今天终于完成了近一个月的App开发工作，对程序进行混淆导出签名apk包时，却出现了如下的错误：
Proguard returned with error code 1. See console
Note: there were 4 duplicate class definitions.
Warning: library class android.content.res.XmlResourceParser extends or implements program class org.xmlpull.v1.XmlPullParser
Warning: library class android.content.Intent depends on program class org.xmlpull.v1.XmlPullParser
。。。

心里想着，真是好事多磨呀！
那就赶紧问度娘呀，终于在一位网友那里找到了答案。
对于Android导入了第三方jar包时，proguard混淆脚本会出现错误，而出现上
面的错误是因为程序中引入了第三方jar包[ksoap2-android-assembly-2.6.5-jar-with-
dependencies.jar]，二话不说，立马行动：

在proguard-project.txt中增加了
-ignorewarnings
-libraryjars lib/ksoap2-android-assembly-2.5.4-jar-with-dependencies.jar （jar包路径）

即在文件中增加了如下红色的两行：

-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-verbose
-ignorewarnings

# 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
#-dontoptimize
# 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.
-libraryjars libs/ksoap2-android-assembly-2.6.5-jar-with-dependencies.jar

-keepattributes *Annotation*
-keep public class com.google.vending.licensing.ILicensingService
-keep public class com.android.vending.licensing.ILicensingService

最后，重新打包，一切OK。