alt Hacker NewsIt is basically a revamped Java.
Google lost the opportunity to actually make it take off, had they replaced the Java stack with Dart, instead of staying in the Java world and adopt Kotlin.
However the Android team was never a great supporter from Dart in first place, hence why you won't find anything Dart on https://developer.android.com.
Google uses Flutter/Dart for their own apps fairly frequently. Obviously not the right choice for the most complex apps. Android system programming and cross platform apps are use cases that are divergent enough that trying to smash them together would result in nobody being happy about the outcome.