ndk ffmpeg实践

1、ndk ffmpeg不行，那么先自己做一个简单的myso

2、先直接用gcc编译果然链接不行，

gcc -shared -fPIC -o libmyso.so myso.c

用ndk里按照网上说的，还是有问题，报错，但是错误里明显把android studio的调用命令给出来了，那么用这个命令

Build command failed.

Error while executing process /Users/wangt/Library/Android/sdk/cmake/3.10.2.4988404/bin/ninja with arguments {-C /Users/wangt/AndroidStudioProjects/NativeTestSo/app/.cxx/Debug/6e5m5423/arm64-v8a nativetestso}

ninja: Entering directory `/Users/wangt/AndroidStudioProjects/NativeTestSo/app/.cxx/Debug/6e5m5423/arm64-v8a'

[1/1] Linking CXX shared library /Users/wangt/AndroidStudioProjects/NativeTestSo/app/build/intermediates/cxx/Debug/6e5m5423/obj/arm64-v8a/libnativetestso.so

FAILED: /Users/wangt/AndroidStudioProjects/NativeTestSo/app/build/intermediates/cxx/Debug/6e5m5423/obj/arm64-v8a/libnativetestso.so 

: && /Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64 --sysroot=/Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security   -O0 -fno-limit-debug-info  -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libgcc_real.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -shared -Wl,-soname,libnativetestso.so -o /Users/wangt/AndroidStudioProjects/NativeTestSo/app/build/intermediates/cxx/Debug/6e5m5423/obj/arm64-v8a/libnativetestso.so CMakeFiles/nativetestso.dir/native-lib.cpp.o  ../../../../libs/libmyso.so -llog -latomic -lm && :

CMakeFiles/nativetestso.dir/native-lib.cpp.o: In function `Java_com_example_nativetestso_MainActivity_stringFromJNI':

/Users/wangt/AndroidStudioProjects/NativeTestSo/app/src/main/cpp/native-lib.cpp:9: undefined reference to `getDataFromSo()'

clang++: error: linker command failed with exit code 1 (use -v to see invocation)

ninja: build stopped: subcommand failed.

/Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64 --sysroot=/Users/wangt/Library/Android/sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/darwin-x86_64/sysroot -shared -fPIC -o libmyso.so myso.c

4 生成 apk 出错

abiFilters "arm64-v8a" 加上这个，不去生成其他的了

别忘了

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

现在运行出错

--------- beginning of crash
2021-08-27 05:25:44.159 17208-17208/com.example.nativetestso E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nativetestso, PID: 17208
java.lang.UnsatisfiedLinkError: dlopen failed: library "../../../../libs/libmyso.so" not found: needed by /data/app/~~iNqDlLH21o2dB9AsKojg5Q==/com.example.nativetestso-CMkPfzF7qn_2Ir-QclsDUQ==/lib/arm64/libnativetestso.so in namespace classloader-namespace

5

set(DIR ../../../../libs)

add_library(myso
        SHARED
        IMPORTED)
set_target_properties(myso
        PROPERTIES IMPORTED_LOCATION
        ${DIR}/libmyso.so)

可以直接用这一句替换

set(FF ${CMAKE_SOURCE_DIR}/../../../libs/)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -L${FF}")

5 java.lang.UnsatisfiedLinkError: dlopen failed: library "libmyso.so" not found: needed by
原来报这个错

拷贝到这个位置后，报java.lang.UnsatisfiedLinkError: dlopen failed: library "libc++_shared.so" not found: needed by /data/app/~~p8tRq5oyoGWLks5，看来有用

---还是不行啊，刚才怎么搞出来另外一个问题的？？

 看来第5条没有用

6、把生成的apk 重命名为 zip,然后解压，发现lib里面没有，看来找到问题原因了，后面像早一样记录在笔记本上，to thi.

最后还是要建立 架构的子目录来解决（终于解决）

最后的cmake

cmake_minimum_required(VERSION 3.10.2)

# Declares and names the project.

project("nativetestso")

#set(DIR ../../../../libs)

set(FF ${CMAKE_SOURCE_DIR}/../../../libs/arm64-v8a/)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -L${FF}")

#set(distribution_DIR ${CMAKE_SOURCE_DIR}/../../../libs/)

#set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/../../../libs/)

add_library( # Sets the name of the library.
        nativetestso
        SHARED
        native-lib.cpp )


find_library( # Sets the name of the path variable.
        log-lib
        log)


target_link_libraries( # Specifies the target library.
        nativetestso
        myso
        ${log-lib})

最后的build.gradle(module app)

plugins {
    id 'com.android.application'
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.example.nativetestso"
        minSdk 21
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ''
                abiFilters "arm64-v8a"
                arguments "-DANDROID_STL=c++_shared"
            }
        }
    }
    sourceSets{
        main{
            jniLibs.srcDirs = ['libs']
        }
    }