当引用到*.jar文件时，报错“Unable to resolve superclass 。。。”

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Just started to get this issue after upgrading to ADT 17.

Discovered that external .jar files need to be in a ‘libs‘ (with an s) folder otherwise their classes are not included in the .dex file that is created. Before the upgrade everything worked fine with my .jar files in a ‘lib‘ folder (no s).

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在使用ADT 17之后，需要将jar文件放到“libs”文件夹下，注意此处的‘s’。否则jar文件里面的类不会被包含到.dex文件中。