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How to build OpenCV for Android using Clang and the latest NDK r15b

How can I build OpenCV for Android using Clang and the latest NDK r15b?
On the latest NDK r15b toolchains folder does not contain special subfolders with Clang except llvm and android.toolchain.cmake script ignores llvm subfolder. So I can't figure out how to make things work?

You can compile it like this:
cd $OPENCV_SRC_DIR
mkdir build
export ANDROID_NDK=$YOUR_NDK_PATH
cmake -DCMAKE_TOOLCHAIN_FILE=$YOUR_NDK_PATH/build/cmake/android.toolchain.cmake ..
make -j7
make install
cd install
NOTE:
Tested with the last ndk16 version + opencv-2.4.11.
(Clang is the default compiler in the new ndk's)

i can't get opencv to work in android

I'm using eclipse to write android programs and i can successfully run them on adt but recently i had to write a program that uses opencv but i can't get opencv to work with android i got ndk and add it to system variables and also downloaded opencv4android sdk from this link: http://docs.opencv.org/doc/tutorials/introduction/android_binary_package/O4A_SDK.html and i imported all the examples now i get numerous error for any of the examples and when i click project->clean->clean all it comes up with following error :
C:\Documentation_Android\android-ndk-r9d-windows-x86_64\android-ndk-r9d\ndk-build.cmd
Android NDK: WARNING:jni/Android.mk:mixed_sample: non-system libraries
in linker flags: -lopencv_java Android NDK: This is likely to
result in incorrect builds. Try using LOCAL_STATIC_LIBRARIES
Android NDK: or LOCAL_SHARED_LIBRARIES instead to list the library
dependencies of the Android NDK: current module
[armeabi-v7a] Install : libmixed_sample.so =>
libs/armeabi-v7a/libmixed_sample.so
I also tried Fix Project Properties but nothing happened and i tried to change jni/Application.mk and change armeabi-v7a to armeabi and that didn't helped too what should i do now ? is there anything I missing here ?

have you added LOCAL_LDLIBS in android.mk file?
LOCAL_LDLIBS := $(LOCAL_PATH)/jniLibs/libmixed_sample.so //path of .so file

OK i found the answer ! How stupid I am ! i just have to go to opencv library project properties in android tab select project build target as android 4.2.2 and everything worked well

Could not build OpenCV Android sample project

I'm trying to build the OpenCV Android sample projects. I added the "OpenCV Library - 2.4.8" as a project to eclipse and trying to build "OpenCV Sample - 15 Puzzle" sample project. When I build the lsample project It gives me the following error.
make: *** Android NDK: Aborting...
It prints the following in the console.
**** Clean-only build of configuration Default for project OpenCV Sample - 15 puzzle ****
D:\ProgramFiles\android-ndk-r9c\ndk-build.cmd clean
Android NDK: WARNING: APP_PLATFORM android-19 is larger than android:minSdkVersion 14 in ./AndroidManifest.xml
D:/ProgramFiles/android-ndk-r9c/build/core/add-application.mk:187: *** Android NDK: Aborting... . Stop.
Android NDK: Your APP_BUILD_SCRIPT points to an unknown file: ./jni/Android.mk
In the imported sample project I do not have a Android.mk file. Do I have to include such a file in this sample project? Could somebody please help me to fix this issue? I'm using Windows 8, Eclipse Juno provided in ADT bundle and these are the OpenCV 2.4.8 sample projects.

You will have to create Android.mk and Application.mk file. Refer to tutorial-2-mixedprocessing which comes along with the samples.
I would suggest starting from the easiest sample code, ie, tutorial1.
The details of files that are to be compiled are present in Android.mk

Android: ndk-build is returning nothing?

I'm trying to rebuild my Native android project, however all of a sudden, ndk-build decides it doesn't want to, and seems to be sulking on me.
Here's my output:
nathan#nathan-K52F:~/COMBAT/engine/android-build$ android update project -p . -t 1 -s
Updated project.properties
Updated local.properties
Updated file ./proguard-project.txt
nathan#nathan-K52F:~/COMBAT/engine/android-build$ cd jni && ndk-build
nathan#nathan-K52F:~/COMBAT/engine/android-build/jni$ ndk-build
nathan#nathan-K52F:~/COMBAT/engine/android-build/jni$ cd ../
nathan#nathan-K52F:~/COMBAT/engine/android-build$ ndk-build
nathan#nathan-K52F:~/COMBAT/engine/android-build$ //should be erroring here - yet nothing?
It however at least tries to build another native project:
nathan#nathan-K52F:~/GamePlay/samples/browser/android/jni$ ndk-build
/home/nathan/android-ndk-r8e/build/core/add-application.mk:128: Android NDK: WARNING: APP_PLATFORM android-14 is larger than android:minSdkVersion 9 in /home/nathan/GamePlay/samples/browser/android/AndroidManifest.xml
Android NDK: ERROR:/home/nathan/GamePlay/samples/browser/android/jni/Android.mk:gameplay: LOCAL_SRC_FILES points to a missing file
Android NDK: Check that /home/nathan/GamePlay/samples/browser/android/jni/../../../../gameplay/android/obj/local/armeabi/libgameplay.a exists or that its path is correct
/home/nathan/android-ndk-r8e/build/core/prebuilt-library.mk:45: *** Android NDK: Aborting . Stop.
nathan#nathan-K52F:~/GamePlay/samples/browser/android/jni$
The error's are suppose to be there by the way.
I just haven't a clue why it isn't compiling the project I WANT it to compile - I don't think it likes me anymore :L
I'm running on the latest Ubuntu OS, with NDK r8 and JDK 1.7

