YouTube application for Android

I want to develop a YouTube application for Android w开发者_如何学Pythonith the following functionalities:

1. Login
2. Comment on videos
3. Download on Android
4. Play videos by streaming and also by download

Please give me some useful way to solve this problem.

please refer to youtube api here : https://developers.google.com/youtube/

You can find options to login, comment on videos and view videos. For downloading videos,check:

1. http://www.ngcoders.com/php-script/php-youtube-video-downloader-script/
2. http: //code.google.com/p/pytube/