Eclipse.Error.gen already exists not a source folder.

在Eclipse ADT来开发Android App时会遇到以下问题：
"myproject/gen already exists but is not a source folder. Convert to a source folder or rename it"

The solution is:

1.Right Click on the project and go to "Properties"

2.Select "Java Build Path"
on the Left

3.Open "Source" tab

4.Click "Add Folder ..." and check "gen" and "src
"

Reference

1.

Http://stackoverflow.com/questions/9532045/gen-already-exists-but-is-not-a-source-folder

Eclipse.Error.gen already exists not a source folder.