I didn't add my the new files to my makefile to be compiled.

Android ndk-build command does nothing

I have a similar question to that posted here:
Android NDK: why ndk-build doesn't generate .so file and a new libs folder in Eclipse?
...though I am running Windows 7, not Mac os. Essentially the ndk-build command is run, gives no error but doesn't create an .so file (also, since I'm on windows this should create a .dll and not an .so?). I tried running the command from the root, jni, src folders etc. but got the same result; cmd just returns to the prompter after a few seconds. I ran it again from the jni folder with NDK_LOG=1 parameter to see what was happening. Here is a portion of the transcript of the log results after running ndk-build in the jni folder (after it successfully identified the platform, etc.)...
Android NDK: Looking for jni/Android.mk in /workspace/NdkFooActivity/jni
Android NDK: Looking for jni/Android.mk in /workspace/NdkFooActivity
Android NDK: Found it !
Android NDK: Found project path: /workspace/NdkFooActivity
Android NDK: Ouput path: /workspace/NdkFooActivity/obj
Android NDK: Parsing /cygdrive/c/android-ndk-r8/build/core/default-application.mk
Android NDK: Found APP_PLATFORM=android-15 in /workspace/NdkFooActivity/project.properties
Android NDK: Application local targets unknown platform 'android-15'
Android NDK: Switching to android-14
Android NDK: Using build script /workspace/NdkFooActivity/jni/Android.mk
Android NDK: Application 'local' is not debuggable
Android NDK: Selecting release optimization mode (app is not debuggable)
Android NDK: Adding import directory: /cygdrive/c/android-ndk-r8/sources
Android NDK: Building application 'local' for ABI 'armeabi'
Android NDK: Using target toolchain 'arm-linux-androideabi-4.4.3' for 'armeabi' ABI
Android NDK: Looking for imported module with tag 'cxx-stl/system'
Android NDK: Probing /cygdrive/c/android-ndk-r8/sources/cxx-stl/system/Android.mk
Android NDK: Found in /cygdrive/c/android-ndk-r8/sources/cxx-stl/system
Android NDK: Cygwin dependency file conversion script:
...after which point it just runs the script mentioned in the last line, then terminates. Any ideas? Thanks!

Set up a builder. Refer to following article for how to do that:
http://maxters.net/2011/02/android-ndk-builder-for-eclipse-in-windows/
There is a "small" change beginning NDK r8 – Cygwin is not necessary anymore and I had a trouble when building native libraries with Cygwin and NDK r8 – there was some error message about cxx-stl...
Almost everything in the link above is OK, but leave Arguments in the Main tab blank and change Location to:
${env_var:ANDROID_NDK_ROOT}/ndk-build.cmd
I use system variable path ANDROID_NDK_ROOT, but you can provide a full path to the ndk-build.cmd.
Also, there is no need to set any variable in the Environment tab.
Set up your builder this way and you will be fine.
Just a note, Android is built on the top of the Linux OS, so even if you are on Windows you will get Linux libraries with .so extension.

Following link was instructive but missing a detail if you are configuring NDK support in Eclipse after CDT it already depricated (summer of 2017 already).
http://maxters.net/2011/02/android-ndk-builder-for-eclipse-in-windows/
Where you need to configure your external builder Location, instead of pointing to cygwin\bin\bash.exe and adding as Argument your ndk-build.cmd location this is what worked for me on Windows 7 and 10.
In "Edit Configuration" dialog for external builder do following:
- for Location -> specify where your "ndk-build.cmd" is. i.e "D:\Android\NDK\ndk-build.cmd"
- for Arguments -> just specify "all"

The NDK build system relies on wildcards to find the sources to compile. If you have a path wrong somewhere, it will find no sources and do nothing. Check Android.mk very carefully. More can't be said unless you post Android.mk and a description of the source tree.