flutter_gauge widget won't update index value on setState
After toying around with the package in a new flutter project I have been unable to get it to update after creation using many different ways and after looking at all available documentation for the package at this time, I am not sure it is meant to be used in this way. There are no examples of changing the gauge after it is built so it appears to be an immutable widget.
I did some digging and the syncfusion_flutter_gauges looks like a promising alternative and this article goes over how to do what I think you are attempting in your project. Hope it helps
I think I found the solution. This worked for me. Open flutter_gauge.dart and remove all the commented section. Reinstall back your app and refresh your data. This steps works for me.