Although I did this solution which is in stackoverflow, the icon still the same.
<meta-data android:name="com.google.firebase.messaging.default_notification_icon"
android:resource="@mipmap/ic_launcher" />
here top icon:
and when I slide top bar, I see this:
Where is the problem? I also use this website for creating transparent icon: https://jgilfelt.github.io/AndroidAssetStudio/icons-notification.html#source.space.trim=1&source.space.pad=0&name=ic_stat_ic_launcher
Also my res file like this right now (drawable folders from above link):
The icon to be used for notifications must be white-colored and with transparent background else it will show a grey-colored box.
You can check out this article to know more.
I had the same problem and resolved it by making changes to the icon image.