Develop Reference

How to use Telegram API (to include Chat Application) in my existing android app?

I want to use telegram APIs in order to develop chatting feature in My Existing Android App.
I am not getting how to implement.

I think, it is a good idea to take a look at the Telegram Database Library (Beta) from here TDLib (Russian, but translate with Google) and the Java doc (English) from here.
The information is a little poor yet, but I think you can understand it.

Use this API.
Refer to the Getting Started section to integrate Telegram in your app.

React native get access token social networks

I'm working on react-native app project I need to use login with social networks and get access token of each others. I have problems with some packages i need the best way and cross platform (iOS, Android).

I don't know if there is a one-for-all solution to this problem that integrates well with RN. I've been recently working with the Facebook SDK, which enables Facebook Login in your application. It's fairly easy to set up, and it might be a good starting point for you. As for other social networks, I'd suggest you go over each one and find a way that does the job. Here are some packages that might help you:
LinkedIn
[Instagram]
(https://js.coach/all/react-native-instagram-oauth?search=instagram)
Google
This also might be worth a shot: react-native-social-auth

Android Social networks sdk which use native libs

I know about socialauth-android, but it uses oauth and can't use already installed user's social network apps - but facebook sdk can do it, or I need to use outh requests - better use native methods
Maybe you can advice any lib which contain native libs and give interface to login and share?

You can try ASNE it uses facebook-sdk and you can use other methods from it, or you can post photo directly to instagram app.
It contains most popular networks, just check it - maybe it helps you

SalesForce with Android?

I want connect sales Force from my Android Program please suggest which one is correct way to achieve this I am new to sales Force I have some knowledge in Android Application Developement.
Thanks in Advance.

You definitely want to use the REST API for mobile apps. The SOAP API is really heavy, and is better for Server-to-Server integrations. The best way to get started building an Android app for Salesforce.com is to take a look at the Salesforce Mobile SDK for Android:
http://wiki.developerforce.com/page/Mobile_SDK
There's a very helpful getting started PDF linked on that page.
However, the SDK is meant mostly for starting new apps, so you'll have some work ahead of you integrating it into an existing application. The main things you want are the oAuth 2.0 User-Agent login and REST wrappers.
You may also find this app useful -- I put it together for a presentation at Dreamforce '11, which was shortly before the Mobile SDK for Android came out, so I wrote the oAuth and REST stuff myself. Might be a simpler starting point for you.
https://github.com/tomgersic/DreamforcengerHunt
Hope that helps!

You can either use the RESTful interface or the SOAP webservices. The latter is a bit easier to deal with IMHO.
Under setup in salesforce, download the partner or enterprise WSDL (partner = generic, enterprise = specific for your SF-instance). Now with wsdl2java you can create Stubs for those wsdl entries. Import those into your android app and use them. See here for a Java Exampe by Salesforce.com.
Be sure your user has the permission to "do API". You might want to look into SSO if you want to make a "production"/commercial app. Also, to login, remember to use the correct password, you might need to add the API key (generate using the Setup tab in SF). Hope this helps.

Try checking out some of the open-source SDK projects the developer evangelists have added to the forcedotcom github
Lots of good examples on different platforms, including android with phonegap/html5 and a native SDK for android (iOS and Android) to get you past authentication and onto building your app.

Salesforce Provides mobile SDK for development on mobile device, here is the link for android SDK:
http://wiki.developerforce.com/page/Getting_Started_with_the_Mobile_SDK_for_Android
You need to:
Download SDK.
Add a sample project included in SDK's native/SampleApps folder(make sure you check include to the workspace while importing the project).
Get your remote access form salesforce and update in your app.
--This should get you started with a sample app form salsforce.
After this you need to modify existing code to your own code.

You can go to trailhead and start browsing on it, while working with your own application you will have to learn a lot about smartStore and smartSync,
I did implemented A smartStore App with using salesforce as database provider, if you want i can upload it to drive and share a link to you and
if you have any doubts about using or understanding the flow be free to ask..

Posting ScoreLoop score in Facebook

I'm Using ScoreLoop.
How can I post Scores in a Facebook and twitter using the ScoreLoop SDK?

Once you have downloaded the Scoreloop SDK, you have the option to use the ScoreloopUI or the ScoreloopCore. ScoreloopUI comes with the ready-built UI along with the core APIs (this will be a quick start for developers). ScoreloopCore has the Core APIs which developers can use but here developers have to write their own UI.
Most of the developers use the ScoreloopUI, so, I am assuming you would also be using the ScoreloopUI. In the downloaded Scoreloop SDK package, there is a docs folder, inside that, please open up ScoreloopUI_doc.html and navigate to Integration Guide - Advanced Integration - Posting Scores to Social Networks. There you will find the steps you need to integrate Social network posting into your app.
In case you come across any issues, please post your query on support.scoreloop.com and the support team would help you out.
Thanks,
Prenitha