如何配置JComboBox在创建时不选择FIRST元素？
问题：
更新：
从Java SE 6 API：
public JComboBox（）使用默认数据模型创建JComboBox。 默认数据模型是一个空的对象列表。 使用addItem添加项目。 默认情况下，数据模型中的第一项将被选中。
所以我改为JComboBox（模型），因为API说：
public JComboBox（ComboBoxModel aModel）创建一个JComboBox，从现有的ComboBoxModel获取其项目。 由于提供了ComboBoxModel，使用此构造函数创建的combobox不会创建默认的combobox模型，并且可能会影响插入，移除和添加方法的行为方式。
我尝试了以下方法：
DefaultComboBoxModel model = new DefaultComboBoxModel(); model.setSelectedItem(null); suggestionComboBox = new JComboBox(model); suggestionComboBox.setModel(model); 但无法让它工作，第一个项目仍然被选中。
任何能够提出工作实例的人都会非常感激。
post的老部分：
我正在使用JComboBox，并尝试在我的代码中使用setSelectionIndex(-1) （此代码放在caretInvoke() ）
suggestionComboBox.removeAllItems(); for (int i = 0; i < suggestions.length; i++) { suggestionComboBox.addItem(suggestions[i]); } suggestionComboBox.setSelectedIndex(-1); suggestionComboBox.setEnabled(true);
这是添加到窗格时的初始设置：
suggestionComboBox = new JComboBox(); suggestionComboBox.setEditable(false); suggestionComboBox.setPreferredSize(new Dimension(25, 25)); suggestionComboBox.addActionListener(new SuggestionComboBoxListener());
当caretInvoke触发ComboBox初始化时，即使在用户选择元素之前，actionPerformed已经被触发（我在这里尝试了一个JOptionPane）： http ： //i126.photobucket.com/albums/p109/eXPeri3nc3/StackOverflow/combo1.png http://sofzh.miximages.com/java/combo2.png http://sofzh.miximages.com/java/combo3.png
问题是：当用户从ComboBox中选择一个元素时，我的程序会自动插入所选文本。 因此，无需用户选择任何内容，它就会自动插入。
在这种情况下如何克服这个问题呢？ 谢谢。
这是我的SSCCE :(最后）
package components; import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.GridLayout; import java.awt.Insets; import java.awt.Rectangle; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JSplitPane; import javax.swing.JTextArea; import javax.swing.JTextPane; import javax.swing.JToolBar; import javax.swing.SwingUtilities; import javax.swing.UIManager; import javax.swing.event.CaretEvent; import javax.swing.event.CaretListener; import javax.swing.text.AbstractDocument; import javax.swing.text.BadLocationException; import javax.swing.text.StyledDocument; public class Temp extends JFrame { JTextPane textPane; AbstractDocument doc; JTextArea changeLog; String newline = "\n"; private JComboBox suggestionComboBox; private JPanel suggestionPanel; private JLabel suggestionLabel; private JButton openButton, saveButton, aboutButton; public Temp() { super("Snort Ruleset IDE"); //Create the text pane and configure it. textPane = new JTextPane(); textPane.setCaretPosition(0); textPane.setMargin(new Insets(5, 5, 5, 5)); StyledDocument styledDoc = textPane.getStyledDocument(); if (styledDoc instanceof AbstractDocument) { doc = (AbstractDocument) styledDoc; //doc.setDocumentFilter(new DocumentSizeFilter(MAX_CHARACTERS)); } else { System.err.println("Text pane's document isn't an AbstractDocument!"); System.exit(-1); } JScrollPane scrollPane = new JScrollPane(textPane); scrollPane.setPreferredSize(new Dimension(700, 350)); //Create the text area for the status log and configure it. //changeLog = new JTextArea(10, 30); //changeLog.setEditable(false); //JScrollPane scrollPaneForLog = new JScrollPane(changeLog); //Create a JPanel for the suggestion area suggestionPanel = new JPanel(new BorderLayout()); suggestionPanel.setVisible(true); suggestionLabel = new JLabel("Suggestion is not active at the moment."); suggestionLabel.setPreferredSize(new Dimension(100, 50)); suggestionLabel.setMaximumSize(new Dimension(100, 50)); suggestionComboBox = new JComboBox(); suggestionComboBox.setEditable(false); suggestionComboBox.setPreferredSize(new Dimension(25, 