我正在使用Java Swing创建一个模拟器。我使用JComboBox来显示公用事业单位，如“KW，KL，KM”等，以测量功率，水和距离。将一堆项添加到JComboBox很简单。用户选择一个单位，单击“保存”按钮时，JFrame将保存选择。
JComboBox comboBox = new JComboBox();
for(ValueUnits u: ValueUnits.values()){
comboBox.addItem(u.returnUnits());
}
comboBox.setSelectedIndex(-1);
unitColumn.setCellEditor(new DefaultCellEditor(comboBox));
现在我想创建一个多层JComboBox（也许是JMenu？）。这样的功能应该表现为多层JMenu。当单击JComboBox时，它将显示第一层 - 类别，例如“电力，水，距离...”，然后当鼠标悬停在电力上时，电力单位列表如“KW，MW，W ......” “ 将会呈现。这些集合是从Enumerations中获取的。我想知道创建这样的组件最正确的方法是什么。
非常感谢你！
答案 0 :(得分：0)
使用它......
public class ComboLayer extends javax.swing.JPanel {
String Category1 = null;
String Category2 = null;
String Category3 = null;
Hashtable<String, String> hsItems;
public ComboLayer() {
this.hsItems = new Hashtable<>();
hsItems.put("Main", "Power,Water,Distance");
hsItems.put("Power", "KW,MW,W");
hsItems.put("Water", "ML,L,KL");
hsItems.put("Distance", "CM,M,KM");
initComponents();
String[] item = hsItems.get("Main").split(",");
for (String i : item) {
cmbItem.addItem(i);
}
cmbItem.addItem("Back");
cmbItem.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String selectText = null;
selectText = (String) cmbItem.getSelectedItem();
Enumeration enmKeys = hsItems.keys();
while (enmKeys.hasMoreElements()) {
String sKey = (String) enmKeys.nextElement();
if (selectText.equalsIgnoreCase("back")) {
if (hsItems.get(sKey).contains(cmbItem.getItemAt(0).toString())) {
Enumeration enumkeysBack = hsItems.keys();
while (enumkeysBack.hasMoreElements()) {
String sKeyBack = (String) enumkeysBack.nextElement();
if (hsItems.get(sKeyBack).contains(sKey)) {
String[] item = hsItems.get(sKeyBack).split(",");
cmbItem.removeAllItems();
for (String i : item) {
cmbItem.addItem(i);
}
if (!sKeyBack.equalsIgnoreCase("Main")) {
cmbItem.addItem("Back");
}
break;
}
}
}
} else if (sKey.contains(selectText)) {
String[] item = hsItems.get(sKey).split(",");
cmbItem.removeAllItems();
for (String i : item) {
cmbItem.addItem(i);
}
if (!sKey.equalsIgnoreCase("Main")) {
cmbItem.addItem("Back");
}
break;
}
}
}
});
}
public static void main(String... arg) {
ComboLayer cmbLyr = new ComboLayer();
JDialog dg = new JDialog();
dg.add(cmbLyr);
dg.setVisible(true);
}
答案 1 :(得分：0)
也许使用2个组合框？也就是说，你在第一个中选择一个值，然后在第二个中显示单位：
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JPanel implements ActionListener
{
private JComboBox<String> mainComboBox;
private JComboBox<String> subComboBox;
private Hashtable<String, String[]> subItems = new Hashtable<String, String[]>();
public ComboBoxTwo()
{
String[] items = { "Select Item", "Color", "Shape", "Fruit" };
mainComboBox = new JComboBox<String>( items );
mainComboBox.addActionListener( this );
// prevent action events from being fired when the up/down arrow keys are used
mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
add( mainComboBox );
// Create sub combo box with multiple models
subComboBox = new JComboBox<String>();
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
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);
}
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 ) );
}
}
private static void createAndShowUI()
{
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( new ComboBoxTwo() );
frame.setLocationByPlatform( true );
frame.pack();
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
答案 2 :(得分：0)
这是一个自定义弹出窗口JMenu的效果组合。隐藏实际弹出窗口，并在适当时显示第二个弹出窗口。
选择JMenuItem后，组合中只填充一个项目，以面包屑格式显示。
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.plaf.basic.*;
import javax.swing.plaf.metal.*;
public class JMenuComboBoxDemo implements Runnable
{
private Map<String, String[]> menuData;
private JComboBox<String> combo;
private AbstractButton arrowButton;
private JPopupMenu popupMenu;
private List<String> flattenedData;
public static void main(String[] args)
{
SwingUtilities.invokeLater(new JMenuComboBoxDemo());
}
public JMenuComboBoxDemo()
{
menuData = new HashMap<String, String[]>();
menuData.put("Colors", new String[]{"Black", "Blue"});
menuData.put("Flavors", new String[]{"Lemon", "Lime"});
popupMenu = new JPopupMenu();
popupMenu.setBorder(new MatteBorder(1, 1, 1, 1, Color.DARK_GRAY));
List<String> categories = new ArrayList<String>(menuData.keySet());
Collections.sort(categories);
// copy of the menuData, flattened into a List
flattenedData = new ArrayList<String>();
for (String category : categories)
{
JMenu menu = new JMenu(category);
for (String itemName : menuData.get(category))
{
menu.add(createMenuItem(itemName));
flattenedData.add(category + " > " + itemName);
}
popupMenu.add(menu);
}
combo = new JComboBox<String>();
combo.setPrototypeDisplayValue("12345678901234567890");
combo.setUI(new EmptyComboBoxUI());
for (Component comp : combo.getComponents())
{
if (comp instanceof AbstractButton)
{
arrowButton = (AbstractButton) comp;
}
}
arrowButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
setPopupVisible(! popupMenu.isVisible());
}
});
combo.addMouseListener(new MouseAdapter()
{
@Override
public void mouseClicked(MouseEvent e)
{
setPopupVisible(! popupMenu.isVisible());
}
});
}
public void run()
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container c = frame.getContentPane();
c.setLayout(new FlowLayout());
c.add(new JLabel("Options"));
c.add(combo);
frame.setSize(300, 200);
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
/*
* Toggle the visibility of the custom popup.
*/
private void setPopupVisible(boolean visible)
{
if (visible)
{
popupMenu.show(combo, 0, combo.getSize().height);
}
else
{
popupMenu.setVisible(false);
}
}
/*
* Create a JMenuItem whose listener will display
* the item in the combo.
*/
private JMenuItem createMenuItem(final String name)
{
JMenuItem item = new JMenuItem(name);
item.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
setComboSelection(name);
}
});
return item;
}
/*
* Search for the given name in the flattened list of menu items.
* If found, add that item to the combo and select it.
*/
private void setComboSelection(String name)
{
Vector<String> items = new Vector<String>();
for (String item : flattenedData)
{
/*
* We're cheating here: if two items have the same name
* (Fruit->Orange and Color->Orange, for example)
* the wrong one may get selected. This should be more sophisticated
* (left as an exercise to the reader)
*/
if (item.endsWith(name))
{
items.add(item);
break;
}
}
combo.setModel(new DefaultComboBoxModel<String>(items));
if (items.size() == 1)
{
combo.setSelectedIndex(0);
}
}
/*
* Prevents the default popup from being displayed
*/
class EmptyComboBoxUI extends MetalComboBoxUI
{
@Override
protected ComboPopup createPopup()
{
BasicComboPopup thePopup = (BasicComboPopup) super.createPopup();
thePopup.setPreferredSize(new Dimension(0,0)); // oh, the horror!
return thePopup;
}
}
}