Tag Archives: Develop

Start building Actions on Google

Posted by Jason Douglas, PM Director for Actions on Google

The Google Assistant brings together all of the technology and smarts we've been building for years, from the Knowledge Graph to Natural Language Processing. To be a truly successful Assistant, it should be able to connect users across the apps and services in their lives. This makes enabling an ecosystem where developers can bring diverse and unique services to users through the Google Assistant really important.

In October, we previewedActions on Google, the developer platform for the Google Assistant. Actions on Google further enhances the Assistant user experience by enabling you to bring your services to the Assistant. Starting today, you can build Conversation Actions for Google Home and request to become an early access partner for upcoming platform features.

Conversation Actions for Google Home

Conversation Actions let you engage your users to deliver information, services, and assistance. And the best part? It really is a conversation -- users won't need to enable a skill or install an app, they can just ask to talk to your action. For now, we've provided two developer samples of what's possible, just say "Ok Google, talk to Number Genie " or try "Ok Google, talk to Eliza' for the classic 1960s AI exercise.

You can get started today by visiting the Actions on Google website for developers. To help create a smooth, straightforward development experience, we worked with a number of development partners, including conversational interaction development tools API.AI and Gupshup, analytics tools DashBot and VoiceLabs and consulting companies such as Assist, Notify.IO, Witlingo and Spoken Layer. We also created a collection of samples and voice user interface (VUI) resources or you can check out the integrations from our early access partners as they roll out over the coming weeks.

Introduction to Conversation Actions by Wayne Piekarski

Coming soon: Actions for Pixel and Allo + Support for Purchases and Bookings

Today is just the start, and we're excited to see what you build for the Google Assistant. We'll continue to add more platform capabilities over time, including the ability to make your integrations available across the various Assistant surfaces like Pixel phones and Google Allo. We'll also enable support for purchases and bookings as well as deeper Assistant integrations across verticals. Developers who are interested in creating actions using these upcoming features should register for our early access partner program and help shape the future of the platform.

Build, explore and let us know what you think about Actions on Google! And to say in the loop, be sure to sign up for our newsletter, join our Google+ community, and use the “actions-on-google” tag on StackOverflow.

Saving Data: Reducing the size of App Updates by 65%

Posted by Andrew Hayden, Software Engineer on Google Play

Android users are downloading tens of billions of apps and games on Google Play. We're also seeing developers update their apps frequently in order to provide users with great content, improve security, and enhance the overall user experience. It takes a lot of data to download these updates and we know users care about how much data their devices are using. Earlier this year, we announced that we started using the bsdiff algorithm (by Colin Percival). Using bsdiff, we were able to reduce the size of app updates on average by 47% compared to the full APK size.

Today, we're excited to share a new approach that goes further — File-by-File patching. App Updates using File-by-File patching are, on average, 65% smaller than the full app, and in some cases more than 90% smaller.

The savings, compared to our previous approach, add up to 6 petabytes of user data saved per day!

In order to get the new version of the app, Google Play sends your device a patch that describes the differences between the old and new versions of the app.

Imagine you are an author of a book about to be published, and wish to change a single sentence - it's much easier to tell the editor which sentence to change and what to change, rather than send an entirely new book. In the same way, patches are much smaller and much faster to download than the entire APK.

Techniques used in File-by-File patching

Android apps are packaged as APKs, which are ZIP files with special conventions. Most of the content within the ZIP files (and APKs) is compressed using a technology called Deflate. Deflate is really good at compressing data but it has a drawback: it makes identifying changes in the original (uncompressed) content really hard. Even a tiny change to the original content (like changing one word in a book) can make the compressed output of deflate look completely different. Describing the differences between the original content is easy, but describing the differences between the compressed content is so hard that it leads to inefficient patches.

Watch how much the compressed text on the right side changes from a one-letter change in the uncompressed text on the left:

File-by-File therefore is based on detecting changes in the uncompressed data. To generate a patch, we first decompress both old and new files before computing the delta (we still use bsdiff here). Then to apply the patch, we decompress the old file, apply the delta to the uncompressed content and then recompress the new file. In doing so, we need to make sure that the APK on your device is a perfect match, byte for byte, to the one on the Play Store (see APK Signature Schema v2 for why).

