I have 2 projects:
1 - Android Native project
2 - C/C++ Project
I'm building my shared library files (.so) in a C/C++ project and want to use those .so files in Android Native project.
I don't want to copy and paste these library files from one project to another.
First of all is it possible to use those .so files from my native Android project by using some reference etc to C++ library project?
Would it be easier to find a way to automatically copy the .so files from the C++ library project to the Android native project?
Well you'll need to re-compile your libs for ARM first. You can use the ndk's "standalone toolchain" functionality for that. There's a doc explaining more about it in the ndk dir (docs/STANDALONE-TOOLCHAIN.html). I needed to use libexpat in a project so I whipped up a bash file to compile expat using the standalone toolchain like so:
NDK_PATH=/android-ndk-r7
NDK_GCC=${NDK_PATH}/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc
export CC="${NDK_GCC} --sysroot=${NDK_PATH}/platforms/android-8/arch-arm"
export CFLAGS='-mthumb'
export LDFLAGS='-Wl,--fix-cortex-a8'
./configure --host=arm-eabi
make
Then you can copy the so wherever you want and reference it from Android.mk:
LOCAL_LDLIBS := \
-Lvendor/expat/sdk/lib/android \
-lexpat
Note that I built expat and linked it statically so I didn't have to worry about copying the resulting so
Related
I have to build 2 separate C++ projects which have Cmake build files setup for different platforms. I want to build them both for Android using NDK so that I can use them as prebuilt libs in Android Studio.
How do I build them for Android using NDK to generate a .a/.so for Arm architectures? Can I do it using cmake itself? Please provide detailed steps
Finally when I have 2 libraries, how do I integrate to Android Studio?
I kind of learnt how to create Android.mks for prebuilt libraries from this link
Using Pre-built Shared Library in Android Studio
But my lib2 depends on lib1 for both compilation and running. Jni code will depend on the combined library of both lib2 and lib1
I am new to NDK. So please provide detailed answers
Most likely, the CMake scripts that work for other platforms will require some changes for Android. Also, we often need special treatment for external dependencies, e.g. if we want CMake to find the correct version of boost.
But the main skeleton of CMakeLists.txt should be a good start. You can run CMake 'manually' for your libraries:
cmake \
-DCMAKE_TOOLCHAIN_FILE=${NDK_ROOT}/build/cmake/android.toolchain.cmake \
-DANDROID_NDK=${NDK_ROOT} \
-DANDROID_ABI=armeabi-v7a \
-DANDROID_PLATFORM=android-19 \
-DANDROID_STL=c++_shared \
-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=${LIB1_DIRECTORY}/libs/armeabi-v7a \
${LIB1_DIRECTORY}
In the main CMakeLists.txt that builds your JNI wrapper, you can add
add_library(lib1 SHARED IMPORTED)
set_target_properties(lib1 PROPERTIES IMPORTED_LOCATION ${LIB1_DIRECTORY}/libs/armeabi-v7a/lib1.so )
target_link_libraries(jni_wrapper lib1 … log)
Android Studio will not build lib1.so for you, but it will pick it from the correct location and pack it into the APK.
Same trick with IMPORTED will provide lib1 for build of lib2 if the CMake script does not already handle this dependency.
I want to use ffmpeg library in my Android Application. I have downloaded the source from here
And I followed the steps INSTALL.md file to build the library. (Compilation Environment is OSX)
Unfortunately I'm getting only the .a files (like libavutil.a, libavcore.a, libavcodec.a etc).
How can I compile the library to produce the .so files.
Is there any configuration option to change?
I have compiled the source in Linux machine and successfully got the .so files.
While compiling you need to specify the configuration option:
./configure --enable-shared --disable-static
This will give only the shared library files (.so files).
I use Qt Creator to compile an Android application. I needed to integrate OpenCV into it, and it took me half a day to configure it properly, so I want to document the steps I took here, in case somebody else ever has to do it.
Edit: For OpenCV 4.x see the answers below. My answer was tested on OpenCV 2.4 only.
