Where is the warnings screen option in Android Studio?

If, on the toolbar, you click Analyze -> Inspect Code; then in the window that pops up select how much of your project you want to inspect (I usually do Whole Project, but you might want to select a specific module), then click okay.

Android Studio will work for a bit, then the inspection window will pop up from the bottom with a list of results, subdivided by inspection.

you can use F2 to next problems, see more here: Navigating to Next/Previous Error

Build -> Make Project (Ctrl + F9) gives what we can get equivalent of Eclipse's “Problems” view on Android Studio