Develop Reference

Why does Prefab NDK Dependencies not work?

I have some native code that depends on OpenSSL. In the beginning, I tried manually compiling OpenSSL for Android, but it simply wouldn't find the definitions.
Then I decided to move on and try using Prefabs instead. I followed the example Android NDK Prefab example, but it just doesn't work.
My CMakeLists contains the following
find_package(openssl REQUIRED CONFIG)
target_link_libraries(
testproject
openssl::openssl)
My build.gradle:
android {
compileSdk 31
defaultConfig {
minSdk 21
targetSdk 32
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
consumerProguardFiles "consumer-rules.pro"
externalNativeBuild {
cmake {
cppFlags ""
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
buildFeatures {
prefab true
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
version "3.10.2"
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies {
implementation 'androidx.appcompat:appcompat:1.4.0'
implementation 'com.google.android.material:material:1.4.0'
implementation 'com.android.ndk.thirdparty:openssl:1.1.1l-beta-1'
testImplementation 'junit:junit:4.+'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}
But whenever I compile, I get
Could not find a package configuration file provided by "openssl" with any
of the following names:
opensslConfig.cmake
openssl-config.cmake
Looking into the downloaded data, I see the openSSL folder under cmake only contains opensslConfigVersion.cmake and not opensslConfig.cmake, as it does with curl, for example.
What is going on? Why is this not working? Any help is appreiciated.

The curl-ssl example in the [ndk samples](gitclo https://github.com/android/ndk-samples)
only builds because it allows C++ and STL.
But openssl is C only.
The maven repo ndk thirdparty
links to the sources for the prefab package for openssl and curl among others,
i.e. ndkports.
There is no reference to C++ there for openssl.
It seems the problem is by prefab.
I found this issues: OpenSSL forces c++_shared – why?
Judging from this and other issues there is a high chance that prefab might just not fit your and my project as of yet.
You don't get an according curl message, because curl depends on openssl,
which makes the latter build first.
If you remove openssl you get:
Error: curl depends on unknown dependency openssl
I first did have no ndkVersion defined, as you.
Only afterward I got more error messages:
... //openssl/crypto. Rejected the following libraries:
C/C++: prefabandroid.arm64-v8a: User is targeting armeabi-v7a but library is for arm64-v8a
Removing armeabi-v7a from
ndk.abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
I got
... //openssl/ssl. Rejected the following libraries:
C/C++: prefabandroid.arm64-v8a: User requested no STL but library requires libc++
C/C++: prefabandroid.armeabi-v7a: User is targeting arm64-v8a but library is for armeabi-v7a
Another sign that prefab is ealily getting confused.
And because it was not built finally:
Could not find a package configuration file provided by "openssl" with any
of the following names:
··
opensslConfig.cmake
openssl-config.cmake
The file refers to
app/.cxx/cmake/debug/prefab/arm64-v8a/prefab/lib/aarch64-linux-android/cmake/openssl/opensslConfig.cmake
This has links that point to ~/.gradle.
So the include and link directories are somewhere deep down in ~/.gradle and not under the project directory.
One can include native code directly via cmake.
The ndkports are a starting point for to configuration.

Android Tensorflow Lite C++ .SO libraries not linked on runtime

I'm trying to build Tensorflow lite with C++ natively on Android device. I've built a .So file of tensorflow for every architecture and placed into the jniLibs folder. This is my Cmake file:
set(pathToProject /ih/user/project/NativeTfLite/app)
set(libs ${pathToProject}/src/main/jniLibs)
add_library(libtensorflowLite SHARED IMPORTED
)
set_target_properties(libtensorflowLite PROPERTIES IMPORTED_LOCATION
${libs}/${ANDROID_ABI}/libtensorflowLite.so)
find_library(
log-lib
log )
add_library(
native-lib
SHARED
native-lib.cpp)
target_include_directories(native-lib PRIVATE
${lib}/include)
target_link_libraries( # Specifies the target library.
native-lib. #Problem is here when linking native-lib with libtensorflowlite
libtensorflowLite
${log-lib} )
During compile time these files are found. However in target_link_libraries line, the linking of the 2 libraries libtensorflowlite and native-lib there is a runtime crash with the following error:
java.lang.UnsatisfiedLinkError: dlopen failed: library "/Users/ih/project/cameraFrames/NativeTfLite/app/src/main/jniLibs/arm64-v8a/libtensorflowLite.so" not found
Additionally the .SO files are not linked to the APK.
Here is my build.gradle file:
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
compileSdkVersion 29
buildToolsVersion "29.0.3"
defaultConfig {
applicationId "com.proj.nativetflite"
minSdkVersion 24
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
sourceSets {
main {
jniLibs.srcDir 'src/main/jniLibs'
jniLibs.srcDirs = ["src/main/jniLibs"]
}
}
externalNativeBuild {
cmake {
cppFlags "-std=c++11"
arguments '-DCMAKE_VERBOSE_MAKEFILE=ON'
}
}
ndk {
abiFilters "armeabi-v7a", "x86" , "arm64-v8a"
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
version "3.10.2"
}
}
}
dependencies {
implementation fileTree(dir: 'jniLibs', include: '**/*.so')
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'androidx.core:core-ktx:1.2.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test.ext:junit:1.1.1'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}
What is causing this?

