Como criar uma biblioteca nativa para Android

É fácil criar e fazer o aplicativo funcionar com uma pequena quantidade de código nativo. Se você deseja usar uma biblioteca nativa, na qual existem muitos arquivos, fica mais difícil. A dificuldade é que as bibliotecas nativas são distribuídas na forma de código-fonte que precisa ser compilado para a arquitetura de processador desejada. Usando o codec de áudio Opus como exemplo, mostrarei como fazê-lo.

Opus , Android, Opus, . - .so .a, , C/C++ . . Opus , NDK .so .a, Android-.

, C/C++, . Opus (.a).

NDK c 19 « ». , . , , , . , .

Opus

: (git clone), . Opus Autoconf — , . Autoconf toolchain , ENV-. Autoconf, , Unix . Windows, , , .

4 .a : armeabi-v7a, arm64-v8a, x86, x86-64.

ENV-. NDK, HOST_TAG TOOLCHAIN. Linux, ENV- , export:

export NDK=/home/vital/Android/Sdk/ndk/20.1.5948944
export HOST_TAG=linux-x86_64
export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/$HOST_TAG

ENV- , , . , . ENV- , .bashrc, (~). .bashrc. , , . ENV-, :

# arm64-v8a
export AR=$TOOLCHAIN/bin/aarch64-linux-android-ar
export AS=$TOOLCHAIN/bin/aarch64-linux-android-as
export CC=$TOOLCHAIN/bin/aarch64-linux-android21-clang
export CXX=$TOOLCHAIN/bin/aarch64-linux-android21-clang++
export LD=$TOOLCHAIN/bin/aarch64-linux-android-ld
export RANLIB=$TOOLCHAIN/bin/aarch64-linux-android-ranlib
export STRIP=$TOOLCHAIN/bin/aarch64-linux-android-strip

# armeabi-v7a
export AR=$TOOLCHAIN/bin/arm-linux-androideabi-ar
export AS=$TOOLCHAIN/bin/arm-linux-androideabi-as
export CC=$TOOLCHAIN/bin/armv7a-linux-androideabi21-clang
export CXX=$TOOLCHAIN/bin/armv7a-linux-androideabi21-clang++
export LD=$TOOLCHAIN/bin/arm-linux-androideabi-ld
export RANLIB=$TOOLCHAIN/bin/arm-linux-androideabi-ranlib
export STRIP=$TOOLCHAIN/bin/arm-linux-androideabi-strip

# x86
export AR=$TOOLCHAIN/bin/i686-linux-android-ar
export AS=$TOOLCHAIN/bin/i686-linux-android-as
export CC=$TOOLCHAIN/bin/i686-linux-android21-clang
export CXX=$TOOLCHAIN/bin/i686-linux-android21-clang++
export LD=$TOOLCHAIN/bin/i686-linux-android-ld
export RANLIB=$TOOLCHAIN/bin/i686-linux-android-ranlib
export STRIP=$TOOLCHAIN/bin/i686-linux-android-strip

# x86-64
export AR=$TOOLCHAIN/bin/x86_64-linux-android-ar
export AS=$TOOLCHAIN/bin/x86_64-linux-android-as
export CC=$TOOLCHAIN/bin/x86_64-linux-android21-clang
export CXX=$TOOLCHAIN/bin/x86_64-linux-android21-clang++
export LD=$TOOLCHAIN/bin/x86_64-linux-android-ld
export RANLIB=$TOOLCHAIN/bin/x86_64-linux-android-ranlib
export STRIP=$TOOLCHAIN/bin/x86_64-linux-android-strip

arm64-v8a, .bashrc ENV- . , CC CXX 21, Android API level. , , minSdkVersion. 21, , . NDK 16 29 32- ABI (armeabi-v7a x86) 21 29 64- ABI (arm64-v8a x86-64).

, ENV-, toolchain , Opus. Readme Opus , - :

$ ./autogen.sh
$ ./configure
$ make

. , 4 .

NDK r19 « » toolchains. , ENV- ( .bashrc), , . configure host. arm64-v8a :

$ source ~/.bashrc
$ ./autogen.sh
$ ./configure --host aarch64-linux-android
$ make

source ~/.bashrc , «» .

, Opus .libs. , libopus.a.

.bashrc /, ENV- armeabi-v7a, host:

$ source ~/.bashrc
$ ./configure --host armv7a-linux-androideabi
$ make

./autogen.sh , configure, .

make . , - . , , , , ( configure host). , , , , , .

. , Opus. , .

