Swing开发之JComboBox篇

JList和ComboBox很相似，因为这两个组件都显示一个项列表。因此，它们都有扩展ListModel接口的模型。而且，这两个组件都有绘制器，这些绘制器通过实现ListCellBenderer接口来绘制列表单元。

　　但是，列表和组合框在施工方面还是有差别的。列表单是不可编辑的，但是组合框可以配备一个编辑器。JComboBox组件把编辑工作交给实现ComboBoxEdit接口的一个对象来处理。

　　列表支持三个选取模式，并把选取工作实现ListSelectionModel接口的一个对象来处理。组合框在一个时刻只有一个可选取的项，而且选取工作由组合框模型来处理。另一方面，组合框支持键选取，即在某项上按下一下键就可以选取这个项，但列表不能这样做。

构造函数

JComboBox()

创建具有默认数据模型的
JComboBox。

JComboBox(ComboBoxModel aModel)

创建一个
JComboBox，其项取自现有的 ComboBoxModel 中。

JComboBox(Object[] items)

创建包含指定数组中的元素的
JComboBox。

JComboBox(Vector<?> items)

创建包含指定
Vector 中的元素的 JComboBox。

常用方法

addActionListener(ActionListener l)

添加
ActionListener。

addItem(Object anObject)

为项列表添加项。

addItemListener(ItemListener aListener)

添加
ItemListener。

configureEditor(ComboBoxEditor anEditor, Object anItem)

利用指定项初始化编辑器。

getEditor()

返回用于绘制和编辑
JComboBox 字段中所选项的编辑器。

getItemAt(int index)

返回指定索引处的列表项。

getItemCount()

返回列表中的项数。

getModel()

返回
JComboBox 当前使用的数据模型。

getRenderer()

返回用于显示
JComboBox 字段中所选项的渲染器。

getSelectedIndex()

返回列表中与给定项匹配的第一个选项。

getSelectedItem()

返回当前所选项。

insertItemAt(Object anObject, int index)

在项列表中的给定索引处插入项。

isEditable()

如果
JComboBox 可编辑，则返回 true。

removeAllItems()

从项列表中移除所有项。

removeItem(Object anObject)

从项列表中移除项。

removeItemAt(int anIndex)

移除
anIndex 处的项。

setModel(ComboBoxModel aModel)

设置
JComboBox 用于获取项列表的数据模型。

setRenderer(ListCellRenderer aRenderer)

设置渲染器，该渲染器用于绘制列表项和从
JComboBox 字段的列表中选择的项。

setSelectedIndex(int anIndex)

选择索引
anIndex 处的项。

setSelectedItem(Object anObject)

将组合框显示区域中所选项设置为参数中的对象。

例 1：给JComboBox增加ItemListener和ActionListener

import java.awt.BorderLayout;

import java.awt.ItemSelectable;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.ItemEvent;

import java.awt.event.ItemListener;

import javax.swing.JComboBox;

import javax.swing.JFrame;

public class ItemListenerSelectingComboSample
{

static
private String selectedString(ItemSelectable is) {

Object
selected[] = is.getSelectedObjects();

return
((selected.length == 0) ? "null" : (String) selected[0]);

}

public
static void main(String args[]) {

String
labels[] = { "A", "B", "C", "D", "E", "F" };

JFrame
frame = new JFrame("Selecting JComboBox");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JComboBox
comboBox = new JComboBox(labels);

comboBox.setEditable(true);

comboBox.addActionListener(new
ActionListener() {

public
void actionPerformed(ActionEvent e) {

System.out.println("Selected
index=" + ((JComboBox)e.getSource()).getItemCount());

}

});

frame.add(comboBox,
BorderLayout.SOUTH);

ItemListener
itemListener = new ItemListener() {

public
void itemStateChanged(ItemEvent itemEvent) {

int
state = itemEvent.getStateChange();

System.out.println((state
== ItemEvent.SELECTED) ? "Selected" : "Deselected");

System.out.println("Item:
" + itemEvent.getItem());

ItemSelectable
is = itemEvent.getItemSelectable();

System.out.println(",
Selected: " + selectedString(is));

}

};

comboBox.addItemListener(itemListener);

frame.setSize(400,
200);

frame.setVisible(true);

}

}

例 2：采用模板创建JComboBox，同一个模板创建的两个不同JComboBox，对模板操作时两个JComboBox会同时改变

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.DefaultComboBoxModel;

import javax.swing.JButton;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JPanel;

public class SharedDataBetweenComboBoxSample
{

public
static void main(String args[]) {

final
String labels[] = { "A", "B", "C", "D", "E", "F", "G" };

final
DefaultComboBoxModel model = new DefaultComboBoxModel(labels);

