关于jComboBox 的 .removeAllItem();

jcb.removeAllItems()正常来说是不会出问题的，你是自定义了ComboBoxModel、或者做了什么别的操作？最好还是把代码看一下

嗯,我贴一下,貌似有点长,
没定义ComboBoxModel[code]
public class Main extends JFrame {
    JPanel contentPane;
    BorderLayout borderLayout1 = new BorderLayout();
    JMenuBar jMenuBar1 = new JMenuBar();
    JMenu jMenuFile = new JMenu();
    JMenuItem jMenuFileExit = new JMenuItem();
    JMenu jMenuHelp = new JMenu();
    JMenuItem jMenuHelpAbout = new JMenuItem();
    JToolBar jToolBar = new JToolBar();
    JButton jButton1 = new JButton();
    JButton jButton2 = new JButton();
    JButton jButton3 = new JButton();
    ImageIcon image1 = new ImageIcon(insertjs.Main.class.getResource(
            "openFile.png"));
    ImageIcon image2 = new ImageIcon(insertjs.Main.class.getResource(
            "closeFile.png"));
    ImageIcon image3 = new ImageIcon(insertjs.Main.class.getResource("help.png"));
    JLabel statusBar = new JLabel();
    JPanel jPanel1 = new JPanel();
    JPanel jPanel2 = new JPanel();
    BorderLayout borderLayout2 = new BorderLayout();
    JPanel jPanel3 = new JPanel();
    JButton jButton4 = new JButton();
    JButton jButton5 = new JButton();
    JButton jButton6 = new JButton();
    FlowLayout flowLayout1 = new FlowLayout();
    JPanel jPanel4 = new JPanel();
    Border border1 = BorderFactory.createLineBorder(Color.white, 2);
    JButton jButton7 = new JButton();
    GridLayout gridLayout1 = new GridLayout();
    TitledBorder titledBorder1 = new TitledBorder("");
    TitledBorder titledBorder2 = new TitledBorder("");
    JScrollPane jScrollPane1 = new JScrollPane();
    JScrollPane jScrollPane2 = new JScrollPane();
    JComboBox jComboBox1;
    JButton jButton8 = new JButton();
    JButton jButton9 = new JButton();
    JButton jButton10 = new JButton();
    static JTextField jTextField1 = new JTextField();
    JPanel jPanel5 = new JPanel();
    JPanel jPanel6 = new JPanel();
    JPanel jPanel7 = new JPanel();
    BorderLayout borderLayout3 = new BorderLayout();
    BorderLayout borderLayout4 = new BorderLayout();
    BorderLayout borderLayout5 = new BorderLayout();
    FlowLayout flowLayout2 = new FlowLayout();
    JLabel jLabel1 = new JLabel();
    static JTextPane jTextPane1 = new JTextPane();
    static JTextPane jTextPane2 = new JTextPane();
    Border border2 = BorderFactory.createBevelBorder(BevelBorder.LOWERED,
            Color.white, Color.white, new Color(103, 101, 98),
            new Color(148, 145, 140));
    Border border3 = new TitledBorder(border2, "111");
    JPanel jPanel8 = new JPanel();
    JPanel jPanel9 = new JPanel();
    BorderLayout borderLayout6 = new BorderLayout();
    BorderLayout borderLayout7 = new BorderLayout();
    Border border4 = BorderFactory.createEtchedBorder(EtchedBorder.RAISED,
            Color.white, new Color(148, 145, 140));
    Border border5 = new TitledBorder(border4, "修改前");
    Border border6 = BorderFactory.createEmptyBorder();
    Border border7 = new TitledBorder(border6, "修改后");
    Border border8 = BorderFactory.createEtchedBorder(EtchedBorder.RAISED,
            Color.white, new Color(148, 145, 140));
    Border border9 = new TitledBorder(border8, "修改前");
    public Main() {
        try {
            setDefaultCloseOperation(EXIT_ON_CLOSE);
            jbInit();
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

