Android Studio CMake依赖第三方库

这里实现一个简单的功能在APP里调用libnative-lib.so里的add。libnative-lib.so去调用libthird.so里的third_add来实现

JniUtil 

public class JniUtil {
    static {
        System.loadLibrary("native-lib");
        System.loadLibrary("third");
    }

    public  static native int add(int x,int y);
}

libnative.cpp

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

extern "C"{
JNIEXPORT jint JNICALL
Java_com_test_ndkthirdso_JniUtil_add(JNIEnv *env, jclass type, jint x, jint y) {

    // TODO
    return  third_add(x,y);
}

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

}

这里编译好一个自己写一个libthird.so库实现一个加法功能

third.h

#ifndef __H_THIRD
#define __H_THIRD

#ifdef __cplusplus
extern "C" {
#endif

int third_add(int a, int b);

#ifdef __cplusplus
}
#endif

#endif // __H_THIRD

third.cpp

#include <jni.h>
#include "third.h"

int third_add(int a, int b){
return a+b;
};

生成如下

项目工程结构如下：

CMakeLists.txt

cmake_minimum_required(VERSION 3.4.)
add_library(native-lib
             SHARED
             src/main/cpp/native-lib.cpp )

find_library(log-lib
              log )
#动态方式加载 third是libxxxx.so的xxxx部分
add_library(third SHARED IMPORTED)

SET(third_path ${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libthird.so)

#设置要连接的so的相对路径，${ANDROID_ABI}表示so文件的ABI类型的路径,这一步引入了动态加入编译的so
set_target_properties(third  PROPERTIES IMPORTED_LOCATION ${third_path})

MESSAGE(STATUS “src  third so path= ${third_path}”)

#配置加载native依赖
include_directories( ${ProjectRoot}/app/src/main/cpp/external/include )

target_link_libraries(native-lib third ${log-lib} )

gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"
    defaultConfig {
        applicationId "com.test.ndkthirdso"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-frtti -fexceptions"
            }
        }
        ndk {
            // Specifies the ABI configurations of your native
            // libraries Gradle should build and package with your APK.
            abiFilters  'armeabi', 'armeabi-v7a'
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
}