EdenYouTube
The purpose of this repo is to demonstrate the functionality of the YouTube Library for Android which acts as an API for the main YouTube application. You can use it as reference for implementing playback functionality within your own application.
The app covers everything from popup players: 
To embedded players: 
How to Get
You can either clone this repo or download the app from the Play Store:
https://play.google.com/store/apps/details?id=com.eden.youtubesample
Documentation
I've written extensively about this application, it's source code and the YouTube API in a blog post that you can find here:
http://createdineden.com/blog/2015/may/12/android-tutorial-how-to-integrate-youtube-videos-into-your-app/
License
The MIT License (MIT) Copyright (c) 2015 Scott Cooper Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.