添加库时如何合并两个 Android.mk 文件？

Question

我是 Android 新手，所以我不完全了解如何制作 Android.mk 文件。 我的项目运行良好，遵循提供 Android.mk 的在线教程。但后来我需要添加一个缺少的库，并且该教程有另一个 Android.mk，现在我正在尝试将两者合并在一起。

这是我的 Android.mk：

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

#opencv
OPENCVROOT:= C:\OpenCV-2.4.10-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_SRC_FILES := com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp


LOCAL_LDLIBS += -llog

LOCAL_MODULE := MyOpencvLibs


include $(BUILD_SHARED_LIBRARY)

这是我需要添加的 Android.mk：

LOCAL_PATH  := $(call my-dir)
OPENCV_PATH := D:/CODE/OpenCV-2.4.10-android-sdk/sdk/native/jni

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
OPENCV_INSTALL_MODULES := on
OPENCV_CAMERA_MODULES  := off
include $(OPENCV_PATH)/OpenCV.mk

LOCAL_C_INCLUDES :=             \
    $(LOCAL_PATH)               \
    $(OPENCV_PATH)/include

LOCAL_SRC_FILES :=              \
    nonfree_jni.cpp

LOCAL_MODULE := nonfree_demo
LOCAL_CFLAGS := -Werror -O3 -ffast-math
LOCAL_LDLIBS := -llog -ldl
LOCAL_SHARED_LIBRARIES += nonfree

include $(BUILD_SHARED_LIBRARY)

我对最后一个Android.mk感兴趣的是libnonfree.so而已，我不需要cpp文件。

这是我的项目结构：

编辑：

感谢您的回答。我已经按照建议做了，我的 Android.mk 现在看起来像这样：

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

#opencv
OPENCVROOT:= C:\OpenCV-2.4.10-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_SRC_FILES := com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp
LOCAL_LDLIBS += -llog
LOCAL_SHARED_LIBRARIES += nonfree
LOCAL_MODULE := MyOpencvLibs
include $(BUILD_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)

但问题仍然存在。我对 libnonfree.so 应该添加的方法有“未定义的引用”。我认为问题出在 Android.mk 上，但可能出在其他地方。

我已将System.loadLibrary("nonfree"); 添加到我的MainACtivity 和

#include "opencv2/nonfree/nonfree.hpp"
#include "opencv2/nonfree/features2d.hpp"

我不知道我做错了什么。

编辑 2：

这是错误：

Application.mk：

APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a
APP_PLATFORM := android-16

我不知道在我的 build.gradle 中在哪里设置 arguments="V=1"

我的 build.gradle：

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.example.adrien.ndkopencvtest4"
        minSdkVersion 15
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    sourceSets.main {
        //jniLibs.srcDirs = ['src/main/jniLibs']
        jni.srcDirs = [] //disable automatic ndk-build call
    }
    task ndkBuild(type: Exec, description: 'Compile JNI source via NDK') {
        commandLine "C:/Users/Adrien/AppData/Local/Android/sdk/ndk-bundle/ndk-build.cmd",
                'NDK_PROJECT_PATH=build/intermediates/ndk',
                'NDK_LIBS_OUT=src/main/jniLibs',
                'APP_BUILD_SCRIPT=src/main/jni/Android.mk',
                'NDK_APPLICATION_MK=src/main/jni/Application.mk'
    }
    tasks.withType(JavaCompile) {
        compileTask -> compileTask.dependsOn ndkBuild
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.github.wseemann:FFmpegMediaMetadataRetriever-armeabi-v7a:1.0.14'
    compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
    compile project(':openCVLibrary2410')

}

编辑 3：

“ndk-build V=1”的结果：

C:\Users\Adrien\AndroidStudioProjects\NDKOpencvTest4\app\src\main\jni>ndk-build V=1

