BuildContext vs State Context

Question

I've noticed that a state's build method passes in a BuildContext, and I've also noticed that the State itself also has a member called context. I was wondering when it's appropriate to use the BuildContext, and when is it appropriate to use the member variable? Are they interchangeable?

Are there times when using one over the other can cause errors and how do we take measures to insure we don't do this?

Answer 1

From the flutter documentation for State and the build function:

The BuildContext argument is always the same as the context property of this State object and will remain the same for the lifetime of this object. The BuildContext argument is provided redundantly here so that this method matches the signature for a WidgetBuilder.

Answer 2

They are strictly equal.

It may not be obvious, but the BuildContext passed as parameter to build never ever change.

The context field of State is only pointing to that constant BuildContext. Why a duplicate ? Because StatefulWidgets tend to update over time. So you may need to access this BuildContext inside methods such as didUpdateWidget.

StatelessWidget doesn't need that because it only as a build method.