artilla's blog

https://www.bountysource.com/issues/44127272-android-ndk-build-fails http://www.myandroidonline.com/2015/06/09/compile-assimp-open-source-library-for-android/ https://developer.android.com/ndk/guides/standalone_toolchain.html $NDK/build/tools/make-standalone-toolchain.sh --arch=arm --verbose --toolchain=arm-linux-androideabi-4.8 --platform=android-21 --install-dir=./my-android-toolchain cmake -DCMAKE_TOOLCHAIN_FILE=$ANDTOOLCHAIN \       -DANDROID_NDK=$ANDROID_NDK \       -DASSIMP_ANDROID_JNIIOSYSTEM=ON \       -DCMAKE_BUILD_TYPE=Release \       -DANDROID_ABI="armeabi-v7a" \       -DANDROID_NATIVE_API_LEVEL=android-21 \       -DANDROID_FORCE_ARM_BUILD=TRUE \       -DCMAKE_INSTALL_PREFIX=install \       -DASSIMP_BUILD_TESTS=OFF \       ./$ASSIMP cmake --build .

to include other modules in the project, in the module's Android.mk file - using a shared ( .so ):  PREBUILT_SHARED_LIBRARY  - using a static ( .a ) library:  PREBUILT_STATIC_LIBRARY don't set LOCAL_SRC_FILES one item each LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := mobule_b LOCAL_SRC_FILES := ./lib/module_a.a include $(PREBUILT_STATIC_LIBRARY) include $(CLEAR_VARS) LOCAL_MODULE := module_b LOCAL_SRC_FILES := ./lib/module_b.a include $(PREBUILT_STATIC_LIBRARY)

It is odd that when loading OpenCV NDK module in static statement makes app slow. Don't load the module like this.  static {       System. loadLibrary ( "ndk_module" );  } Load NDK module at onManagerConnected() in BaseLoaderCallback. private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback( this ) { @Override public void onManagerConnected( int status) { switch (status) { case LoaderCallbackInterface. SUCCESS : { System. loadLibrary ( "ndk_module" ); mOpenCvCameraView .enableView(); } break ; default : { super .onManagerConnected(status); } break ; } } };

It is really frustrating to build OpenCV native code with new Android Studio. The new Android Studio doesn't use make files, instead, sets compile options in app's builde.gradle file. The new gradle experimental(0.6.0-beta4) has some changes in DSL. It uses '.add' function, not '+='. Look at Sample Project at github AndroidOpenCVNDKDemo . It use Android Studio 2.0 beta5, gradle-experimental:0.6.0-beta, and OpenCV 3.1.0. I hope this will save your time. Useful sites http://tools.android.com/tech-docs/new-build-system/gradle-experimental http://ph0b.com/new-android-studio-ndk-support/ https://github.com/joaopedronardari/OpenCV-AndroidSamples -- 2016.03.06 Updated step by step explanation for Android NDK http://web.guohuiwang.com/technical-notes/androidndk1

check  OPENCV_INSTALL_MODULES:=on in your Android.mk. http://stackoverflow.com/questions/25045046/android-opencv-error-cannot-find-lopencv-java

In Application.mk file, change APP_ABI to other value like APP_ABI := armeabi-v7a