上一篇文章介绍了如何在Mac平台下编译FFMPEG，这篇主要介绍如何将编译后的so文件导入Android项目中，

1. 项目文件目录结构

   WX20190619-162908.png

   • src/main/cpp/include包下的文件可以从FFMPEG编译后的任意CPU架构目录下直接拷贝到cpp目录下即可

   • src/main/jniLibs/包下的文件可以从FFMPEG编译后的对应的CPU架构Lib包下拷贝，只需要拷贝以带版本号的so文件即可，如：libavcodec-57.so

     WX20190619-163538@2x.png

2. 配置项目的build.gradle文件

   android {
     .....
       
       externalNativeBuild {
           cmake {
               path "CMakeLists.txt"
           }
       }
     
       sourceSets{
           main{
               jniLibs.srcDirs = ["src/main/jniLibs"]
           }
       }
   }
   

3. 配置CMakeLists.txt文件

   # Cmake版本号
   cmake_minimum_required(VERSION 3.4.1)
   #项目自动生成的代码
   add_library(
           native-lib
           SHARED
           src/main/cpp/native-lib.cpp)
   
   #复用NDK中一些基础的库，如输出log等
   find_library(
           log-lib
           log)
   
   #导入FFMPEG动态库：
   
   #1.导入FFMEPG头文件夹路径
   include_directories(src/main/cpp/include)
   #2. 添加动态库: 库名 SHARED IMPORTED
   add_library(avcodec-57 SHARED IMPORTED)
   #3. 设置动态库路径：${CMAKE_SOURCE_DIR}表示CmakeList文件目录 ${ANDROID_ABI}表示系统CPU架构
   set_target_properties(avcodec-57
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavcodec-57.so)
   #其他so文件按照第2、3步重复操作即可，只需要替换对应的so库名称即可
   add_library( avdevice-57 SHARED IMPORTED)
   set_target_properties( avdevice-57
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavdevice-57.so)
   
   
   add_library( avfilter-6 SHARED IMPORTED)
   set_target_properties( avfilter-6
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavfilter-6.so)
   
   
   add_library( avformat-57 SHARED IMPORTED)
   set_target_properties( avformat-57
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavformat-57.so)
   
   
   add_library( avutil-55 SHARED IMPORTED)
   set_target_properties( avutil-55
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libavutil-55.so)
   
   add_library( postproc-54 SHARED IMPORTED)
   set_target_properties( postproc-54
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libpostproc-54.so)
   
   add_library( swresample-2 SHARED IMPORTED)
   set_target_properties( swresample-2
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libswresample-2.so)
   
   
   add_library( swscale-4 SHARED IMPORTED)
   set_target_properties( swscale-4
           PROPERTIES IMPORTED_LOCATION
           ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libswscale-4.so)
   
   #4. 链接动态库
   target_link_libraries(
           native-lib
           ${log-lib}
           # FFMPEG相关的类库
           avcodec-57
           avdevice-57
           avfilter-6
           avformat-57
           avutil-55
           postproc-54
           swresample-2
           swscale-4)
   

4. 编写C++测试代码：

   #include <jni.h>
   #include <string>
   #include <android/log.h>
   
   //由于调用时是用C语言写的，所以也要用extern声明是C，否则编译时会报错
   extern "C"{
   #include <libavformat/avformat.h>
   }
   
   
   //定义打印Log方法
   #define LOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,"MyPlayer",FORMAT,##__VA_ARGS__);
   
   extern "C" JNIEXPORT jstring JNICALL
   Java_cn_rongrtc_mylibrary_Demo_stringFromJNI(
           JNIEnv *env,
           jobject /* this */) {
       //注册所有的解码器
       av_register_all();
       //获取所有的解码器
       AVCodec *c_temp = av_codec_next(NULL);
        //遍历解码器并打印解码器名称
       while (c_temp != NULL)
       {
           switch (c_temp->type)
           {
               case AVMEDIA_TYPE_VIDEO:
                   LOGI("[Video]:%s", c_temp->name);
                   break;
               case AVMEDIA_TYPE_AUDIO:
                   LOGI("[Audio]:%s", c_temp->name);
                   break;
               default:
                   LOGI("[Other]:%s", c_temp->name);
                   break;
           }
           c_temp = c_temp->next;
       }
       std::string hello = "Hello from Demo C++";
       return env->NewStringUTF(hello.c_str());
   }
   
   

5. 编写Java层代码

   public class Demo {
       // Used to load the 'native-lib' library on application startup.
       static {
           System.loadLibrary("native-lib");
           System.loadLibrary("avcodec-57");
           System.loadLibrary("avdevice-57");
           System.loadLibrary("avfilter-6");
           System.loadLibrary("avformat-57");
           System.loadLibrary("avutil-55");
           System.loadLibrary("postproc-54");
           System.loadLibrary("swresample-2");
           System.loadLibrary("swscale-4");
       }
   
       /**
        * A native method that is implemented by the 'native-lib' native library,
        * which is packaged with this application.
        */
       public static native String stringFromJNI();
   }
   

   遇到的问题

   • 同步代码或编译时如果有类似的报错:

     Error while executing process /Users/www/Library/Android/sdk/cmake/3.10.2.4988404/bin/cmake with arguments {--build /Users/www/codeSamples/ffmpeg/MusicPlayer/mylibrary/.externalNativeBuild/cmake/debug/arm64-v8a --target native-lib}
     ninja: error: '../../../../src/main/jniLibs/arm64-v8a/libavcodec-57.so', needed by '../../../../build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so', missing and no known rule to make it

如果出现类似报错则有可能是你的so库不支持你手机CPU架构，你需要编译一份对应的CPU架构so库并拷贝到jniLibs目录下即可。具体如何编译可以参考上一篇文章Mac平台下编译FFMPEG