Proguard 是Android tools包中提供用来对代码进行压缩，优化和进行混淆的工具，它能够移除无用的代码，对类名，方法名，字段名进行重命名，但不改变代码的结构，从而达到对代码混淆的作用。而这样做的好处是我们可以得到一个更小的apk文件和一份更难以被反编译的代码。
在项目中使用Proguard，必须在project.properties修改如下：
# This file is automatically generated by Android Tools.# Do not modify this file -- YOUR CHANGES WILL BE ERASED!## This file must be checked in Version Control Systems.## To customize properties used by the Ant build system edit# "ant.properties", and override values to adapt the script to your# project structure.## To enable ProGuard to shrink and obfuscate your code, uncomment this (available properties: sdk.dir, user.home):proguard.config=${sdk.dir}/tools/proguard/proguard-android-optimize.txt:proguard-project.txt...Android本身已经提供了两份关于proguard的配置文件，放在sdk目录下面，如下：
所以，当然，我们也可以自己创建一个配置文件，放在指定的任意位置上，然后将改变这份配置文件就好，如下：
#proguard.config=${sdk.dir}/tools/proguard/proguard-android-optimize.txt:proguard-project.txtproguard.config=proguard-project.cfg下面是Android 提供的 proguard-android.txt文件，如下：
# This is a configuration file for ProGuard.# http://proguard.sourceforge.net/index.html#manual/usage.html-dontusemixedcaseclassnames-dontskipnonpubliclibraryclasses-verbose# Optimization is turned off by default. Dex does not like code run# through the ProGuard optimize and preverify steps (and performs some# of these optimizations on its own).-dontoptimize-dontpreverify# Note that if you want to enable optimization, you cannot just# include optimization flags in your own project configuration file;# instead you will need to point to the# "proguard-android-optimize.txt" file instead of this one from your# project.properties file.-keepattributes *Annotation*-keep public class com.google.vending.licensing.ILicensingService-keep public class com.android.vending.licensing.ILicensingService# For native methods, see http://proguard.sourceforge.net/manual/examples.html#native-keepclasseswithmembernames class * { native <methods>;}# keep setters in Views so that animations can still work.# see http://proguard.sourceforge.net/manual/examples.html#beans-keepclassmembers public class * extends android.view.View { void set*(***); *** get*();}# We want to keep methods in Activity that could be used in the XML attribute onClick-keepclassmembers class * extends android.app.Activity { public void *(android.view.View);}# For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations-keepclassmembers enum * { public static **[] values(); public static ** valueOf(java.lang.String);}-keep class * implements android.os.Parcelable { public static final android.os.Parcelable$Creator *;}-keepclassmembers class **.R$* { public static <fields>;}# The support library contains references to newer platform versions.# Don't warn about those in case this app is linking against an older# platform version. We know about them, and they are safe.-dontwarn android.support.**其实基本上上面提供的也是Android不建议进行混淆的代码，所以我们的如果要对自己使用的类进行混淆，可以在这份文档的基本上进行加工就可以。
前面说过，Proguard其实做的不只混淆，还有压缩优化代码（移除掉一些无用的代码和重命名类名，方法名，字段名等），当进行过Proguard之后，会在项目的根目录生成一个proguard目录，其下面有几个文件：
其中seeds是我们上面配置中不进行proguard的文件，其内容如下：
android.support.v4.accessibilityservice.AccessibilityServiceInfoCompatandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: android.support.v4.accessibilityservice.AccessibilityServiceInfoCompat$AccessibilityServiceInfoVersionImpl IMPLandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int CAPABILITY_CAN_RETRIEVE_WINDOW_CONTENTandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int CAPABILITY_CAN_REQUEST_TOUCH_EXPLORATIONandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int CAPABILITY_CAN_REQUEST_ENHANCED_WEB_ACCESSIBILITYandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int CAPABILITY_CAN_FILTER_KEY_EVENTSandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int FEEDBACK_BRAILLEandroid.support.v4.accessibilityservice.AccessibilityServiceInfoCompat: int FEEDBACK_ALL_MASK而mapping.txt则是进行过proguard，被重新命名过的文件，其内容如下：
com.xxx.xxx.xxx.xxx.xxx.xxxActivity$Get~~~~Task -> com.xxx.activity.xx.aa com.xxx.xxx.xxx.xxx.xxx.activity.account.xxxActivity this$0 -> a void onPreExecute() -> onPreExecute android.util.SparseArray doInBackground$7d5cdb5d() -> a void onPostExecute(android.util.SparseArray) -> a java.lang.Object doInBackground(java.lang.Object[]) -> doInBackground18002240500可以看到 类名会变成a，b等无明显意义的字母表示。
在进行proguard之后，应用可能运行起来会有或多或少，这样那样的问题，所以每一次进行过proguard之后，可以将这个seeds和mapping.txt给保存起来，前后进行比对，从而快速定位到在proguard中出现的问题。
在我们的应用中，有很多情况下是需要使用到第三方的jar包的，别的不说，本身 support包就已经是以第三方jar包形式存在了。
在应用这些第三方jar包的时候，最好不要对这些jar包进行proguard，尤其是跟第三方系统有接口交互的时候，因为混淆了话，两边类名，或者字段名，或者方法名不一致，就有可能出现问题，所以对第三方jar包进行开放，在配置文件中配置如下：
-dontwarn com.thoughtworks.xstream.**-keep class com.thoughtworks.xstream.** {*; }-keep interface com.thoughtworks.xstream.** {*; }-keep options，顾名思义，就是保持那些文件，不进行代码混淆。
不过有一点要注意的是，如果在开放的代码中有应用到泛型的话，我们还必须开放下面的属性，如下：
# The "Signature" attribute is required to be able to access generic types when compiling in JDK 5.0 and higher.-keepattributes Signature
而如果用到注释annotation的话，下面的属性也是要放开的，
-keepattributes *Annotation*
结束。