title: ERROR: Module 'app': platform 'android-28' not found. and Design editor is unavailable until after a successful project sync
body: <p>So, I am new here just installed Android Studio and then wanted to create a basic activity. But the thing is they want me to install the SDKs and Haxm which is not being installed through SDK manager. I have tried a lot and have used all the ways stated in Stack-overflow to get rid of this but none of their ways has functioned.</p>
  
  <p><a href="https://i.stack.imgur.com/EiWme.png" rel="noreferrer"><img src="https://i.stack.imgur.com/EiWme.png" alt="enter image description here"></a></p>