Develop Reference

How do I build the arcore camera_utility shared library in NDK-BUILD?

I'm trying to build the 'arcore camera utility' library in NDK_BUILD, here: https://github.com/google-ar/arcore-unity-sdk/tree/master/Assets/GoogleARCore/Examples/ComputerVision/Plugins/src
Using this guide: https://yeephycho.github.io/2016/10/20/How-to-Use-NDK-to-Build-A-Shared-Android_Native-Library/ I was at least able to get it to compile in a libarcore_camera_utility.so file. Not only that but it was actually recognized by my app on the phone and instead of getting a DLL missing error I got the error: "EntryPointNotFoundException: Unable to find an entry point named 'TextureReader_create' in 'arcore_camera_utility'." which means it at least found the file, now.
The filesize of the .so is only 6k so it seems like I'm not compiling it correctly as the already working 32bit version that comes with the package is 100k, based on this question it seems like I'm leaving something out?: Entry point not found, Android .so file
My Android.mk file is:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := arcore_camera_utility_shared
LOCAL_C_INCLUDES += \
LOCAL_SRC_FILES := camera_utility.cc gl_utility.cc texture_reader.cc
include $(BUILD_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := arcore_camera_utility
LOCAL_WHOLE_STATIC_LIBRARIES := arcore_camera_utility_shared
include $(BUILD_SHARED_LIBRARY)
And my Application.mk file contains:
APP_ABI := arm64-v8a
APP_PLATFORM := android-24
APP_STL := c++_static
APP_BUILD_SCRIPT := ./jni/Android.mk
Am I building it in such a way as to leave the code out?

To compile arcore_camera_utility for the arm 64bit target-
1.) Create a new directory called 'arcorelibrary', then a subdirectory called 'jni'
2.) Download this zip: https://github.com/google-ar/arcore-unity-sdk/blob/master/Assets/GoogleARCore/Examples/ComputerVision/Plugins/src/arcore_camera_utility.zip
3.) get the three .cc files and the three .h files and place them in the jni directory
4.) Create a file called 'Android.mk' and place it in the jni directory, with the following contents:
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE:= arcore_camera_utility_static
LOCAL_SRC_FILES:= camera_utility.cc gl_utility.cc texture_reader.cc
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
LOCAL_EXPORT_LDLIBS := -llog -landroid -lEGL -lGLESv2 -lGLESv3
include $(BUILD_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := arcore_camera_utility
LOCAL_WHOLE_STATIC_LIBRARIES := arcore_camera_utility_static
include $(BUILD_SHARED_LIBRARY)
5.) Create a file called 'Application.mk' and place it in the jni directory, with the following contents:
APP_ABI := arm64-v8a
APP_PLATFORM := android-24
APP_STL := c++_static
APP_BUILD_SCRIPT := ./jni/Android.mk
6.) Download Android NDK and unzip somewhere (The version you need depends on which Unity version you're using) https://developer.android.com/ndk/downloads/older_releases.html
7.) Open a terminal or powershell, go to the root directory (arcorelibrary) of your project
8.) Create a path to where ever you unzipped Android NDK (Powershell example):
$env:Path += ";C:\[where-ever-you-unzipped]\android-ndk-r13b-windows-x86_64\android-ndk-r13b"
9.) Run:
ndk-build.cmd

How to include a prebuilt "*.a" library (from tensorflow) to my android NDK project with no Android.mk file?

I'm trying to compile my application to use tensorflow C++ library after building lintensorflow_core.a into my NDK application. The application has the main java layer, that communicates with the NDK component. In that NDK component, I'm looking to call the tensorflow as such: using namespace ::tensorflow::ops; // NOLINT(build/namespaces)
I've seen bunch of links on how to do it with Android.mk file. But apparently, that does not gets created anymore in the new version of android studio. If it is possible with just Android.mk and ndk-build command, that would be great as well. However, the combination of Android.mk and ndk-build has also failed me. The output basically nothing.
I did have plenty of variation of Android.mk file and here's one of them:
LOCAL_PATH := $(call my-dir)
TENSORFLOW_HOME := $(LOCAL_PATH)/../../../../../tensorflow
TENSORFLOW_CORE := $(LOCAL_PATH)/../../../../../tensorflow/tensorflow/core
TENSORFLOW_OPS := $(LOCAL_PATH)/../../../../../tensorflow/tensorflow/core/ops
include $(CLEAR_VARS)
LOCAL_MODULE := tensorflow
LOCAL_SRC_FILES := $(TENSORFLOW_HOME)/tensorflow/contrib/makefile/gen/lib/android_armeabi-v7a/libtensorflow-core.a
LOCAL_LDLIBS := -static -Wl,--build-id -Wl,--allow-multiple-definition -Wl,--whole-archive
LOCAL_CFLAGS := -std=c++11 -I$(TENSORFLOW_HOME)
LOCAL_C_INCLUDES := $(TENSORFLOW_OPS)
TARGET_ARCH_ABI := armeabi
include $(PREBUILT_STATIC_LIBRARY)
But this has been a total failure. Could someone point me to the right direction?