private void jbInit() throws Exception {        border7 = new TitledBorder(BorderFactory.createEtchedBorder(Color.white,
                new Color(148, 145, 140)), "修改后");
        border9 = new TitledBorder(BorderFactory.createEtchedBorder(Color.white,
                new Color(148, 145, 140)), "修改前");
        border5 = new TitledBorder(BorderFactory.createEtchedBorder(Color.white,
                new Color(148, 145, 140)), "修改前");
        Public_Var pv = new Public_Var();
        contentPane = (JPanel) getContentPane();
        contentPane.setLayout(borderLayout1);
        this.setIconImage(null);
        setSize(new Dimension(640, 480));
        setTitle("代码嵌入工具");
        statusBar.setBorder(BorderFactory.createLoweredBevelBorder());
        statusBar.setText(" ");
        jMenuFile.setText("File");
        jMenuFileExit.setText("Exit");
        jMenuFileExit.addActionListener(new Main_jMenuFileExit_ActionAdapter(this));
        jMenuHelp.setText("Help");
        jMenuHelpAbout.setText("About");
        jMenuHelpAbout.addActionListener(new Main_jMenuHelpAbout_ActionAdapter(this));
        jPanel1.setLayout(borderLayout2);
        jPanel2.setLayout(gridLayout1);
        jPanel3.setLayout(flowLayout1);
        jButton4.setText("保存当前文件");
        jButton4.addActionListener(new Main_jButton4_actionAdapter(this));
        jButton5.setText("保存全部文件");
        jButton5.addActionListener(new Main_jButton5_actionAdapter(this));
        jButton6.setText("　退出程序　");
        jButton6.addActionListener(new Main_jButton6_actionAdapter(this));
        jPanel4.setLayout(borderLayout3);
        jPanel2.setBorder(BorderFactory.createLoweredBevelBorder());
        jButton7.setPreferredSize(new Dimension(83, 23));
        jButton7.setText("添加文件");
        jButton7.addActionListener(new Main_jButton7_actionAdapter(this));
        jComboBox1 = new JComboBox();
        jComboBox1.addActionListener(new Main_jComboBox1_actionAdapter(this));
        jButton1.addActionListener(new Main_jButton1_actionAdapter(this));
        jComboBox1.setMinimumSize(new Dimension(100, 21));
        jComboBox1.setPreferredSize(new Dimension(33, 21));
        jComboBox1.setToolTipText("");
        jButton8.setPreferredSize(new Dimension(83, 23));
        jButton8.setToolTipText("");
        jButton8.setText("移除文件");
        jButton8.addActionListener(new Main_jButton8_actionAdapter(this));
        jButton9.setPreferredSize(new Dimension(83, 23));
        jButton9.setText("重新选择");
        jButton9.addActionListener(new Main_jButton9_actionAdapter(this));
        jButton10.setPreferredSize(new Dimension(83, 23));
        jButton10.setText("全部移除");
        jButton10.addActionListener(new Main_jButton10_actionAdapter(this));
        jButton2.addActionListener(new Main_jButton2_actionAdapter(this));
        flowLayout1.setAlignment(FlowLayout.RIGHT);
        jTextField1.setPreferredSize(new Dimension(72, 20));
        jTextField1.setText("1234");
        jTextField1.addActionListener(new Main_jTextField1_actionAdapter(this));
        jPanel6.setLayout(borderLayout4);
        jPanel5.setLayout(borderLayout5);
        jPanel4.setMinimumSize(new Dimension(463, 30));
        jPanel4.setPreferredSize(new Dimension(462, 25));
        jPanel5.setMinimumSize(new Dimension(6, 20));
        jPanel5.setPreferredSize(new Dimension(72, 20));
        jPanel7.setMinimumSize(new Dimension(357, 25));
        jPanel7.setPreferredSize(new Dimension(357, 26));
        jPanel7.setLayout(flowLayout2);
        flowLayout2.setVgap(1);
        borderLayout5.setHgap(3);
        borderLayout5.setVgap(3);
        borderLayout4.setHgap(3);
        borderLayout4.setVgap(3);
        jLabel1.setText("MyID");
        jTextPane1.setEditable(false);
        jPanel8.setLayout(borderLayout6);
        jPanel9.setLayout(borderLayout7);
        jPanel8.setBorder(border7);
        jPanel9.setBorder(border9);
        jMenuBar1.add(jMenuFile);
        jMenuFile.add(jMenuFileExit);
        jMenuBar1.add(jMenuHelp);
        jMenuHelp.add(jMenuHelpAbout);
        setJMenuBar(jMenuBar1);
        jButton1.setIcon(image1);
        jButton1.setToolTipText("打开文件");
        jButton2.setIcon(image2);
        jButton2.setToolTipText("关闭文件");
        jButton3.setIcon(image3);
        jButton3.setToolTipText("Help");
        jToolBar.add(jButton1);
        jToolBar.add(jButton2);
        jToolBar.add(jButton3);
        contentPane.add(statusBar, BorderLayout.SOUTH);
        contentPane.add(jToolBar, java.awt.BorderLayout.NORTH);
        contentPane.add(jPanel1, java.awt.BorderLayout.CENTER);
        jPanel1.add(jPanel2, java.awt.BorderLayout.CENTER);
        jPanel2.add(jPanel9);
        jPanel2.add(jPanel8);
        jScrollPane2.getViewport().add(jTextPane2);
        jPanel1.add(jPanel3, java.awt.BorderLayout.SOUTH);
        jPanel3.add(jButton4, null);
        jPanel3.add(jButton5, null);
        jPanel3.add(jButton6, null);
        jPanel1.add(jPanel4, java.awt.BorderLayout.NORTH);
        jPanel4.add(jPanel6, java.awt.BorderLayout.CENTER);
        jPanel4.add(jPanel7, java.awt.BorderLayout.EAST);
        jPanel4.add(jPanel5, java.awt.BorderLayout.WEST);
        jPanel6.add(jComboBox1, java.awt.BorderLayout.CENTER);
        jPanel7.add(jButton7);
        jPanel7.add(jButton8);
        jPanel7.add(jButton9);
        jPanel7.add(jButton10);
        jPanel5.add(jTextField1, java.awt.BorderLayout.CENTER);
        jPanel5.add(jLabel1, java.awt.BorderLayout.WEST);
        jPanel9.add(jScrollPane1, java.awt.BorderLayout.CENTER);
        jPanel8.add(jScrollPane2, java.awt.BorderLayout.CENTER);
        jScrollPane1.getViewport().add(jTextPane1);
    }    /**
     * File | Exit action performed.
     *
     * @param actionEvent ActionEvent
     */
    void jMenuFileExit_actionPerformed(ActionEvent actionEvent) {
        System.exit(0);
    }

