android studio: add support for existing C ++ project

Beginning when creating a project and did not check "include C ++ support" options:

Late increased steps:

1. Copy the existing support CMakeLists.txt C ++ project files to the app directory under existing projects;

2. In the app / src / main directory under the new cpp folder;

3. Modify build.gradle file in the app directory, respectively, add "externalNativeBuild" item in defaultConfig braces braces and android in:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.yongdaimi.android.ffapitest"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-std=c++11"
            }
            NDK {
                abiFilters "armeabi-v7a"
            }
        }
        sourceSets {
            main {
                jniLibs.srcDirs=['libs']
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    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'
}

 Last sync files look like gradle, attention: ndk abiFilters and sourceSets not necessary, because I was quoted the other libraries so before adding the two words.