1. NDK Android jni开发 2种so库编译 cmake(相机图片美化)

jni步骤开发：

https://www.jianshu.com/p/58a551c0c09f

 

NDK和CMake 的下载和安装

local.properties文件, 在里面添加:

//后面改成自己下载后解压的路径名
ndk.dir=C\:\\Users\\Lulu\\AppData\\Local\\Android\\android-ndk-r13

 

NDK两种开发模式

1. ndk-build 形式; Android Studio 2.2之前的模式
2. CMake 形式: CLion C/C++编辑器; AS2.2之后整合了CLion代码, AS就支持了CMake形式的NDK开发

 

第一种方式：CMake 形式:

1.直接建立项目，include C++

2.项目配置NDK

ndk.dir=/Users/mac/Library/Android/sdk/ndk-bundle
sdk.dir=/Users/mac/Library/Android/sdk

3.cMakeList:定义cmakeListd的路径

externalNativeBuild {
    cmake {
        path "CMakeLists.txt"
    }
}

4.点击Link C++ Project with Gradle

右击jni目录，选择Link C++ Project with Gradle标签

5.修改生成so库都类型

externalNativeBuild {
    cmake {
        cppFlags ""
        abiFilters "armeabi-v7a"
    }
}

添加java方法，studio自动提示，会写好方法名。

都是自动生成文件

注意：类名和方法名不要乱改，否则会找不到。

 

CMakeLists.txt文件解析：

 

# 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)

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

# 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})

来源： https://www.jianshu.com/p/65013d2b14fa

 

1.cmake_minimum_required(VERSION 3.4.1)
用来声明编译本地库文件时需要的Cmake最小版本，在AndroidStudio构建版本时会自动生成；
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY {ANDROID_ABI})
将libxx.so生成到jniLibs文件夹下

2.add_library(）

native-lib : 编译本地本地lib生成的库文件的名称
SHARED : （生成的库种类）SHARED表示编译生成的是动态链接库
src/main/cpp/native-lib.cpp : 表示编译文件的相对路径,这里可以是一个文件的路径也可以是多个文件的路径

 

3.find_library()

这个的作用是声明编译本地库的时候，需要用的到一些依赖库.
log-lib 是这个库的别名,方便我们以后引用
log 是我们调试的时候打印log的一个库

4.target_link_libraries(）

target_link_libraries( # Specifies the target library.
        native-lib

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

目的是用来关联我们本地的库跟第三方的库.这里就是把native-lib库和log库关联起来.

 

cmake主要是：

 

修改native-lib.cpp

这时候我们修改下native-lib.cpp，native-lib.cpp内容如下：

 

第二种方式：mk 形式:

 

步骤如下：

 

1. 用命令编译

2. 先进入jni目录下

3. 找到studo里面的loacal.perpert

/Users/ex_wljr_peng/Library/Android/sdk/ndk-bundle/ndk-build NDK_PROJECT_PATH=. APP_BUILD_SCRIPT=./Android.mk

 

 

参考博客：

https://blog.csdn.net/meiliangdeng1990/article/details/50784553

 

ndk-build使用的编译器是我们下载的ndk包里的

 

Android.mk和Application.mk

 

通过ndk-build命令会生成2个文件夹，一个是debug，另外一个是release