多个JComboBox

好的，有两个jcombobox显示一个是航class离开的城市列表，另一个是当用户从两个combobox中选择一个选项时飞行的城市列表我希望它显示你从巴黎飞到贝尔法斯特，我有以下代码，但我不知道如何添加另一个选择，因为它只是说你从巴黎飞来。

if(e.getSource() == ownerList ) { JComboBox cb = (JComboBox)e.getSource(); String ownerName = (String)cb.getSelectedItem(); if(ownerName.equals("Paris")) { text9.setText(ownerName); int flag = 10; drawApp(flag); } } if(e.getSource() == cityList ) { JComboBox cb = (JComboBox)e.getSource(); String cityName = (String)cb.getSelectedItem(); if(cityName.equals("Belfast")) { text10.setText(cityName); int flag = 10; drawApp(flag); } } 

Answer 1

我有点改写了整个剧本（对不起）……

 import javax.swing.*; import java.awt.*; import java.awt.event.*; class FlightBooker extends JFrame implements ActionListener { FlightBooker() { super("Book a Flight!"); JLabel fromLabel = new JLabel("Current Location:"); JComboBox fromLocations = new JComboBox(); fromLocations.addItem("Paris"); //fromLocations.addItem(someLocation); //... JLabel toLabel = new JLabel("Destination:"); JComboBox destinations = new JComboBox(); destinations.addItem("Belfast"); //destinations.addItem(someLocation); //... JButton okButton = new JButton("OK"); JLabel status = new JLabel(""); add(fromLabel); add(fromLocations); add(toLabel); add(destinations); okButton.addActionListener(this); add(okButton); add(status); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); pack(); } public void actionPerformed(ActionEvent event) { Object from = fromLocations.getSelectedItem(); String FROM = from.toString(); Object to = destinations.getSelectedItem(); String TO = to.toString(); status.setText("You're flying from " + FROM + "to " + TO + "."); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { new FlightBooker().setVisible(true); } }); } } 

这应该做你想要的。 🙂

Answer 2

这是您的SSCCE ，但是我将ActionListener更改为JLboBox的ItemListener ，并将您的main方法包装到invokeLater（）中 ，将setBounds(int, int, int, int)更改为LayoutManager的完全作业， JComponents返回顶层的 Size 容器等等……

然后

来自代码

 import java.awt.*; import java.awt.event.*; import javax.swing.*; public class ComboBoxListeners { private JFrame f; private JComboBox flyFromCombo; private JComboBox flyToCombo; private JLabel tripLabel = new JLabel(); private Object[] itemsFrom; private Object[] itemsTo; public ComboBoxListeners() { itemsFrom = new Object[]{"-", "First - From", "Second - From", "Third - From"}; itemsTo = new Object[]{"-", "First - To", "Second - To", "Third - To"}; //flyFromCombo.setPrototypeDisplayValue("################################################"); flyFromCombo = new JComboBox(itemsFrom); flyFromCombo.addItemListener(new ItemListener() { @Override public void itemStateChanged(ItemEvent e) { if ((e.getStateChange() == ItemEvent.SELECTED)) { String str = flyFromCombo.getSelectedItem().toString(); String str1 = flyToCombo.getSelectedItem().toString(); setLabelText(str, str1); } } }); flyToCombo = new JComboBox(itemsTo); flyToCombo.addItemListener(new ItemListener() { @Override public void itemStateChanged(ItemEvent e) { if ((e.getStateChange() == ItemEvent.SELECTED)) { String str = flyFromCombo.getSelectedItem().toString(); String str1 = flyToCombo.getSelectedItem().toString(); setLabelText(str, str1); } } }); tripLabel.setPreferredSize(new Dimension(400, 30)); f = new JFrame("ComboBox ItemListeners"); f.setLayout(new GridLayout(0, 1, 15, 15)); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.add(flyFromCombo); f.add(flyToCombo); f.add(tripLabel); f.setLocation(150, 150); f.pack(); f.setVisible(true); } private void setLabelText(String str1, String str2) { String textForLabel = ""; String helpStringFirst = str1.trim(); if (helpStringFirst != null && helpStringFirst.length() > 0) { if (!helpStringFirst.equals("-")) { textForLabel = "Flight No57. from : " + helpStringFirst; } else { textForLabel = "Flight from Un-Know : "; } } String helpStringSecond = str2.trim(); if (helpStringSecond != null && helpStringSecond.length() > 0) { if (!helpStringSecond.equals("-")) { textForLabel = textForLabel + " --> to : " + helpStringSecond; } else { textForLabel += " to : Un-Know "; } } final String pushTextForLabel = textForLabel; SwingUtilities.invokeLater(new Runnable() { @Override public void run() { tripLabel.setText(pushTextForLabel); } }); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { ComboBoxListeners comboBoxListeners = new ComboBoxListeners(); } }); } } 