When recompressing the new file, we hit two complications. First, Deflate has a number of settings that affect output; and we don't know which settings were used in the first place. Second, many versions of deflate exist and we need to know whether the version on your device is suitable.

Fortunately, after analysis of the apps on the Play Store, we've discovered that recent and compatible versions of deflate based on zlib (the most popular deflate library) account for almost all deflated content in the Play Store. In addition, the default settings (level=6) and maximum compression settings (level=9) are the only settings we encountered in practice.

Knowing this, we can detect and reproduce the original deflate settings. This makes it possible to uncompress the data, apply a patch, and then recompress the data back to exactly the same bytes as originally uploaded.

However, there is one trade off; extra processing power is needed on the device. On modern devices (e.g. from 2015), recompression can take a little over a second per megabyte and on older or less powerful devices it can be longer. Analysis so far shows that, on average, if the patch size is halved then the time spent applying the patch (which for File-by-File includes recompression) is doubled.

For now, we are limiting the use of this new patching technology to auto-updates only, i.e. the updates that take place in the background, usually at night when your phone is plugged into power and you're not likely to be using it. This ensures that users won't have to wait any longer than usual for an update to finish when manually updating an app.

How effective is File-by-File Patching?

Here are examples of app updates already using File-by-File Patching:


Application
Original Size
Previous (BSDiff) Patch Size
(% vs original)
File-by-File Patch Size (% vs original)
71.1 MB
13.4 MB (-81%)
8.0 MB (-89%)
32.7 MB
17.5 MB (-46%)
9.6 MB (-71%)
17.8 MB
7.6 MB (-57%)
7.3 MB (-59%)
18.9 MB
17.2 MB (-9%)
13.1 MB (-31%)
52.4 MB
19.1 MB (-64%)
8.4 MB (-84%)
16.2 MB
7.7 MB (-52%)
1.2 MB (-92%)


Disclaimer: if you see different patch sizes when you press "update" manually, that is because we are not currently using File-by-file for interactive updates, only those done in the background.

Saving data and making our users (& developers!) happy

These changes are designed to ensure our community of over a billion Android users use as little data as possible for regular app updates. The best thing is that as a developer you don't need to do anything. You get these reductions to your update size for free!

If you'd like to know more about File-by-File patching, including the technical details, head over to the Archive Patcher GitHub project where you can find information, including the source code. Yes, File-by-File patching is completely open-source!

As a developer if you're interested in reducing your APK size still further, here are some general tips on reducing APK size.

AMP Cache Updates

Posted by John Coiner, Software Engineer

Today we are announcing a change to the domain scheme of the Google AMP Cache. Beginning soon, the Google AMP Cache will serve each site from its own subdomain of https://cdn.ampproject.org. This change will allow content served from the Google AMP Cache to be protected by the fundamental security model of the web: the HTML5 origin.

No immediate changes are required for most publishers of AMP documents. However, to benefit from the additional security, it is recommended that all AMP publishers update their CORS implementation in preparation for the new Google AMP Cache URL scheme. The Google AMP Cache will continue to support existing URLs, but those URLs will eventually redirect to the new URL scheme.

How subdomain names will be created on the Google AMP Cache

The subdomains created by the Google AMP Cache will be human-readable when character limits and technical specs allow, and will closely resemble the publisher's own domain.

When possible, the Google AMP Cache will create each subdomain by first converting the AMP document domain from IDN (punycode) to UTF-8. Every "-" (dash) will be replaced with "--"(2 dashes) and every "." (dot) will be replaced with a "-" (dash). For example, pub.com will map to pub-com.cdn.ampproject.org. Where technical limitations prevent a human readable subdomain, a one-way hash will be used instead.

