Greetings Vinay,
I started working on the Strava APIs just a few days ago, and yes, as you said, even I was unable to find many samples for Android. To make Strava API calls like getting user's activities etc. you have to get the user to authenticate using his Strava account. I achieved the authentication process using a WebView and WebViewClient. This is a good place for you to start.
http://strava.github.io/api/v3/oauth/In your WebView you will have to load the url which is given in
Request access header along with the right query parameters. The user will then go on to authorize access to your application, after which you will receive an access token. All subsequent Strava API calls have to made using the received access token. Feel free to comment here if you need any more help.
Cheers.
Amogh