一、前言

为何需要混淆呢？简单的说，就是将原本正常的项目文件，对其类，方法，字段，重新命名,a,b,c,d,e,f…之类的字母，达到混淆代码的目的，这样反编译出来，结构乱糟糟的，看了也头大。

另外说明一下，本文的混淆总结基于Android Studio的IDE开发环境。

二、官方默认的混淆配置

其实在android Studio中做混淆，基本就是对Proguard-rules.pro文件的操作。混淆的过程也是有规律可循的。先看看官方的proguard-android.txt文件，位于/tools/proguard目录下，不知道怎么写，可以当成模板，复制一份出来到自己的工程，改成自己项目所需的混淆配置。内容如下：

# 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);
}

-keepclassmembers class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator 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.**

# Understand the @Keep support annotation.
-keep class android.support.annotation.Keep

-keep @android.support.annotation.Keep class * {*;}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <methods>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <fields>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <init>(...);
}

这个混淆默认采取一些通用的规则，view，activity，Parcelable，注解，R文件，枚举这类的东西都不会混淆，我们也不能混淆这些，否则release版本会报错。

三、Android Studio开启混淆配置

很简单，只要设置minifyEnabled为true即可。

buildTypes {
        release {
            minifyEnabled true//true开启混淆配置，false关闭
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.duqian_android_keystore
        }
       debug{//省略}
}

四、Android混淆的通用规则

1. 系统混淆配置

-dontusemixedcaseclassnames          #混淆时不使用大小写混合类名
-dontskipnonpubliclibraryclasses     #不跳过library中的非public的类
-verbose                             #打印混淆的详细信息
-dontoptimize                        #不进行优化，建议使用此选项，
-dontpreverify                       #不进行预校验,Android不需要,可加快混淆速度。
-ignorewarnings                      #忽略警告
#-optimizationpasses 5               #指定代码的压缩级别

2. 常用的一些混淆配置

-keepattributes Signature #范型
#native方法不混淆
-keepclasseswithmembernames class * {
    native <methods>;
}
#v4包不混淆
-keep class android.support.v4.app.** { *; }
-keep interface android.support.v4.app.** { *; }
#Gson混淆配置
-keep class sun.misc.Unsafe { *; }
-keep class com.idea.fifaalarmclock.entity.***
-keep class com.google.gson.** { *; }
#JavaBean
-keepclassmembers public class cn.net.duqian.bean.** {
   void set*(***);
   *** get*();
}
-keep class com.xx.duqian_cloud.JavaScriptInterface { *; }#webview js

#忽略 libiary 混淆
-keep class io.vov.vitamio.** { *; }

#butterknife不混淆
-keep class butterknife.** { *; }
-dontwarn butterknife.internal.**
-keep class **$$ViewBinder { *; }
-keepclasseswithmembernames class * {
    @butterknife.* <fields>;
}
-keepclasseswithmembernames class * {
    @butterknife.* <methods>;
}

3. 第三方框架一般不混淆（但也要看具体情况）

-keepclassmembers class * {
   public <init> (org.json.JSONObject);
}
#okhttp
-dontwarn okhttp3.**
-keep class okhttp3.**{*;}
-keep interface okhttp3.**{*;}

#okio
-dontwarn okio.**
-keep class okio.**{*;}
-keep interface okio.**{*;}

-dontwarn retrofit2.**
-keep class retrofit2.** { *; }
-keepattributes Signature
-keepattributes Exceptions

-dontwarn rx.**
-keep class rx.**{*;}

四、Android混淆的方法和通配符对照表

五、Android混淆的总结

1. 不能混淆的情况总结

Java的反射，为什么不能混淆呢？因为代码混淆，类名、方法名、属性名都改变了，而反射它还是按照原来的名字去反射，结果只射出一个程序崩溃
注解用了反射，所以不能混淆。不混淆任何包含native方法的类的类名以及native方法名，否则找不到本地方法。
Activity不能混淆，因为AndroidManifest.xml文件中是完整的名字
自定义view也是带了包名写在xml布局中，不能混淆

2. 混淆后使用时常见问题

当项目中出现so的native代码找不到Java的方法的时候，可以尝试将

-keepclasseswithmembernames class * {
    native <methods>;
}

更改为：

-keep class * {
    native <methods>;
}

Android 代码混淆配置总结