Updates needed for hosts and service providers with remote endpoints

Due to the changes described above, CORS endpoints will begin seeing requests with new origins. The following updates will be required:

  • Expand request acceptance to the new subdomain: Sites that currently only accept CORS requests from https://cdn.ampproject.organd the publisher's own origins must update their systems to accept requests from https://[pub-com].cdn.ampproject.org, https://cdn.ampproject.org, and the AMP publisher's own origins.
  • Tighten request acceptance for security: Sites that currently accept CORS requests from https://*.ampproject.org as described in the AMP spec, can improve security by restricting acceptance to requests from https://[pub-com].cdn.ampproject.org, https://cdn.ampproject.org, and the AMP publisher's own origins. Support for https://*.ampproject.org is no longer necessary.
  • Support for new subdomain pattern by ads, analytics, and other technology providers: Service providers such as analytics and ads vendors that have a CORS endpoint will also need to ensure that their systems accept requests from the Google AMP Cache's subdomains (e.g.https://ampbyexample-com.cdn.ampproject.org), in addition to their own hosts.

Retrieving the Google AMP Cache URL

For platforms that display AMP documents and serve from the Google AMP Cache, the best way to retrieve Google AMP Cache URLs is to continue using the Google AMP Cache URL API. The Google AMP Cache URL API will be updated in Q1 2017 to return the new cache URL scheme that includes the subdomain.

You can use an interactive tool to find the Google AMP Cache subdomain generated for each site over at ampbyexample.com.


Timing

Google Search is planning to begin using the new URL scheme as soon as possible and is monitoring sites' compatibility. In addition, we will be reaching out to impacted parties, and we will make available a developer testing sandbox prior to launching to ensure a smooth transition.

Welcoming Android 7.1.1 Nougat

Posted by Dave Burke, VP of Engineering

Android Nougat

Android 7.1.1 Nougat!

Today we're rolling out an update to Nougat -- Android 7.1.1 for Pixel and Pixel XL devices and the full lineup of supported Nexus devices. We're also pushing the Android 7.1.1 source code to the Android Open Source Project (AOSP) so that device makers can get their hands on the latest version of Android.

With Android 7.1.1 officially on it's way to users, it's a good time to make sure your apps are ready.

What's in Android 7.1.1?

Android 7.1.1 is an incremental release that builds on the features already available on Pixel and Pixel XL devices, adding a handful of new features for consumers as well as optimizations and bug fixes on top of the base Android 7.1 platform (API level 25).

If you haven't explored the developer features, you'll want to take a look at app shortcuts, round icon resources, and image keyboard support, among others -- you can see the full list of developer features here. For details on API Level 25, check out the API diffs and the API reference.

You can find an overview of all of the Android Nougat developer resources here, including details on the core Android 7.0 Nougat behavior changes and developer features.c

Coming to consumer devices soon

We're starting the Android 7.1.1 rollout today, and we expect it to reach all eligible devices over the next several weeks. Pixel and Pixel XL devices will get the over-the-air (OTA) update, as will Nexus 5X, Nexus 6P, Nexus 6, Nexus 9, Nexus Player, Pixel C, and General Mobile 4G (Android One) devices. Devices enrolled in the Android Beta Program will receive the final version as well. As always, you can also download and flash this update manually.

We've also been working with our device manufacturer partners to bring Android 7.1.1 to their devices in the months ahead.

Make sure your apps are ready

Take this opportunity to test your apps for compatibility and optimize them to look their best on Android 7.1.1, such as by providing round icons and adding app shortcuts. We recommend compiling your app with, and ideally targeting, API 25. See our recent post for details.

With the final platform we’re updating the platform and build tools in Android Studio, as well as the API Level 25 emulator system images. The latest version of the support library (25.0.1) is also available for you to add image keyboard support, bottom navigation, and other features for devices running API Level 25 or earlier.

We're also providing downloadable factory and OTA images on the Nexus Images page to help you do final testing on your Pixel and Nexus devices. To help scale your testing, make sure to take advantage of Firebase Test Lab for Android and run your tests in the cloud at no charge through the end of December.

After your final testing, publish your apps to your alpha, beta, or production channels in the Google Play Developer Console.

What's next?

