For API 26+ default Android application template defines another icon resource folder
mipmap-anydpi-v26
That folder (usually) contains two xml
files ic_launcher
and ic_launcher_round
that match icon resources declared in manifest for API 26+
Content of those files looks like following:
<?xml version="1.0" encoding="utf-8"?>
<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
<background android:drawable="@drawable/ic_launcher_background"/>
<foreground android:drawable="@drawable/ic_launcher_foreground"/>
</adaptive-icon>
In order to have your icon you also need to change all drawables (in all density buckets) listed there - namely ic_launcher_background
and ic_launcher_foreground
Or you can just delete that folder, in which case android will fallback to using your png icons, but they will not appear as-is and will be commonly drawn on top of white background.
You can read more at: Adaptive icons