NDK需要特别注意的armeabi等架构问题

我们在编写NDK时候，有时候需要依赖第三方so库，如ffmpeg。

如果这里配置的是多种架构:

 externalNativeBuild {
            cmake {
                cppFlags ""
                //生成.so库的目标平台
                abiFilters 'armeabi','armeabi-v7a'
            }
        }

假如cmakeList.txt配置如下，则会生成 两个libless.so库，并分别存在
armeabi和 armeabi-v7 目录下。

cmake_minimum_required(VERSION 3.4.1)

#源码树的顶层路径。
set(distribution_DIR ${PROJECT_SOURCE_DIR}/src/main/jniLibs)

# 查看gradle Console 调试信息 PROJECT_SOURCE_DIR => E:/Codes/android_code/TPlayer/ffmpeg
message(STATUS "========> the PROJECT_SOURCE_DIR is : ${PROJECT_SOURCE_DIR}")
message(STATUS "========> the PROJECT_BINARY_DIR is : ${PROJECT_BINARY_DIR}")
message(STATUS "========> the cmakeList.txt PATH is : ${CMAKE_CURRENT_SOURCE_DIR}")
message(STATUS "========> distribution_DIR is : ${distribution_DIR}")

#判断编译器类型,如果是gcc编译器,则在编译选项中加入c++11支持
if(CMAKE_COMPILER_IS_GNUCXX)
    set(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}")
    message(STATUS "optional:-std=c++11")
endif(CMAKE_COMPILER_IS_GNUCXX)

#支持-std=gnu++11
#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")

# 个人库
add_library( # Sets the name of the library.
             less

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/cpp/native-lib.cpp
             )
# 系统库
find_library( # Sets the name of the path variable.
              log-lib
              log )

find_library( # Sets the name of the path variable.
              z-lib
              z )

find_library( # Sets the name of the path variable.
              android-lib
              android )

# 第三方库
add_library(avcodec-57 SHARED IMPORTED)
set_target_properties(avcodec-57 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavcodec-57.so)

add_library(avfilter-6 SHARED IMPORTED)
set_target_properties(avfilter-6 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavfilter-6.so)

add_library(avformat-57 SHARED IMPORTED)
set_target_properties(avformat-57 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavformat-57.so)

add_library(avutil-55 SHARED IMPORTED)
set_target_properties(avutil-55 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavutil-55.so)

add_library(swresample-2 SHARED IMPORTED)
set_target_properties(swresample-2 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libswresample-2.so)

add_library(swscale-4 SHARED IMPORTED)
set_target_properties(swscale-4 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libswscale-4.so)

add_library(avdevice-57 SHARED IMPORTED)
set_target_properties(avdevice-57 PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavdevice-57.so)

include_directories(${PROJECT_SOURCE_DIR}/src/main/jniLibs/include)
target_link_libraries(
                       less avcodec-57 avfilter-6 avformat-57 avutil-55 swresample-2 swscale-4 avdevice-57

                       ${log-lib}
                       ${z-lib}
                       ${android-lib}
                       )

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开发的时候，NDK虽然依赖其他的so,但是它只会生成我们自己的so并放在相应架构 的目录中，其他的so它不会管的也管不着。我们CmakeList.txt依赖的so库是可以放在任何地方的(D盘，F盘都行)，但这里为了不用构建apk时候 重复拷贝 就直接放在了armeabi下，那么打包的时候就出现了上面的情景。

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所以说： 平常建议 依赖第三方的so库 的架构 要和 我们自己构建的 so库 架构 一致 ，

要么都是只有一个armeabi,要么都是两个 armeabi和armeabi-v7

开发建议

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armeabi 改为${ANDROID_ABI}来根据${ANDROID_ABI}选择依赖。

add_library(myjpeg SHARED IMPORTED)
set_target_properties(jpeg PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libjpeg.so)

${ANDROID_ABI}是根据gradle中声明的abiFilters来指定的。

apply plugin: 'com.android.library'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 14
        versionCode 1
        versionName "1.0"
        externalNativeBuild {
            cmake {
                cppFlags ""
                //生成.so库的目标平台
                abiFilters 'armeabi','armeabi-v7'
            }
        }
    }
    buildTypes {
        debug {
            minifyEnabled false
        }
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path 'CMakeLists.txt'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
}