25)); //suggestionComboBox.addActionListener(new SuggestionComboBoxListener()); suggestionComboBox.addItemListener(new SuggestionComboBoxListener()); //suggestionComboBox.setSelectedIndex(-1); //add the suggestionLabel and suggestionComboBox to pane suggestionPanel.add(suggestionLabel, BorderLayout.CENTER); suggestionPanel.add(suggestionComboBox, BorderLayout.PAGE_END); JScrollPane sp = new JScrollPane(suggestionPanel); JScrollPane scrollPaneForSuggestion = new JScrollPane(suggestionPanel); //Create a split pane for the change log and the text area. JSplitPane splitPane = new JSplitPane( JSplitPane.VERTICAL_SPLIT, scrollPane, scrollPaneForSuggestion); splitPane.setOneTouchExpandable(true); splitPane.setResizeWeight(1.0); //Disables the moving of divider splitPane.setEnabled(false); //splitPane.setDividerLocation(splitPane.getHeight()); //splitPane.setPreferredSize(new Dimension(640,400)); //Create the status area. JPanel statusPane = new JPanel(new GridLayout(1, 1)); CaretListenerLabel caretListenerLabel = new CaretListenerLabel("Status: Ready"); statusPane.add(caretListenerLabel); //Create the toolbar JToolBar toolBar = new JToolBar(); toolBar.setFloatable(false); toolBar.setRollover(true); openButton = new JButton("Open Snort Ruleset"); toolBar.add(openButton); saveButton = new JButton("Save Ruleset"); toolBar.add(saveButton); toolBar.addSeparator(); aboutButton = new JButton("About"); toolBar.add(aboutButton); //Add the components. getContentPane().add(toolBar, BorderLayout.PAGE_START); getContentPane().add(splitPane, BorderLayout.CENTER); getContentPane().add(statusPane, BorderLayout.PAGE_END); JMenu editMenu = createEditMenu(); JMenu styleMenu = createStyleMenu(); JMenuBar mb = new JMenuBar(); mb.add(editMenu); mb.add(styleMenu); setJMenuBar(mb); //Put the initial text into the text pane. //initDocument(); textPane.setCaretPosition(0); //Start watching for undoable edits and caret changes. textPane.addCaretListener(caretListenerLabel); SwingUtilities.invokeLater(new Runnable() { public void run() { textPane.requestFocusInWindow(); } }); } //This listens for and reports caret movements. protected class CaretListenerLabel extends JLabel implements CaretListener { public CaretListenerLabel(String label) { super(label); } //Might not be invoked from the event dispatch thread. public void caretUpdate(CaretEvent e) { caretInvoke(e.getDot(), e.getMark()); } protected void caretInvoke(final int dot, final int mark) { SwingUtilities.invokeLater(new Runnable() { public void run() { try { Rectangle caretCoords = textPane.modelToView(dot); //Find suggestion suggestionComboBox.removeAllItems(); for (int i = 0; i < 5; i++) { suggestionComboBox.addItem(Integer.toString(i)); } //suggestionComboBox.setSelectedItem(null); suggestionComboBox.setEnabled(true); suggestionLabel.setText("The following keywords are normally used as well. Click to use keyword(s). "); //changeLog.setText("The following keywords are suggested to be used together: " + str); } catch (BadLocationException ble) { setText("caret: text position: " + dot + newline); System.out.println("Bad Location Exception"); } } }); } } public class SuggestionComboBoxListener implements ItemListener { //public void actionPerformed(ActionEvent e) { public void itemStateChanged(ItemEvent e) { if (e.getStateChange() == ItemEvent.SELECTED) { JComboBox cb = (JComboBox)e.getSource(); String selection = (String) cb.getSelectedItem(); JOptionPane.showMessageDialog(null, "Item is