One of the presentations from Android talks lectures, done by employees of Infinum Ltd. Retrofit is a type-safe REST client for Android which we recently use pretty often. Dario explains Retrofit's perks and the way it can be used. (by Dario Penić Omer)

1. Retrofit
- REST client abstraction based on OkHttp
(HTTP client for Android)
- by Square (Jake Wharton)

2. Retrofit
●
Turns yor REST API into a Java interface

3. Retrofit example
●
Twitter API
●
Obtain token

4. Twitter – obtain token request
●
Host: https://api.twitter.com
●
POST /oauth2/token
●
Headers
–
–
●
Authorization: base64 encoded consumer key +
consumer secret
Content-Type: application/x-www-form-urlencoded;
charset=UTF-8
Body: “grant_type=client_credentials”

5. Twitter – obtain token response
{"token_type":"bearer","access_token":"AAAAAAAAAAAAAAAAAAAAA
DryUgAAAAAAzGlUwrr%2B7WL%2FWUvOMLdsQapBr9w
%3DVdxZkBQC1tfFSRFrs8J2AklGAJO9xxuo6tMz0t7wUDo2nV3NIn"}

6. Retrofit
public interface TwitterService {
@FormUrlEncoded
@POST("/oauth2/token")
TwitterTokenType getToken(
@Header("Authorization") String authorization,
@Field("grant_type") String grantType
);
}

7. Retrofit - async
@FormUrlEncoded
@POST("/oauth2/token")
void getToken(
@Header("Authorization") String authorization,
@Field("grant_type") String grantType,
Callback<TwitterTokenType> response
);

8. Retrofit – initialize service
RestAdapter.Log log = new RestAdapter.Log() {
@Override
public void log(String s) {
Log.d("DARIO", s);
}
};
RestAdapter restAdapter = new RestAdapter.Builder()
.setServer(Constants.TWITTER_API_URL)
.setLog(log)
.setLogLevel(RestAdapter.LogLevel.FULL)
.build();
service = restAdapter.create(TwitterService.class);

9. Retrofit – send request
service.getToken("Basic " +
getBase64String(Constants.BEARER_TOKEN_CREDENTIALS),
"client_credentials", callback);

10. Retrofit - callback
private Callback<TwitterTokenType> callback = new
Callback<TwitterTokenType>() {
@Override
public void success(TwitterTokenType token, Response response) {
Toast.makeText(HomeActivity.this, token.getAccessToken(),
Toast.LENGTH_LONG).show();
}
@Override
public void failure(RetrofitError retrofitError) {
Toast.makeText(HomeActivity.this, "Retrofit error",
Toast.LENGTH_SHORT).show();
}
};

11. Retrofit - GET
@GET("/1.1/statuses/user_timeline.json")
void getUserTimeline(
@Header("Authorization") String authorization,
@Query("count") int count,
@Query("screen_name") String screenName,
Callback<Object> response
);

12. Retrofit exampel on Github
●
https://github.com/infinum/RetrofitExample