error: package com.android.annotations does not exist

To automatically fix all android to androidx issues for React Native (prerequisite npx)

Add the following two flags to true in your gradle.properties file at ProjectFolder/android/gradle.properties

android.useAndroidX=true
android.enableJetifier=true

Execute

npm install --save-dev jetifier
npx jetify
npx react-native run-android

In your package.json add the following to scripts

  "postinstall" : "npx jetify"

More info at https://github.com/mikehardy/jetifier

Update: This is now in-built in react-native 0.60. If you migrate to react-native 0.60 you won't need this step. - https://facebook.github.io/react-native/blog/2019/07/03/version-60#androidx-support

Use implementation androidx.appcompat:appcompat:1.0.2 in gradle and then

change import android.support.annotation.Nullable; to import androidx.annotation.NonNull; in the classes imports