ffmpeg-android studio创建jni项目

一、创建native项目

1.1、选择Native C++

1.2、命名项目名称

1.3、选择C++标准

1.4、项目结构

1.5、app的build.gradle

plugins {
    id 'com.android.application'
}

android {
    compileSdk 32

    defaultConfig {
        applicationId "com.anniljing.ffmpegnative"
        minSdk 25
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags '-std=c++11'
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    externalNativeBuild {
        cmake {
            path file('src/main/cpp/CMakeLists.txt')
            version '3.18.1'
        }
    }
    buildFeatures {
        viewBinding true
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.9.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
}

• android -> defaultConfig ->externalNativeBuild -> cmake
  配置c++使用标准
• android -> externalNativeBuild -> cmake
  1 、配置cmake文件路径
  2、配置cmake的版本

1.6、CMakeLists.txt

cmake_minimum_required(VERSION 3.18.1)

project("ffmpegnative")


add_library( # Sets the name of the library.
        ffmpegnative

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        native-lib.cpp)

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)


target_link_libraries( # Specifies the target library.
        ffmpegnative

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

• cmake_minimum_required

  cmake最低版本要求

• project

  设置项目名称

• add_library

  添加库并设置库的源文件

  1、 Normal Libraries

add_library(<name> [STATIC | SHARED | MODULE]
            [EXCLUDE_FROM_ALL]
            [<source>...])

name:库名称

STATIC|SHARED|MODULE:库类型（静态、动态、模块）

source:源文件

2、Imported Libraries

add_library(<name> <type> IMPORTED [GLOBAL])

导入已经生成的库,通常情况搭配set_target_properties，指定库的相关配置信息

set_target_properties(target1 target2 ...
                      PROPERTIES prop1 value1
                      prop2 value2 ...)

• find_library
  查找本地库，一般位于NDK中

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)

• target_link_libraries
  用于指定目标（target）与其所需的库之间的链接关系。它被用于在构建过程中将库文件链接到可执行文件或共享库。

target_link_libraries(
        ffmpegnative
        ${log-lib})

将log-lib库链接到ffmpegnative中

二、配置FFmpeg头文件和so库

2.1、配置FFmpeg头文件

#设置头文件路径
include_directories(${CMAKE_SOURCE_DIR}/include)

2.2、配置ffmpeg相关的so库

2.2.1、添加so库

#声明ffmpeg_lib_dir变量，设置统一的库文件路径
set(ffmpeg_lib_dir ${CMAKE_SOURCE_DIR}/../jniLibs/${ANDROID_ABI})
#添加ffmpeg相关的库
#avutil库
add_library( avutil
        SHARED
        IMPORTED )
set_target_properties( avutil
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libavutil.so )
#swresample库
add_library( swresample
        SHARED
        IMPORTED )
set_target_properties( swresample
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libswresample.so )
#avcodec库
add_library( avcodec
        SHARED
        IMPORTED )
set_target_properties( avcodec
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libavcodec.so )
#avfilter库
add_library( avfilter
        SHARED
        IMPORTED)
set_target_properties( avfilter
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libavfilter.so )
#swscale库
add_library( swscale
        SHARED
        IMPORTED)
set_target_properties( swscale
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libswscale.so )
#avformat库
add_library( avformat
        SHARED
        IMPORTED)
set_target_properties( avformat
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libavformat.so )
#avdevice库
add_library( avdevice
        SHARED
        IMPORTED)
set_target_properties( avdevice
        PROPERTIES IMPORTED_LOCATION
        ${ffmpeg_lib_dir}/libavdevice.so )

2.2.2、链接ffmpeg库

target_link_libraries(
        ffmpegnative
        #链接ffmpeg相关库
        avutil
        swresample
        avcodec
        avfilter
        swscale
        avformat
        avdevice
        #链接本地日志库
        ${log-lib})

三、编译测试

3.1、错误一

• 把1.6.1修改为1.5.1

3.2、编译arm64-v8a错误

• 因为我们只配置了armeabi-v7a,所以我们需要指定只编译armeabi-v7a的
  

3.3、多个相同文件问题

 sourceSets {
        main {
            jniLibs.srcDirs = ['libs']
        }
    }

四、调用ffmpeg相关api

4.1、声明native函数

public native String getFFmpegVersion();

4.2、实现native函数

#include <libavformat/avformat.h>

extern "C"
JNIEXPORT jstring JNICALL
Java_com_anniljing_ffmpegnative_MainActivity_getFFmpegVersion(JNIEnv *env, jobject thiz) {
    const char* version = av_version_info();

    return env->NewStringUTF(version);
}

• 没有正确添加依赖，指定确保C++编译器按照C语言的约定处理函数
  

4.3、调用测试