public class G extends Application {

    public static Context APP_CONTEXT;
    public static ServerApi API;
    
    @Override
    public void onCreate() {
        super.onCreate();

        APP_CONTEXT = getApplicationContext();

        API = new ServerApi(APP_CONTEXT);
        API.getConfig()
                .setLogging(true)
                .setLoggingTag("Mansour_API")
                .setHeaderAcceptJson();

        API.setErrorMessageHandler(new MyApiCallbackDefaultHandler());

    }

    public static void message(String msg) {
        Toast.makeText(APP_CONTEXT, msg, Toast.LENGTH_SHORT).show();
    }

    private static class MyApiCallbackDefaultHandler extends BaseApi.CallbackDefaultHandler {

        @Override
        public void handleErrorMessage(String message, JsonObject data) {
            G.message("Server error: " + message);
        }

        @Override
        public void handleFailure() {
            G.message("Connection Error!");
        }
    }


}

    G.API.request("http://192.168.1.22:8084/api/v1/app/ping")
        .setMethod(Request.Method.GET)
        .setRequestJason(new JsonBuilder("key1", "value1").add("key2", "value2").build())
        .setRequestTimeout(10) //seconds
        .setHeaderAcceptJson() // adds "Accept" -> "application/json header
        .addToken("public") //adds value to "token" header
        .addHeader("custom", "header")
        .setCustomCallback(new SerfApiCallback() {
            @Override
            public void onSuccess(String message, JsonObject response) {
                    //response code is //200-299
                    }
            
            @Override
            public void onErrorMessage(String message, JsonObject response) {
                    //response code is //400-499
                    }
            
            @Override
            public void onResponse() {
                    //request in finished
                    //used for thins like loading(false)
                    }
            
            @Override
            public void onFailure() {
                    // response code is 500+
                    //no proper response
                    //e.g. no internet or parse error
                    }
        });

//Api Request Helper class
public class AR {
    public static String getBaseIp() {
        return AppSettings.getInstance().getServerIp();
    }

    public static void setBaseIp(String baseIp) {
        AppSettings.getInstance().setServerIp(baseIp);
    }

    public static String getBasePort() {
        return AppSettings.getInstance().getServerPort();
    }

    public static void setBasePort(String port) {
        AppSettings.getInstance().setServerPort(port);
    }
    
    public static String baseUrl() {
        String Prefix = "https://";
        if (BuildConfig.DEBUG && AppSettings.getInstance().useHttpDebug())
            Prefix = "http://";
        return Prefix + getBaseIp() + ":" + getBasePort() + "/api/v1";
    }

    public static class App {
        public static String baseUrl() {
            return AR.baseUrl() + "/app";
        }

        public static UrlHelper ping() {
            return UrlHelper.get(baseUrl() + "/ping");
        }
        public static UrlHelper sendCode() {
            return UrlHelper.post("http://192.168.1.11:8084/api/v1/app/sendCode");
        }
    }
}

//There are custom callbacks based on what we need this one uses success callback
// (the only callback we can access in onSuccess, onError and onfailure use the default bahviour defined in G.java)
G.API.request(AR.App.ping())
                .setCustomCallback((message, response) -> {
                    
                });