1.Error generating final archive: Debug Certificate expired on
在Eclipse菜单Window -> Preferences -> Android-> Build，找到那个Default debug keystore显示的路径，就是debug.keystore这个文件（expired）过期了,它的路径就是文章《Android环境搭建及相关命令http://www.2cto.com/kf/201203/123793.html》里面说的设置SD卡img文件的上一层目录.android。
所以不论Windows系统还是Linux系统，只要删除这个debug.keystore就行了，Eclipse会自动生成一个新的，默认有效期也是一年。
2.Android Error: Unable to open class file R.java
Solution:解决方法：
The “Build Path”for your Java environment is not setup correctly in Eclipse. To fix this,follow these steps:
1) Open the Preferences Window by clicking“Window -> Preferences”
2) Find the “Java”sectionand expand it
3) Select “Build Path”
4) Change the value of Source and outputfolder from Folders to “Project”
5) Click Apply and then “OK”
Your problem should be resolved!
摘自 ch_jinyi的专栏
