Adding the Lifecycle Components

You will need a runtime dependency and an annotation processor, akin to how Room is set up:

dependencies {
  implementation "com.android.support:recyclerview-v7:28.0.0"
  implementation "com.android.support:support-fragment:28.0.0"
  implementation "android.arch.lifecycle:runtime:1.1.1"
  implementation "android.arch.lifecycle:common-java8:1.1.1"
  implementation "android.arch.core:runtime:1.1.1"
}

android {
    compileSdkVersion 28
    

  defaultConfig {
      minSdkVersion 21
      targetSdkVersion 28
  }

  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

However, making sense of the artifact versions — particularly when transitive dependencies come into play — will be difficult.

If your project directly or indirectly depends upon support-compat version 26.1.0 or higher, support-compat has a dependency on android.arch.lifecycle:runtime, for some version of that artifact. What version that is will depend on the version of support-compat:

In addition, we have a dependency on android.arch.lifecycle:common-java8, which provides better Java 8 support for the lifecycle system.

How these versions will work out in the future is anyone’s guess right now.