Original answer:
First, I downloaded OpenCV-2.4.10-android-sdk, and put into my project directory. It contains static libraries, and link order matters for static libraries for GCC. So you need to order them just so. This is how my .pro file looked in the end ($$_PRO_FILE_PWD_ refers to the project directory):
INCLUDEPATH += "$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/jni/include"
android {
LIBS += \
-L"$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a"\
-L"$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/libs/armeabi-v7a"\
-llibtiff\
-llibjpeg\
-llibjasper\
-llibpng\
-lIlmImf\
-ltbb\
-lopencv_core\
-lopencv_androidcamera\
-lopencv_flann\
-lopencv_imgproc\
-lopencv_highgui\
-lopencv_features2d\
-lopencv_calib3d\
-lopencv_ml\
-lopencv_objdetect\
-lopencv_video\
-lopencv_contrib\
-lopencv_photo\
-lopencv_java\
-lopencv_legacy\
-lopencv_ocl\
-lopencv_stitching\
-lopencv_superres\
-lopencv_ts\
-lopencv_videostab
ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android
}
After that the project will compile but it will fail to run with the error
E/AndroidRuntime(11873): java.lang.UnsatisfiedLinkError: Cannot load library: link_image[1891]: 176 could not load needed library 'libopencv_java.so' for 'libMyProject.so' (load_library[1093]: Library 'libopencv_java.so' not found)
To overcome this, you need to add libopencv_java.so to your APK, and then manually load it from QtActivity.java. That's what the ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android line at the end was for. Now you need to place libopencv_java.so here:
project_root/android/libs/armeabi-v7a/libopencv_java.so
project_root/android/src/org/qtproject/qt5/android/bindings/QtActivity.java
You can get QtActivity.java from the Android target build directory, in my case the full path was c:\Workspace\build-MyProject-Android_for_armeabi_v7a_GCC_4_9_Qt_5_4_0-Debug\android-build\src\org\qtproject\qt5\android\bindings\QtActivity.java, and just copy it.
Then you find those lines in it:
// now load the application library so it's accessible from this class loader
if (libName != null)
System.loadLibrary(libName);
And load libopencv_java.so before them, so they become:
// This is needed for OpenCV!!!
System.loadLibrary("opencv_java");
// now load the application library so it's accessible from this class loader
if (libName != null)
System.loadLibrary(libName);
Note that you pass opencv_java to System.loadLibrary(), even though the file is libopencv_java.so.
Edit: I forgot to mention, but I already had installed OpenCV Manager on my phone when trying to run one of the samples that come with OpenCV-2.4.10-android-sdk, so I don't know if it's needed or not. In any event, keep it in mind, if it fail even after my steps, you might need to download OpenCV Manager (it's available on the Google Store).
Edit 2: I'm using adt-bundle-windows-x86-20140702, android-ndk-r10d, OpenCV-2.4.10-android-sdk, Qt Creator 3.3.0, and my build target is "Android for armeabi-v7a (GCC 4.9, Qt 5.4.0)".
Edit 3: From Daniel Saner's comment:
In OpenCV 3.x, opencv_java has been renamed to opencv_java3. Also, while I didn't look into the specific changes that might have effected this, the workaround regarding that library in the final step seems to no longer be necessary. The app compiles and runs without the ANDROID_PACKAGE_SOURCE_DIR line
Edit 4: #myk's comment:
Worked for me with OpenCV 3.2. To workaround the build issues with carotene finish the LIBS+ section with: -lopencv_videostab\ -ltegra_hal\ – myk 2 hours ago
For OpenCV 4, sashoalm's approach did not work for me until I adapted it:
Download the Android-Pack and unzip it somewhere. We'll create a qmake-variable OPENCV_ANDROID which points to that directory later.
