The EPO has long had the best API for patent data/process access. I you want a free Flutter widget (or app) to build on use the contact form on the site.
Great set of refs and links … although a few seem for Android than DART.
Flutter is out of Beta … so we have Flutter 1.0 using Dart 2.1 as its default programming language. Here is a collection of articles on the release. The best: Everything That Google Announced About the Flutter 1.0 Others: Flutter 1.0 Is Now Available: Stable
Some Android Studio update fallout left a very pesky problem with a new Gradle build error issue. Finally found a simple fix:
Another web page collection with good basic examples.
Some more good articles on flutter development.
I have long sought an analysis of the ROI for Object Oriented Programming (OOP) … as it seems like a long term productivity booster. Lots of folks say it is needed to improve long term app/application maintenance. Great. Search for some studies of actual outcomes:
Hundreds of Flutter ready packages ready to jump start some complex functionality. Check it out at: https://pub.dartlang.org/packages
Great set of front screens and descriptions to show what is possible using flutter. Of course you need to load it on your phone to experience their functionality. Click here: https://itsallwidgets.com/
A very nice and recent article (June 2018) with some great visuals that really de-tangle some of the relationships between state, context and widgets. Nice code samples as well. Looks like the beginning of a nice book on the subject.