Look and Feel---JAVA界面（换肤术）
与“Look and Feel”密切相关的是LookAndFeel抽象类和UIManager类。
LookAndFeel类
LookAndFeel是一个抽象类，除了提供了一些static方法，还定义了一些抽象的个性化设置方法来由子类实现。
从JDK1.1.3开始，Sun提供了三个LookAndFeel的子类 Javax.Swing.plaf.metal.MetalLookAndFeel、
com.sun.java.swing.plaf.motif.MotifLookAndFeel、
com.sun.java.swing.plaf.Windows. WindowsLookAndFeel。
它们分别提供了“Metal”、“Motif”与“Windows”的界面式样。也就是说，任何基于Swing的界面程序本身都可以使用三种系统提供的皮肤。实际上我们也可以直接或间接继承LookAndFeel类，自己编写一种“皮肤”。
开放源代码的产品Skin Look And Feel 1.2.2
在http://www.l2fprod.com/可以找到它的全部源代码。Skin Look And Feel本身还可以更换http://www.l2fprod.com/提供的各种“皮肤”，让你的程序可以各种“皮肤”示人。
UIManager类
这个类就是Swing界面管理的核心，管理Swing的小应用程序以及应用程序样式的状态。UIManager类提供了下列静态方法用于更换与管理“Look and Feel”:
static void addAuxiliaryLookAndFeel(LookAndFeel laf)
//增加一个“Look And Feel”到辅助的“look and feels”列表
static LookAndFeel[] getAuxiliaryLookAndFeels()
//返回辅助的“look and feels”列表（可能为空）。
static String getCrossPlatformLookAndFeelClassName()
//返回缺省的实现了跨平台的Look and Feel——即Java Look and Feel（JLF）。
static UIManager.LookAndFeelInfo[] getInstalledLookAndFeels()
//返回了在目前已经安装的LookAndFeel的信息。
static LookAndFeel getLookAndFeel()
//返回当前使用的Look and Feel
static String getSystemLookAndFeelClassName()
//返回与当前系统相关的本地系统Look and Feel，如果没有实现本地Look and
Feel则返回缺省的跨平台的Look and Feel。
static void installLookAndFeel(String name, String className)
//创建一个新的Look and Feel并安装到当前系统。
static void installLookAndFeel(UIManager.LookAndFeelInfo info)
//创建一个新的Look and Feel并安装到当前系统。
static boolean removeAuxiliaryLookAndFeel(LookAndFeel laf)
//从辅助的“look and feels”列表删除一个“Look And Feel”
static void setInstalledLookAndFeels(UIManager.LookAndFeelInfo[] infos)
//设置当前的已安装Look and Feel信。
static void setLookAndFeel(LookAndFeel newLookAndFeel)
//设置当前使用的LookAndFeel。
static void setLookAndFeel(String className)
//设置当前使用的LookAndFeel。参数是类名。
下面的源代码可以在Skin Look And Feel 1.2.2下的源代码根目录下找到：
public class Skinit extends javax.swing.JApplet
{
/**
* The main program for the Skinit class
*
* @param args The command line arguments
* @exception Exception Description of Exception
*/
public static void main(String[] args) throws Exception
{
if (args.length == 0) {
printUsage();
}
int mainClassNameIndex = -1;
String gtktheme = null;
String kdetheme = null;
String packtheme = null;
for (int i = 0, c = args.length; i < c; i++) {
if (args[i].equals("-gtk")) {
gtktheme = args[++i];
}
else if (args[i].equals("-kde")) {
kdetheme = args[++i];
}
else if (args[i].equals("-pack")) {
packtheme = args[++i];
}
else {
mainClassNameIndex = i;
break;
}
}
String[] realArgs = new String[args.length - mainClassNameIndex - 1];
for (int i = 0, c = realArgs.length; i < c; i++) {
realArgs[i] = args[mainClassNameIndex + i + 1];
}
// First try to find the class
Class clazz = null;
try {
clazz = Class.forName(args[mainClassNameIndex]);
} catch (ClassNotFoundException e) {
System.err.println("The class " + args[mainClassNameIndex] + "
was not found in the classpath.");
System.exit(1);
} catch (Throwable e) {
e.printStackTrace();
