AndroidStudio3.*+ jni 开发配置cmake模式

本文简介：
  最近看了一些文章，看到大部分关于Android jni的配置都还是ndkBuild模式的；有的则是说怎么引用已经编译好的os文件。本文主要以一个小dome为列，记录Android jni cmake模式下的配置。
一、环境配置

  Android 开发的环境配置网上已经很多了，这里就不重复。我们做jni开发的，需要用到snk，所以我们第一步，在Android studio 上引入ndk

这里我们主要需要勾选NDK、CMake。为啥要勾选CMake因为我们自己常常用传统方法生成，配置太过于麻烦，所以我们这里用CMake,直接生成一个标准的例子，进行修改。这样就会减少很多问题的产生，节省我们的时间。

二、项目创建

（一）首先创建新项目，选择创建NativityC++项目

（二）填写项目信息。

选择对c++标准，这里选择的默认。

（三）创建成功后项目架构是如下图

三、与Android项目有些差别及说明

（一）app下的build.gradle

这里多了些关于编译ndk的入口配置数据

externalNativeBuild {
    cmake {
        cppFlags ""
    }
}

这里的cppFlags 值为引用的其他类库比如：

cppFlags "-fexceptions"

编译snk异常捕获的

externalNativeBuild {
    cmake {
        path "src/main/cpp/CMakeLists.txt"
        version "3.10.2"
    }
}

path ：指定编译的目标配置文件地址
version：编译版本的
 

（二）结构上：
main下面多了cpp的包，里面有多了一个CMakeLists.txt和native-lib.cpp

这两个文件，CMakeLists.txt是关于cmake的一些基础配置和编译ndk的文件关联配置

native-lib.cpp则是C++将要编译的代码文件

1、首先看CMakeLists.txt的内容：

# 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).
        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_librari