27 January 2016

Android Developer Story: Travel app Wego, increases monthly user retention by 300% with material design

Posted by Lily Sheringham, Google Play team

Headquartered in Singapore, Wego is a popular online travel marketplace for flights and hotels for users in South East Asia and the Middle East. They launched their Android app in early 2014, and today, more than 62 percent of Wego app users are on Android. Wego recently redesigned their app using material design principles to provide their users a more native Android experience for consistency and easier navigation.

Watch Ross Veitch, co-founder and CEO, and the Wego team talk about how they increased monthly user retention by 300 percent and reduced uninstall rates by up to 25 percent with material design.

Learn more about material design, how to use Android Studio, and how to find success on Google Play with the new guide ‘Secrets to App Success on Google Play.’

26 January 2016

How Fabulous and Yummly grew with App Invites

Posted by Laurence Moroney, Developer Advocate

Introduced in May 2015, App Invites is an out-of-the-box solution for conducting app referrals and encouraging sharing. So far, we’ve seen very positive results on how the feature improves app discovery. While 52 percent of users discover apps by word of mouth, we have seen 92 percent of users trust recommendations from family and friends with App Invites. In this post, we’ll share some success stories from companies that have already used App Invites to grow their user base.

Fabulous is a research-based app incubated in Duke University's Center for Advanced Hindsight. The app helps users to embark on a journey to resetting poor habits, replacing them with healthy rituals, with the ultimate goal of improving health and well-being.

Users started taking advantage of App Invites within the app to share their experience with their friends and family. App Invites installs now account for 60 percent of all Fabulous installs via referrals. Sharing clicks also increased by 10 percent once App Invites were used. Fabulous also noticed increased user retention, with 2x the Life Time Value of the app for users that came in to it via App Invites. Fabulous simplified their user experience, combining SMS and email into a single interface, allowing users to focus on sharing.

Additionally, users that were acquired via App Invites versus other channels were found to be twice as likely to stay with the app.

CTO of Fabulous, Amine Laddhari, commented, “It took me only a few hours to implement App Invites versus several days of work when we built our own solution. It was straightforward!”

You can view the full case study from Fabulous here.

Yummly, a food discovery platform that views cooking a meal as a personalized, shareable experience wanted to expand its user base and generate awareness on the Android platform. It added App Invites so that users could recommend the app to their family and friends, giving functionality to share specific recipes, dinner ideas or shipping lists.

With App invites, they found that installation rates were about 60 percent higher compared to other sharing channels. Additionally, Yummly was able to take advantage of the seamless integration of Google Analytics. It’s the only share channel that has this integration, allowing data such as the number of invites sent, accepted and resulting installs to be accurately tracked.

Melissa Guyre, Product Manager at Yummly, commented, “The App Invites Integration process was seamless. A bonus feature is the excellent tracking tie-in with Google Analytics.”

You can view the full case study from Yummly here.

App Invites is available for Android or iOS, and you can learn how you can build it into your own apps at g.co/appinvites.

25 January 2016

New features to better understand player behavior with Player Analytics

Posted by Lily Sheringham, Developer Marketing at Google Play

Google Play games services includes Player Analytics, a free reporting tool available in the Google Play Developer Console, to help you understand how players are progressing, spending, and churning. Now, you can see what Player Analytics looks like with an exemplary implementation of Play games services: try out the new sample game in the Google Play Developer Console, which we produced with help from Auxbrain, developer of Zombie Highway 2. The sample game uses randomized and anonymized data from a real game and will also let you try the new features we’re announcing today. Note: You need a Google Play Developer account in order to access the sample game.

Use predictive analytics to engage players before they might churn

To help you better understand your players’ behavior, we’ve extended the Player Stats API in Player Analytics with predictive functionality. The churn prediction method will return data on the probability that the player will churn, i.e., stop playing the game, so you can create content in response to this to entice them to stay in your game. Additionally, the spend prediction method will return the probability that the player will spend, and you could, for example, provide discounted in-app purchases or show ads based on these insights.