JFrame
frame = new JFrame("Shared Data");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel
panel = new JPanel();

JComboBox
comboBox1 = new JComboBox(model);

comboBox1.setEditable(true);

JComboBox
comboBox2 = new JComboBox(model);

comboBox2.setEditable(true);

panel.add(comboBox1);

panel.add(comboBox2);

frame.add(panel,
BorderLayout.NORTH);

JButton
button = new JButton("Add");

frame.add(button,
BorderLayout.SOUTH);

ActionListener
actionListener = new ActionListener() {

public
void actionPerformed(ActionEvent actionEvent) {

model.addElement("New
Added");

}

};

button.addActionListener(actionListener);

frame.setSize(300,
200);

frame.setVisible(true);

}

}

//JComboBox与JList共用一个模板

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.DefaultComboBoxModel;

import javax.swing.JButton;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JList;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

public class SharedDataBetweenComboBoxAndListSample
{

public
static void main(String args[]) {

final
String labels[] = { "A", "B", "C", "D", "E", "F", "G" };

final
DefaultComboBoxModel model = new DefaultComboBoxModel(labels);

JFrame
frame = new JFrame("Shared Data");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel
panel = new JPanel();

JComboBox
comboBox1 = new JComboBox(model);

comboBox1.setEditable(true);

panel.add(comboBox1);

frame.add(panel,
BorderLayout.NORTH);

JList
jlist = new JList(model);

JScrollPane
scrollPane = new JScrollPane(jlist);

frame.add(scrollPane,
BorderLayout.CENTER);

JButton
button = new JButton("Add");

frame.add(button,
BorderLayout.SOUTH);

ActionListener
actionListener = new ActionListener() {

public
void actionPerformed(ActionEvent actionEvent) {

model.addElement("New
Added");

}

};

button.addActionListener(actionListener);

frame.setSize(300,
200);

frame.setVisible(true);

}

}

例 3：采用ArrayList组装JComboBox

import java.awt.BorderLayout;

import java.util.ArrayList;

import java.util.Collection;

import javax.swing.AbstractListModel;

import javax.swing.ComboBoxModel;

import javax.swing.JComboBox;

import javax.swing.JFrame;

class ArrayListComboBoxModel extends AbstractListModel implements ComboBoxModel {

private
Object selectedItem;

private
ArrayList anArrayList;

public
ArrayListComboBoxModel(ArrayList arrayList) {

anArrayList
= arrayList;

}

public
Object getSelectedItem() {

return
selectedItem;

}

public
void setSelectedItem(Object newValue) {

selectedItem
= newValue;

}

public
int getSize() {

return
anArrayList.size();

}

public
Object getElementAt(int i) {

return
anArrayList.get(i);

}

}

public class ArrayListComboBoxModelDemo
{

public
static void main(String args[]) {

JFrame
frame = new JFrame("ArrayListComboBoxModel");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

ArrayList<Object>
arrayList = new ArrayList<Object>();

arrayList.add("A");

arrayList.add("B");

arrayList.add("C");

ArrayListComboBoxModel
model = new ArrayListComboBoxModel(arrayList);

arrayList.add("A");

arrayList.add("B");

arrayList.add("C");

JComboBox
comboBox = new JComboBox(model);

frame.add(comboBox,
BorderLayout.NORTH);

frame.setSize(300,
225);

frame.setVisible(true);

}

}

例 4：给JComboBox每项增加图片

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Component;

import java.awt.Font;

import java.awt.Graphics;

import javax.swing.DefaultListCellRenderer;

import javax.swing.Icon;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JList;

import javax.swing.ListCellRenderer;

class ComplexCellRenderer implements ListCellRenderer {

protected
DefaultListCellRenderer defaultRenderer = new DefaultListCellRenderer();

public
Component getListCellRendererComponent(JList
list, Object value, int index,

boolean
isSelected, boolean cellHasFocus) {

Font
theFont = null;

Color
theForeground = null;

Icon
theIcon = null;

String
theText = null;

JLabel
renderer = (JLabel) defaultRenderer.getListCellRendererComponent(list,
value, index,

isSelected,
cellHasFocus);

if
(value instanceof Object[]) {

Object
values[] = (Object[]) value;

theFont
= (Font) values[0];

theForeground
= (Color) values[1];

theIcon
= (Icon) values[2];

theText
= (String) values[3];

}
else {

theFont
= list.getFont();

theForeground
= list.getForeground();

theText
= "";

}

if
(!isSelected) {

renderer.setForeground(theForeground);

}

if
(theIcon != null) {

renderer.setIcon(theIcon);

}

renderer.setText(theText);

renderer.setFont(theFont);

return
renderer;