We'll soon be closing open bugs logged against Developer Preview builds, but please keep the feedback coming! If you still see an issue that you filed in the preview tracker, just file a new issue against Android 7.1 in the AOSP issue tracker. You can also continue to give us feedback or ask questions in the developer community.

As mentioned back in August, we've moved Android Nougat into a regular maintenance cycle and we're already started work on refinements and bug fixes for the next incremental update. If you have an eligible device that's currently enrolled in the Android Beta Program, your device will automatically receive preview updates of upcoming Android Nougat releases as soon as they are available. If you don't want to receive those updates, just visit the Beta site and unenroll the device.

Thanks for being part of the developer preview. Let us know how this year's preview met your needs by taking a short survey. Your feedback helps to shape our future releases.

Generating slides from spreadsheet data

Originally posted on G Suite Developers Blog

Posted by Wesley Chun (@wescpy), Developer Advocate, G Suite

The G Suite team recently launched the very first Google Slides API, opening up a whole new set of possibilities, including leveraging data already sitting in a spreadsheet or database, and programmatically generating slide decks or slide content based on that data. Why is this a big deal? One of the key advantages of slide decks is that they can take database or spreadsheet data and make it more presentable for human consumption. This is useful when the need arises to communicate the information reflected by that data to management or potential customers.

Walking developers through a short application demonstrating both the Sheets and Slides APIs to make this happen is the topic of today's DevByte video. The sample app starts by reading all the necessary data from the spreadsheet using the Sheets API. The Slides API takes over from there, creating new slides for the data, then populating those slides with the Sheets data.

Developers interact with Slides by sending API requests. Similar to the Google Sheets API, these requests come in the form of JSON payloads. You create an array like in the JavaScript pseudocode below featuring requests to create a cell table on a slide and import a chart from a Sheet:


var requests = [
   {"createTable": {
       "elementProperties":
           {"pageObjectId": slideID},
       "rows": 8,
       "columns": 4
   }},
   {"createSheetsChart": {
       "spreadsheetId": sheetID,
       "chartId": chartID,
       "linkingMode": "LINKED",
       "elementProperties": {
           "pageObjectId": slideID,
           "size": {
               "height": { ... },
               "width": { ... }
           },
           "transform": { ... }
       }
   }}
];
If you've got at least one request, say in a variable named requests (as above), including the Sheet's sheetID and chartID plus the presentation page's slideID. You'd then pass it to the API with just one call to the presentations().batchUpdate() command, which in Python looks like the below if SLIDES is your API service endpoint:
SLIDES.presentations().batchUpdate(presentationId=slideID,
       body=requests).execute()

Creating tables is fairly straightforward. Creating charts has some magical features, one of those being the linkingMode. A value of "LINKED" means that if the Sheet data changes (altering the chart in the Sheet), the same chart in a slide presentation can be refreshed to match the latest image, either by the API or in the Slides user interface! You can also request a plain old static image that doesn't change with the data by selecting a value of "NOT_LINKED_IMAGE" for linkingMode. More on this can be found in the documentationon creating charts, and check out the video where you'll see both those API requests in action.

For a detailed look at the complete code sample featured in the video, check out the deep dive post. We look forward to seeing the interesting integrations you build with the power of both APIs!

TensorFlow 0.12 adds support for Windows

Posted by Derek Murray, Software Engineer
Today we are launching preliminary Windows support for TensorFlow.

Native support for TensorFlow on Windows was one of the first requests we received after open-sourcing TensorFlow. Although some Windows users have managed to run TensorFlow in a Docker container, we wanted to provide a more complete experience including GPU support.

With the release of TensorFlow r0.12, we now provide a native TensorFlow package for Windows 7, 10, and Server 2016. This release enables you to speed up your TensorFlow training with any GPU that runs CUDA 8.

We have published the latest release as a pip package in PyPI, so now you can install TensorFlow with a single command:

     C:\> pip install tensorflow

And for GPU support:

     C:\> pip install tensorflow-gpu

More details about Windows support and all of the other new features in r0.12 are included in the release notes.

We're excited to offer more people the opportunity to use TF at maximum speed. Follow us on Twitter to be the first to hear about future releases – we're @tensorflow.