Create charts in the new funnels report to quickly visualize sequences of events

The funnels report enables you to create a funnel chart from any sequence events, such as achievements, spend, and custom events. For example, you could log custom events for each step in a tutorial flow (e.g., tutorial step 1, step 2, step 3), and then use the funnel report to visualize the exit points in your tutorial.

Measure and compare the effect of changes and cumulative values by new users with cohort’s report

The cohorts report allows you to take any event such as sessions, cumulative spend, and custom events, and compare the cumulative event values by new user cohorts - providing valuable insight into the impact of your decisions on your gaming model. For example, you can view users that started the day before you made a change and the day after. This allows you to measure and compare the effect of changes made, so if you doubled the price of all your items in your in-game store, you can see if the cumulative sessions started after the change was lower or higher than the users that started before the change.

Updated C++, iOS SDKs and Unity plug-in to support Player Stats API

We have updated the C++ and iOS SDKs, and the Unity plug-in, all of which now support the Player Stats API, which includes the basic player stats as well as spend and churn predictions. Be sure to check out the sample game and learn more about Play Games Services. You can also get top tips from game developer Auxbrain to help you find success with Google Play game services.

23 January 2016

Play Games Permissions are changing in 2016

Posted by Wolff Dobson, Developer Advocate

We’re taking steps to reduce sign-in friction and unnecessary permission requests for players by moving the Games APIs to a new model. The new interaction is:

  • Players are prompted to sign-in once per account, rather than once per game
  • Players no longer need their account upgraded to Google+ to use Play Games services
  • Once players have signed-in for the first time, they will no longer need to sign in to any future games; they will be automatically signed in
  • Note: Players can turn off auto-sign-in through the Play Games App’s settings
  • Once a user signs in for first time, new games will generally be able to sign in without any user interaction
  • There is no consent screen required for signing in on any particular game. Sign-in will be automatic to each new game.

In order to respect user’s privacy and avoid revealing their real name, we also have to change the way player IDs work.

  • For existing players: Games will continue to get their Google+ ID (also called “player ID” in previous documentation) when they sign in.
  • For new players: Games will get a new player ID which is not the same as the previous IDs we’ve used.

Potential issues

Most games should see no interruption or change in service. There are a handful of cases, however, where some change is required.

Below are some issues, along with potential solutions.

These are:

  1. Asking for the Google+ scope unnecessarily
    • Issue: Your users will get unnecessary, potentially disturbing pop-up consent windows
    • Solution: Don’t request any additional scopes unless you absolutely need them
  2. Using the Play Games player ID for other Google APIs that are not games
    • Issue: You will not get valid data back from these other endpoints.
    • Solution: Don’t use player ID for other Google APIs.
  3. Using mobile/client access tokens on the server
    • Issue: Your access token may not contain the information you’re looking for
      • ...and this is not recommended in the first place.
    • Solution: Use the new GetServerAuthCode API instead.

Let’s cover each of these issues in detail.

Issue: Asking for unnecessary scopes

Early versions of our samples and documentation created a GoogleApiClient as follows:

 // Don’t do it this way!  
 GoogleApiClient gac = new GoogleApiClient.Builder(this, this, this)  
           .addScope(Plus.SCOPE_PLUS_LOGIN) // The bad part  
 // Don’t do it this way!  

In this case, the developer is specifically requesting the plus.login scope. If you ask for plus.login, your users will get a consent dialog.

Solution: Ask only for the scopes you need

Remove any unneeded scopes from your GoogleApiClient construction along with any APIs you no longer use.

 // This way you won’t get a consent screen  
 GoogleApiClient gac = new GoogleApiClient.Builder(this, this, this)  
 // This way you won’t get a consent screen  

For Google+ users

If your app uses specific Google+ features, such as requiring access to the player’s real-world Google+ social graph, be aware that new users will still be required to have a G+ profile to use your game. (Existing users who have already signed in won’t be asked to re-consent).

