I'm trying to add native code to my app. I have everything in ../main/jni
as it was in my Eclipse project. I have added ndk.dir=...
to my local.properties
. I haven't done anything else yet (I'm not sure what else is actually required, so if I've missed something let me know). When I try and build I get this error:
Execution failed for task ':app:compileDebugNdk'.
> com.android.ide.common.internal.LoggedErrorException: Failed to run command:
/Users/me/android-ndk-r8e/ndk-build NDK_PROJECT_PATH=null
APP_BUILD_SCRIPT=/Users/me/Project/app/build/ndk/debug/Android.mk APP_PLATFORM=android-19
NDK_OUT=/Users/me/Project/app/build/ndk/debug/obj
NDK_LIBS_OUT=/Users/me/Project/app/build/ndk/debug/lib APP_ABI=all
Error Code:
2
Output:
make: *** No rule to make target `/Users/me/Project/webapp/build/ndk/debug//Users/me/Project/app/src/main/jni/jni_part.cpp',
needed by `/Users/me/Project/app/build/ndk/debug/obj/local/armeabi-v7a/objs/webapp//Users/me/Project/app/src/main/jni/jni_part.o'.
Stop.
What do I need to do?
Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
# OpenCV
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
include .../OpenCV-2.4.5-android-sdk/sdk/native/jni/OpenCV.mk
LOCAL_MODULE := native_part
LOCAL_SRC_FILES := jni_part.cpp
LOCAL_LDLIBS += -llog -ldl
include $(BUILD_SHARED_LIBRARY)
Application.mk:
APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi armeabi-v7a
APP_PLATFORM := android-8
This question is related to
android
java-native-interface
gradle
android-studio
android-ndk-r7
gradle supports ndk compilation by generating another Android.mk file with absolute paths to your sources. NDK supports absolute paths since r9 on OSX, r9c on Windows, so you need to upgrade your NDK to r9+.
You may run into other troubles as NDK support by gradle is preliminary. If so you can deactivate the ndk compilation from gradle by setting:
sourceSets.main {
jni.srcDirs = []
jniLibs.srcDir 'src/main/libs'
}
to be able to call ndk-build yourself and integrate libs from libs/.
btw, you have any issue compiling for x86 ? I see you haven't included it in your APP_ABI.
Android Studio 2.2 came out with the ability to use ndk-build and cMake. Though, we had to wait til 2.2.3 for the Application.mk support. I've tried it, it works...though, my variables aren't showing up in the debugger. I can still query them via command line though.
You need to do something like this:
externalNativeBuild{
ndkBuild{
path "Android.mk"
}
}
defaultConfig {
externalNativeBuild{
ndkBuild {
arguments "NDK_APPLICATION_MK:=Application.mk"
cFlags "-DTEST_C_FLAG1" "-DTEST_C_FLAG2"
cppFlags "-DTEST_CPP_FLAG2" "-DTEST_CPP_FLAG2"
abiFilters "armeabi-v7a", "armeabi"
}
}
}
See http://tools.android.com/tech-docs/external-c-builds
NB: The extra nesting of externalNativeBuild
inside defaultConfig
was a breaking change introduced with Android Studio 2.2 Preview 5 (July 8, 2016). See the release notes at the above link.
In my case, I'm on Windows and following the answer by Cameron above only works if you use the full name of the ndk-build which is ndk-build.cmd. I have to clean and rebuild the project, then restart the emulator before getting the app to work (Actually I imported the sample HelloJni from NDK, into Android Studio). However, make sure the path to NDK does not contain space.
Finally, my build.gradle is full listed as below:
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion "21.1.2"
defaultConfig {
applicationId "com.example.hellojni"
minSdkVersion 4
targetSdkVersion 4
ndk {
moduleName "hello-jni"
}
testApplicationId "com.example.hellojni.tests"
testInstrumentationRunner "android.test.InstrumentationTestRunner"
}
sourceSets.main {
jni.srcDirs = [] // This prevents the auto generation of Android.mk
// sourceSets.main.jni.srcDirs = []
jniLibs.srcDir 'src/main/libs' // This is not necessary unless you have precompiled libraries in your project.
}
task buildNative(type: Exec, description: 'Compile JNI source via NDK') {
def ndkDir = android.plugin.ndkFolder
commandLine "$ndkDir/ndk-build.cmd",
'-C', file('src/main/jni').absolutePath, // Change src/main/jni the relative path to your jni source
'-j', Runtime.runtime.availableProcessors(),
'all',
'NDK_DEBUG=1'
}
task cleanNative(type: Exec, description: 'Clean JNI object files') {
def ndkDir = android.plugin.ndkFolder
commandLine "$ndkDir/ndk-build.cmd",
'-C', file('src/main/jni').absolutePath, // Change src/main/jni the relative path to your jni source
'clean'
}
clean.dependsOn 'cleanNative'
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn buildNative
}
}
dependencies {
compile 'com.android.support:support-v4:21.0.3'
}
My issue on OSX it was gradle version. Gradle was ignoring my Android.mk. So, in order to override this option, and use my make instead, I have entered this line:
sourceSets.main.jni.srcDirs = []
inside of the android
tag in build.gradle
.
I have wasted lot of time on this!
In the module build.gradle, in the task field, I get an error unless I use:
def ndkDir = plugins.getPlugin('com.android.application').sdkHandler.getNdkFolder()
I see people using
def ndkDir = android.plugin.ndkFolder
and
def ndkDir = plugins.getPlugin('com.android.library').sdkHandler.getNdkFolder()
but neither of those worked until I changed it to the plugin I was actually importing.
Source: Stackoverflow.com