Acknowledgements

Many people have contributed to making this release possible. In particular, we'd like to thank Guenther Schmuelling and Vit Stepanovs from Microsoft for their significant contributions to Windows support.

It’s that time again: Google Code-in starts today!

Originally posted on Google Open Source Blog
By Mary Radomile, Open Source Programs Office
Today marks the start of the 7th year of Google Code-in (GCI), our pre-university contest introducing students to open source development. GCI takes place entirely online and is open to students between the ages of 13 and 17 around the globe.
The concept is simple: complete bite-sized tasks (at your own pace) created by 17 participating open source organizations on topic areas you find interesting:

  • Coding
  • Documentation/Training
  • Outreach/Research
  • Quality Assurance
  • User Interface

Tasks take an average of 3-5 hours to complete and include the guidance of a mentor to help along the way. Complete one task? Get a digital certificate. Three tasks? Get a sweet Google t-shirt. Finalists get a hoodie. Grand Prize winners get a trip to Google headquarters in California.

Over the last 6 years, 3213 students from 99 countries have successfully completed tasks in GCI. Intrigued? Learn more about GCI by checking out our rules and FAQs. And please visit our contest site and read the Getting Started Guide.

Teachers, if you are interested in getting your students involved in Google Code-in you can find resources here to help you get started.

Final update to Android 7.1 Developer Preview

Posted by Dave Burke, VP of Engineering

Today we're rolling out an update to the Android 7.1 Developer Preview -- the last before we release the final Android 7.1.1 platform to the ecosystem. Android 7.1.1 includes the developer features already available on Pixel and Pixel XL devices and adds optimizations and bug fixes on top of the base Android 7.1 platform. With Developer Preview 2, you can make sure your apps are ready for Android 7.1.1 and the consumers that will soon be running it on their devices.

As highlighted in October, we're also expanding the range of devices that can receive this Developer Preview update to Nexus 5X, Nexus 6P, Nexus 9, and Pixel C.

If you have a supported device that's enrolled in the Android Beta Program, you'll receive an update to Developer Preview 2 over the coming week. If you haven't enrolled your device yet, just visit the site to enroll your device and get the update.

In early December, we'll roll out Android 7.1.1 to the full lineup of supported devices as well as Pixel and Pixel XL devices.

What's in this update?

Developer Preview 2 is a release candidate for Android 7.1.1 that you can use to complete your app development and testing in preparation for the upcoming final release. In includes near-final system behaviors and UI, along with the latest bug fixes and optimizations across the system and Google apps.

It also includes the developer features and APIs (API level 25) already introduced in Developer Preview 1. If you haven't explored the developer features, you'll want to take a look at app shortcuts, round icon resources, and image keyboard support, among others -- you can see the full list of developer features here.

With Developer Preview 2, we're also updating the SDK build and platform tools in Android Studio, the Android 7.1.1 platform, and the API Level 25 emulator system images. The latest version of the support library (25.0.1) is also available for you to add image keyboard support, bottom navigation, and other features for devices running API Level 25 or earlier.

For details on API Level 25 check out the API diffs and the updated API reference on the developer preview site.

Get your apps ready for Android 7.1

Now is the time to optimize your apps to look their best on Android 7.1.1. To get started, update to Android Studio 2.2.2 and then download the API Level 25 platform, emulator system images, and tools through the SDK Manager in Android Studio.

After installing the API Level 25 SDK, you can update your project's compileSdkVersion to 25 to build and test against the new APIs. If you're doing compatibility testing, we recommend updating your app's targetSdkVersion to 25 to test your app with compatibility behaviors disabled. For details on how to set up your app with the API Level 25 SDK, see Set up the Preview.

If you're adding app shortcuts or circular launcher icons to your app, you can use Android Studio's built-in Image Asset Studio to quickly help you create icons of different sizes that meet the material design guidelines. You can test your round icons on the Google APIs emulator for API Level 25, which includes support for round icons and the new Google Pixel Launcher.

Android Studio and the Google APIs emulator let you quickly create and test your round icon assets.