To require Google+ accounts to use your game, change your Games.API declaration to the following:

 .addApi(Games.API, new GamesOptions.Builder()  

This will ensure that your game continues to ask for the necessary permissions/scopes to continue using the player’s real-world social graph and real name profile.

Issue: Using the Player ID as another ID

If you call the Games.getCurrentPlayerId() API, the value returned here is the identifier that Games uses for this player.

Traditionally, this value could be passed into other APIs such as Plus.PeopleApi.load. In the new model, this is no longer the case. Player IDs are ONLY valid for use with Games APIs.

Solution - Don’t mix IDs

The Games APIs (those accessed from com.google.android.gms.games) all use the Player ID, and as long as you use only those, they are guaranteed to work with the new IDs.

Issue: Using mobile/client access tokens on the server

A common pattern we’ve seen is:

  • Use GoogleAuthUtil to obtain an access token
  • Send this token to a server
  • On the server, call Google to verify the authenticity. This is most commonly done by calling https://www.googleapis.com/oauth2/v1/tokeninfo and looking at the response

This is not recommended in the first place, and is even more not-recommended after the shift in scopes.

Reasons not to do this:

  • It requires your app to know the current account the user is using, which requires holding the GET_ACCOUNTS permission. On Android M, this will result in the user being asked to share their contacts with your app at runtime, which can be intimidating.
  • The tokeninfo endpoint isn’t really designed for this use case - it’s primarily designed as a debugging tool, not as a production API. This means that you may be rate limited in the future if you call this API.
  • The user_id returned by token info may no longer be present with the new model. And even if it is present, the value won’t be the same as the new player ID. (See problem 2 above)
  • The token could expire at any time (access token expiration times are not a guarantee).
  • Using client tokens on the server require extra validation checks to make sure the token is not granted to a different application.

Solution: Use the new GetServerAuthCode flow

Fortunately, the solution is known, and is basically the same as our server-side auth recommendations for web.

  1. Upgrade to the latest version of Google Play Services SDK - at least 8.4.87.

  2. Create a server client ID if you don’t already have one

    1. Go to the Google Developer Console, and select your project

    2. From the left nav, select API Manager, then select Credentials

    3. Select “New Credentials” and choose “OAuth Client ID”

    4. Select “Web Application” and name it something useful for your application

    5. The client id for this web application is now your server client id.

  3. In your game, connect your GoogleApiClient as normal.

  4. Once connected, call the following API:

    1. Games.getGamesServerAuthCode(googleApiClient, “your_server_client_id”)

    2. If you were using GoogleAuthUtil before, you were probably calling this on a background thread - in which case the code looks like this:

 // Good way  
      GetServerAuthCodeResult result =   
           Games.getGamesServerAuthCode(gac, clientId).await();  
      if (result.isSuccess()) {  
           String authCode = result.getCode();  
            // Send code to server.  
 // Good way  

  1. Send the auth code to your server, exactly the same as before.

  2. On your server, make an RPC to https://www.googleapis.com/oauth2/v4/token to exchange the auth code for an access token, probably using a Google Apis Client Library.

    1. You’ll have to provide the server client ID, server client secret (listed in the Developer Console when you created the server client ID), and the auth code.

    2. See more details here: https://developers.google.com/identity/protocols/OAuth2WebServer?utm_campaign=play games_discussion_permissions_012316&utm_source=anddev&utm_medium=blog#handlingresponse

    3. No, really:  You should use a Google Apis Client Library to make this process easier.

  3. Once you have the access token, you can now call www.googleapis.com/games/v1/applications/<app_id>/verify/ using that access token.

