Hi,
Following items are minimums(must have the) experience.
Experience : 2 year plus in Android
*) Basic java : Thread, Collections, File operation, Xml, json
*) UI-1 : Activity, Fragment, Dialogs, PopupWindow, Menu, Drawer, ActionBar
*) UI-2 : Material deisgn, Animation, Different screen resolutions, Orientation, Sessnors
*) Url/uri connecion i.e upload/download files from/to server
*) Web - HTML, js
Experience : 4 year plus in Android
*) Streaming/send/receive - data over network (audio, video, stream, etc.,)
*) GCM(FCM), google maps, google drive.
*) Android APIs - Camera2, MediaRecorder, MediaCodec i.e raw data(Audio/video) capture and encoding
*) Image processing
*) NDK - C++, cygwin
*) Web - HTML, Js, server scripting