ANDROID: How to properly link against static libraries while creating shared libraries with dependencies on the static ones

I have to use some c++ code in my android application. This code was used successfully in an iOS project.
The code depends on 2 external libraries: zero-mq and protocol buffers.
I compiled the zmq library as an static library like explained here. I added the static (.a) library and the .jar to my project.
I created the protobuf library with the following configurations:
./configure --host=arm-eabi --with-sysroot=x/android-ndk-r10d/platforms/android-21/arch-arm CC="x/android-ndk-r10d/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc --sysroot x/android-ndk-r10d/platforms/android-21/arch-arm" --enable-cross-compile --with-protoc=protoc LIBS=-lc
make
I changed the real directories to x to make them shorter.
In my Android Project(IDE: Android Studio) I prepared everything which is necessary. I created a JNI Folder and deactivated the auto-creation of the makefiles.
Application.mk:
APP_MODULE := proxy
APP_STL := gnustl_shared
APP_CPPFLAGS := -frtti -fexceptions --std=c++11
APP_ABI := armeabi-v7a ##all later
NDK_TOOLCHAIN_VERSION := 4.9
Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := zmq_static
LOCAL_SRC_FILES := zmq/libzmq.a
include $(PREBUILD_STATIC_LIBRARY)
LOCAL_MODULE := protobuf_static1
LOCAL_SRC_FILES := protobuf/libprotobuf.a
LOCAL_EXPORT_C_INCLUDES := google/protobuf protobuf/
include $(PREBUILD_STATIC_LIBRARY)
LOCAL_MODULE := protobuf_static2
LOCAL_SRC_FILES := protobuf/libprotobuf-lite.a
LOCAL_EXPORT_C_INCLUDES := google/protobuf protobuf/
include $(PREBUILD_STATIC_LIBRARY)
LOCAL_MODULE := protobuf_static3
LOCAL_SRC_FILES := protobuf/libprotoc.a
LOCAL_EXPORT_C_INCLUDES := google/protobuf protobuf/
include $(PREBUILD_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := proxy
LOCAL_CFLAGS := -I/include -pthread -lpthread -D__GXX_EXPERIMENTAL_CXX0X__ - frtti
LOCAL_CPPFLAGS := -I/include -pthread -lpthread -D__GXX_EXPERIMENTAL_CXX0X__ -frtti
LOCAL_CPP_FEATURES += exceptions
LOCAL_LDLIBS := -llog
LOCAL_SRC_FILES := \
usersession.cpp\
## LOCAL_ALLOW_UNDEFINED_SYMBOLS := true will compile the code but shutdown on runtime
LOCAL_C_INCLUDES += C:\Users\M\Dropbox\Workspace\ndk_swig_test\app\src\main\jni
LOCAL_C_INCLUDES += C:\Users\M\Dropbox\Workspace\ndk_swig_test\app\src\arm\jni
LOCAL_C_INCLUDES += C:\Users\M\Dropbox\Workspace\ndk_swig_test\app\src\debug\jni
LOCAL_C_INCLUDES += C:\Users\M\Dropbox\Workspace\ndk_swig_test\app\src\armDebug\jni
LOCAL_C_INCLUDES += \zmq
LOCAL_C_INCLUDES += \protobuf
LOCAL_STATIC_LIBRARIES := zmq_static protobuf_static1 protobuf_static2 protobuf_static3
LOCAL_WHOLE_STATIC_LIBRARIES := zmq_static protobuf_static1 protobuf_static2 protobuf_static3
include $(BUILD_SHARED_LIBRARY)
The zmq library is in the subdirectory zmq and the protobuf library is in the subfolder protobuf.
Now the linking of the Objects still does not work. The Error Output when I execute ndk-build:
C:\Users\M\Dropbox\Workspace\ndk_swig_test\app\src\main\jni>ndk-build
[armeabi-v7a] SharedLibrary : libproxy.so
C:/Users/M/Documents/ndk/sources/cxx-stl/gnu- libstdc++/4.9/include/ext/new_allocator.h:127: error: undefined reference to 'ControlledInstance::ControlledInstan (std::shared_ptr<protogen::Application>, std:
:shared_ptr<protogen::Role>, std::shared_ptr<protogen::User>)'
C:/Users/M/Documents/ndk/sources/cxx-stl/gnu- libstdc++/4.9/include/bits/shared_ptr_base.h:511: error: undefined reference to 'protogen::User::User()'
C:/Users/M/Documents/ndk/sources/cxx-stl/gnu- libstdc++/4.9/include/bits/shared_ptr_base.h:914: error: undefined reference to 'google::protobuf::internal::empty tring_'
C:/Users/M/Dropbox/Workspace/ndk_swig_test/app/src/main//jni/controlledinstance.h :23: error: undefined reference to 'protogen::MetaGraph::~MetaGraph()'
collect2.exe: error: ld returned 1 exit status
make.exe: *** [C:/Users/M/Dropbox/Workspace/ndk_swig_test/app/src/main//obj/local/armeabi- v7a/libproxy.so] Error 1
I tried many versions of the Android.mk and recreated the library more than once with different options which I found all over the internet.
I also looked at dozens of threads on stackoverflow which did not help me.(I'm not allowed to link them because of low reputation)
Additionally i read most of the doc files from the ndk e.g. PREBUILTS.
I added some other directories to my JNI directory e.g. the directory with the original files and directories (compiler, io, stubs...). I think this directory should offer the export of the necessary methods if the prebuild library was successfully linked to my shared library - which is not the case.
I tried far more than I can explain in few minutes and I think it would be overkill if i added everything I've tried because nothing helped.
Because this is my first question I dont have the reputation to include more than 2 links. Sorry for that.

