JCombobox改变了另一个JCombobox

我正在尝试组合2个jcomboboxes。 1个combobox用于显示类别的开销。 第二个combobox是从文本文件中读取文件以显示产品类型。 如果我改变第一个combobox，我希望第二个combobox将根据用户在第一个combobox中选择的内容而改变。

我还有机会从文本文件中加载其他combobox吗？ 这个子项目不是Arrays，但与之前一样，因为它位于cboperson的代码底部。

编辑的代码：

private JComboBox cboCategory; private JComboBox cboPerson; private JComboBox cboItem; public String itemChange = "groceries.txt"; public ExpenditureTracker() {...... String[] items = {"Select Item", "Groceries", "Bills", "Travelling", "Leasure", "Other"}; mainComboBox = new JComboBox(items); mainComboBox.addActionListener(this); mainComboBox.addItemListener(this); //prevent action events from being fired when the up/down arrow keys are used //mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE); mainComboBox.setBounds(113, 138, 85, 20); importPanel.add(mainComboBox); subComboBox = new JComboBox();// Create sub combo box with multiple models subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4 subComboBox.addItemListener(this); subComboBox.setBounds(113, 188, 85, 20); importPanel.add(subComboBox); String[] subItems1 = {"Select Color", "Red", "Blue", "Green"}; subItems.put(items[1], subItems1); String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"}; subItems.put(items[2], subItems2); String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"}; subItems.put(items[3], subItems3); String[] subItems4 = {"Select Fruit", "Apple", "Orange", "Banana"}; subItems.put(items[4], subItems3); String[] subItems5 = {"Select Fruit", "Apple", "Orange", "Banana"}; subItems.put(items[5], subItems3); loadDataTocboPerson(); } private void loadDataToCboPerson() { Scanner fileReader = new Scanner(getClass().getResourceAsStream( itemChange)); try { DefaultComboBoxModel model = new DefaultComboBoxModel(); while (fileReader.hasNextLine()) { model.addElement(fileReader.nextLine()); } cboItem.setModel(model); } finally { fileReader.close(); } } 

Answer 1

例如

 import java.awt.*; import java.awt.event.*; import java.util.*; import javax.swing.*; public class ComboBoxTwo extends JFrame implements ActionListener, ItemListener { private static final long serialVersionUID = 1L; private JComboBox mainComboBox; private JComboBox subComboBox; private Hashtable subItems = new Hashtable(); public ComboBoxTwo() { String[] items = {"Select Item", "Color", "Shape", "Fruit"}; mainComboBox = new JComboBox(items); mainComboBox.addActionListener(this); mainComboBox.addItemListener(this); //prevent action events from being fired when the up/down arrow keys are used //mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE); getContentPane().add(mainComboBox, BorderLayout.WEST); subComboBox = new JComboBox();// Create sub combo box with multiple models subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4 subComboBox.addItemListener(this); getContentPane().add(subComboBox, BorderLayout.EAST); String[] subItems1 = {"Select Color", "Red", "Blue", "Green"}; subItems.put(items[1], subItems1); String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"}; subItems.put(items[2], subItems2); String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"}; subItems.put(items[3], subItems3); // mainComboBox.setSelectedIndex(1); } @Override public void actionPerformed(ActionEvent e) { String item = (String) mainComboBox.getSelectedItem(); Object o = subItems.get(item); if (o == null) { subComboBox.setModel(new DefaultComboBoxModel()); } else { subComboBox.setModel(new DefaultComboBoxModel((String[]) o)); } } @Override public void itemStateChanged(ItemEvent e) { if (e.getStateChange() == ItemEvent.SELECTED) { if (e.getSource() == mainComboBox) { if (mainComboBox.getSelectedIndex() != 0) { FirstDialog firstDialog = new FirstDialog(ComboBoxTwo.this, mainComboBox.getSelectedItem().toString(), "Please wait, Searching for ..... "); } } } } private class FirstDialog extends JDialog { private static final long serialVersionUID = 1L; FirstDialog(final Frame parent, String winTitle, String msgString) { super(parent, winTitle); setModalityType(Dialog.ModalityType.APPLICATION_MODAL); JLabel myLabel = new JLabel(msgString); JButton bNext = new JButton("Stop Processes"); add(myLabel, BorderLayout.CENTER); add(bNext, BorderLayout.SOUTH); bNext.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent evt) { setVisible(false); } }); javax.swing.Timer t = new javax.swing.Timer(1000, new ActionListener() { @Override public void actionPerformed(ActionEvent e) { setVisible(false); } }); t.setRepeats(false); t.start(); setLocationRelativeTo(parent); setSize(new Dimension(400, 100)); setVisible(true); } } public static void main(String[] args) { JFrame frame = new ComboBoxTwo(); frame.setDefaultCloseOperation(EXIT_ON_CLOSE); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } } 

Answer 2

首先，不要将字符串与==进行比较，而是使用equals或equalsIgnoreCase方法。 例如，

改变这个：

 if (item == "Groceries") { 

对此：

 if ("Groceries".equalsIgnoreCase(item.toString())) { 

您需要在item上调用toString（）以确保将String与String进行比较。 在执行任何此操作之前，您还需要确保该项不为null。

Answer 3

  if(jComboBox1.getSelectedItem() == "First Choice"){ jComboBox2.removeAllItems(); jComboBox2.addItem("First Choice Item 1"); } if(jComboBox1.getSelectedItem() == "Another Choice"){ jComboBox2.removeAllItems(); jComboBox2.addItem("Another Choice Item 1"); } 

或者你可以在数组中包含太多的项目。