title: where to store gradle dependency versions
body: <p>I have looked online and come across two different ways of storing the gradle versions for an android app.  One is the <code>gradle.properties</code> and the other is the root <code>build.gradle</code> file under an ext object.  Both of these are accessible from all other modules.  I am just trying to figure out the difference between each and which one is recommended to use and why?</p>
  
  <p>build.gradle</p>
  
  <pre><code>ext {
      versionName = "1.10.10"
      androidGradleTools = "3.4.1"
      compileSdkVersion = 29
      minSdkVersion = 23
      targetSdkVersion = 29
      versionCode = 2
      appCompat = "1.1.0-rc01"
      archCore = "2.0.1"
      material = "1.1.0-alpha09"
      kotlinVersion = "1.3.31"
      kotlinExtensions = "1.1.0-rc01"
      constraintLayout = "1.1.3"
      awsAuth = "2.7.4"
      coordinatorLayout = "1.1.0-beta01"
      eventBus = "3.1.1"
      jUnit = "4.13-beta-3"
      testRunner = "1.2.0"
      espressoCore = "3.2.0"
      annotation = "1.1.0"
      lifecycleViewModel = "2.2.0-alpha02"
      lifecycleExtensions = "2.2.0-alpha02"
      roomVersion = "2.1.0"
      retrofit = "2.6.0"
      okHttp3 = "4.0.0"
      firebaseCommon = "11.4.2"
      crashlytics = "2.10.1"
      slf4Android = "0.1.5"
      butterknife = "10.1.0"
      rabbitMQ = "4.11.1"
      picasso = "2.5.2"
      gson = "2.8.5"
      javaPusher = "1.8.2"
      androidVolley = "1.0.19"
      multidex = "2.0.0"
      googlePlayCore = "1.6.1"
      volley = "1.0.19"
      navController = "2.2.0-alpha01"
      kotlinCoroutines = "1.1.1"
      ktor_version = "1.2.3"
      asyncHttp = "1.4.9"
  }
  </code></pre>
  
  <p>gradle.properties</p>
  
  <pre><code># Dependent library versions
  android_google_gson_version=2.7
  android_google_play_core_version=1.4.1
  eventbus_version=3.0.0
  squareup_retrofit2_version=2.1.0
  squareup_ok_http_version=3.3.1
  network_ok_http_logging_interceptor=3.3.1
  aws_sdk_auth_core_version=2.7.4
  fb_stetho_version=1.5.0
  fb_sdk_version=4.37.0
  picasso_lib_version=2.5.2
  crashlytics_lib_version=2.9.4@aar
  volley_lib_version=1.0.19
  butterknife_lib_version=8.8.1
  commons_io_lib_version=2.4
  simbio_encryption_lib_version=1.2.0
  anko_common_lib_version=0.8.3
  slf_4_android_logger_version=0.1.5
  </code></pre>