Proguard怎麼實現增量混淆，我們查看proguard的選項：
-applymapping filename
Specifies to reuse the given name mapping that was printed out in a previous obfuscation run of ProGuard. Classes and class members that are listed in the mapping file receive the names specified along with them. Classes and class members that are not mentioned receive new names. The mapping may refer to input classes as well as library classes. This option can be useful for incremental obfuscation, i.e. processing add-ons or small patches to an existing piece of code. If the structure of the code changes fundamentally, ProGuard may print out warnings that applying a mapping is causing conflicts. You may be able to reduce this risk by specifying the option -useuniqueclassmembernames in both obfuscation runs. Only a single mapping file is allowed. Only applicable when obfuscating.
-useuniqueclassmembernames
Specifies to assign the same obfuscated names to class members that have the same names, and different obfuscated names to class members that have different names (for each given class member signature). Without the option, more class members can be mapped to the same short names like 'a', 'b', etc. The option therefore increases the size of the resulting code slightly, but it ensures that the saved obfuscation name mapping can always be respected in subsequent incremental obfuscation steps.
For instance, consider two distinct interfaces containing methods with the same name and signature. Without this option, these methods may get different obfuscated names in a first obfuscation step. If a patch is then added containing a class that implements both interfaces, ProGuard will have to enforce the same method name for both methods in an incremental obfuscation step. The original obfuscated code is changed, in order to keep the resulting code consistent. With this option in the initial obfuscation step, such renaming will never be necessary.
This option is only applicable when obfuscating. In fact, if you are planning on performing incremental obfuscation, you probably want to avoid shrinking and optimization altogether, since these steps could remove or modify parts of your code that are essential for later additions.
增量混淆：
http://proguard.sourceforge.net/manual/examples.html#incremental
-dontusemixedcaseclassnames 不要混合大小寫的類名。
-injars proguardgui.jar
-outjars proguardgui_out.jar
-injars proguard.jar
-outjars proguard_out.jar
-libraryjars <java.home>/lib/rt.jar
-applymapping proguard.map
-keep public class proguard.gui.ProGuardGUI {
public static void main(java.lang.String[]);
}
增量編譯， 前一個步驟中，應該使用