Add the following snippet to your *.pro-file:
android {
contains(ANDROID_TARGET_ARCH,arm64-v8a) {
isEmpty(OPENCV_ANDROID) {
error("Let OPENCV_ANDROID point to the opencv-android-sdk, recommended: v4.0")
}
INCLUDEPATH += "$$OPENCV_ANDROID/sdk/native/jni/include"
LIBS += \
-L"$$OPENCV_ANDROID/sdk/native/libs/arm64-v8a" \
-L"$$OPENCV_ANDROID/sdk/native/3rdparty/libs/arm64-v8a" \
-llibtiff \
-llibjpeg-turbo \
-llibjasper \
-llibpng \
-lIlmImf \
-ltbb \
-lopencv_java4 \
ANDROID_EXTRA_LIBS = $$OPENCV_ANDROID/sdk/native/libs/arm64-v8a/libopencv_java4.so
} else {
error("Unsupported architecture: $$ANDROID_TARGET_ARCH")
}
}
This will work for the arm64-v8a only. If you happen to build for another architecture (apparently 32-Bit is still the default for Qt#Android), you must change the .../libs/arm64-v8a part of the paths (occurs 3 times) and the same to match your actual target-architecture (the contains(...)-part in the second line of the snippet).
Tell qmake where to find the SDK. Add the following to qmake-call: "OPENCV_ANDROID=/path/to/OpenCV-android-sdk".
e.g., this looks like qmake example.pro "OPENCV_ANDROID=/home/user/OpenCV-android-sdk" from command line.
when you use QtCreator, add "OPENCV_ANDROID=..." to the "Additional arguments"-field. You can find it after enabling the Project-Mode in the Build-section of the android-kit. Expand the qmake-field under Build Steps
Starting from Android android-ndk-r18b, with Qt Creator 4.9.x kits, I could not use the openCV-4.1.1 pre-compiled shared libraries (.so) with Qt Android ABI armeabi-v7a target and ABI arm64-v8a, as Opencv standard is based on GCC, While the NDK-r18b removed gcc and uses clang compiler. ( I am getting
Fatal signal 11 (SIGSEGV), code 1
On initialize calling android_getCpuFeatures() when the application starts)
Thus, openCV shared libs must be compiled from sources for clang in order to be used with Qt Android kits.
This reference Compiling OpenCV on Android from C++ (Without OpenCVManager) was of real help. I would leave a reference here as well for a simple procedure I used under windows 10, to get opencv compiled with NDK 18 (clang) for Qt Android:
Downloaded openCV source code
Downloaded openCV contrib source for selected openCV version
Used cmake for windows
in the unzipped opencv source folder, created a new build folder.
MinGW from Qt installation can generally be used for building, So I used Qt 5.11.x (MinGW 5.3.0 32 bit) command line tool from Qt menu.
from command line, in new build folder, I could generate cmake configuration :
C:\opencv-4.1.1\build> "C:\program files\cmake\bin\cmake" .. -G"MinGW Makefiles"
-DBUILD_SHARED_LIBS=ON
-DANDROID_STL=c++_shared
-DANDROID_ABI="armeabi-v7a with NEON"
-DANDROID_NATIVE_API_LEVEL=23
-DANDROID_TOOLCHAIN=clang
-DCMAKE_TOOLCHAIN_FILE=D:\Qt\android-ndk-r18b\build\cmake\android.toolchain.cmake
-DANDROID_NDK=D:\Qt\android-ndk-r18b
-DANDROID_SDK=C:\Users\moham\AppData\Local\Android\sdk
-DCMAKE_BUILD_TYPE=Debug
-DBUILD_ANDROID_PROJECTS=OFF
-DWITH_OPENCL=ON -DWITH_TBB=ON -DENABLE_NEON=ON
-DBUILD_TESTS=OFF -DBUILD_PERF_TESTS=OFF
-DBUILD_FAT_JAVA_LIB=OFF
Then , C:\opencv-4.1.1\build>\mingw32-make -jx and C:\opencv-4.1.1\build>\mingw32-make install
the result libs can be picked from opencv-4.1.1\build\install folder
Link in Qt Android project:
