The project was not built since its build path is incomplete错误的解决

在我最近的Android开发中，这个错误不知道从何时起在我的Eclipse中出现，打开Eclipse1/10的概率出现（不解决的话，30分钟后会自动消失，但是看着就是很蛋疼）

错误提示: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
The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files

最后解决的方法：

1.重新选择JDK路径然后clean

2.如果上面的步骤都做了还是不行，那就有可能是你Eclipse的版本过高，Eclipse没反应过来，通过如下方法解决

打开工程下的：project.properties-->target=android-20(修改为更低版本)-->保存后-->Fix project properties

完美解决！！