Java JList Model addElement（）破壞了列表的可視化表示

Question

只是有奇怪的行為，然后將元素添加到JList模型。 調用addElement（）方法時，列表變為空白，而是添加巨大的空元素，或者將新元素向下移動幾行。 對該方法的另一次調用將問題放回原處，並將其放到問題發生之前和之后的所有元素，包括通過“不穩定”調用添加的項目。 首先，它似乎是繪畫問題，只是repaint調用無濟於事，僅添加新元素即可解決問題。

然后發生問題，然后添加部分元素，涉及不同啟動的相同索引。 從來沒有見過它很快就失敗了。

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                   
}

現在添加了完整的示例代碼。 對造成的不便表示歉意！

Answer 1

這是框架的內部類，用於創建新線程來接收數據並將字符串添加到JList。

Swing組件需要在事件分發線程上進行更新，因此您不能直接在線程中更新該組件。

因此，您可以將更新模型的代碼包裝在SwingUtilities.invokeLater(...)

或者，可以使用SwingWorker並在結果可用時“發布”而不是使用單獨的線程。

閱讀Swing 並發教程中的這一節，以獲取有關這些概念和工作示例的更多信息。