What are the most popular android open source ui libraries [closed]

Question

What are the most popular used android open source UI libraries used, like calendars, action-bar, widgets, graphs, utilities(barcode scanner, documents reader like .pdf and .doc), and

Answer 1

I do not know many, but definitely square libraries are worth to explore:

Libraries: Dagger, Otto, Retrofit, Okhttp, Butterknife, Flow, Mortar ...

You can find at: https://github.com/square

And some good libraries listed by CodePath: https://github.com/codepath/android_guides/wiki/Must-Have-Libraries

And lots of libraries listed snowdream: https://github.com/snowdream/awesome-android