build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    ext.kotlin_version = '1.5.0'

    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:7.0.3'
        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.31'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

// added by me===========================
ext {
    roomVersion = '2.3.0'
    lifecycleVersion = '2.3.1'
    activityVersion = '1.2.3'
    appCompatVersion = '1.3.0'
    constraintLayoutVersion = '2.0.4'
    coreTestingVersion = '2.1.0'
    coroutines = '1.5.0'
    materialVersion = '1.3.0'
}