app\src\main\cpp\CMakeLists.txt：C/C++调试|arm64-v8a：配置失败

Question

我在jnilibs 文件夹下复制了必要的.so 文件，并使用jni 接口在android ndk 项目中配置了以下文件。当运行项目时，它抛出如下所示的错误。

build.gradle

defaultConfig{
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-frtti -fexceptions"
                abiFilters 'arm64-v8a'
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "src/main/cpp/CMakeLists.txt"
            version "3.10.2"
        }
    }

这是我的CMakeLists.txt

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
cmake_minimum_required(VERSION 3.4.1)
# Sets the minimum version of CMake required to build the native library.
#Import header file
include_directories(src/main/jniLibs/include)

#Declare the import file to change the directory variable ARM_DIR, which uses the relative directory with the system, because using the relative path does not seem to work
set(ARM_DIR C:/Users/Username/AndroidStudioProjectsFolder/ExamplAppName/app/src/main/jniLibs)

#Add an example of so library.
add_library(avdevice
        SHARED
        IMPORTED)
set_target_properties(avdevice
        PROPERTIES IMPORTED_LOCATION
        ${ARM_DIR}/arm64-v8a/libavdevice.so)

#Adding other so libraries in the same format as above
#Link library
target_link_libraries(
        native-lib
        avdevice
        avformat
        ${log-lib} )

# 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.

#add_library( # Sets the name of the library.
#             native-lib
#
#             # Sets the library as a shared library.
#             SHARED
#
#             # Provides a relative path to your source file(s).
#             native-lib.cpp )
#
## Searches for a specified prebuilt library and stores the path as a
## variable. Because CMake includes system libraries in the search path by
## default, you only need to specify the name of the public NDK library
## you want to add. CMake verifies that the library exists before
## completing its build.
#
#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 )
#
## Specifies libraries CMake should link to your target library. You
## can link multiple libraries, such as libraries you define in this
## build script, prebuilt third-party libraries, or system libraries.
#
#target_link_libraries( # Specifies the target library.
#                       native-lib
#
#                       # Links the target library to the log library
#                       # included in the NDK.
#                       ${log-lib} )

它的原生-lib.cpp文件在cpp/目录下：

#include <jni.h>
#include <string>

extern "C"
{
#include "libavformat/avformat.h"
}

extern "C" JNIEXPORT jstring JNICALL
Java_com_examples_examplappname_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    av_register_all();
    return env->NewStringUTF(hello.c_str());
}

.java源代码：

static {
            System.loadLibrary("avdevice");
            System.loadLibrary("avformat");
            System.loadLibrary("native-lib");
        }

    TextView tv = findViewById(R.id.sample_text);
    tv.setText(stringFromJNI());

错误：

**Starting Gradle Daemon...
Gradle Daemon started in 4 s 270 ms
KotlinDslScriptsParameter(correlationId=22803889351800, scriptFiles=[]) => StandardKotlinDslScriptsModel(scripts=[], commonModel=CommonKotlinDslScriptModel(classPath=[], sourcePath=[], implicitImports=[]), dehydratedScriptModels={}) - took 0.128 secs

app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed.
app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : CMake Error at app\src\main\cpp\CMakeLists.txt:21 (target_link_libraries):
  Cannot specify link libraries for target "native-lib" which is not built by
  this project

app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed.
executing external native build for cmake 
app\src\main\cpp\CMakeLists.txt

CONFIGURE SUCCESSFUL in 3m 33s**

Answer 1

此处明显的问题涉及 CMake 文件中的行：

target_link_libraries(
        native-lib
        avdevice
        avformat
        ${log-lib} )

它引用库（native-lib 目标和 ${log-lib} 库变量）甚至在它们被定义之前。这肯定会导致 CMake 报错。您应该取消注释 CMake 文件的其余部分，并且 link 您导入的库目标为 existing target_link_libraries() 调用中的 native-lib：

add_library( # Sets the name of the library.
             native-lib
             # 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.
                       native-lib
                       # Link your imported library targets here also.
                       avdevice
                       avformat
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

app\src\main\cpp\CMakeLists.txt：C/C++调试|arm64-v8a：配置失败

app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed

c++

cmake

android-ndk

java-native-interface

android-ffmpeg