Youtube thumbnails:
<br> http://img.youtube.com/vi/<youtube-video-id>/0.jpg<br>
You can replace 0 with
1
2
3
default
hqdefault
mqdefault
sddefault
maxresdefault
Also i3.ytimg.com works in place of img.youtube.com
Open files using storage access framework [ https://developer.android.com/guide/topics/providers/document-provider ]
Android Media Store Sample [ https://github.com/android/storage-samples/tree/master/MediaStore ]
Multiple samples showing the best practices in storage APIs on Android. [ https://github.com/android/storage-samples ]