Prior to AGP 4.0 you need to explicitly package prebuilt libraries with jniLibs: https://developer.android.com/studio/projects/gradle-external-native-builds#jniLibs. Note that the docs say you don't need to do this for anything declared by CMake, but I'm fairly certain the docs are wrong here (I've reached out to the doc owner to see if we need to fix that or not, since it is correct for 4.0).
This should be unnecessary in 4.0, but that hasn't reached stable yet.

Although I think Dan Albert's answer should be accepted, I'd like to add that I got the exact same error because I had not set the correct path to my tflite lib.
I kept my .so files in src/main/cpp/tflite/lib/${ANDROID_ABI}/, so in build.gradle I needed to add:
main {
jniLibs.srcDirs = ['src/main/cpp/tflite/lib']
}
also, it could be worth checking out this answer (also from Dan) regarding making sure the SONAME of the .so is correct.

Native code debug is not working in Android Studio 3

I've tried all the ways found on StackOverflow and still facing the issue.
I've created a demo Android project with native support, added a library to it and moved all native code into the library.
Now I'm unable to stop on breakpoints in native code, native debugger became active only after a SEGFAULT crash.
I've added defaultPublishConfig "debug" into mylibrary build.gradle and debuggable true to app build.fradle. There was enough for native debugging earlier. But it is not working since Android Studio upgrade.
Here are the full build.gradle files
app
apply plugin: 'com.android.application'
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.raistlin.myapplication"
minSdkVersion 16
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
debug {
debuggable true
}
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation project(path: ':mylibrary')
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
mylibrary
apply plugin: 'com.android.library'
android {
compileSdkVersion 28
defaultConfig {
minSdkVersion 16
targetSdkVersion 28
versionCode 1
versionName "1.0"
defaultPublishConfig "debug"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
arguments "-DANDROID_TOOLCHAIN=clang"
cppFlags "-fexceptions", "-std=c++11", "-DJSONCPP_NO_LOCALE_SUPPORT"
version "3.10.2"
}
}
}
buildTypes {
debug {
debuggable true
}
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

First, check debug variant is selected for library.
As your build.gradle has a setting, path "src/main/cpp/CMakeLists.txt", it won't build I think. So set targets, rebuild and check again.
If breakpoints doesn't work after build, old garbage may be left in the build cache and causes problems. Open project directory in explorer and delete build cache (.externalNativeBuild folder) manually and build the project again. I also delete build folder, as it contains .so files in intermediate directory, but it's optional.
Android Studio does not clean libraries in the test device. They are overwritten basically, but clear them manually depending on needs. Files are in /data/app/(package name)/lib/(cpu arch.)/.
NB: Synchronize menu of device file explorer does not synchronize properly under lib or (cpu arch.) directory. To synchronize, select /data or /data/app and choose Synchronize.
NB.1 If targets is omitted, Android Studio seems to build no targets. The built output is in (project)/app/build/intermediates/cmake/(flavor)/obj/(cpu architecture). If it seems to work without any targets, check files on device. They confuse test results.
NB.2 debuggable true is for release build to enable debugging. No need to set it for debug build, as debuggable flag is set as default.
NB.3 Seems version dependent but Gradle in Android Studio does not clean .externalNativeBuild tree properly even if clean or rebuild is called, and confuses native code build configs. It was around AS3.0, as I remember.
NB.4 My environment is
Android Stuidio 3.2.1
classpath 'com.android.tools.build:gradle:3.2.1'
gradle-4.7-all
CMake: default(3.6.4111459)
I know there are newer versions for Android Studio, Gradle and CMake but they are buggy, so I chose current environment. As far as I've experienced, Android Studio 3.3, gradle:3.3.0, gradle-4.10.1-all have severe bug in VCS(git). Wrong file contents are shown in editor and build fails, sometimes. Setting CMake version to 3.10.x (3.10.2 for me) also seems buggy.
Here's a copy from my project as a sample, partially modified from original one but may work.
I've checked breakpoints in a library work in Android Studio 3.2.1.
apply plugin: 'com.android.library'
android {
compileSdkVersion 28
defaultConfig {
minSdkVersion 23
targetSdkVersion 28
versionCode 1
versionName "0.0.1"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
consumerProguardFiles 'proguard-rules.pro'
externalNativeBuild {
cmake {
cppFlags "-std=c++11"
arguments "-DANDROID_STL=c++_static"
targets "sample"
}
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
Update
targets is mentioned here Guide - Link Gradle to your native library - Specify optional configurations.

