After I update my Android ADT to newer version, something is wrong [closed]

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http://stackoverflow.com – I have my android project A which was build in old adt version. Today I update my adt to newer version, the project always crashes for "ClassNotFoundError...", The project has no "Android Dependencies" but only "libs". But after I add jars in "libs" to the build path, it crashes too! Now I have to add my libs folder as source folder but this method will increase the app's size!!! If anyone has a better way or ever had this problem and solved this , please tell me. Thanks in advance. (HowTos)