[armeabi-v7a] SharedLibrary  : libMyOpencvLibs.so
C:/Users/Adrien/AppData/Local/Android/sdk/ndk-bundle/build//../toolchains/llvm/preb
uilt/windows-x86_64/bin/clang++.exe -Wl,-soname,libMyOpencvLibs.so -shared --sysroo
t=C:/Users/Adrien/AppData/Local/Android/sdk/ndk-bundle/build//../platforms/android-
16/arch-arm C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/obj/l
ocal/armeabi-v7a/objs/MyOpencvLibs/com_example_adrien_ndkopencvtest4_OpencvNativeCl
ass.o C:/Users/Adrien/AppData/Local/Android/sdk/ndk-bundle/build//../sources/cxx-st
l/gnu-libstdc++/4.9/libs/armeabi-v7a/libgnustl_static.a -lgcc C:/Users/Adrien/Andro
idStudioProjects/NDKOpencvTest4/app/src/main/obj/local/armeabi-v7a/libopencv_java.s
o C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/obj/local/armea
bi-v7a/libnonfree.so  -gcc-toolchain C:/Users/Adrien/AppData/Local/Android/sdk/ndk-
bundle/build//../toolchains/arm-linux-androideabi-4.9/prebuilt/windows-x86_64 -no-c
anonical-prefixes -target armv7-none-linux-androideabi -Wl,--fix-cortex-a8  -Wl,--b
uild-id -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -Wl,--warn-sh
ared-textrel -Wl,--fatal-warnings   -LC:/Users/Adrien/AppData/Local/Android/sdk/ndk
-bundle/build//../platforms/android-16/arch-arm/usr/lib -llog -lc -lm -o C:/Users/A
drien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/obj/local/armeabi-v7a/libMy
OpencvLibs.so
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_a
drien_ndkopencvtest4_OpencvNativeClass.cpp:214: error: undefined reference to 'cv::
SURF::SURF(double, int, int, bool, bool)'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_a
drien_ndkopencvtest4_OpencvNativeClass.cpp:222: error: undefined reference to 'cv::
SURF::SURF()'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_a
drien_ndkopencvtest4_OpencvNativeClass.cpp:204: error: undefined reference to 'VTT
for cv::SURF'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_a
drien_ndkopencvtest4_OpencvNativeClass.cpp:204: error: undefined reference to 'VTT
for cv::SURF'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_a
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp:204: error: undefined
reference to 'VTT for cv::SURF'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp:449: error: undefined
reference to 'cv::SURF::SURF(double, int, int, bool, bool)'
C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/jni/com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp:457: error: undefined
reference to 'cv::SURF::SURF()'
clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [C:/Users/Adrien/AndroidStudioProjects/NDKOpencvTest4/app/src/main/obj/local/armeabi-v7a/libMyOpencvLibs.so] Error 1

解决方案：

我的 libnonfree.so 文件不正确，我下载了另一个。我还将我的Application.mk 文件更改为：

APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a
APP_PLATFORM := android-16

Answer 1

如果您想在项目中添加预构建的共享库，则不需要单独的 Android.mk

让我们来看看你的剧本，

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

#opencv
OPENCVROOT:= C:\OpenCV-2.4.10-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_SRC_FILES := com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp


LOCAL_LDLIBS += -llog

LOCAL_MODULE := MyOpencvLibs


include $(BUILD_SHARED_LIBRARY)

只需在底部添加您需要的额外模块：

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)

现在C:\Users\Adrien\AndroidStudioProjects\NDKOpencvTest4\app\src\main\jni\libnonfree.so 文件将被打包到您的 APK 中。

如果您需要此库来链接您的 libMyOpencvLibs.so（这意味着，如果您在 com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp 中的代码使用从 libnonfree.so 导出的一些函数，你也应该在你的模块中引用它：

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

#opencv
OPENCVROOT:= C:\OpenCV-2.4.10-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_SRC_FILES := com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp
LOCAL_LDLIBS += -llog
LOCAL_SHARED_LIBRARIES += nonfree
LOCAL_MODULE := MyOpencvLibs
include $(BUILD_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)

Answer 2

修改你的 android.mk 为：

LOCAL_PATH  := $(call my-dir)
OPENCV_PATH := D:/CODE/OpenCV-2.4.10-android-sdk/sdk/native/jni

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

#opencv
OPENCVROOT:= C:\OpenCV-2.4.10-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_SRC_FILES := com_example_adrien_ndkopencvtest4_OpencvNativeClass.cpp

LOCAL_SHARED_LIBRARIES += nonfree

LOCAL_LDLIBS += -llog

LOCAL_MODULE := MyOpencvLibs

include $(BUILD_SHARED_LIBRARY)

这里的预编译库，即 libnonfree.so 在 android.mk 中声明，稍后通过

引用它

LOCAL_SHARED_LIBRARIES += nonfree

现在要使用它，您需要在您的 MainActivity 中加载最新构建的库，即

System.loadLibrary("MyOpencvLibs");

就是这样，现在您已经将两个 android.mk 文件合并到一个名为：MyOpencvLibs 的新模块中

为了更好地理解你可以阅读我的博客：https://androidtutsweb.wordpress.com/2017/04/04/android-mk-for-ndk-build-using-pre-build-libraries/