android/app/build.gradle

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

android {
  compileSdkVersion 30
  buildToolsVersion "30.0.2"

  defaultConfig {
    applicationId "com.flatbuffers.app"
    minSdkVersion 16
    targetSdkVersion 30
    versionCode 1
    versionName "1.0"

    compileOptions {
      sourceCompatibility JavaVersion.VERSION_1_8
      targetCompatibility JavaVersion.VERSION_1_8
    }

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    externalNativeBuild {
      cmake {
        arguments "-DFLATBUFFERS_SRC=${rootProject.projectDir}/.."
      }
    }
  }

  buildTypes {
    release {
      minifyEnabled false
      proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
  }

  ndkVersion "21.3.6528147"
  externalNativeBuild {
    cmake {
      path "src/main/cpp/CMakeLists.txt"
    }
  }

  task generateFbsCpp(type: Exec) {
    def inputDir = file("$projectDir/src/main/fbs")
    def outputCppDir = file("$projectDir/src/main/cpp/generated/")
    def fbsFiles = layout.files { file(inputDir).listFiles() }.filter { File f -> f.name.endsWith(".fbs") }.toList()
    ignoreExitValue(true)

    standardOutput = new ByteArrayOutputStream()
    errorOutput = new ByteArrayOutputStream()
    def commandLineArgs = ['flatc', '-o', outputCppDir, '--cpp']
    fbsFiles.forEach{
      commandLineArgs.add(it.path)
    }
    commandLine commandLineArgs

    doFirst {
      delete "$outputCppDir/"
      mkdir "$outputCppDir/"
    }
    doLast {
      if (execResult.getExitValue() != 0) {
        println(standardOutput.toString())
        throw new GradleException("flatc command line failed")
      }
    }
  }

  task generateFbsKotlin(type: Exec) {
    def inputDir = file("$projectDir/src/main/fbs")
    def outputKotlinDir = file("$projectDir/src/main/java/generated/")
    def fbsFiles = layout.files { file(inputDir).listFiles() }.filter { File f -> f.name.endsWith(".fbs") }.toList()
    ignoreExitValue(true)

    standardOutput = new ByteArrayOutputStream()
    errorOutput = new ByteArrayOutputStream()
    def commandLineArgs = ['flatc', '-o', outputKotlinDir, '--kotlin']
    fbsFiles.forEach{
      commandLineArgs.add(it.path)
    }
    commandLine commandLineArgs

    doFirst {
      delete "$outputKotlinDir/"
      mkdir "$outputKotlinDir/"
    }
    doLast {
      if (execResult.getExitValue() != 0) {
        println(standardOutput.toString())
        throw new GradleException("flatc command line failed")
      }
    }
  }

  afterEvaluate {
    android.applicationVariants.all { variant ->
      variant.javaCompiler.dependsOn(generateFbsKotlin)
      variant.javaCompiler.dependsOn(generateFbsCpp)
    }
  }

  flavorDimensions "stl-variant"
  productFlavors {
    gnustl {
      dimension "stl-variant"
      applicationIdSuffix ".gnustl"
      versionNameSuffix "-gnustl"
      externalNativeBuild {
        ndkBuild {
          arguments "APP_STL=gnustl_static"
        }
      }
    }
    libcpp {
      dimension "stl-variant"
      applicationIdSuffix ".libcpp"
      versionNameSuffix "-libcpp"
      externalNativeBuild {
        ndkBuild {
          arguments "APP_STL=c++_static"
        }
      }
    }
  }
}

dependencies {
  implementation fileTree(dir: "libs", include: ["*.jar"])
  implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
  implementation 'androidx.core:core-ktx:1.3.2'
  implementation 'androidx.appcompat:appcompat:1.2.0'
  implementation 'com.google.flatbuffers:flatbuffers-java:2.0.0'

}