ext sample. app level

build.gradle

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

android {
    compileSdkVersion rootProject.ext.compileSdkVersion
    defaultConfig {
        applicationId "com.example.koheiando.twittervolleysample"
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation "com.android.support:appcompat-v7:$appcompatV7Version"
    implementation "com.android.support.constraint:constraint-layout:$constraintVersion"
    implementation "com.android.support:design:$designVersion"
    implementation "android.arch.lifecycle:extensions:$lifecycleVersion"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutinesVersion"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutinesVersion"
    implementation "com.android.volley:volley:$volleyVersion"
    testImplementation "junit:junit:$junitVersion"
    androidTestImplementation "com.android.support.test:runner:$runnerVersion"
    androidTestImplementation "com.android.support.test.espresso:espresso-core:$espressoVersion"
}