Why Android Studio rebuilds project so slow even when no changes in sources?

Question

When I make some changes in source code, Android Studio (actually gradle) needs to rebuild the project. It\'s obvious.

Why the second build takes almost the sam

Answer 1

To avoid rebuild EACH TIME, i'm going to my module project settings -> Dependencies and up or down one of my library item -> Apply -> Ok -> Make regenerating R.java. You could also try unchecking "Use external build" in compiler settings:

File -> Settings (Ctrl+Alt+S) -> Compiler -> Uncheck "Use external build"