    1. Pass the auth token in a header as follows:

      1. “Authorization: OAuth <access_token>”

    2. The response value will contain the player ID for the user. This is the correct player ID to use for this user.

    3. This access token can be used to make additional server-to-server calls as needed.

Note: This API will only return a 200 if the access token was actually issued to your web app.

In summary

Let’s be very clear: If you do nothing, unless you are depending explicitly on Google+ features, you will see no change in functionality, and a smoother sign-in experience.

If you are:

  • Requesting Google+ scopes without using them, it’s a good idea to stop using them from here out.
  • Sending client access tokens to your server, we strongly suggest you use getGamesServerAuthCode() instead.

Thanks, and keep making awesome games!

20 January 2016

Android Developer Story: Music app developer DJIT builds higher quality experiences and successful businesses on Android

Posted by Lily Sheringham, Google Play team

Paris-based DJiT is the creator of edjing, one of the most downloaded DJ apps in the world, it now has more than 60 million downloads and a presence in 182 countries. Following their launch on Android, the platform became the largest contributor of business growth, with 50 percent of total revenue and more than 70 percent of new downloads coming from their Android users.

Hear from Jean-Baptiste Hironde, CEO & Co-founder, Séverine Payet, Marketing Manager, and Damien Delépine, Android Software Engineer, to learn how DJit improved latency on new Android Marshmallow, as well as leveraged other Android and Google Play features to create higher quality apps.

Find out more about building great audio apps and how to find success on Google Play.

15 January 2016

Create promo codes for your apps and in-app products in the Google Play Developer Console

Posted by Yoshi Tamura, Product Manager, Google Play

Over the past six months, a number of new tools in the Google Play Developer Console have been added to help you grow your app or game business on Google Play. Our improved beta testing features help you gather more feedback and fix issues. Store Listing Experiments let you run A/B tests on your app’s Play Store listing. Universal App Campaigns and the User Acquisition performance report help you grow your audience and better understand your marketing.

Starting today, you can now generate and distribute promo codes to current and new users on Google Play to drive engagement. Under the Promotions tab in the Developer Console, you can set up promo codes for your apps, games, and in-app products to distribute in your own marketing campaigns (up to 500 codes per app, per quarter). Consider using promo codes to reward loyal users and attract new customers.

How to use promo codes

  1. Choose your app in the Developer Console.
  2. Under the Promotions tab choose Add new promotion.
  3. Review and accept the additional terms of service if you haven’t run a promotion before.
  4. Choose from the options available, then generate and download your promo codes.
  5. Distribute your promo codes via your marketing channels such as social networks, in email, on the web, to your app’s beta testers, or in your app or game itself.
  6. Users can redeem your promo codes in a number of ways, including:
  1. From Google Play, using the Redeem menu option.
  2. From your app. They’ll be directed to the Play checkout flow before being redirected back to your app.
  3. By following a link that embeds the promo code (see tips below).

For more details about running a promotion for your app or game, read this article on the Google Play Developer Help Center.

Tips for making the most of promo codes

Some things to keep in mind when running a successful promotion:

  • There’s a limit of 500 promo codes per app every quarter.
  • You can embed your code in a URL so that users don’t have to enter it themselves (for example, if you’re sending your codes in an email). You can use the URL: https://play.google.com/redeem?code={CODE} (where {CODE} is a generated promo code).
  • To use promo codes for in-app products, you should implement In-app Promotions in your app. Note that promo codes can’t be used for subscriptions.
  • Review and adhere to the Promotional Code Terms Of Service.

We hope you find interesting ways to use promo codes to find new users and engage existing fans. To learn more about the many tools and best practices you can use to grow your business on Google Play, download our new developer playbook, “The Secrets to App Success on Google Play”.

14 January 2016

Using Google Sign-In with your server

Posted by Laurence Moroney, Developer Advocate

This is the third part in a blog series on using Google Sign-In on Android, and how you can take advantage of world-class security in your Android apps. In part 1, we spoke about the user experience improvements that are available to you. In part 2, we then took a deeper dive into the client-side changes to the Google Sign-In APIs that make coding a lot simpler.