selected", "Information", JOptionPane.INFORMATION_MESSAGE); } } } /* * Menu Creation */ //Create the edit menu. protected JMenu createEditMenu() { JMenu menu = new JMenu("Edit"); return menu; } protected JMenu createStyleMenu() { JMenu menu = new JMenu("Style"); return menu; } private static void createAndShowGUI() { //Create and set up the window. final Temp frame = new Temp(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } //The standard main method. public static void main(String[] args) { //Schedule a job for the event dispatch thread: //creating and showing this application's GUI. SwingUtilities.invokeLater(new Runnable() { public void run() { //Turn off metal's use of bold fonts UIManager.put("swing.boldMetal", Boolean.FALSE); createAndShowGUI(); } }); } }
在对combobox进行任何更改之前，需要删除ItemListener，并在完成后将其添加回来。
像这样的东西：
import java.awt.BorderLayout; import java.awt.Component; import java.awt.Dimension; import java.awt.Insets; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTextPane; import javax.swing.SwingUtilities; import javax.swing.event.CaretEvent; import javax.swing.event.CaretListener; public class Suggestions { private JFrame frame; private JTextPane textPane; private JComboBox suggestionComboBox; private SuggestionComboBoxListener selectionListener; public Suggestions() { frame = new JFrame("Snort Ruleset IDE"); textPane = new JTextPane(); textPane.setCaretPosition(0); textPane.setMargin(new Insets(5, 5, 5, 5)); textPane.addCaretListener(new SuggestionCaretListener()); JScrollPane textEntryScrollPane = new JScrollPane(textPane); textEntryScrollPane.setPreferredSize(new Dimension(300, 400)); selectionListener = new SuggestionComboBoxListener(frame); suggestionComboBox = new JComboBox(); suggestionComboBox.setEditable(false); suggestionComboBox.setPreferredSize(new Dimension(25, 25)); suggestionComboBox.addItemListener(selectionListener); JPanel suggestionPanel = new JPanel(new BorderLayout()); suggestionPanel.add(suggestionComboBox, BorderLayout.PAGE_END); frame.getContentPane().add(textEntryScrollPane, BorderLayout.NORTH); frame.getContentPane().add(suggestionPanel, BorderLayout.SOUTH); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.pack(); frame.setVisible(true); } private final class SuggestionCaretListener implements CaretListener { @Override public void caretUpdate(CaretEvent e) { SwingUtilities.invokeLater(new Runnable() { public void run() { generateSuggestions(); } }); } } public static final class SuggestionComboBoxListener implements ItemListener { Component parent; public SuggestionComboBoxListener(Component parent) { this.parent = parent; } public void itemStateChanged(ItemEvent e) { if (e.getStateChange() == ItemEvent.SELECTED) { JComboBox cb = (JComboBox) e.getSource(); String selection = (String) cb.getSelectedItem(); JOptionPane.showMessageDialog(parent, "The selected item is: " + selection, "Information", JOptionPane.INFORMATION_MESSAGE); } } } void generateSuggestions() { suggestionComboBox.removeItemListener(selectionListener); suggestionComboBox.removeAllItems(); for (int i = 0; i < 5; i++) { suggestionComboBox.addItem(Integer.toString(i)); } suggestionComboBox.setEnabled(true); suggestionComboBox.addItemListener(selectionListener); } public static void main(String[] args) { new Suggestions(); } }
顺便说一下，你发布的不是SSCCE它是你的代码转储。 SSCCE应该只有足够的代码来重现您遇到的问题。
使用
setSelectedItem(null);
请尝试使用ItemListener而不是ActionListener。
如果您想在第一次输入之后想要，并且您的combox立即为空，那么只需记下下面提到的代码：
jComboBox1.setSelectedIndex(0);
并且您的combox将自动重置