I don't know who reported Emma1 or why, but she is absolutely correct. For all things Android Studio, youtube is probably the best place to go for beginner tutorials.
(That drives me bonkers, personally, since sitting through a ten minute tutorial to learn something I could have read in a few paragraphs feels like a colossal waste of time to me.)
I got a problem here, I open a sample code provided by the college then I found that the tree under the android is changed, previously if i open a new project, there are two nodes, one app , one gradle scripts . Under app , got manifest, java,res. But after i open the sample code, It only show .gradle, .idea, app, build , gradle. Why is that so? Can anyone provide clue? Thanks a lot.