Problem Statement
How do you effectively use StreamBuilder in Flutter? Explain handling different stream states.
Explanation
Pass the stream to StreamBuilder's stream parameter, ensuring it's the same stream instance across rebuilds just like FutureBuilder. Store the stream in State or receive it through constructor, never create streams in build method. StreamBuilder automatically manages subscription - subscribing when widget is inserted and unsubscribing when removed, preventing memory leaks.
In the builder function, handle different states using AsyncSnapshot properties. When connectionState is waiting and no data yet, show loading indicator. When hasData is true, display snapshot.data. When hasError, show error UI with snapshot.error details. For streams that emit multiple values, each emission triggers a rebuild with new data, making StreamBuilder perfect for real-time updates.
Use initialData parameter to provide initial value shown before the first stream emission, preventing loading states for streams that should immediately have data. This is useful for streams built on top of existing data or when you want to show cached data while waiting for updates. StreamBuilder intelligently rebuilds only when necessary based on stream emissions.
For Firestore or other database streams, StreamBuilder is the standard pattern - create a stream query in State, pass it to StreamBuilder, and your UI automatically updates when data changes. Combine multiple streams using stream transformers or RxDart for complex reactive UIs. StreamBuilder is powerful for building reactive applications where UI automatically reflects backend data changes in real-time.
