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What is r apk abi and why does it matter for Android developers?

If you are an Android developer who uses native code in your app, you might have come across the term “r apk abi” in your build settings or documentation. But what does it mean and why is it important for your app’s performance and compatibility? In this article, we will explain what an ABI is, how it affects Android apps, and how to check and build your app with 64-bit libraries.

What is an ABI and how does it affect Android apps?

An ABI, or Application Binary Interface, is a set of rules and conventions that define how different components of a software system interact with each other. An ABI includes information such as:

• The CPU instruction set (and extensions) that can be used.
• The endianness of memory stores and loads at runtime. Android is always little-endian.
• Conventions for passing data between applications and the system, including alignment constraints, and how the system uses the stack and registers when it calls functions.
• The format of executable binaries, such as programs and shared libraries, and the types of content they support. Android always uses ELF.
• How C++ names are mangled. For more information, see Generic/Itanium C++ ABI.

Different Android devices use different CPUs, which in turn support different instruction sets. Each combination of CPU and instruction set has its own ABI. The NDK supports four ABIs for Android devices:

ABI	Supported Instruction Sets	Notes
armeabi-v7a	armeabi Thumb-2 VFPv3-D16	Incompatible with ARMv5/v6 devices.
arm64-v8a	AArch64 Armv8.0 only.
x86	x86 (IA-32) MMX SSE/2/3 SSSE3	No support for MOVBE or SSE4.
x86_64	x86-64 MMX SSE/2/3 SSSE3 SSE4.1, 4.2 POPCNT	x86-64-v1 only.

Supporting multiple ABIs means that your app can run on more devices, regardless of their CPU architecture. It also means that your app can take advantage of the performance improvements offered by 64-bit architectures, such as more registers, larger address space, and faster calculations.

How to check and build your app with 64-bit libraries

If your app uses only code written in Java or Kotlin, including all libraries or SDKs, then your app supports 64-bit devices by default. However, if your app uses native code, either directly or through a third-party library or SDK, then you need to make sure that your app includes 64-bit libraries for each ABI that you support. Google Play requires that apps using native code provide 64-bit versions in addition to 32-bit versions by August 1, 2023. To check and build your app with 64-bit libraries, you can use the following tools:

How to use APK Analyzer to inspect your app’s native libraries

APK Analyzer is a tool that lets you inspect the contents of your APK files, including the native libraries. You can use it to verify that your app has 64-bit libraries for each supported ABI, and to identify any issues or opportunities for optimization. To use APK Analyzer, follow these steps:

1. Open Android Studio and select Build > Analyze APK from the menu bar.
2. Select the APK file that you want to analyze. You can choose a debug APK from your project’s build output directory, or a release APK from your app bundle.
3. In the APK Analyzer window, expand the lib folder and look for the subfolders corresponding to each ABI. For example, arm64-v8a for 64-bit ARM devices, or x86_64 for 64-bit x86 devices.
4. Click on each subfolder and check the size and number of the native libraries. You can also double-click on a library to see its symbols and dependencies.
5. If you see any missing or mismatched libraries, you need to fix them before publishing your app. For example, if you have a library that is only available for armeabi-v7a and not for arm64-v8a, you need to either find a 64-bit version of that library, or exclude it from your app’s dependencies.

How to use Android Studio or Gradle to generate multiple APKs per ABI

One way to support multiple ABIs is to generate multiple APKs per ABI, each containing only the native libraries for that specific ABI. This reduces the size of each APK and avoids wasting space and bandwidth on unnecessary libraries. To generate multiple APKs per ABI, you can use Android Studio or Gradle. Here are the steps:

1. In Android Studio, open your app module’s build.gradle file and add the following code inside the android block:

android {     ...     splits {         abi {             enable true             reset()             include "armeabi-v7a", "arm64-v8a", "x86", "x86_64"             universalApk false         }     } }

This code enables ABI splits and specifies which ABIs to include in the APKs. You can modify the list of ABIs according to your app’s requirements. Setting universalApk to false means that no additional APK containing all ABIs will be generated.