System.exit(1);
}
// if the class exists, get the main method
Method mainMethod = null;
try {
mainMethod = clazz.getMethod("main", new Class[]{String[].class});
} catch (NoSuchMethodException e) {
System.err.println("No method public static void main(String[] args) in " +
clazz.getName());
System.exit(1);
} catch (Throwable e) {
e.printStackTrace();
System.exit(1);
}
// try to make sure the main method is Accessible
try {
mainMethod.setAccessible(true);
} catch (Throwable e) {
}
// main class and main method found, time to load the skin
Skin skin = null;
if (packtheme != null) {
if (SkinUtils.DEBUG) {
System.out.println("Loading themepack " + packtheme);
}
skin = SkinLookAndFeel.loadThemePack(packtheme);
}
else if (gtktheme != null) {
if (kdetheme != null) {
skin = new CompoundSkin(SkinLookAndFeel.loadSkin(gtktheme),
SkinLookAndFeel.loadSkin(kdetheme));
}
else {
skin = SkinLookAndFeel.loadSkin(gtktheme);
}
}
/*
* try to use the user default skin
*/
if (skin == null) {
if (SkinUtils.DEBUG) {
System.out.println("Trying user skin");
}
skin = SkinLookAndFeel.getSkin();
}
if (skin != null) {
SkinLookAndFeel.setSkin(skin);
SkinLookAndFeel lnf = new SkinLookAndFeel();
UIManager.setLookAndFeel(lnf);
UIManager.addPropertyChangeListener(
new PropertyChangeListener() {
public void propertyChange(PropertyChangeEvent event) {
Object newLF = event.getNewValue();
if ((newLF instanceof SkinLookAndFeel) == false) {
try {
UIManager.setLookAndFeel(new SkinLookAndFeel());
} catch (Exception e) {
e.printStackTrace();
}
}
}
});
}
else {
System.out.println("No GTK theme provided, defaulting to application Look And
Feel");
}
try {
mainMethod.invoke(null, new Object[]{realArgs});
} catch (IllegalAccessException e) {
System.err.println("Please make sure the class " + clazz.getName() +
" and the method main(String[] args) are public.");
System.exit(1);
} catch (Throwable e) {
e.printStackTrace();
System.exit(1);
}
}
/**
* Description of the Method
*/
static void printUsage() {
String usage = "Skinit - Skin Look And Feel wrapper/n" +
"Usage: skinit [options] class [args...]/n" +
"/n" +
"where options include:/n" +
"/t-gtk GTK Theme Filename/n" +
"/t-kde KDE Theme Filename/n" +
"/t-pack Theme Pack Filename/n";
System.out.println(usage);
System.exit(1);
}
}
在此程序中使用了Java的反射技术（Reflection）。在JDK文档中有它的详细介绍。
此程序最重要的是在：
……
SkinLookAndFeel.setSkin(skin);
SkinLookAndFeel lnf = new SkinLookAndFeel();
UIManager.setLookAndFeel(lnf);
//这里是将当前的Look and Feel设置为自己定义的SkinLookAndFeel对象。
UIManager.addPropertyChangeListener(
new PropertyChangeListener() {
public void propertyChange(PropertyChangeEvent event) {
Object newLF = event.getNewValue();
if ((newLF instanceof SkinLookAndFeel) == false) {
try {
UIManager.setLookAndFeel(new SkinLookAndFeel());
}
catch (Exception e) {
e.printStackTrace();
}
}
}
});
//监听属性改变事件，不允许用户更改LookAndFeel。即在用户要求改变Look and
Feel时重新将LookAndFeel设置成SkinLookAndFeel。
……
实际上这里只演示了一种皮肤，在http://www.l2fprod.com/有更多的皮肤可以尝试。