}

}

public class ComplexRenderingSample {

public
static void main(String args[]) {

Object
elements[][] = {

{
new Font("Helvetica", Font.PLAIN, 20), Color.RED, new MyIcon(), "A" },

{
new Font("TimesRoman", Font.BOLD, 14), Color.BLUE, new MyIcon(), "A" },

{
new Font("Courier", Font.ITALIC, 18), Color.GREEN, new MyIcon(), "A" },

{
new Font("Helvetica", Font.BOLD | Font.ITALIC, 12), Color.GRAY, new MyIcon(), "A" },

{
new Font("TimesRoman", Font.PLAIN, 32), Color.PINK, new MyIcon(), "A" },

{
new Font("Courier", Font.BOLD, 16), Color.YELLOW, new MyIcon(), "A" },

{
new Font("Helvetica", Font.ITALIC,

,
Color.DARK_GRAY, new MyIcon(), "A" } };

JFrame
frame = new JFrame("Complex Renderer");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

ListCellRenderer
renderer = new ComplexCellRenderer();

JComboBox
comboBox = new JComboBox(elements);

comboBox.setRenderer(renderer);

frame.add(comboBox,
BorderLayout.NORTH);

frame.setSize(300,
200);

frame.setVisible(true);

}

}

class MyIcon implements Icon {

public
MyIcon() {

}

public
int getIconHeight() {

return
20;

}

public
int getIconWidth() {

return
20;

}

public
void paintIcon(Component c, Graphics g, int x, int y) {

g.setColor(Color.RED);

g.drawRect(0,
0, 25, 25);

}

}

例 5：改变JComboBox编辑框颜色

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Component;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.ComboBoxEditor;

import javax.swing.JButton;

import javax.swing.JColorChooser;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.event.EventListenerList;

class ColorComboBoxEditor implements ComboBoxEditor {

final
protected JButton editor;

protected
EventListenerList listenerList = new EventListenerList();

public
ColorComboBoxEditor(Color initialColor) {

editor
= new JButton("");

editor.setBackground(initialColor);

ActionListener
actionListener = new ActionListener() {

public
void actionPerformed(ActionEvent e) {

Color
currentBackground = editor.getBackground();

Color
color = JColorChooser.showDialog(editor, "Color Chooser", currentBackground);

if
((color != null) && (currentBackground != color)) {

editor.setBackground(color);

fireActionEvent(color);

}

}

};

editor.addActionListener(actionListener);

}

public
void addActionListener(ActionListener l) {

listenerList.add(ActionListener.class,
l);

}

public
Component getEditorComponent() {

return
editor;

}

public
Object getItem() {

return
editor.getBackground();

}

public
void removeActionListener(ActionListener l) {

listenerList.remove(ActionListener.class,
l);

}

public
void selectAll() {

//
Ignore

}

public
void setItem(Object newValue) {

if
(newValue instanceof Color) {

Color
color = (Color) newValue;

editor.setBackground(color);

}
else {

try
{

Color
color = Color.decode(newValue.toString());

editor.setBackground(color);

}
catch (NumberFormatException e) {

}

}

}

protected
void fireActionEvent(Color color) {

Object
listeners[] = listenerList.getListenerList();

for
(int i = listeners.length - 2; i >= 0; i -= 2) {

if
(listeners[i] == ActionListener.class) {

ActionEvent
actionEvent = new ActionEvent(editor, ActionEvent.ACTION_PERFORMED, color

.toString());

((ActionListener)
listeners[i + 1]).actionPerformed(actionEvent);

}

}

}

}

public class ColorComboBoxEditorDemo {

public
static void main(String args[]) {

Color
colors[] = { Color.RED, Color.BLUE, Color.BLACK, Color.WHITE };

JFrame
frame = new JFrame("Editable JComboBox");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

final
JComboBox comboBox = new JComboBox(colors);

comboBox.setEditable(true);

comboBox.setEditor(new
ColorComboBoxEditor(Color.RED));

frame.add(comboBox,
BorderLayout.NORTH);

frame.setSize(300,
200);

frame.setVisible(true);

}

}

例 6：编辑 JComboBox框，实现颜色切换

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Component;

import java.awt.Dimension;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.ComboBoxEditor;

import javax.swing.DefaultListCellRenderer;

import javax.swing.JButton;

import javax.swing.JColorChooser;

import javax.swing.JComboBox;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JList;

import javax.swing.ListCellRenderer;

import javax.swing.border.LineBorder;

import javax.swing.event.EventListenerList;

class ColorComboBoxEditor implements ComboBoxEditor {

final
protected JButton editor;

protected
EventListenerList listenerList = new EventListenerList();

public
ColorComboBoxEditor(Color initialColor) {

editor
= new JButton("");

editor.setBackground(initialColor);

