Question 1

When do you use FutureBuilder, and when not?

Accepted Answer

Draw the line. I use it for a one-off load belonging to a single screen — a detail page, a simple list — where all four states can be handled without adding a layer. I do not when the data is needed on several screens, when caching or retry logic is involved, or when the state must survive the screen closing; those call for Riverpod or Bloc. Finish with the trap: creating the future inside build means a new request on every rebuild, so I hold it in State and recreate it deliberately for retry.

Question 2

What is the difference between StreamBuilder and a manual listen?

Accepted Answer

StreamBuilder manages the subscription itself: it cancels when the widget leaves the tree and detaches from the old stream when given a new one. With a manual listen all of that is yours, and a forgotten cancel() in dispose() keeps the State alive — the classic leak. The criterion: if the result is rendered directly, use StreamBuilder; if you need a side effect (navigation, a SnackBar, analytics), use a manual listen, because a builder is no place for side effects — it can run again on any rebuild.

Question 3

How do you handle all four states with FutureBuilder?

Accepted Answer

I use two fields of the snapshot. connectionState == waiting → a loading indicator. hasError → the error state with a human message and a retry button. hasData with an empty result → an empty state, explanatory rather than presented as a failure. Otherwise → the data. One detail matters: the order of the hasData and hasError checks, and remembering to test for an empty result separately — that is the case most often skipped. For retry you have to create a new future via setState, since FutureBuilder offers nothing for it.

Tool	Where it fits	Weakness
`FutureBuilder`	A one-off load on a simple screen	The recreated-future trap; retry is awkward
`StreamBuilder`	A continuous stream: real-time data, notifications	You must mind the subscription lifetime
State management (Riverpod/Bloc)	Retry, caching, shared state	An extra layer and setup cost

FutureBuilder, StreamBuilder and the alternatives

📚 Sources and documentation