在我們建立專案的時候，如果勾選 Include C++ Support ，就會在 main 的同級目錄下生成一個CMakeLists.text

下面來一一介紹

# 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
             )

# 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.

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 )

# 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

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )
 

我們可以直接翻譯來看：

# 有關使用Android工作室使用CMAGE的更多資訊,
# 閱讀文件: https://d.android.com/studio/projects/add-native-code.html

# 設定建立本地庫所需的最小CMake版本

cmake_minimum_required(VERSION 3.4.1)

# 建立和命名庫, 將其設定為STATIC 或者SHARED, 
# 並提供其原始碼的相對路徑。
# 您可以定義多個庫，CMake為您構建它們。
# 用Apk自動打包共享庫.

add_library( # 設定庫的名稱.
             native-lib

             # 將庫設定為共享庫.
             SHARED

             # 為原始檔提供相對路徑.
             src/main/cpp/native-lib.cpp
             )

# 搜尋指定的預構建庫並將路徑儲存為變數。
# 因為CMake預設包含搜尋路徑中的系統庫
# 您只需指定要新增的公共NDK庫的名稱即可.
# CMake 在完成構建之前驗證該庫是否存在

find_library( # 設定路徑變數的名稱.
              log-lib

              # 指定希望CMake定位的NDK庫的名稱.
              log )

# 指定庫CMake 應該連結到目標庫.
# 你可以連結多個庫 ，作為在這個構建指令碼中定義的庫,
# 預構建的第三方庫或系統庫.

target_link_libraries( # 指定目標庫.
                       native-lib

                       # 將目標庫連結到日誌庫
                       # 包含在NDK中.
                       ${log-lib} )
 

解析：

1、制定CMake 所需的最小版本，有系統自動生成，無需更改
    cmake_minimum_required(VERSION 3.4.1)

2、add_library()：用來設定編譯生成本地庫的相關屬性

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
             )
 

native-lib ：

生成動態庫的名稱

SHARE:

設定連結庫的型別， 分為 ：SHARE 動態連結庫，SATTIC 靜態連結庫

src/main/cpp/native-lib.cpp：

你寫的c/c++ 程式碼的相對路徑。目前我的cpp 目錄中有個natice-lib.cpp檔案。如果，我又添加了一個 hello.cpp，則直接在下面新增、

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

             SHARED

             src/main/cpp/native-lib.cpp
             src/main/cpp/hello.cpp
             )

3、find_library():用來讓我們加一些編譯本地NDK庫的時候所用的到一些依賴庫.

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 )

log-lib:依賴庫的別名

log: log 日誌庫

4、target_link_libraries():  用來關聯我們本地的庫跟第三方的庫

target_link_libraries( # Specifies the target library.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

native-lib:

我們自己的庫，和add_library 中的名稱一致

${log-lib}:

需要關聯的庫的名稱。

二、使用cmake  生成so庫

CMakeLists.text 中新增 如下程式碼： 

set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI})

編譯執行後，會在目錄中直接生成 .so 

還可以 在app 下的  build.gradle中指定abi abiFilters

    defaultConfig {

       ......
       ......
       ......

        externalNativeBuild {
            cmake {
                cppFlags ""
                abiFilters 'x86','armeabi-v7a';
            }
        }
    }

如果不指定，會生成所有當前支援的 abi庫

指定之後，只會生成響應版本的abi

注： 參考借鑑：https://blog.csdn.net/hktkfly6/article/details/79593127