Android Studio 3.1: Erroneous unresolved references in editor

Kotlin Programming

Question or issue of Kotlin Programming:

I’m running Ubuntu 17.10, and I’ve just updated Android Studio from version 3.0.1 to 3.1. Here’s the version information in Help -> About:

Android Studio 3.1
Build #AI-173.4670197, built on March 22, 2018
JRE: 1.8.0_152-release-1024-b01 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 4.13.0-37-generic

Unfortunately, while the IDE was able to resolve android-specific references before in my (first ever) Kotlin project, in the new version it appears unable to. Here’s a screenshot showing what I mean:

In Android Studio 3.1, it’s claiming that core Android functions such as setContentView() don’t exist, and keeps prompting me to create an abstract function for it – which I clearly don’t want to do. However, if I hit the build button, I get a BUILD SUCCESSFUL in 8s.

Does anyone know why my editor is doing this, and how I get get Android-related functions and classes to resolve correctly again?

Edit: Update: I’ve got more information on the issue now, but it’s still not resolved:

How to solve this issue?

Solution no. 1:

  1. Exit Studio.
  2. Delete .idea/ (seems to me that’s most important), build/, app/build directories.
  3. Start Studio
  4. Set Settings -> Build -> Gradle settings back (last stable Gradle local distribution in my case).
  5. Clean&rebuild project.

Helps me.

Solution no. 2:

Delete {projectDir}/.idea/libraries, then go to File -> Sync Project with Gradle Files.

Solution no. 3:

I had the same problem on Android Studio 3.2.1.

The solution was to use stable ‘’, not alpha…

In the project build.gradle change the version like the code below (or if there is a newer stable version)

dependencies {
  classpath ''

If this doesn’t solve your problem than in File >> choose Invalidate caches/Restart… and on the next dialog choose Invalidate and Restart

1 step

2 step

Solution no. 4:

I tried all the solutions proposed here but they did not work. What worked for me was to disable and then re-enable the Kotlin plugin.

Solution no. 5:

I had the same problem. None of the “fixes” listed above helped.

Just run in a terminal:

./gradlew --stop
./gradlew --rerun-tasks assemble{flavour}

For example:

./gradlew --stop
./gradlew --rerun-tasks assembleDevDebug

Solution no. 6:

I had a very similar issue:

Layout resources (ie: activity_view.xml) that worked fine would all of a sudden not be detected or show up in the autocomplete lists, etc.

I tried all these “delete .idea folder/invalidate caches/restart Android studio” solutions and nothing worked..

Solution that worked:

Turned out that an import statement of the entire R package (import android.R) had at some point been added to the import statements and was somehow creating the issue (for specific layout resources only for some bizarre reason)

Removing import android.R instantly resolved the issue, and putting it back recreated it instantly as well.

Hope that helps any that come across this post for the same/similar reason

Solution no. 7:

If it happens to you after refactoring, and you’ve tried all the mentioned below (I will elaborate the list in a moment), try going to the class which has unresolved references and delete all its imports.
Then do the imports again, making sure you import the correct classes.

I tried the following which didn’t worked for me:

  • Invalidate Cache and restart Android Studio
  • Delete .build, app/build, and .idea
  • Sync Gradle files
  • Enable and Disable the Kotlin plugin.
  • Clean/Rebuild project
  • Restart my pc (MacOS).

Solution no. 8:

For me this step works :

I) Delete .idea folder from the android studio

II) Go to File > Invalidated caches/ Restarts

III) It will ask you to confirm and click on invalidate and restart.

IV) Go to Build > Clean project

V) Go to Build > Rebuild project

Try with this.

Happy Coding..!

Solution no. 9:

It helped when I deleted Android Studio and installed again. The advices above didn’t help.

Solution no. 10:

What helped me was
Using AS 3.6.3
I go to build.gradle (module: app)
change the buildToolsVersion from “29.0.3” to “28.0.3”
sync my project and it worked

I think there was something wrong with the 29.0.3 version.

I uninstall the 29.0.3 version and install it again and use it.
29.0.3 version is working perfectly for me

Solution no. 11:

Make sure you have not import android.R in any of your activities/fragments. This can happened when Android Studio tries to convert code from Java to Kotlin.

Delete this line and try to run your project.

enter image description here

Solution no. 12:

Goto File->Invalidate Cache/Restart works for me

Solution no. 13:

Read till the end 🙂

Surprisingly after so many answers, none of them worked for me.
I figured out the issue was with the android tools version and gradle distribution.

I upgraded classpath from


to ''

and also upgraded distributionUrl from


to distributionUrl=https\://

So, if clean/build, invalidating cache, deleting .idea doesn’t work for you. Please try upgrading (or downgrading if your recent change caused this issue) these versions.

Hope this helps!