有些时候并不需要添加lib库进行编译，例如在使用xposed的jar包时，只需要在eclipse里Build Path-Add to Build Path即可，如果作为lib库添加进去反而会出现异常。

以下是引用的原文：

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Next, make the XposedBridge API known to the project. You can downloadXposedBridgeApi-<version>.jar from the first post of this XDA thread. Copy it into a subfolder called lib. Then right-click on it and select Build Path => Add to Build Path. The <version> from the file name is the one you insert asxposedminversion in the manifest.

Make sure that the API classes are not included (but only referenced) in your compiled APK, otherwise you will get an IllegalAccessError. Files in thelibs (with "s") folder are automatically included by Eclipse, so don‘t put the API file there.

在androidstudio对应的设置方法为：

F4打开工程结构，选择Modules-当前项目-Dependencies-+-选择“Jar or directiories”，

选择jar包后，在“Scope”栏选择“Provided”，不要选择“Complie”。

eclipse中Build Path-Add to Build Path对应到androidstudio的设置