Android ProGuard: Please correct the above warnings first

编译与反编译，一对相辅相成的矛盾。反编译有时候会和不光彩的事情联系在一起，以致于编译者常常费劲心思，加大反编译的难度，比如采用混淆代码等方式。ProGuard正是这么一个工具：

The ProGuard tool shrinks, optimizes, and obfuscates your code by removing unused code and renaming classes, fields, and methods with semantically obscure name.

Android SDK整合了ProGuard，并在文档中用了一个章节来描述如何使用它。依照文档来实施，多半没有问题，不过在我使用中遇到了一个问题：

[proguard] Warning: there were 2 unresolved references to classes or interfaces.
[proguard] You may need to specify additional library jars (using ‘-libraryjars’),
[proguard] or perhaps the ‘-dontskipnonpubliclibraryclasses’ option.
[proguard] Warning: there were 5 unresolved references to program class members.
[proguard] Your input classes appear to be inconsistent.
[proguard] You may need to recompile them and try again.
[proguard] Alternatively, you may have to specify the options
[proguard] ‘-dontskipnonpubliclibraryclasses’ and/or
[proguard] ‘-dontskipnonpubliclibraryclassmembers’.

BUILD FAILED
/Users/xuhj/Develop/android-sdk-mac_x86/tools/ant/main_rules.xml:453: Please correct the above warnings first.

依照以往的惯例，发生warning，可忽视之，只有看到error，才会小紧张一把。不过这次的warning导致了BUILD FAILED，这回问题大了。

按照提示，在proguard.cfg里，加入-dontskipnonpubliclibraryclasses，再试，还是有问题。

那就到官网找找答案吧，Manual -> Troubleshooting -> “Warning: can’t find referenced class”，找到这么一句话：try your luck with the -ignorewarnings option, or even the -dontwarn option.再对比日志信息，发现：

[proguard] Warning: net.poemcode.Digest: can’t find referenced class org.apache.CastleProvider

打开proguard.cfg，加入-dontwarn net.poemcode.**，再次执行ant release，万事大吉。