1.前言
在这里我以导入静态库(.a)为例进行分析,动态库(.so)是类似的。在导入前,各位要先编译好ffmpeg库,需要注意的是在编译的时候要开启交叉编译,目标平台为Android,其他平台的库(windows,linux)在Android平台使用不了,我这里编译的是armeabi-v7a架构的库。
2.步骤
(1)新建一个native c++项目,然后在main目录下面新建一个jniLibs目录,将编译好的库放入这个目录下,这里贴出我的:
由于我开启了对x264编解码的支持,所以把libx264库也导入了。
(2)修改app下的build.gradle文件,配置一下支持哪些ABI(应用程序二进制接口),也就是支持的CPU架构类型。
defaultConfig { applicationId "cn.siat.importedffmpeg" minSdk 24 targetSdk 33 versionCode 1 versionName "1.0" testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" ndk{ abiFilters "armeabi-v7a" } }
(3)在cpp目录下新建一个include文件夹,用于存放ffmpeg的头文件。
(4)修改CMakeLists.txt文件,导入ffmpeg头文件,并链接jniLibs下的库文件,代码如下:
# For more information about using CMake with Android Studio, read the # documentation: https://d.android.com/studio/projects/add-native-code.html. # For more examples on how to use CMake, see https://github.com/android/ndk-samples. # Sets the minimum CMake version required for this project. cmake_minimum_required(VERSION 3.22.1) # Declares the project name. The project name can be accessed via ${ PROJECT_NAME}, # Since this is the top level CMakeLists.txt, the project name is also accessible # with ${CMAKE_PROJECT_NAME} (both CMake variables are in-sync within the 服务器托管网top level # build script scope). project("importedffmpeg") # 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. # # In this top level CMakeLists.txt, ${CMAKE_PROJECT_NAME} is used to define # the target library name; in the sub-module's CMakeLists.txt, ${PROJECT_NAME} # is preferred for the same purpose. # # In order to load a library into your app from Java/Kotlin, you must call # System.loadLibrary() and pass the name of the library defined here; # for GameActivity/NativeActivity derived applications, the same library name must be # used in the AndroidManifest.xml file. include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include) add_library(${CMAKE_PROJECT_NAME} SHARED # 将自己写的cpp源文件编译成动态库 native-lib.cpp)
#添加已有的静态库 add_library(avcodec STATIC IMPORTED)
#告知cmake静态库的路径 set_target_properties(avcodec PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libavcodec.a) add_library(avdevice STATIC IMPORTED) set_target_properties(avdevice PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libavdevice.a) add_library(avfilter STATIC IMPORTED) set_target_properties(avfilter PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libavfilter.a) add_library(avformat STATIC IMPORTED) set_target_properties(avformat PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libavformat.a) add_library(avutil STATIC IMPORTED) set_target_properties(avutil PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libavutil.a) add_library(postproc STATIC IMPORTED) set_target_properties(postproc PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libpostproc.a) add_library(swresample STATIC IMPORTED) set_target_properties(swresample PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libswresample.a) add_library(swscale STATIC IMPORTED) set_target_properties(swscale PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libswscale.a) add_library(x264 STATIC IMPORTED) set_target_properties(x264 PROPERTIES IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/armeabi-v7a/libx264.a) target_link_librari服务器托管网es(${CMAKE_PROJECT_NAME} # List libraries link to the target library android log avcodec avformat avdevice avfilter avutil postproc swresample swscale x264 z)
(5)修改native-lib.cpp文件,返回ffmpeg的版本号,并进行显示。
#include #include string> extern "C"{ #include } extern "C" JNIEXPORT jstring JNICALL Java_cn_siat_importedffmpeg_MainActivity_stringFromJNI( JNIEnv* env, jobject /* this */) { std::string hello = "Hello from C++"; return env->NewStringUTF(av_version_info()); }
(6)运行程序
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