    /**
     * Help | About action performed.
     *
     * @param actionEvent ActionEvent
     */
    void jMenuHelpAbout_actionPerformed(ActionEvent actionEvent) {
        Main_AboutBox dlg = new Main_AboutBox(this);
        Dimension dlgSize = dlg.getPreferredSize();
        Dimension frmSize = getSize();
        Point loc = getLocation();
        dlg.setLocation((frmSize.width - dlgSize.width) / 2 + loc.x,
                        (frmSize.height - dlgSize.height) / 2 + loc.y);
        dlg.setModal(true);
        dlg.pack();
        dlg.setVisible(true);
    }    public void jComboBox1_actionPerformed(ActionEvent e) {
        fileChange();
    }    public void fileChange(){
        File f = (File)this.jComboBox1.getSelectedItem();
        if (f.exists()) {
            try {
                int size = (int) f.length();
                if (size > 1024 * 1024 * 1) {
                    jTextPane1.setText("文件过大，建议人工修改！");
                    return;
                }
                int chars_read = 0;
                FileReader fr = new FileReader(f);
                char[] data = new char[size];
                while (fr.ready()) {
                    chars_read += fr.read(data, chars_read, size - chars_read);
                }
                fr.close();
                String tot = new String(data);
                tot = tot.trim();
                jTextPane1.setText(tot);
                jTextPane1.setCaretPosition(0);                if(tot.indexOf(functions.getJS(this.jTextField1.getText()))!=-1){
                    jTextPane2.setText(tot);
                    jTextPane1.setCaretPosition(tot.replaceAll("\r","").lastIndexOf(functions.getJS(this.jTextField1.getText())));
                    return;
                }
                int where = tot.replaceAll("\r","").lastIndexOf("</body>");
                if(where==-1){
                    where = tot.replaceAll("\r","").length();
                }                StyleContext sc = StyleContext.getDefaultStyleContext();
                AttributeSet aset = sc.addAttribute(SimpleAttributeSet.EMPTY,StyleConstants.Foreground, Color.black);
                jTextPane2.setCharacterAttributes(aset, false);
                jTextPane2.setText(tot);                aset = sc.addAttribute(SimpleAttributeSet.EMPTY,StyleConstants.Foreground, Color.red);
                jTextPane2.setCaretPosition(where); //定位
                jTextPane2.setCharacterAttributes(aset, false);
                jTextPane2.replaceSelection(functions.getJS(this.jTextField1.getText()));
            } catch (Exception ex) {
                statusBar.setText("Error opening:" + ex);
                System.out.println("select:" + ex);
            }
        }    }    public void jButton1_actionPerformed(ActionEvent e) {
        chooseFiles(false);
    }    public void chooseFiles(boolean del) {
        String ID = Main.jTextField1.getText();
        if(!functions.isNum(ID)){
            functions.messageBox("请正确输入您的唯一合法ID，确保嵌入代码的正确。");
            return;
        }
        Public_Var.centerid=ID;
        JFileChooser jfc = new JFileChooser();
        jfc.setDialogType(JFileChooser.FILES_ONLY);
        jfc.setMultiSelectionEnabled(true);        ExtensionFileFilter filter = new ExtensionFileFilter();
        filter.addExtension("txt");
        filter.addExtension("htm");
        filter.addExtension("html");
        filter.addExtension("shtml");
        filter.addExtension("shtm");
        filter.addExtension("jsp");
        filter.addExtension("asp");
        filter.addExtension("php");
        filter.addExtension("do");
        filter.addExtension("aspx");
        filter.setDescription("各种文本文档");
        jfc.setFileFilter(filter);        int result = jfc.showOpenDialog(this);
        if (result == jfc.APPROVE_OPTION) {
            if (del) { //重新添加全部
                this.jComboBox1.removeAllItems();
            }
            File[] files = jfc.getSelectedFiles();
            for (int i = 0; i < files.length; i++) {
                this.jComboBox1.addItem(files[i].getAbsoluteFile());
                if(i==files.length-1){
                    this.jComboBox1.setSelectedItem(files[i].getAbsoluteFile());
                }
            }
            fileChange();
        }    }

