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androidkotlinkotlin-extension

Kotlin Extension Functions suddenly require api level 24

I just noticed this lint error:

Call requires API Level 24 (current min is 19) java.util.map#foreach

when I use the extension function forEach on a MutableMap in Kotlin. This didn't happen when I wrote the line, but its there now. And I'm not seeing this error on my other machine.

Solution

  • What you are using is not kotlin.collections.MutableMap.forEach.

    What you are using seems to be Map.forEach in Java 8.

    Refer to this article: http://blog.danlew.net/2017/03/16/kotlin-puzzler-whose-line-is-it-anyways/

    This seems to be a common mistake.

    Java 8 is well-supported from Android API level 24.

    For short, do not use forEach like map.forEach { t, u -> Log.i("tag", t + u) } (this is using Java 8 API, which does not work for Android API level <= 23).
    Use it like map.forEach { (t, u) -> Log.i("tag", t + u) } (this is using Kotlin API).
    (Not two parameters. Just one parameter that is a pair.)