[JNI]add prebuilt shared library

1. library 추가시, 아래와 같이 armeabi-v7a로 구성하지 않으면 apk 빌드시 포함되지 않으므로 반드시 추가해 줄 것.

(ndk build시 arch 구분없이 모두 포함하도록 구성하는게 나을듯)

2. 각자 환경에 맞도록 빨간색으로 된 부분을 추가.

app gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "simplendk.android.com.ndksample"
        minSdkVersion 25
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
        ndk{
            abiFilters 'armeabi-v7a'
        }

    }
    sourceSets {
        main{
        // let gradle pack the shared library into apk
            jniLibs.srcDirs = ['src/main/cpp/libtest']
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "src/main/cpp/CMakeLists.txt"
        }
    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.1'
    implementation 'com.android.support:design:27.1.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

3. CMakeLists.txt 수정

cmake_minimum_required(VERSION 3.4.1)


add_library(
             native-lib

             SHARED

             native-lib.cpp )


add_library(test_jni SHARED IMPORTED)

set_target_properties(
                    test_jni

                    PROPERTIES IMPORTED_LOCATION

                    ${CMAKE_SOURCE_DIR}/libtest/${ANDROID_ABI}/libtest_jni.so )

#include_directories(${CMAKE_SOURCE_DIR}/libtest/include/)
include_directories(${CMAKE_SOURCE_DIR}/libtest/include/)

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(
                       native-lib

                       test_jni

                       ${log-lib}  )

하기 링크 참조

https://developer.android.com/studio/projects/add-native-code?hl=ko#create-cmake-script

https://proandroiddev.com/android-ndk-how-to-integrate-pre-built-libraries-in-case-of-the-ffmpeg-7ff24551a0f