将原有Android项目转成ndk项目
本文所描述的是3.0版本及以上Android Studio
首先3.0之后新增了cmake插件，所以我们需要的是新增CMakeLists.txt
然后我们需要的是关联，在相应的模块包的build.gradle下面添加以下代码：
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"//这里填自己新建的路径
version "3.10.2"
}
}
但是现在会出现一个问题，就是我们没有指定c++的版本还有我们本地并没有相关ndk的头文件和jni的头文件，怎么办？
首先我们可以指定c++的版本，还是在相应模块下的build.gradle中添加:
externalNativeBuild {
cmake {
cppFlags ""
}
}
不过这次的位置不是和上次一样的，上次是在Android的父级，这个是defaultConfig父级，cppFlags后面的引号不写的话就是自适应的版本，后面像指定版本需要添加:-std=c++14，
我的完整build.gradle
这样build.project的配置就完成了
现在的问题就是我们需要添加相应的ndk头文件和实现文件
需要在cmake文件里面添加以下代码:
# 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(
#你可以自定义的动态库名字
native-lib
# Sets the library as a shared library.
SHARED
#你写好的cpp文件
main.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.
#你想添加的动态库名字
native-lib
# Links the target library to the log library
# included in the NDK.
${log-lib} )
Make一下即可