public void jButton7_actionPerformed(ActionEvent e) {
        chooseFiles(false);
    }    public void jButton9_actionPerformed(ActionEvent e) {
        chooseFiles(true);
    }    public void jButton10_actionPerformed(ActionEvent e) {
        removeall();
    }    public void jButton8_actionPerformed(ActionEvent e) {
        remove();
    }    public void remove() {
        if(jComboBox1.getItemCount()==1){
            removeall();
        }
        else{
            Object o = this.jComboBox1.getSelectedItem();
            try {
                this.jComboBox1.removeItem(o);
            } catch (Exception e) {
                System.out.println("remove():" + e);
            }
        }
    }    public void removeall() {
        try{
            //System.out.println(this.jComboBox1.isValid());
            this.jComboBox1.removeAllItems();
            jTextPane1.setText("");
            jTextPane2.setText("");
        }catch(Exception e){
            System.out.println("removeall():"+e);
        }
    }    public void jButton2_actionPerformed(ActionEvent e) {
        remove();
    }    public void jTextField1_actionPerformed(ActionEvent e) {    }    public void jButton6_actionPerformed(ActionEvent e) {
        if(functions.confirmBox("确认退出？")==0){
            System.exit(0);
        }
    }    public void jButton4_actionPerformed(ActionEvent e) {
        if(this.jComboBox1.getItemCount()>0){
            saveFile();
        }
        else{
            functions.messageBox("当前未打开任何文件。");
        }
    }
    public void saveFile(){
        JFileChooser jfc = new JFileChooser();
        jfc.setSelectedFile((File)this.jComboBox1.getSelectedItem());
        if(jfc.showSaveDialog(this)==JFileChooser.APPROVE_OPTION){
            File f = jfc.getSelectedFile();
            String fcontent = Main.jTextPane2.getText();
            if (f.canWrite()) {
                try {
                    FileWriter fw = new FileWriter(f, true);
                    fw.write(fcontent);
                    fw.close();
                } catch (Exception ex) {
                    System.out.println("saveFile:" + ex);
                }
                functions.messageBox("当前文件保存完毕。");
            } else {
                functions.messageBox("当前文件无法保存，请关闭其他操作本文件的程序。");
            }
        }
    }    public void saveAllFiles(){
        for(int i=0;i<this.jComboBox1.getItemCount();i++){
            try{
                File f = (File)this.jComboBox1.getItemAt(i);
                int size = (int) f.length();
                if (size > 1024 * 1024 * 1) {
                    jTextPane1.setText("文件过大，建议人工修改！");
                    return;
                }
                int chars_read = 0;
                FileReader fr = new FileReader(f);
                char[] data = new char[size];
                while (fr.ready()) {
                    chars_read += fr.read(data, chars_read, size - chars_read);
                }
                fr.close();
                String tot = new String(data);
                tot = tot.trim();
                if(tot.indexOf(functions.getJS(this.jTextField1.getText()))!=-1){
                    continue;
                }
                int b = tot.lastIndexOf("</body>");
                if(b!=-1){
                    String tot1=tot.substring(0,b);
                    String tot2=tot.substring(b);
                    tot = tot1 + functions.getJS(this.jTextField1.getText()) + tot2;
                }
                else{
                    tot = tot + functions.getJS(this.jTextField1.getText());
                }
                FileWriter fw = new FileWriter(f, true);
                fw.write(tot);
                fw.close();
            }
            catch(Exception e){
                System.out.println("saveAllFiles():"+e);
            }
        }
        functions.messageBox("修改完毕，共"+this.jComboBox1.getItemCount()+"个文件。");
    }    public void jButton5_actionPerformed(ActionEvent e) {
        if(functions.confirmBox("确认保存所有打开文件？")==0){
            saveAllFiles();
        }
    }
}说我回复太快！如果你是恶意刷楼，将会受到严厉惩罚！ ???