- 4 ENV- . , bash-, . :

#!/bin/bash
export NDK=/home/vital/Android/Sdk/ndk/20.1.5948944
export HOST_TAG=linux-x86_64
export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/$HOST_TAG

if [[ $# -ne 3 && $# -ne 2 ]] 
then
  echo "You should specify at least minSdkVersion and path to Opus directory"
  echo "Example ./buildOpus.sh 21 <pathToOpusDir> <pathToBuildDir>"
  exit
fi

# minSdkVersion that will used for complinig Opus source
minSdk=$1

# Path to directory where Opus sources are located
opusPath=$2

# Path to directory where to place build artifacts
# By default it creates dir where this script is located
if [[ $# -eq 3 ]]
then
  buildPath=$3
else
  buildPath=./opus_android_build
  if [[ -d $buildPath ]]; then
    echo "opus_android_build directory already existed..."
    echo "clearing opus_android_build directory..."
    rm -rfv $buildPath && mkdir $buildPath
  else
    echo "creating opus_android_build directory..."
    mkdir opus_android_build
  fi
fi

echo "Executing autogen.sh"
$opusPath/autogen.sh

if [[ $minSdk -lt 21 ]]
then
  triples=("armv7a-linux-androideabi" "i686-linux-android")
  abis=("armeabi-v7a" "x86")
else
  triples=("aarch64-linux-android" "armv7a-linux-androideabi" "i686-linux-android" "x86_64-linux-android")
  abis=("arm64-v8a" "armeabi-v7a" "x86" "x86-64")  
fi

BIN=$TOOLCHAIN/bin
cd $buildPath 

for i in ${!triples[@]}
do
  triple=${triples[$i]}
  abi=${abis[$i]}
  echo "Building $abi..."

  if [[ $triple == "armv7a-linux-androideabi" ]]
  then
    export AR=$BIN/arm-linux-androideabi-ar
    export AS=$BIN/arm-linux-androideabi-as
    export CC=$BIN/$triple$minSdk-clang
    export CXX=$BIN/$triple$minSdk-clang++
    export LD=$BIN/arm-linux-androideabi-ld
    export RANLIB=$BIN/arm-linux-androideabi-ranlib
    export STRIP=$BIN/arm-linux-androideabi-strip
  else
    export AR=$BIN/$triple-ar
    export AS=$BIN/$triple-as
    export CC=$BIN/$triple$minSdk-clang
    export CXX=$BIN/$triple$minSdk-clang++
    export LD=$BIN/$triple-ld
    export RANLIB=$BIN/$triple-ranlib
    export STRIP=$BIN/$triple-strip
  fi

  mkdir $abi && cd $abi 
  $opusPath/configure --host $triple
  make
  cd ..  
done

echo "Artifacts successfully built for minSdkVersion=$minSdk and ABIs:" 
printf '%s ' "${abis[@]}"
echo ""
echo "Artifacts are located in .libs directory"

, ENV- .bashrc , .

, :

$ sudo chmod +x buildOpus.sh

NDK HOST_TAG, Linux ( linux-x86_64):

• 32-bit Windows: windows
• 64-bit Windows: windows-x86_64
• macOS: darwin-x86_64

:

$ ./buildOpus.sh 21 <pathToOpusDir> <pathToBuildDir>

minSdkVersion Opus. , . opus_android_build , buildOpus.sh.

. opus_android_build , , ABI, . , .libs, .

, 4 libopus.a , . Android- CmakeLists.txt, .so Opus.

app/src/main/cpp, C- (jniopus.c), external Kotlin. includes. include Opus. (.h). Opus C-. , , .

app/src/main/cpp libopus, 4 , ABI, Opus: armeabi-v7a, arm64-v8a, x86, x86-64. libopus.a, .

CmakeLists.txt, , Opus . «» . :

set(NATIVE_SOURCES_PATH "${PROJECT_SOURCE_DIR}/src/main/cpp")
set(OPUS_HEADERS_PATH "${NATIVE_SOURCES_PATH}/includes")
set(OPUS_LIB_PATH "${NATIVE_SOURCES_PATH}/libopus")

Opus :

add_library(
        libopus
        STATIC
        IMPORTED)

add_library . , , STATIC(.a) SHARED(.so) , IMPORTED, . () :

set_target_properties( # Specifies the target library.
        libopus PROPERTIES
        IMPORTED_LOCATION "${OPUS_LIB_PATH}/${ANDROID_ABI}/libopus.a")

ANDROID_ABI NDK toolchain , ABI.

-, external Kotlin, :

add_library( # Sets the name of the library.
        jniopus

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        ${NATIVE_SOURCES_PATH}/jniopus.c)

, « » NDK :

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

:

target_link_libraries(
        # Specifies the target library.
        jniopus

        # Specifies the libraries that should be linked to our target
        libopus ${log-lib})

, , . , Gradle, Run, . , Start call . , , .

, NDK toolchains ABI . , CmakeLists.txt . , Autoconf , pre-19 NDK, . , , .

« Android»: https://vk.com/@forasoft-kak-ispolzovat-nativnye-biblioteki-v-android

: https://gitlab.com/vitaliybelyaev/opus-android

Opus codec: http://opus-codec.org/, https://github.com/xiph/opus

Using the NDK with other build systems: https://developer.android.com/ndk/guides/other_build_systems

Android- CMake: https://developer.android.com/studio/projects/add-native-code#create-cmake-script

ABI Android: https://developer.android.com/ndk/guides/abis