲得關於這些概念和工作示例的更多信息。