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Originally posted on Google Developers blog

Posted by Matteo Vallone, Google Play Games Business Development

To build awareness of the awesome innovation and art that indie game developers
are bringing to users on Google Play, we have invested hea…

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.

Posted by Paul Crowley, Senior Software Engineer and Paul Lawrence, Senior Software Engineer

Encryption protects your data if your phone falls into someone else’s hands. The
new Google Pixel and Pixel XL are encrypted by default to offer strong data
protection, while maintaining a great user experience with high I/O performance
and long battery life. In addition to encryption, the Pixel phones debuted
running the Android Nougat release, which has even more security
improvements.

This blog post covers the encryption implementation on Google Pixel devices and
how it improves the user experience, performance, and security of the device.

File-Based Encryption Direct Boot experience

One of the security features introduced in Android Nougat was file-based
encryption. File-based encryption (FBE) means different files are encrypted
with different keys that can be unlocked independently. FBE also separates data
into device encrypted (DE) data and credential encrypted (CE) data.

Direct
boot uses file-based encryption to allow a seamless user experience when a
device reboots by combining the unlock and decrypt screen. For users, this means
that applications like alarm clocks, accessibility settings, and phone calls are
available immediately after boot.

Enhanced with TrustZone® security

Modern processors provide a means to execute code in a mode that remains secure
even if the kernel is compromised. On ARM®-based processors this mode is known
as TrustZone. Starting in Android Nougat, all disk encryption keys are stored
encrypted with keys held by TrustZone software. This secures encrypted data in
two ways:

• TrustZone enforces the Verified Boot
  process. If TrustZone detects that the operating system has been modified, it
  won’t decrypt disk encryption keys; this helps to secure device encrypted (DE)
  data.
• TrustZone enforces a waiting period between guesses at the user credential,
  which gets longer after a sequence of wrong guesses. With 1624 valid four-point
  patterns and TrustZone’s ever-growing waiting period, trying all patterns would
  take more than four years. This improves security for all users, especially
  those who have a shorter and more easily guessed pattern, PIN, or
  password.

Encryption on Pixel phones

Protecting different folders with different keys required a distinct approach
from full-disk
encryption (FDE). The natural choice for Linux-based systems is the
industry-standard eCryptFS. However, eCryptFS didn’t meet our performance
requirements. Fortunately one of the eCryptFS creators, Michael Halcrow, worked
with the ext4 maintainer, Ted Ts’o, to add encryption natively to ext4, and
Android became the first consumer of this technology. ext4 encryption
performance is similar to full-disk encryption, which is as performant as a
software-only solution can be.

Additionally, Pixel phones have an inline hardware encryption engine, which
gives them the ability to write encrypted data at line speed to the flash
memory. To take advantage of this, we modified ext4 encryption to use this
hardware by adding a key reference to the bio structure, within the ext4 driver
before passing it to the block layer. (The bio structure is the basic container
for block I/O in the Linux kernel.) We then modified the inline encryption block
driver to pass this to the hardware. As with ext4 encryption, keys are managed
by the Linux keyring. To see our implementation, take a look at the source
code for the Pixel kernel.

While this specific implementation of file-based encryption using ext4 with
inline encryption benefits Pixel users, FBE is available in AOSP and ready to
use, along with the other features mentioned in this post.

Posted by Wojtek Kaliciński, Android Developer Advocate

Android Studio 2.2 launched recently with many
new and improved features. Some of the changes are easy to miss because they
happened under the hood in the Android Gradle plugin, such as the newly
rewritten integrated APK packaging and signing step.

APK Signature Scheme v2

With the introduction of the new APK Signature
Scheme v2 in Android 7.0 Nougat, we decided to rewrite how assembling APKs
works in the Android Gradle plugin. You can read all about the low-level
technical details of v2 signatures in the documentation,
but here’s a quick tl;dr summary of the info you need as an Android app
developer:

• The cryptographic signature of the APK that is used to verify its integrity
  is now located immediately before the ZIP Central Directory.
• The signature is computed and verified over the binary contents of the whole
  APK file, as opposed to decompressed file contents of each file in the archive
  in v1.
• An APK can be signed by both v1 and v2 signatures at the same time, so it
  remains backwards compatible with previous Android releases.

Why introduce this change to how Android verifies APKs? Firstly, for enhanced
security and extensibility of this new signing format, and secondly for
performance – the new signatures take significantly less time to verify on the
device (no need for costly decompression), resulting in faster app installation
times.

