使用Eclipse生成generated serial version ID的時候,Eclipse彈出出錯信息

當我想要使用Eclipse生成generated serial version ID的時候,Eclipse彈出出錯信息.
The following problem occurred.
could not find class file.

make sure the file is compilable.

我的解決方法就是

右鍵src==>build path==>remove from build path

右鍵src==>build path==>==>use as source folder