安装cmake以及ndk {#安装cmake以及ndk}

工具栏： Tools-->SDK Manager-->Android SDK

选择SDK Tools，选中NDK 以及 CMake 下载安装

新建工程 {#新建工程}

修改build.gradle

|---------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | defaultConfig { minSdk 28 targetSdk 32 versionCode 1 versionName "1.0" testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" consumerProguardFiles "consumer-rules.pro" externalNativeBuild { cmake { // Passes optional arguments to CMake. arguments "-DANDROID_ARM_NEON=TRUE", "-DANDROID_TOOLCHAIN=clang" // Sets a flag to enable format macro constants for the C compiler. //cFlags "-D__STDC_FORMAT_MACROS" // Sets optional flags for the C++ compiler. cppFlags "-fexceptions", "-frtti" //仅生成单个平台 //abiFilters "armeabi-v7a"//,"arm64-v8a" //"x86", "x86_64" } } //生成多个平台共享库 ndk{ abiFilters "armeabi-v7a","arm64-v8a" //"x86", "x86_64" } sourceSets { main { jniLibs.srcDirs = ['libs'] } } } externalNativeBuild { cmake { path "src/main/cpp/CMakeLists.txt" version "3.10.2" } } |

CMakeLists.txt 修改要点 {#CMakeLists-txt-修改要点}

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 | # 设置本地库编译所需的最小cmake版本 cmake_minimum_required(VERSION 3.10.2) # 本地native项目名 project("ffmpeg") ## 配置 ## # 设置本地库根目录 set(native_root_dir ${CMAKE_CURRENT_LIST_DIR}) # 设置本地库源码路径 set(native_source_dir ${native_root_dir}/native) # 设置第三方静态库ffmpeg路径 set(native_ffmpeg_dir ${native_root_dir}/ffmpeg/armeabi_v7a) # 设置第三方库libyuv源码路径 set(native_yuv_dir ${native_root_dir}/libyuv) # 设置第三方库libyuv编译资源路径 set(native_yuv_build_dir ${native_yuv_dir}/build) # 设置第三方库libyuv头文件路径 set(native_yuv_inc_dir ${native_yuv_dir}/include) # 设置本地库编译目标名称 set(native_lib_name "ffmpeg") # 设置本地库编译输出路径 set(native_build_output_dir ${native_root_dir}/../../../build/intermediates/library_jni/debug/jni/${ANDROID_ABI}) ## 第三方子目录libyuv配置 ## # 构建编译文件依赖路径 file(MAKE_DIRECTORY ${native_yuv_build_dir}) # 构建添加一个子路径；添加libyuv子目录，执行子目录中的CMakeLists.txt add_subdirectory( ${native_yuv_dir} ${native_yuv_build_dir} ) # 创建一个static库lib_yuv 直接引用${native_yuv_build_dir}/libyuv_static.a add_library( lib_yuv STATIC IMPORTED ) set_target_properties( lib_yuv PROPERTIES IMPORTED_LOCATION ${native_yuv_build_dir}/libyuv_static.a ) # 指定native头文件路径 include_directories(${native_source_dir} ) # 指定libyuv头文件路径 include_directories( ${native_yuv_dir}/include ) # 指定ffmpeg静态库头文件路径 include_directories( ${native_ffmpeg_dir}/include ) # 设置native源码文件集合 set(native_source_files ${native_source_dir}/native_jni.cpp ) # 用native_source_files源文件集合编译生成SHARED库 add_library(${native_lib_name} SHARED ${native_source_files} ) # 设置${native_lib_name}库编译输出路径 set_target_properties(${native_lib_name} PROPERTIES LIBRARY_OUTPUT_DIRECTORY "${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI}") ## import ffmpeg static lib # 创建一个static库avcodec 直接引用${native_ffmpeg_dir}/lib/libavcodec.a add_library( avcodec STATIC IMPORTED ) set_target_properties( avcodec PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libavcodec.a ) # 创建一个static库avfilter 直接引用{native_ffmpeg_dir}/lib/libavfilter.a add_library( avfilter STATIC IMPORTED ) set_target_properties( avfilter PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libavfilter.a ) add_library( avformat STATIC IMPORTED ) set_target_properties( avformat PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libavformat.a ) add_library( avutil STATIC IMPORTED ) set_target_properties( avutil PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libavutil.a ) add_library( swresample STATIC IMPORTED ) set_target_properties( swresample PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libswresample.a ) add_library( swscale STATIC IMPORTED ) set_target_properties( swscale PROPERTIES IMPORTED_LOCATION ${native_ffmpeg_dir}/lib/libswscale.a ) # 查找动态库log find_library(log-lib log ) #链接所有动态库/静态库到工程ffmpeg target_link_libraries(ffmpeg avcodec avfilter avformat avutil swresample swscale lib_yuv ${log-lib}) #set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI}) #拷贝库文件. add_custom_command(TARGET ${native_lib_name} POST_BUILD COMMAND "${CMAKE_COMMAND}" -E copy "${native_build_output_dir}/libffmpeg.so" "${native_root_dir}/../../../../app/libs/libffmpeg.so" COMMENT "Copying ${native_lib_name} to output directory") |