There may probably be other issues as well, but you at least have got a typo - it should be include $(PREBUILT_STATIC_LIBRARY), as in, BUILT, not BUILD.

Android NDK: Linking x86 shared library

I was given a shared library built on Linux x86, let's call it libA.so, and I want to use the function calls provided by this library SDK.
I am having issues building and have a few questions:
1) I will be able to build for x86, but will I be able to build for arm? I believe the answer is no, meaning I cannot run on a Nexus 5 for example.
2) The ndk-build complains of the #include that should be resolved by my LOCAL_SHARED_LIBRARIES. I am not sure why that is. My Android.mk is as follow:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := B
LOCAL_SRC_FILES := B.cpp
LOCAL_SHARED_LIBRARIES := A
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)
Can someone please help me resolve my Android.mk? I don't understand why it is complaining about my include statement in B.cpp. Please let me know if I can run B in an arm environment, although the SDK I am relying on was built on x86.

If your shared library libA.so has been compiled for linux-x86, it will certainly not run on android x86 targets (mainly because it needs to be linked to Bionic C library instead of glibc), and absolutely not on android arm devices.
Then, to solve your second issue, if you can get properly compiled android shared libraries for your android targets, you would include your library this way:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := A
LOCAL_SRC_FILES := ../libA/prebuilts/$(TARGET_ARCH_ABI)/libA.so # path to libA .so file, depending on the target ABI.
LOCAL_EXPORT_C_INCLUDES := ../libA/includes # path to libA headers.
include $(PREBUILT_SHARED_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := B
LOCAL_SRC_FILES := B.cpp
LOCAL_SHARED_LIBRARIES := A
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)

android google play game services error : c++ symbol std::function couldn't be resolved

I'm using NDK-r9d and trying to integrate C++ Google Play Game (GPG) Services to my sample native-activity project.
Now native-activity (sample from NDK ) compiles perfectly and runs fine on my android phone.
But when I add GPG using this code
gpg::AndroidPlatformConfiguration platform_configuration;
platform_configuration.SetActivity(state->activity->clazz);
I got error
"Symbol 'function' could not be resolved" at achievement_manager.h /HelloJni/modules/gpg-cpp-sdk/android/include/gpg line 54 Semantic Error
I've added includes to STL and everything needed from this link Eclipse indexer errors when using STL with Android NDK with no success.
This is my Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.cpp
LOCAL_STATIC_LIBRARIES := android_native_app_glue libgpg-1
LOCAL_LDLIBS := -llog -landroid -lEGL -lGLESv1_CM
LOCAL_CFLAGS := -std=c++11
include $(BUILD_SHARED_LIBRARY)
$(call import-add-path,$(LOCAL_PATH)/../modules)
$(call import-module,gpg-cpp-sdk/android)
$(call import-module,android/native_app_glue)
And this is my Application.mk
APP_PLATFORM := android-10
APP_ABI := armeabi-v7a
APP_STL := c++_static
Any suggestions?

I had some problems with compiling gpg sources until I specified the toolchain in Application.mk like this:
NDK_TOOLCHAIN_VERSION := 4.8
Note that I am on SDK 19, google play services 21, and NDK r9d.