In this post, we will demonstrate how you can use Google Sign-In with your backend. By doing so, users signing in on their device can be securely authenticated to access their data on your backend servers.

Using Credentials on your server

First, let’s take a look at what happens if a user signs in on your app, but they also need to authenticate for access to your back-end server. Consider this scenario: You’ve built an app that delivers food to users at their location. They sign into your app, and your app gets their identity. You store their address and order preferences in a database on your server.

Unless your server endpoints are protected with some authentication mechanism, attackers could read and write to your user database by simply guessing the email addresses of your users.

Figure 1. An attacker could submit a fake request to your server with an email address

This isn’t just a bad user experience, it’s a risk that customer data can be stolen and misused. You can prevent this by getting a token from Google when the user signs in to the app, and then passing this token to your server. Your server would then validate that this token really was issued by Google, to the desired user, and intended for your app (based on your audience setting, see below). At this point your server can know that it really is your user making the call, and not a nefarious attacker. It can then respond with the required details.

Figure 2. Attacker’s Forged Tokens will be rejected

Let’s take a look at the steps for doing this:

Step 1: Your Android app gets an ID token (*) after signing in with Google. There’s a great sample that demonstrates this here. To do this, the requestIdToken method is called when creating the GoogleSignInOptions object.

 GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)  

This requires you to get a client ID for your server. Details on how to obtain this are available here (see Step 4).

Once your Android app has the token, it can POST it over HTTPS to your server, which will then try to validate it.

(*) An ID token is represented using JSON Web Token, as defined by RFC7519 and the OpenID Connect spec. These are an open, industry standard method for representing claims securely between two parties.

Step 2: Your Server receives the token from your Android client. It should then validate the token with methods that are provided in the Google API Client libraries, in particular, verifying that it was issued by Google and that the intended audience is your server.

Your server can use the GoogleIdTokenVerifier class to verify the token and then extract the required identity data. The ‘sub’ field (available from the getSubject() method) provides a stable string identifier that should be used to identify your users even if their email address changes, and key them in your database. Other ID token fields are available, including the name, email address and photo URL. Here’s an example of a servlet that was tested on Google App Engine that can verify tokens using a provided library. These libraries allow you to verify the token locally without a network call for every verification.

 GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory)  
       // Here is where the audience is set -- checking that it really is your server  
       // based on your Server’s Client ID  
       // Here is where we verify that Google issued the token  
 GoogleIdToken idToken = verifier.verify(idTokenString);  
 if (idToken != null) {  
       Payload payload = idToken.getPayload();  
       String userId = payload.getSubject();   
       // You can also access the following properties of the payload in order  
       // for other attributes of the user. Note that these fields are only  
       // available if the user has granted the 'profile' and 'email' OAuth  
       // scopes when requested. (e.g. you configure GoogleSignInOptions like   
       // the sample code above and got a successful GoogleSignInResult)   
       // Note that some fields may still be null.  
       String email = payload.getEmail();  
       boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());  
       String name = (String) payload.get("name");  
       String pictureUrl = (String) payload.get("picture");  
       String locale = (String) payload.get("locale");  
       String familyName = (String) payload.get("family_name");  
       String givenName = (String) payload.get("given_name");  

Note that if you have an existing app using GoogleAuthUtil to get a token to pass to your backend, you should switch to the latest ID token validation libraries and mechanisms described above. We’ll describe recommendations for server-side best practices in a future post.

This post demonstrates how to use authentication technologies to ensure your user is who they claim they are. In the next post, we’ll cover using the Google Sign-In API for authorization, so that users can, for example, access Google services such as Google Drive from within your app and backend service.

You can learn more about authentication technologies from Google at the Google Identity Platform developers site.

