Proguard for Android问题

Question

我想用proguard构建我的android项目。虽然导出它会给出这样的错误日志。请给我一个解决方案。

 Warning: there were 28 unresolved references to classes or interfaces.
          You may need to specify additional library jars (using '-libraryjars').
java.io.IOException: Please correct the above warnings first.
    at proguard.Initializer.execute(Initializer.java:321)
    at proguard.ProGuard.initialize(ProGuard.java:211)
    at proguard.ProGuard.execute(ProGuard.java:86)
    at proguard.ProGuard.main(ProGuard.java:492)