android {
#opencv
OPENCVLIBS = $$PWD/../opencv-4.1.1\build\install/sdk/native
INCLUDEPATH = $$OPENCVLIBS/jni/include
contains(ANDROID_TARGET_ARCH,armeabi-v7a) {
# might need libs to be copied into app's library folder and loaded on start-up, in case android ships older libs??!
ANDROID_EXTRA_LIBS = \
$$OPENCVLIBS/libs/armeabi-v7a/libopencv_core.so \
$$OPENCVLIBS/libs/armeabi-v7a/libopencv_imgproc.so \
$$OPENCVLIBS/libs/armeabi-v7a/libtbb.so
LIBS += -L"$$OPENCVLIBS/libs/armeabi-v7a"\
-lopencv_core -lopencv_imgproc -ltbb
}
ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
}
Also, copy the libs to ANDROID_PACKAGE_SOURCE_DIR
Note: If detailed control over cmake configuration is needed, cmake windows gui can be used, while not a must and not tested. AmMIN's procedure is helpful for cmake tool, remember to add flag for shared Android STL.
I use Qt Creator to compile an Android application. I needed to integrate OpenCV into it, and it took me half a day to configure it properly, so I want to document the steps I took here, in case somebody else ever has to do it.
Edit: For OpenCV 4.x see the answers below. My answer was tested on OpenCV 2.4 only.
Original answer:
First, I downloaded OpenCV-2.4.10-android-sdk, and put into my project directory. It contains static libraries, and link order matters for static libraries for GCC. So you need to order them just so. This is how my .pro file looked in the end ($$_PRO_FILE_PWD_ refers to the project directory):
INCLUDEPATH += "$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/jni/include"
android {
LIBS += \
-L"$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a"\
-L"$$_PRO_FILE_PWD_/OpenCV-2.4.10-android-sdk/sdk/native/libs/armeabi-v7a"\
-llibtiff\
-llibjpeg\
-llibjasper\
-llibpng\
-lIlmImf\
-ltbb\
-lopencv_core\
-lopencv_androidcamera\
-lopencv_flann\
-lopencv_imgproc\
-lopencv_highgui\
-lopencv_features2d\
-lopencv_calib3d\
-lopencv_ml\
-lopencv_objdetect\
-lopencv_video\
-lopencv_contrib\
-lopencv_photo\
-lopencv_java\
-lopencv_legacy\
-lopencv_ocl\
-lopencv_stitching\
-lopencv_superres\
-lopencv_ts\
-lopencv_videostab
ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android
}
After that the project will compile but it will fail to run with the error
E/AndroidRuntime(11873): java.lang.UnsatisfiedLinkError: Cannot load library: link_image[1891]: 176 could not load needed library 'libopencv_java.so' for 'libMyProject.so' (load_library[1093]: Library 'libopencv_java.so' not found)
To overcome this, you need to add libopencv_java.so to your APK, and then manually load it from QtActivity.java. That's what the ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android line at the end was for. Now you need to place libopencv_java.so here:
project_root/android/libs/armeabi-v7a/libopencv_java.so
project_root/android/src/org/qtproject/qt5/android/bindings/QtActivity.java
You can get QtActivity.java from the Android target build directory, in my case the full path was c:\Workspace\build-MyProject-Android_for_armeabi_v7a_GCC_4_9_Qt_5_4_0-Debug\android-build\src\org\qtproject\qt5\android\bindings\QtActivity.java, and just copy it.
Then you find those lines in it:
// now load the application library so it's accessible from this class loader
if (libName != null)
System.loadLibrary(libName);
And load libopencv_java.so before them, so they become:
// This is needed for OpenCV!!!
System.loadLibrary("opencv_java");
// now load the application library so it's accessible from this class loader
if (libName != null)
System.loadLibrary(libName);
Note that you pass opencv_java to System.loadLibrary(), even though the file is libopencv_java.so.
Edit: I forgot to mention, but I already had installed OpenCV Manager on my phone when trying to run one of the samples that come with OpenCV-2.4.10-android-sdk, so I don't know if it's needed or not. In any event, keep it in mind, if it fail even after my steps, you might need to download OpenCV Manager (it's available on the Google Store).