CMake子目录库关联路径问题：

子目录CMakeLists.txt 匹配：

编译实际结果：

so输出路径 CMAKE_LIBRARY_OUTPUT_DIRECTORY
.a 静态库输出路径 CMAKE_ARCHIVE_OUTPUT_DIRECTORY
获取当前编译的abi ， ANDROID_ABI
编译选项：
CMAKE_C_FLAGS
CMAKE_CXX_FLAGS
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wfatal-errors -fPIC")
CMAKE_CXX_FLAGS_DEBUG/CMAKE_CXX_FLAGS_RELEASE
子目录编译: ADD_SUBDIRECTORY

关键语句 {#关键语句}

判断语句 {#判断语句}

|---------------------------------|-------------------------------------------------------------------------------| | 1 2 3 4 5 6 7 8 9 10 11 | set(BUDEG ON) if(BUDEG ) //do something else() //do something endif() |

常用变量 {#常用变量}

CMAKE_SOURCE_DIR ( 相当于工程根目录 )
this is the directory, from which cmake was started, i.e. the top level source directory
CMAKE_CURRENT_SOURCE_DIR
this is the directory where the currently processed CMakeLists.txt is located in
PROJECT_SOURCE_DIR ( =CMAKE_SOURCE_DIR 相当于工程根目录 )
contains the full path to the root of your project source directory, i.e. to the nearest directory where CMakeLists.txt contains the PROJECT() command
CMAKE_PREFIX_PATH （用于找 Findxxx.cmake文件，找库和头文件）
Path used for searching by FIND_XXX(), with appropriate suffixes added.
CMAKE_INSTALL_PREFIX ( 安装目录 )
Install directory used by install.
If "make install" is invoked or INSTALL is built, this directory is prepended onto all install directories. This variable defaults to /usr/local on UNIX and c:/Program Files on Windows.
例如： cmake .. -DCMAKE_INSTALL_PREFIX=/my/paht/to/install

基本指令 {#基本指令}

PROJECT (HELLO)
指定项目名称，生成的VC项目的名称，使用${HELLO_SOURCE_DIR}表示项目根目录。
INCLUDE_DIRECTORIES
指定头文件的搜索路径，相当于指定gcc的-I参数
INCLUDE_DIRECTORIES(${HELLO_SOURCE_DIR}/Hello) #增加Hello为include目录
TARGET_LINK_LIBRARIES
添加链接库，相同于指定-l参数
TARGET_LINK_LIBRARIES(demoHello) #将可执行文件与Hello连接成最终文件demo
LINK_DIRECTORIES
动态链接库或静态链接库的搜索路径，相当于gcc的-L参数
LINK_DIRECTORIES(${HELLO_BINARY_DIR}/Hello)#增加Hello为link目录
ADD_DEFINITIONS
向C/C++编译器添加-D定义，比如：
ADD_DEFINITIONS(-DENABLE_DEBUG-DABC)
参数之间用空格分割。如果代码中定义了:
这个代码块就会生效。如果要添加其他的编译器开关,可以通过CMAKE_C_FLAGS变量和CMAKE_CXX_FLAGS变量设置。
ADD_DEPENDENCIES
定义target依赖的其它target，确保在编译本target之前，其它的target已经被构建。ADD_DEPENDENCIES(target-name depend-target1 depend-target2 ...)
ADD_EXECUTABLE
ADD_EXECUTABLE(helloDemo demo.cxx demo_b.cxx)
指定编译，好像也可以添加.o文件，将cxx编译成可执行文件
ADD_LIBRARY
ADD_LIBRARY(Hellohello.cxx) #将hello.cxx编译成静态库如libHello.a
ADD_SUBDIRECTORY
ADD_SUBDIRECTORY(Hello) #包含子目录