The consequence of this new signing scheme, however, is that there are new
constraints on the APK creation process. Since only uncompressed file contents
were verified in v1, that allowed for quite a lot of modifications to be made
after APK signing – files could be moved around or even recompressed. In fact,
the zipalign tool which was part of the build process did exactly
that – it was used to align ZIP entries on correct byte boundaries for improved
runtime performance.

Because v2 signatures verify all bytes in the archive and not individual ZIP
entries, running zipalign is no longer possible after
signing. That’s why compression, aligning and signing now happens in a
single, integrated step of the build process.

If you have any custom tasks in your build process that involve tampering with
or post-processing the APK file in any way, please make sure you disable them or
you risk invalidating the v2 signature and thus making your APKs incompatible
with Android 7.0 and above.

Should you choose to do signing and aligning manually (such as from the command
line), we offer a new tool in the Android SDK, called apksigner,
that provides both v1 and v2 APK signing and verification. Note that you need to
run zipalign before running apksigner
if you are using v2 signatures. Also remember the jarsigner tool
from the JDK is not compatible with Android v2 signatures, so you can’t use it
to re-sign your APKs if you want to retain the v2 signature.

In case you want to disable adding v1 or v2 signatures when building with the
Android Gradle plugin, you can add these lines to your signingConfig
section in build.gradle:

v1SigningEnabled false
v2SigningEnabled false

Note: both signing schemes are enabled by default in Android Gradle plugin 2.2.

Release builds for smaller APKs

We took this opportunity when rewriting the packager to make some optimizations
to the size of release APKs, resulting in faster downloads, smaller
delta updates on the Play Store, and less wasted space on the device. Here
are some of the changes we made:

• Files in the archive are now sorted to minimize differences between APK
  builds.
• All file timestamps and metadata are zeroed out.
• Level 6 and level 9 compression is checked for all files in parallel and the
  optimal one is used, i.e. if L9 provides little benefit in terms of size, then
  L6 may be chosen for better performance
• Native libraries are stored uncompressed and page aligned in the APK. This
  brings support for the android:extractNativeLibs="false" option
  from Android 6.0 Marshmallow and lets applications use less space on the device
  as well as generate smaller updates on the Play Store
• Zopfli compression is not used to better support Play Store update
  algorithms. It is not recommended to recompress your APKs with Zopfli.
  Pre-optimizing individual resources such as PNG files in your projects is still
  fine and recommended.

These changes help make your releases as small as possible so that users can
download and update your app even on a slower connection or on less capable
devices. But what about debug builds?

Debug builds for installation speed

When developing apps you want to keep the iteration cycle fast – change code,
build, and deploy on a connected device or emulator. Since Android Studio 2.0
we’ve been working to make all the steps as fast as possible. With Instant Run
we’re now able to update only the changed code and resources during runtime,
while the new Emulator brings multi-processor support and faster ADB speeds for
quicker APK transfer and installation. Build improvements can cut that time even
further and in Android Studio 2.2 we’re introducing incremental packaging and
parallel compression for debug builds. Together with other features like
selectively packaging resources for the target device density and ABI this will
make your development even faster.

A word of caution: the APK files created for Instant Run or by invoking a debug
build are not meant for distribution on the Play Store! They contain additional
instrumentation code for Instant Run and are missing resources for device
configurations other than the one that was connected when you started the build.
Make sure you only distribute release versions of the APK which you can create
using the Android Studio Generate
Signed APK command or the assembleRelease Gradle task.

Posted by Nick Felker and Sachit Mishra, Developer
Programs Engineers

The TV
Input Framework (TIF) on Android TV makes it easy for third-party app
developers to create their own TV channels with any type of linear media. It
introduces a new way for …

Posted by Kathryn Shih, Android Product Manager

In addition to supporting the experimental Gradle plugin, Android
Studio 2.2 enables you to build C/C++ components of Android projects using
CMake and ndk-build.

The Android Studio team plans to continue to support the experimental Gradle plugin.
This will eventually replace the current Gradle plugin, providing additional
tightly-integrated benefits to C/C++ developers such as smarter dependency
management. So if you’re interested in someday having the smartest possible
interface between your IDE and your build system, you shouldn’t ignore the
experimental plugin.