异常:Hit uncaught exception java.lang.NullPointerException
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at insertjs.Main.fileChange(Main.java:271)
at insertjs.Main.jComboBox1_actionPerformed(Main.java:266)
at insertjs.Main_jComboBox1_actionAdapter.actionPerformed(Main.java:623)
at javax.swing.JComboBox.fireActionEvent(JComboBox.java:1197)
at javax.swing.JComboBox.contentsChanged(JComboBox.java:1268)
at javax.swing.JComboBox.intervalRemoved(JComboBox.java:1288)
at javax.swing.AbstractListModel.fireIntervalRemoved(AbstractListModel.java:161)
at javax.swing.DefaultComboBoxModel.removeAllElements(DefaultComboBoxModel.java:169)
at javax.swing.JComboBox.removeAllItems(JComboBox.java:745)
at insertjs.Main.removeall(Main.java:396)
at insertjs.Main.jButton10_actionPerformed(Main.java:372)
at insertjs.Main_jButton10_actionAdapter.actionPerformed(Main.java:575)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5488)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3093)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

我用try catch
处理后
程序不会崩溃，但再添加几个file到这个jComboBox里后，onchange事件就不响应了。

删除的时候会触发 JComboBox的jButton1_actionPerformed。处理的办法是：首先把JComboBox的ActionListener做成一个全局变量listener；在删除之前先JComboBox.removeActionListener(listener);处理逻辑完成；调用JComboBox.addActionListener(listener);

果然是这样，非常感谢，gongfuliang。愿圣光指引你的道路。

调试易

关于jComboBox 的 .removeAllItem();

解决方案 »