Edit 2: I'm using adt-bundle-windows-x86-20140702, android-ndk-r10d, OpenCV-2.4.10-android-sdk, Qt Creator 3.3.0, and my build target is "Android for armeabi-v7a (GCC 4.9, Qt 5.4.0)".
Edit 3: From Daniel Saner's comment:
In OpenCV 3.x, opencv_java has been renamed to opencv_java3. Also, while I didn't look into the specific changes that might have effected this, the workaround regarding that library in the final step seems to no longer be necessary. The app compiles and runs without the ANDROID_PACKAGE_SOURCE_DIR line
Edit 4: #myk's comment:
Worked for me with OpenCV 3.2. To workaround the build issues with carotene finish the LIBS+ section with: -lopencv_videostab\ -ltegra_hal\ – myk 2 hours ago
For OpenCV 4, sashoalm's approach did not work for me until I adapted it:
Download the Android-Pack and unzip it somewhere. We'll create a qmake-variable OPENCV_ANDROID which points to that directory later.
Add the following snippet to your *.pro-file:
android {
contains(ANDROID_TARGET_ARCH,arm64-v8a) {
isEmpty(OPENCV_ANDROID) {
error("Let OPENCV_ANDROID point to the opencv-android-sdk, recommended: v4.0")
}
INCLUDEPATH += "$$OPENCV_ANDROID/sdk/native/jni/include"
LIBS += \
-L"$$OPENCV_ANDROID/sdk/native/libs/arm64-v8a" \
-L"$$OPENCV_ANDROID/sdk/native/3rdparty/libs/arm64-v8a" \
-llibtiff \
-llibjpeg-turbo \
-llibjasper \
-llibpng \
-lIlmImf \
-ltbb \
-lopencv_java4 \
ANDROID_EXTRA_LIBS = $$OPENCV_ANDROID/sdk/native/libs/arm64-v8a/libopencv_java4.so
} else {
error("Unsupported architecture: $$ANDROID_TARGET_ARCH")
}
}
This will work for the arm64-v8a only. If you happen to build for another architecture (apparently 32-Bit is still the default for Qt#Android), you must change the .../libs/arm64-v8a part of the paths (occurs 3 times) and the same to match your actual target-architecture (the contains(...)-part in the second line of the snippet).
Tell qmake where to find the SDK. Add the following to qmake-call: "OPENCV_ANDROID=/path/to/OpenCV-android-sdk".
e.g., this looks like qmake example.pro "OPENCV_ANDROID=/home/user/OpenCV-android-sdk" from command line.
when you use QtCreator, add "OPENCV_ANDROID=..." to the "Additional arguments"-field. You can find it after enabling the Project-Mode in the Build-section of the android-kit. Expand the qmake-field under Build Steps
Starting from Android android-ndk-r18b, with Qt Creator 4.9.x kits, I could not use the openCV-4.1.1 pre-compiled shared libraries (.so) with Qt Android ABI armeabi-v7a target and ABI arm64-v8a, as Opencv standard is based on GCC, While the NDK-r18b removed gcc and uses clang compiler. ( I am getting
Fatal signal 11 (SIGSEGV), code 1
On initialize calling android_getCpuFeatures() when the application starts)
Thus, openCV shared libs must be compiled from sources for clang in order to be used with Qt Android kits.
This reference Compiling OpenCV on Android from C++ (Without OpenCVManager) was of real help. I would leave a reference here as well for a simple procedure I used under windows 10, to get opencv compiled with NDK 18 (clang) for Qt Android:
Downloaded openCV source code
Downloaded openCV contrib source for selected openCV version
Used cmake for windows
in the unzipped opencv source folder, created a new build folder.