App works fine on emulators, but crashes on device with: java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "__aeabi_memcpy"

I'm trying to implement yctung's AndroidLibSvm into my project with Android Studio 3.2.1. While the app works fine on any emulated device (I tried Android 23 and 28, both worked flawlessly), it crashes on my real device (a lenovo tablet with Android 6.0) with the following error:
java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "__aeabi_memcpy" referenced by "/data/app/com.krautkremer.nils.mymirror-2/lib/arm/libjnilibsvm.so"
as soon as the app tries to run the part of the code that uses cytung's lib.
There are a few similar cases on SO e.g. here or here but setting my
arguments "-DANDROID_PLATFORM=android-23"
or any other android-x and my targetSdkVersion to 23 in the build.gradle didn't solve it.
this is my build.gradle:
apply plugin: 'com.android.application'
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.krautkremer.nils.mymirror"
minSdkVersion 23
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags ""
arguments "-DANDROID_PLATFORM=android-23"
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
packagingOptions {
//exclude 'META-INF/proguard/androidx-annotations.pro'
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'androidx.appcompat:appcompat:1.1.0-alpha01'
implementation 'androidx.media:media:1.1.0-alpha01'
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
implementation 'androidx.constraintlayout:constraintlayout:2.0.0-alpha2'
implementation 'com.google.android.material:material:1.1.0-alpha01'
implementation 'androidx.annotation:annotation:1.0.1'
implementation 'com.google.firebase:firebase-core:16.0.6'
implementation 'com.google.firebase:firebase-ml-vision:18.0.2'
implementation 'com.google.firebase:firebase-ml-common:16.1.6'
implementation 'com.google.firebase:firebase-ml-vision-face-model:17.0.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test:runner:1.1.1-alpha01'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1-alpha01'
implementation project(':androidlibsvm-release')
}
apply plugin: 'com.google.gms.google-services'
I even downgraded my NDK version from 18 to 15 with no success.
Any ideas what might be the problem?
Help me, Obi-Wan Kenobi. You're my only hope.
EDIT:
This is my CMakeLists.txt, if it is of any help. I didn't change anything, should I?
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
cmake_minimum_required(VERSION 3.4.1)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/cpp/native-lib.cpp)
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
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)
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
native-lib
# Links the target library to the log library
# included in the NDK.
${log-lib})

Try to change your minSdkVersion and targetSdkVersion, i.e.
minSdkVersion 15
targetSdkVersion 23

How do I parallelize externalNativeBuild for different ABIs?

Background
I'm currently working on an Android project which contains a fair amount of native code. The native code is built for multiple ABIs. For various reasons, the native code has up until now been built using a custom Gradle task that invokes ndk-build.cmd.
Now I'm in the process of changing this to use externalNativeBuild for the NDK integration, and CMake lists instead of the old Android.mk files. It seems like the better supported/documented way of doing things.
Problem
One nice thing about the old ndk-build method was that it would build for multiple ABIs in parallel - e.g. an ARM version and an x86 version of the library could be built in parallel.
This is especially helpful in my case, because I am required to use a 3rd party tool during the linking phase which 1) takes a very long time (minutes) to finish, and 2) is mostly single-threaded. Hence, building the library for multiple ABIs in parallel helped shorten my build times a lot.
When building with CMake / Ninja I cannot replicate this behavior. Ninja is supposed to parallelize builds by default, and it may well be doing that for a given ABI (i.e. compiling multiple source files in parallel for the same ABI). But from what I can tell, it never starts building the library for another ABI until it has finished building for the current ABI.
Question
When using CMake / Ninja through externalNativeBuild, is there any way I can tell the build system that I want it to build my native code for multiple ABIs in parallel?
Example
A minimal example to demonstrate this is as simple as the "New project" template in Android Studio, i.e. something like:
CMakeLists.txt:
cmake_minimum_required(VERSION 3.4.1)
add_library(native-lib SHARED
src/main/cpp/native-lib.cpp )
app/build.gradle:
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
defaultConfig {
applicationId "com.example.cmakemultiabis"
minSdkVersion 21
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags ""
}
}
ndk {
abiFilters 'armeabi-v7a', 'x86'
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
And then building with e.g. gradlew assembleRelease will give you:
> Task :app:externalNativeBuildRelease
Build native-lib x86
[1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
[2/2] Linking CXX shared library ..\..\..\..\build\intermediates\cmake\release\obj\x86\libnative-lib.so
Build native-lib armeabi-v7a
[1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
[2/2] Linking CXX shared library ..\..\..\..\build\intermediates\cmake\release\obj\armeabi-v7a\libnative-lib.so
It may not be obvious from that output that the two libraries are built sequentially, but it does become obvious if you have something that takes a noticeable amount of time to link.
I have tried this both with the CMake / Ninja versions that you can download with the SDK Manager, as well as some newer versions (CMake 3.12.3, Ninja 1.8.2), and saw the same behavior in both cases.