2. Sync your project with Gradle files and build your app as usual. You can use Build > Build Bundle(s) / APK(s) > Build APK(s) from the menu bar, or run the assemble task from the Gradle tool window.
3. In your project’s build output directory, you will find a subdirectory named outputs/apk containing several APK files, one for each ABI. For example, app-arm64-v8a-debug.apk for 64-bit ARM devices, or app-x86_64-release.apk for 64-bit x86 devices.
4. You can test each APK on a device or emulator with the corresponding ABI, or upload them to Google Play using Android App Bundle or Multiple APKs.

How to test your app on 64-bit devices and emulators

Before publishing your app, you should test it on 64-bit devices and emulators to ensure that it works correctly and does not crash or behave unexpectedly. You can use physical devices with 64-bit CPUs, such as Pixel phones or tablets, or create virtual devices with 64-bit system images using Android Studio’s AVD Manager. To create a 64-bit emulator, follow these steps:

1. In Android Studio, select Tools > AVD Manager from the menu bar.
2. Click on Create Virtual Device and choose a device definition that suits your needs.
3. Select a system image that has a 64-bit ABI. For example, R (Google APIs) x86_64 for Android R with Google APIs on x86_64 architecture.
4. Click on Next and review the configuration of your virtual device. You can change the name, orientation, memory, storage, camera, network, and other options.
5. Click on Finish and wait for the emulator to be created.
6. Launch the emulator from the AVD Manager or the toolbar, and install and run your app on it. You can use Run > Run ‘app’ from the menu bar, or click on the green play button in the toolbar.
7. Test your app’s functionality and performance on the emulator, and look for any errors or warnings in the logcat window.

Conclusion and FAQs

In this article, we have learned what r apk abi is and why it matters for Android developers. We have also learned how to check and build our app with 64-bit libraries, and how to test our app on 64-bit devices and emulators. By supporting multiple ABIs, we can ensure that our app runs on more devices, takes advantage of 64-bit architectures, and complies with Google Play’s requirements. Here are some FAQs that you might have:

FAQ 1: What is the difference between armeabi-v7a and arm64-v8a?

Armeabi-v7a is a 32-bit ABI for ARM devices that support the ARMv7-A instruction set and extensions. Arm64-v8a is a 64-bit ABI for ARM devices that support the AArch64 instruction set and extensions. Arm64-v8a has more registers, larger address space, and faster calculations than armeabi-v7a.

FAQ 2: What is the difference between x86 and x86_64?

X86 is a 32-bit ABI for x86 devices that support the IA-32 instruction set and extensions. X86_64 is a 64-bit ABI for x86 devices that support the x86-64 instruction set and extensions. X86_64 has more registers, larger address space, and faster calculations than x86.

FAQ 3: How can I use Neon intrinsics in my native code?

Neon is a set of SIMD (Single Instruction Multiple Data) instructions that can accelerate vector operations on ARM devices. Neon intrinsics are C or C++ functions that map to Neon instructions. You can use Neon intrinsics in your native code by including the <arm_neon.h> header file and using the appropriate functions for your data types and operations. For more information, see Neon Intrinsics Reference.

FAQ 4: How can I reduce the size of my APKs when supporting multiple ABIs?

One way to reduce the size of your APKs when supporting multiple ABIs is to use Android App Bundle instead of APK files. Android App Bundle is a publishing format that lets Google Play generate optimized APKs for each device configuration, including ABI. This way, you only upload one app bundle file to Google Play, and users only download the APKs that they need for their device. For more information, see Android App Bundle.

FAQ 5: How can I ensure that my app is compliant with Google Play’s 64-bit requirement?

To ensure that your app is compliant with Google Play’s 64-bit requirement, you need to do two things:

1. Make sure that your app includes 64-bit libraries for each supported ABI. You can use APK Analyzer or Gradle to check and build your app with 64-bit libraries.
2. Make sure that your app does not use any non-compliant libraries or SDKs that only provide 32-bit versions. You can use Play Console’s pre-launch report to identify any non-compliant libraries or SDKs in your app.

I hope you found this article helpful and informative. If you have any questions or feedback, please leave a comment below. Happy coding!

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