引入so文件CmakeList 配置

做NDK开发的时候，很大程度的是引用成熟类库，我们做逻辑，功能，那么怎么把so文件引入到我们的android工程里面的？
目前AndroidStudio2.2之后官方推荐的是Cmake，之前是Android.mk构建文件，大概类似，我们在只讲解一下Cmake，知识总是要及时更新才是。
通常我们默认编写的时候他会自动书写Cmake

#将指定的源文件生成链接文件，然后添加到工程中去
add_library(
#设置lib的名字
             native-lib
#设置lib的类型 共享型  还有STATIC、和MODULE
             SHARED
 #源码的相对路径
              src/main/cpp/native-lib.cpp
          )
#这个地方是 系统已经集成了很多lib，然后需要find以下 作为声明，表示你要用这些lib
find_library(
#自己起一个 lib的名称
              log-lib

 #lib的文件名
              log )

#将目标文件与库文件进行链接
target_link_libraries( # Specifies the target library.
                       native-lib
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

这是系统根据我们写的C/C++文件生成的，但是我们要加入第三方so怎么配置呢？我就用FFmpeg和Libyuv.so来演示一下。
首先最大的不同是：
需要声明一下文件的基地址，这个后面地址的时候需要用到

set(distribution_DIR ../../../../libs)

然后

#添加lib，SHARED类型，是IMPORTED 引入的库
add_library( libyuv
             SHARED
             IMPORTED)
#设置 库的属性   里面是名称 ，属性：引入地址把我们的真实地址填写进去
set_target_properties( libyuv
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libyuv.so)

最后

target_link_libraries( 
                       native-lib
#指定链接库
                       libyuv
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

这是ffmpeg和libyuv的配置

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
             native-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
              src/main/cpp/native-lib.cpp
             src/main/cpp/mylo.h)

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.



set(distribution_DIR ../../../../libs)
add_library( libyuv
             SHARED
             IMPORTED)
set_target_properties( libyuv
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libyuv.so)

add_library( avcodec
             SHARED
             IMPORTED)
set_target_properties( avcodec
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libavcodec.so)

add_library( avfilter
             SHARED
             IMPORTED)
set_target_properties( avfilter
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libavfilter.so)

add_library( avformat
             SHARED
             IMPORTED)
set_target_properties( avformat
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libavformat.so)

add_library( avutil
             SHARED
             IMPORTED)
set_target_properties( avutil
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libavutil.so)

add_library( swresample
             SHARED
             IMPORTED)
set_target_properties( swresample
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libswresample.so)

add_library( swscale
             SHARED
             IMPORTED)
set_target_properties( swscale
                       PROPERTIES IMPORTED_LOCATION
                       ${distribution_DIR}/armeabi-v7a/libswscale.so)

include_directories(libs/include)

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

              # Specifies the name of the NDK library that
              # you want CMake to locate.
              log )
              find_library( # Sets the name of the path variable.
                            android-lib

                            # Specifies the name of the NDK library that
                            # you want CMake to locate.
                            android )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       native-lib
                       libyuv
                       avcodec
                       avfilter
                       avformat
                       avutil
                       swresample
                       swscale
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib}
                         ${android-lib})

最后的最后不要忘记在build.gradle(app)中配置

 externalNativeBuild {
            cmake {
                cppFlags "-frtti -fexceptions"
            }
        }
        ndk {
            //选择要添加的对应cpu类型的.so库。
            abiFilters 'armeabi-v7a'
            // 还可以添加 'x86', 'x86_64', 'mips', 'mips64'
        }