Native Development Kit.
http://developer.android.com/tools/sdk/ndk/index.html
API needed for native compiled code (e.g. from C) API.
API is exactly like regular JNI, which you should learn first, e.g. at https://github.com/cirosantilli/java-cheat/tree/91caa12e8e4e468441539fe394e5ceb1d09007aa/jni
Alternative: RenderScript http://www.developer.com/ws/android/development-tools/writing-native-android-code-ndk-vs.-renderscript.html TODO vs.
Very incomplete at: http://developer.android.com/ndk/reference/index.html
E.g.: <android/log.h> is not there, but it is mentioned at: http://developer.android.com/ndk/guides/stable_apis.html
http://stackoverflow.com/questions/4638778/ndk-api-reference-docs says that headers under <ndk>/platform/android-$VERSION/$ARCH/usr/include have a lot of documentation comments which you should rely on instead, which is true.
The actual implementation .cpp files seem to be scattered under <ndk>/frameworks of the AOSP. Use find.
NDK updates don't come out together with the newest SDK! E.g., at some point there was SDK 23, but only NDK 21:
- https://groups.google.com/forum/#!topic/android-ndk/5yBELmoFAYg
- https://groups.google.com/forum/#!topic/android-ndk/UZVjlTi_3qo
TODO:
- check NDK toolkit version. I think visible under
cat source.properties - check NDK version that a device supports http://stackoverflow.com/questions/21876813/how-to-retrieve-the-supported-android-jni-version-in-a-device
Samples previously under $ANDROID_NDK/samples/, now seem to be removed to https://github.com/googlesamples/android-ndk?
hello-jni is the most basic one
Build as:
# Tool present on the root of the NDK. Cross compiles to a ton of platforms.
ndk-build
# Create build.xml, as per: http://stackoverflow.com/questions/5572304/how-to-build-the-android-sample-projects-using-ant-build-xml-does-not-exist
android update project -p . -t android-22
ant clean
ant debug
ant installd
In the past, NDK used Makefiles.
As of 2016 the NDK examples are moving to pure Gradle.
Useful options:
LOCAL_CFLAGS := -Werror
LOCAL_LDLIBS := -llog -lGLESv2
toolchains: several build cross compilers, GCC and clang. Those can be used without an Android app: http://developer.android.com/ndk/guides/standalone_toolchain.htmlplatforms/: headers and compiled libraries that you can use inside Android.
http://stackoverflow.com/questions/6602929/which-compiler-does-android-ndk-use
Moved to clang from GCC in 2015:
- https://android.googlesource.com/platform/ndk.git/+/master/CHANGELOG.md
- https://news.ycombinator.com/item?id=10772826
Script that wraps make.
Location: <ndk>/ndk-build.
Show compilation commands:
ndk-build V=1
The move to Gradle removes the need for it.
Clean:
ndk-build clean
http://stackoverflow.com/questions/10534367/how-to-get-ndk-gdb-working-on-android
Supported: http://developer.android.com/ndk/guides/standalone_toolchain.html
"$ANDROID_NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc-4.9" \
--sysroot="$ANDROID_NDK/platforms/android-21/arch-arm" \
hello_world.c -o hello_world
# /tmp is required...
adb push hello_world /data/local/tmp/hello_world
adb shell /data/local/tmp/hello_world
Adding -fPIE -fpie to the gcc command did not help.
Threads:
- http://stackoverflow.com/questions/9868309/how-can-i-run-c-binary-executable-file-in-android-from-android-shell
- http://stackoverflow.com/questions/13690419/writeable-and-executable-location-on-android
- http://android.stackexchange.com/questions/45554/running-own-executable-on-android-shell
- http://stackoverflow.com/questions/17383552/how-to-package-native-commandline-application-in-apk
- http://stackoverflow.com/questions/6168303/compiling-c-code-netcat-to-native-android-executable