Kotlin unresolved reference in IntelliJ

问题:

I started off with the tutorial for learning Kotlin in IntelliJ.When I tried running the example i.e

fun main(args: Array<String>) {
 println("lol")
}

Execution is suspended with this messageError:(5, 5) Kotlin: Unresolved reference: println This is the first time I am using IntelliJ.I have never worked on a Java project either.Am I missing something?

Edit:I have seen the other question already.The answer is not valid for my situation.

回答1:

Your Intellij IDEA plugin and the Kotlin runtime/compiler that you use in the project need to match. For example if IDE plugin is Beta 1, but your Gradle/Maven project using M12, you'll have issues exactly as you described. So check that everything lines up.

If you still have issues, with some older plugins you need to clear the caches in Intellij IDEA (file menu, Clear Caches and Restart, select option to restart).

回答2:

If anyone stumbles across this and NEITHER Invalidate Cache or Update Kotlin's Version work:

1) First, make sure you can build it from outside the IDE. If you're using gradle, for instance:

gradle clean build

If everything goes well , then your environment is all good to work with Kotlin.

2) To fix the IDE build, try the following:

Project Structure -> {Select Module} -> Kotlin -> FIX

As suggested by a JetBrain's member here: https://discuss.kotlinlang.org/t/intellij-kotlin-project-screw-up/597

回答3:

In my case, it was a misconfigured IntelliJ instance.

Project Structure -> SDKs -> Remove and add the Java SDK again

回答4:

Ran into this issue. I had to add the following to my build.grade:

apply plugin: 'kotlin-android'

回答5:

For me, it was due to the project missing Gradle Libraries in its project structure.

Just add in build.gradle: apply plugin: 'idea'

And then run: $ gradle idea

After that gradle rebuilds dependencies libraries and the references are recognized!

回答6:

I tried everything: clean build folders, run gradle clean build, execute AS invalidate cache(x2), reinstall Kotlin plugin, restarting pc.

But in the end after doing all this it still didn't work, but doing also removal from project build.gradle of this line: apply plugin: 'kotlin-android-extensions', gradle sync and then re-adding worked

回答7:

Ok, i've been here a few times and not entirely sure how or why this happens but reading suggests its a Kotlin/JVM mismatch. I have tried a number of things mentioned on this page but not without complete success. This was the sort of symptom the IDE was displaying in the message panel after trying to run tests via the IDE. However the code panel has no red lines indicating that modules can't be found or imported or anything untoward.

My project (at time of writing this) is a gradle 4.10.2 kotlin 1.3 project in IntelliJ (IntelliJ IDEA 2018.2.5 (Ultimate Edition) Build #IU-182.4892.20, built on October 16, 2018)

For starters though, I invalidated caches and restarted. Then ran a gradle clean build. After rebuilding the project still no joy. I went into the project settings and noticed the compiler versions were not set to java 8, I set the Compiler/Kotlin/Target JVM Version and Compiler/Java/Project Byte Code to 1.8/8 (see below), then ran some tests in the IDE and we are back in business! References resolved in my case.

回答8:

Had the same with IDEA 14.1.5, Kotlin v.1.0.0-beta-1038-IJ141-17.
Kotlin gets its own list entry (like Java) when creating new project, but the only working config was:

New | Project | Java | "Kotlin (Java)" (make sure you have Project SDK configured, too)
use library: Create, "Copy to: lib".

回答9:

Sometimes in similar situations (I don't think it is your problem because your case is very simple) it's worth to check kotlin file package.

If you have Kotlin file within the same package and put there some classes and missed the package declaration it looks inside the IntelliJ that you have classes in the same package but without definition of package the IntelliJ shows you:

Error:(5, 5) Kotlin: Unresolved reference: ...

回答10:

A possible solution for standalone Kotlin projects is to include Kotlin standard libs explicitliy inside the root project.

To do that in IntelliJ IDEA:

• press Ctrl+Shift+A (Search actions or options)
• type in "Configure kotlin in project" and let it include standard libs for you

回答11:

Happened to me today.

My issue was that I had too many tabs open (I didn't know they were open) with source code on them.

If you close all the tabs, maybe you will unconfuse IntelliJ into indexing the dependencies correctly