If you're adding image keyboard support, you can use the Messenger and Google Keyboard apps included in the preview system images for testing as they include support for this new API.

Scale your tests using Firebase Test Lab for Android

To help scale your testing, make sure to take advantage of Firebase Test Lab for Android and run your tests in the cloud at no charge during the preview period on all virtual devices including the Developer Preview 2 (API 25). You can use the automated crawler (Robo Test) to test your app without having to write any test scripts, or you can upload your own instrumentation (e.g. Espresso) tests. You can upload your tests here.

Publish your apps to alpha, beta or production channels in Google Play

After you've finished final testing, you can publish your updates compiled against, and optionally targeting, API 25 to Google Play. You can publish to your alpha, beta, or even production channels in the Google Play Developer Console. In this way, push your app updates to users whose devices are running Android 7.1, such as Pixel and Android Beta devices.

Get Developer Preview 2 on Your Eligible Device

If you have an eligible device that's already enrolled in the Android Beta Program, the device will get the Developer Preview 2 update over the coming week. No action is needed on your part. If you aren't yet enrolled in program, the easiest way to get started is by visiting android.com/beta and opt-in your eligible Android phone or tablet -- you'll soon receive this preview update over-the-air. As always, you can also download and flash this update manually.

As mentioned above, this Developer Preview update is available for Nexus 5X, Nexus 6P, Nexus 9, and Pixel C devices.

We're expecting to launch the final release of the Android 7.1.1 in just a few weeks Starting in December, we'll roll out Android 7.1.1 to the full lineup of supported preview devices, as well as the recently launched Pixel and Pixel XL devices. At that time, we'll also push the sources to AOSP, so our device manufacturer partners can bring this new platform update to consumers on their devices.

Meanwhile, we continue to welcome your feedback in the Developer Preview issue tracker, N Preview Developer community, or Android Beta community as we work towards the final consumer release in December!

Calling European game developers, enter the Indie Games Contest by December 31

Originally posted on Google Developers blog

Posted by Matteo Vallone, Google Play Partner Development Manager

To build awareness of the awesome innovation and art that indie game developers are bringing to users on Google Play, we have invested heavily over the past year in programs like Indie Corner, as well as events like the Google Play Indie Games Festivals in North America and Korea.

As part of that sustained effort, we also want to celebrate the passion and innovation of indie game developers with the introduction of the first-ever Google Play Indie Games Contest in Europe. The contest will recognize the best indie talent in several countries and offer prizes that will help you get your game noticed by industry experts and gamers worldwide.

Prizes for the finalists and winners:

  • An open showcase held at the Saatchi Gallery in London
  • YouTube influencer campaigns worth up to 100,000 EUR
  • Premium placements on Google Play
  • Tickets to Google I/O 2017 and other top industry events
  • Promotions on our channels
  • Special prizes for the best Unity game
  • And more!

Entering the contest:

If you're based in Czech Republic, Denmark, Finland, France (coming soon), Germany, Iceland, Israel, Netherlands, Norway, Poland (coming soon), Romania, Spain, Sweden, Turkey, or UK (excl. Northern Ireland), have 15 or less full time employees, and published a new game on Google Play after 1 January 2016, you may now be eligible to enter the contest. If you're planning on publishing a new game soon, you can also enter by submitting a private beta. Check out all the details in the terms and conditions. Submissions close on 31 December 2016.

The process:

Up to 20 finalists will get to showcase their games at an open event at the Saatchi Gallery in London on the 16th February 2017. At the event, the top 10 will be selected by the event attendees and the Google Play team. The top 10 will then get the opportunity to pitch to a jury of industry experts, from which the final winner and runners up will be selected.

Even if someone is NOT entering the contest:

Even if you're not eligible to enter the contest, you can still register to attend the final showcase event in London on 16 February 2017, check out some great indie games, and have fun with various industry experts and indie developers. We will also be hosting a workshop for all indie games developers from across EMEA in the new Google office in Kings Cross the next day, so this will be a packed week.

Get started:

Enter the Indie Games Contest now and visit the contest site to find out more about the contest, the event, and the workshop.