ActionListener
actionListener = new ActionListener() {

public
void actionPerformed(ActionEvent e) {

Color
currentBackground = editor.getBackground();

Color
color = JColorChooser.showDialog(editor, "Color Chooser", currentBackground);

if
((color != null) && (currentBackground != color)) {

editor.setBackground(color);

fireActionEvent(color);

}

}

};

editor.addActionListener(actionListener);

}

public
void addActionListener(ActionListener l) {

listenerList.add(ActionListener.class,
l);

}

public
Component getEditorComponent() {

return
editor;

}

public
Object getItem() {

return
editor.getBackground();

}

public
void removeActionListener(ActionListener l) {

listenerList.remove(ActionListener.class,
l);

}

public
void selectAll() {

}

public
void setItem(Object newValue) {

if
(newValue instanceof Color) {

Color
color = (Color) newValue;

editor.setBackground(color);

}
else {

try
{

Color
color = Color.decode(newValue.toString());

editor.setBackground(color);

}
catch (NumberFormatException e) {

}

}

}

protected
void fireActionEvent(Color color) {

Object
listeners[] = listenerList.getListenerList();

for
(int i = listeners.length - 2; i >= 0; i -= 2) {

if
(listeners[i] == ActionListener.class) {

ActionEvent
actionEvent = new ActionEvent(editor, ActionEvent.ACTION_PERFORMED, color

.toString());

((ActionListener)
listeners[i + 1]).actionPerformed(actionEvent);

}

}

}

}

class ColorCellRenderer implements ListCellRenderer {

protected
DefaultListCellRenderer defaultRenderer = new DefaultListCellRenderer();

//
Width doesn't matter as the combo box will size

private
final static Dimension preferredSize = new Dimension(0, 20);

public
Component getListCellRendererComponent(JList
list, Object value, int index,

boolean
isSelected, boolean cellHasFocus) {

JLabel
renderer = (JLabel) defaultRenderer.getListCellRendererComponent(list,
value, index,

isSelected,
cellHasFocus);

if
(value instanceof Color) {

renderer.setBackground((Color)
value);

}

if(cellHasFocus
|| isSelected){

renderer.setBorder(new
LineBorder(Color.DARK_GRAY));

}else{

renderer.setBorder(null);

}

renderer.setPreferredSize(preferredSize);

return
renderer;

}

}

public class ColorComboBoxEditorRendererDemo
{

public
static void main(String args[]) {

Color
colors[] = { Color.BLACK, Color.BLUE, Color.GREEN, Color.RED, Color.WHITE, Color.YELLOW };

JFrame
frame = new JFrame("Color JComboBox");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

final
JComboBox comboBox = new JComboBox(colors);

comboBox.setEditable(true);

comboBox.setRenderer(new
ColorCellRenderer());

Color
color = (Color) comboBox.getSelectedItem();

ComboBoxEditor
editor = new ColorComboBoxEditor(color);

comboBox.setEditor(editor);

frame.add(comboBox,
BorderLayout.NORTH);

final
JLabel label = new JLabel();

label.setOpaque(true);

label.setBackground((Color)
comboBox.getSelectedItem());

frame.add(label,
BorderLayout.CENTER);

ActionListener
actionListener = new ActionListener() {

public
void actionPerformed(ActionEvent actionEvent) {

Color
selectedColor = (Color) comboBox.getSelectedItem();

label.setBackground(selectedColor);

}

};

comboBox.addActionListener(actionListener);

frame.setSize(300,
200);

frame.setVisible(true);

}

}

例 7：改变JComboBox旁边按钮样式

import java.awt.BorderLayout;

import javax.swing.JButton;

import javax.swing.JComboBox;

import javax.swing.JComponent;

import javax.swing.JFrame;

import javax.swing.plaf.ComboBoxUI;

import javax.swing.plaf.ComponentUI;

import javax.swing.plaf.basic.BasicArrowButton;

import javax.swing.plaf.basic.BasicComboBoxUI;

public class PopupComboSample {

public
static void main(String args[]) {

String
labels[] = { "A", "B", "C", "D", "E", "F", "G" };

JFrame
frame = new JFrame("Popup JComboBox");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JComboBox
comboBox = new JComboBox(labels);

comboBox.setUI((ComboBoxUI)
MyComboBoxUI.createUI(comboBox));

frame.add(comboBox,
BorderLayout.NORTH);

frame.setSize(300,
200);

frame.setVisible(true);

}

static
class MyComboBoxUI extends BasicComboBoxUI {

public
static ComponentUI createUI(JComponent c) {

return
new MyComboBoxUI();

}

protected
JButton createArrowButton() {

JButton
button = new BasicArrowButton(BasicArrowButton.WEST);

return
button;

}

}

}