作为Android应用开发者，不得不面对一个尴尬的局面，就是自己辛辛苦苦开发的应用可以被别人很轻易的就反编译出来。

Google似乎也发现了这个问题，从SDK2.3开始我们可以看到在android-sdk-windows\tools\下面多了一个proguard文件夹

proguard是一个java代码混淆的工具，通过proguard，别人即使反编译你的apk包，也只会看到一些让人很难看懂的代码，从而达到保护代码的作用。

下面具体说一说怎么样让SDK2.3下的proguard.cfg文件起作用，先来看看android-sdk-windows\tools\lib\proguard.cfg的内容：

 

[html]
  1. -optimizationpasses 5
  2. -dontusemixedcaseclassnames
  3. -dontskipnonpubliclibraryclasses
  4. -dontpreverify
  5. -verbose
  6. -optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
  7.  
  8. -keep public class * extends android.app.Activity
  9. -keep public class * extends android.app.Application
  10. -keep public class * extends android.app.Service
  11. -keep public class * extends android.content.BroadcastReceiver
  12. -keep public class * extends android.content.ContentProvider
  13. -keep public class * extends android.app.backup.BackupAgentHelper
  14. -keep public class * extends android.preference.Preference
  15. -keep public class com.android.vending.licensing.ILicensingService
  16.  
  17. -keepclasseswithmembernames class * {
  18. native <methods>;
  19. }
  20.  
  21. -keepclasseswithmembernames class * {
  22. public <init>(android.content.Context, android.util.AttributeSet);
  23. }
  24.  
  25. -keepclasseswithmembernames class * {
  26. public <init>(android.content.Context, android.util.AttributeSet, int);
  27. }
  28.  
  29. -keepclassmembers enum * {
  30. public static **[] values();
  31. public static ** valueOf(java.lang.String);
  32. }
  33.  
  34. -keep class * implements android.os.Parcelable {
  35. public static final android.os.Parcelable$Creator *;
  36. }

-optimizationpasses 5 -dontusemixedcaseclassnames -dontskipnonpubliclibraryclasses -dontpreverify -verbose -optimizations !code/simplification/arithmetic,!field/*,!class/merging/* -keep public class * extends android.app.Activity -keep public class * extends android.app.Application -keep public class * extends android.app.Service -keep public class * extends android.content.BroadcastReceiver -keep public class * extends android.content.ContentProvider -keep public class * extends android.app.backup.BackupAgentHelper -keep public class * extends android.preference.Preference -keep public class com.android.vending.licensing.ILicensingService -keepclasseswithmembernames class * { native <methods>; } -keepclasseswithmembernames class * { public <init>(android.content.Context, android.util.AttributeSet); } -keepclasseswithmembernames class * { public <init>(android.content.Context, android.util.AttributeSet, int); } -keepclassmembers enum * { public static **[] values(); public static ** valueOf(java.lang.String); } -keep class * implements android.os.Parcelable { public static final android.os.Parcelable$Creator *; }

 

从脚本中可以看到，混淆中保留了继承自Activity、Service、Application、BroadcastReceiver、ContentProvider等基本组件以及com.android.vending.licensing.ILicensingService，

并保留了所有的Native变量名及类名，所有类中部分以设定了固定参数格式的构造函数，枚举等等。(详细信息请参考<proguard_path>/examples中的例子及注释。)

让proguard.cfg起作用的做法很简单，就是在eclipse自动生成的default.properties文件中加上一句“proguard.config=proguard.cfg”就可以了

完整的default.properties文件应该如下：

 

[html]
  1. # This file is automatically generated by Android Tools.
  2. # Do not modify this file -- YOUR CHANGES WILL BE ERASED!
  3. #
  4. # This file must be checked in Version Control Systems.
  5. #
  6. # To customize properties used by the Ant build system use,
  7. # "build.properties", and override values to adapt the script to your
  8. # project structure.
  9.  
  10. # Project target.
  11. target=android-9
  12. proguardproguard.config=proguard.cfg

# 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 use, # "build.properties", and override values to adapt the script to your # project structure. # Project target. target=android-9 proguard.config=proguard.cfg

大功告成，正常的编译签名后就可以防止代码被反编译了。反编译经过代码混淆的apk得到的代码应该类似于下面的效果，是很难看懂的：

 

如果您使用的是2.3之前的SDK版本也没关系，把上面的proguard.cfg文件复制一份放到项目中，然后进行相同的操作即可