新手上路，请教几个问题
编写的andorid手机程序，出现以下三个问题，是什么原因，如何解决。1、The project was not built since its build path is incomplete. Cannot find the class file for java.lang.Object. Fix the build path then try building this project
2、Unable to resolve target 'android-8'
3、The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files
