工程结构如下

文件结构如下：

在调用的地方定义在 MainActivity类里

public class MainActivity extends AppCompatActivity {

    // Used to load the 'native-lib' library on application startup.

    static {

        System.loadLibrary("native-lib");

    }

public native String stringFromJNI();

...

}

在native-lib.cpp中实现

#include <jni.h>

#include <string>

extern "C" JNIEXPORT jstring JNICALL

Java_com_xn_helloso_MainActivity_stringFromJNI(

        JNIEnv* env,

        jobject /* this */) {

    std::string hello = "Hello from C++";

    return env->NewStringUTF(hello.c_str());

}

函数名称就是Java+包地址+类+函数名

编译需要在module下的build.gradle文件里加

externalNativeBuild {

        cmake {

            path "CMakeLists.txt"

        }

    }

生成的so动态库在：app\build\intermediates\cmake\debug\obj

CMakeLists.txt文件内容

# For more information about using CMake with Android Studio, read the

# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# 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).

             src/main/cpp/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} )

AndroidStudio引用第三方so库的正确姿势

1、把so文件复制到 \app1\app\libs\ 文件夹下，但是要注意，so文件是放在对应的平台文件夹之下（如arm64-v8a，armeabi-v7a， x86，x86_64），这点非常重要，否则不能成功引用，每个平台文件夹下都放上该so文件，如下图：

2、AndroidStudio打开项目，并切换到 Android 栏，并打开Gradle Scripts\build.gradle(Module:app1.app) ，加入 节点

sourceSets{

    main{

        jniLibs.srcDirs "libs"

    }

}

如下图：

3、加完之后，有一个刷新（同步）的操作 ，之后在app下就可以看到jniLibs文件夹，如下：

通过JNI定义实现调用第三方库so如上面的native-lib.cpp文件