Answer 3

看看这段代码片段， 看看它是如何工作的 。

 package lca; import javax.swing.JFrame; import javax.swing.UIManager; import javax.swing.JComboBox; import javax.swing.JButton; import java.awt.event.ActionListener; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.awt.EventQueue; import java.awt.event.ActionEvent; import java.awt.event.ItemListener; import java.awt.event.ItemEvent; public class combo extends JFrame { Connection connection = null; PreparedStatement prepared = null; ResultSet rs = null; JComboBox comboBox,comboBox_1,comboBox_2; String sel1 , sel2; public combo() { getContentPane().setLayout(null); comboBox = new JComboBox(); comboBox.addItemListener(new ItemListener() { public void itemStateChanged(ItemEvent e) { sel1 = (String) comboBox.getSelectedItem(); popcombo1(); comboBox_1.setSelectedIndex(-1); } }); comboBox.setBounds(41, 77, 146, 20); getContentPane().add(comboBox); comboBox_1 = new JComboBox(); comboBox_1.addItemListener(new ItemListener() { public void itemStateChanged(ItemEvent e) { sel2 = (String) comboBox_1.getSelectedItem(); popcombo2(); } }); comboBox_1.setBounds(41, 108, 146, 20); getContentPane().add(comboBox_1); comboBox_2 = new JComboBox(); comboBox_2.setBounds(41, 139, 146, 20); getContentPane().add(comboBox_2); JButton btnLoad = new JButton("Load"); btnLoad.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { try { String sql1 = "SELECT DISTINCT Name FROM Project_info " ; Class.forName("org.sqlite.JDBC"); Connection connection2 = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\Nitesh\\Desktop\\SM\\Project.sqlite"); prepared = connection2.prepareStatement(sql1); rs = prepared.executeQuery(); while(rs.next()) { String name = rs.getString("Name"); comboBox.addItem(name); } connection2.close();} catch(Exception e3) { System.err.println( e3.getClass().getName() + ": " + e3.getMessage() ); } finally { try{ rs.close(); prepared.close(); //connection2.close(); } catch(Exception e1) { } } comboBox.setSelectedIndex(-1); } }); btnLoad.setBounds(41, 11, 89, 23); getContentPane().add(btnLoad); } public static void main(String[] args) { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Throwable e) { e.printStackTrace(); } EventQueue.invokeLater(new Runnable() { public void run() { try { combo frame = new combo(); frame.setVisible(true); } catch (Exception e) { e.printStackTrace(); } } }); } public void popcombo1() { comboBox_1.removeAllItems(); try { String sql1 = "SELECT DISTINCT Pro_cat FROM Project_info where Name = '" +sel1 + "'" ; Class.forName("org.sqlite.JDBC"); Connection connection2 = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\Nitesh\\Desktop\\SM\\Project.sqlite"); prepared = connection2.prepareStatement(sql1); rs = prepared.executeQuery(); while(rs.next()) { String name = rs.getString("Pro_cat"); comboBox_1.addItem(name); } connection2.close();} catch(Exception e3) { System.err.println( e3.getClass().getName() + ": " + e3.getMessage() ); } finally { try{ rs.close(); prepared.close(); //connection2.close(); } catch(Exception e1) { } } comboBox_1.setSelectedIndex(-1); } public void popcombo2() { comboBox_2.removeAllItems(); try { String sql1 = "SELECT DISTINCT Sub_cat FROM Project_info where Pro_cat = '" +sel2 + "' AND Name = '"+ sel1+ "'" ; Class.forName("org.sqlite.JDBC"); Connection connection2 = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\Nitesh\\Desktop\\SM\\Project.sqlite"); prepared = connection2.prepareStatement(sql1); rs = prepared.executeQuery(); while(rs.next()) { String name = rs.getString("Sub_cat"); comboBox_2.addItem(name); } connection2.close();} catch(Exception e3) { System.err.println( e3.getClass().getName() + ": " + e3.getMessage() ); } finally { try{ rs.close(); prepared.close(); //connection2.close(); } catch(Exception e1) { } } } }