MinGW from Qt installation can generally be used for building, So I used Qt 5.11.x (MinGW 5.3.0 32 bit) command line tool from Qt menu.
from command line, in new build folder, I could generate cmake configuration :
C:\opencv-4.1.1\build> "C:\program files\cmake\bin\cmake" .. -G"MinGW Makefiles"
-DBUILD_SHARED_LIBS=ON
-DANDROID_STL=c++_shared
-DANDROID_ABI="armeabi-v7a with NEON"
-DANDROID_NATIVE_API_LEVEL=23
-DANDROID_TOOLCHAIN=clang
-DCMAKE_TOOLCHAIN_FILE=D:\Qt\android-ndk-r18b\build\cmake\android.toolchain.cmake
-DANDROID_NDK=D:\Qt\android-ndk-r18b
-DANDROID_SDK=C:\Users\moham\AppData\Local\Android\sdk
-DCMAKE_BUILD_TYPE=Debug
-DBUILD_ANDROID_PROJECTS=OFF
-DWITH_OPENCL=ON -DWITH_TBB=ON -DENABLE_NEON=ON
-DBUILD_TESTS=OFF -DBUILD_PERF_TESTS=OFF
-DBUILD_FAT_JAVA_LIB=OFF
Then , C:\opencv-4.1.1\build>\mingw32-make -jx and C:\opencv-4.1.1\build>\mingw32-make install
the result libs can be picked from opencv-4.1.1\build\install folder
Link in Qt Android project:
android {
#opencv
OPENCVLIBS = $$PWD/../opencv-4.1.1\build\install/sdk/native
INCLUDEPATH = $$OPENCVLIBS/jni/include
contains(ANDROID_TARGET_ARCH,armeabi-v7a) {
# might need libs to be copied into app's library folder and loaded on start-up, in case android ships older libs??!
ANDROID_EXTRA_LIBS = \
$$OPENCVLIBS/libs/armeabi-v7a/libopencv_core.so \
$$OPENCVLIBS/libs/armeabi-v7a/libopencv_imgproc.so \
$$OPENCVLIBS/libs/armeabi-v7a/libtbb.so
LIBS += -L"$$OPENCVLIBS/libs/armeabi-v7a"\
-lopencv_core -lopencv_imgproc -ltbb
}
ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
}
Also, copy the libs to ANDROID_PACKAGE_SOURCE_DIR
Note: If detailed control over cmake configuration is needed, cmake windows gui can be used, while not a must and not tested. AmMIN's procedure is helpful for cmake tool, remember to add flag for shared Android STL.
I have written C++ file in JNI folder of my application. I am using Windows system with NDK and Cygwin 1.7.I want reffer to CURL library available in Cygwin.How can we refer to external .h(libraries/header) files while creating JNI application in Android?I have created a combined Android and C++ project. But I am referring CURL header file. When I build the project I am getting fatal error: curl/curl.h: No such file or directory issue.
Follow these steps:
Converting from Android project to C/C++ project:
Right click on your project name, go to 'Android Tools' and click 'Add native support'
Adding paths to external .h files:
Right click on your project name, go to 'Properties', under 'C/C++ General', go to 'Paths and Symbols', under 'Includes' tab, add the folder in which your .h file is. Remember to add to all languages and configurations if asked.
Also, since you are in Windows, I think you will need to change your Build command (which is in the 'C/C++ Build' section in project properties) to "bash C:\Development\android-ndk-r8\ndk-build.cmd"
Add the following to your Android.mk:
LOCAL_CFLAGS += -I$/PATH/TO/YOUR/curl.h
LOCAL_LDLIBS += -L$/PATH/TO/YOUR/libcurl.a.for.android -lcurl
The libcurl.a you have installed in cygwin is not usable for android, you need a version targetting android. If you don't have it, build it yourself.
When you get that libcurl.a file, do not forget to copy the headers folder of curl (get into your usr/include/curl from Cygwin) and add this folder to the JNI one in your project, so it knows the headers while compiling.
Which means also referring in your Android.mk :
for the libcurl library
LOCAL_SRC_FILES := libcurl.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/curl
and for your C++ files
LOCAL_C_INCLUDES := $(LOCAL_PATH)/include/curl
LOCAL_WHOLE_STATIC_LIBRARIES := libcurl
Please used this tutorial is nice one.
Don't forgot to change this setting after convert project to C / C ++ native project.
Builder Settings to Build Command
bash C:\tools\android-ndk-r8b-windows\android-ndk-r8b\ndk-build
This is my path of NDK you can change this path accordingly your NDK path.