Google Play services and Firebase for Android will support API level 14 at minimum

Posted by Doug Stevenson, Developer Advocate

Version 10.0.0 of the Google Play services client libraries, as well as the Firebase client libraries for Android, will be the last version of these libraries that support Android API level 9 (Android 2.3, Gingerbread). The next scheduled release of these libraries, version 10.2.0, will increase the minimum supported API level from 9 to 14 (Android 4.0.1, Ice Cream Sandwich). This change will happen in early 2017.

Why are we discontinuing support for Gingerbread and Honeycomb in Google Play services?

The Gingerbread platform is almost six years old. Many Android developers have already discontinued support for Gingerbread in their apps. This helps them build better apps that make use of the newer capabilities of the Android platform. For us, the situation is the same. By making this change, we will be able to provide a more robust collection of tools for Android developers with greater speed.

What this means for your Android app that uses Google Play services or Firebase:

You may use version 10.0.0 of Google Play services and Firebase as you are currently. It will continue to work with Gingerbread devices as it has in the past.

When you choose to upgrade to the future version 10.2.0, and if your app minimally supports API level 14 or greater (typically specified as "minSdkVersion" in your build.gradle), you will not encounter any versioning problems. However, if your app supports lower than API level 14, you will encounter a problem at build time with an error that looks like this: 

Error:Execution failed for task ':app:processDebugManifest'.
> Manifest merger failed : uses-sdk:minSdkVersion 9 cannot be smaller than version 14 declared in library [com.google.android.gms:play-services:10.2.0]
        Suggestion: use tools:overrideLibrary="com.google.android.gms:play_services" to force usage

Unfortunately, the stated suggestion will not help you successfully run your app on older devices. In order to use Google Play services 10.2.0 and later, you can choose one of the following options:

1. Target API level 14 as the minimum supported API level.

This is the recommended course of action. To discontinue support for API levels that will no longer receive Google Play services updates, simply increase the minSdkVersion value in your app's build.gradle to at least 14. If you update your app in this way and publish it to the Play Store, users of devices with less than that level of support will not be able to see or download the update. However, they will still be able to download and use the most recently published version of the app that does target their device.

A very small percentage of all Android devices are using API levels less than 14. You can read more about the current distribution of Android devices. We believe that many of these old devices are not actively being used.

If your app still has a significant number of users on older devices, you can use multiple APK support in Google Play to deliver an APK that uses Google Play services 10.0.0. This is described below.

2. Build multiple APKs to support devices with an API level less than 14.

Along with some configuration and code management, you can build multiple APKs that support different minimum API levels, with different versions of Google Play services. You can accomplish this with build variants in Gradle. First, define build flavors for legacy and newer versions of your app. For example, in your build.gradle, define two different product flavors, with two different compile dependencies for the components of Play Services you're using: 

productFlavors {
    legacy {
        minSdkVersion 9
        versionCode 901  // Min API level 9, v01
    }
    current {
        minSdkVersion 14
        versionCode 1401  // Min API level 14, v01
    }
}

dependencies {
    legacyCompile 'com.google.android.gms:play-services:10.0.0'
    currentCompile 'com.google.android.gms:play-services:10.2.0'
}

In the above situation, there are two product flavors being built against two different versions of the Google Play services client libraries. This will work fine if only APIs are called that are available in the 10.0.0 library. If you need to call newer APIs made available with 10.2.0, you will have to create a compatibility library for the newer API calls so that they are only built into the version of the application that can use them:

  • Declare a Java interface that exposes the higher-level functionality you want to perform that is only available in current versions of Play services.
  • Build two Android libraries that implement that interface. The "current" implementation should call the newer APIs as desired. The "legacy" implementation should no-op or otherwise act as desired with older versions of Play services. The interface should be added to both libraries.
  • Conditionally compile each library into the app using "legacyCompile" and "currentCompile" dependencies.
  • In the app's code, call through to the compatibility library whenever newer Play APIs are required.

After building a release APK for each flavor, you then publish them both to the Play Store, and the device will update with the most appropriate version for that device. Read more about multiple APK support in the Play Store.