CMake and ndk-build are useful alternatives to Gradle in several cases:

• Projects that are already using CMake or ndk-build, such as legacy Eclipse
  ndk projects
• Projects that are unable to assume the risk of using an experimental plugin
  for their C/C++ builds
• Projects that will share a C/C++ build system across multiple platforms
• C/C++ projects that need to use advanced features currently unavailable in
  experimental Gradle such as NEON support

For new projects, we recommend using CMake or experimental Gradle. For new
Android projects with limited C++, we recommend trying the experimental Gradle
plugin. For projects with substantial amounts of C++, or where you want the
maximally stable build configuration, we recommend using a CMake build. Android
Studio intends CMake to be a permanently supported solution.

While we think that there are substantial advantages to having a single build
system able to handle all parts of an Android application, stabilizing the
experimental plugin is not an option for us because it relies on Gradle APIs
that are still a work in progress. Until the Gradle APIs are stabilized, the
experimental plugin will keep changing, particularly in its Domain Specific
Language, and will be strictly tied to a very specific version of Gradle itself.

Note that the the old, undocumented ndkCompile integration is deprecated. If you
are using it, you need to move away from it as we’ll remove it completely in the
near future. We recommend migrating to gradle+cmake via our migration
guide.

Migrating from Eclipse to Android Studio

We
no longer support the Eclipse ADT. To get started migrating, download and install
Android Studio. For most projects, migration is as simple as importing your
existing Eclipse ADT projects in Android Studio with the File → New→
Import Project menu option. For more details on the migration process,
check out the migration
guide.

Feedback and Open Source Contributions

We’re dedicated to making Android Studio the best possible integrated
development environment for building Android apps, so if there are missing
features or other challenges preventing you from using Android Studio, we want to hear about it [please take our survey]. You
can also file bugs or feature
requests directly with the team, and let us know via our Twitter or Google+ accounts.

Android Studio is an open source
project, available to all at no cost. Check out our Open Source project page if
you’re interested in contributing or learning more.

By Ahmed Mounir Gad, Product Manager, Firebase Test Lab

To deliver the best user experience right out of the gate, Firebase Test Lab for Android allows you to test your apps and ensure their compatibility with multiple device configurations, across OS versions, screen orientations, and locales. With a single click, you can run your tests on hundreds of device configurations in Google Cloud and receive your results quickly.

Today, we’re excited to announce the availability of the Android 7.1 Developer Preview on Firebase Test Lab virtual devices. In addition to testing the Android 7.1 Developer Preview on your physical Android Device with the Android Beta program, or on your local Android Emulator, you can use the Firebase Test Lab to scale your app testing to hundreds of Android virtual devices.

You can also use Firebase Test Lab to perform your own testing. If you don’t have any test scripts, Robo test is ideal for doing your basic compatibility testing on the new platform. It crawls your app in an attempt to find crashes. You can also use the Espresso Test Recorder in Android Studio to record your own instrumentation tests without writing any code.

From now until the end of December (12/31/2016), Firebase Test Lab will be offered at no charge on the Firebase Blaze plan for all virtual devices, to help you ensure the compatibility of your app with the Android 7.1 Developer Preview release, as well as with other Android releases.

Prepare your app for API level 25, then go to the Firebase Test Lab console to run your first test.

Happy testing!

Robo tests uncovering a crash on Android 7.1 Developer Preview for the Flood-It! app.

Posted by Larissa Fontaine, Director, Global Head of Apps Business
Development, Google Play

Almost three
years ago, we started the first of an ongoing series of developer events,
called Playtime, dedicated to educating partners on best practices and…

By Jamal Eason, Product
Manager, Android
With the release of Android
Studio 2.2, the time has now come to say goodbye to the Eclipse Android
Developer Tools. We have formally ended their support and development. There’s
never been a better time to swit…

Posted by Dorothy Kelly, Head of Developer Insights, Google Play Developer
Marketing

Core to our mission, we’re always
focused on the user and delivering the best experience possible. This same
principle underlies how Google Play works with develop…

Posted by Kazushi Nagayama, Search Quality Analyst, and Andrew Ahn, Product
Manager

We strive to continuously make Google Play the best platform for enjoying and
discovering the most innovative and trusted apps. Today we are announcing
additional en…

You can now transfer data from one user to another in the Google Admin Android app, much like you can in the web-based Admin console. The process can be initiated from the User List page or the User Details page and can be done as a standalone action, …

Guest post by Rajiev Timal, Founder of Readfeed

Readfeed was created to help book lovers around the world share and discuss
their favorite reads with each other more easily. Today, we are excited to
officially launch the Readfeed
app on Google Play….