Auto complete not working in android studio

I am a starter in android development and I started off with eclipse.. But it started giving lot of problems. So I switched to android studio. Got it set up successfully and for couple of weeks it was ok. Now, for some reason, the auto complete feature is not working. It is not giving any choices while typing, so I tried ctrl-enter. It says no suggestions. I browsed through similar queries and tried the following.

1. Disabling Power Save in File menu.
2. Checking basic complete and smart type completion in IDE settings (editor)
3. Invalidate caches and restart.

But non of these seems to work.

Try with CTRL + space and you will get the drop down .

These following steps are working for me:

1. Close android studio
2. Go to path/.AndroidStudio3.5/system/ delete caches folder
3. Start Android Studio

I had the same issue and solved it. Go File> Invalidate Caches / Restart... > Click at Invalidate and Restart

Then you can also check if Power Save Mode on File menu is disabled.

Source: Android Studio - Auto complete and other features not working

You should Try this way File->Invalidate Caches/Restart or you can find solution by using below link

https://stackoverflow.com/a/58214439/11404883

In my case on Android Studio Artic Fox edition there were strange problems with autocompletion and suggestions because of old version of Gradle plugin. I have updated to

    classpath 'com.android.tools.build:gradle:4.1.1'
    classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.21'

and it worked as expected. Hope it will be helpful for new visitors like in my case it would.