13 January 2016

Spatial audio comes to the Cardboard SDK

Originally posted on Google Developers Blog

Posted by Nathan Martz, Product Manager, Google Cardboard

Human beings experience sound in all directions—like when a fire truck zooms by, or when an airplane is overhead. Starting today, the Cardboard SDKs for Unity and Android support spatial audio, so you can create equally immersive audio experiences in your virtual reality (VR) apps. All your users need is their smartphone, a regular pair of headphones, and a Google Cardboard viewer.

Sound the way you hear it

Many apps create simple versions of spatial audio—by playing sounds from the left and right in separate speakers. But with today’s SDK updates, your app can produce sound the same way humans actually hear it. For example:

  • The SDK combines the physiology of a listener’s head with the positions of virtual sound sources to determine what users hear. For example: sounds that come from the right will reach a user’s left ear with a slight delay, and with fewer high frequency elements (which are normally dampened by the skull).
  • The SDK lets you specify the size and material of your virtual environment, both of which contribute to the quality of a given sound. So you can make a conversation in a tight spaceship sound very different than one in a large, underground (and still virtual) cave.

Optimized for today’s smartphones

We built today’s updates with performance in mind, so adding spatial audio to your app has minimal impact on the primary CPU (where your app does most of its work). We achieve these results in a couple of ways:

  • The SDK is optimized for mobile CPUs (e.g. SIMD instructions) and actually computes the audio in real-time on a separate thread, so most of the processing takes place outside of the primary CPU.
  • The SDK allows you to control the fidelity of each sound. As a result, you can allocate more processing power to critical sounds, while de-emphasizing others.

Simple, native integrations

It’s really easy to get started with the SDK’s new audio features. Unity developers will find a comprehensive set of components for creating soundscapes on Android, iOS, Windows and OS X. And native Android developers will now have a simple Java API for simulating virtual sounds and environments.

Experience spatial audio in our sample app for developers

Check out our Android sample app (for developer reference only), browse the documentation on the Cardboard developers site, and start experimenting with spatial audio today. We’re excited to see (and hear) the new experiences you’ll create!

07 January 2016

Get your app featured on the first smartphone with Project Tango from Lenovo

Originally posted on Google Developers Blog

Posted by Johnny Lee, Technical Project Lead, Project Tango

Today, at CES, Lenovo announced the development of the first consumer-ready smartphone with Project Tango. By adding a few extra sensors and some computer vision software, Project Tango transforms your smartphone into a magic lens that lets you place digital information on your physical world.

*Renderings only. Not the official Lenovo device.

To support the continued growth of the ecosystem, we’re also inviting developers from around the world to submit their ideas for gaming and utility apps created using Project Tango. We’ll pick the best ideas and provide funding and engineering support to help bring them to life, as part of the app incubator. Even better, the finished apps will be featured on Lenovo’s upcoming device. The submission period closes on February 15, 2016.

All you need to do is tell us about your idea and explain how Project Tango technologies will enable new experiences. Additionally, we’ll ask you to include the following materials:

  • Project schedule including milestones for development –– we’ll reach out to the selected developers by March 15, 2016
  • Visual mockups of your idea including concept art
  • Smartphone app screenshots and videos, such as captured app footage
  • Appropriate narrative including storyboards, etc.
  • Breakdown of your team and its members
  • One pager introducing your past app portfolio and your company profile

For some inspiration, Lowe's Home Improvement teamed with developer Elementals Web to demonstrate a use case they are each working on for the launch. In the app, you can point your Project Tango-enabled smartphone at your kitchen to see where a new refrigerator or dishwasher might fit virtually.

Elsewhere, developer Schell Games let’s you play virtual Jenga on any surface with friends. But this time, there is no cleanup involved when the blocks topple over.

There are also some amazing featured apps for Project Tango on Google Play. You can pick up your own Project Tango Tablet Development Kit here to brainstorm new fun and immersive experiences that use the space around you. Apply now!