StateFlow กับ SharedFlow

To stream live data into Compose you use a hot flow that stays active and emits whether or not anyone is currently collecting it.

A StateFlow always holds exactly one current value. New collectors immediately receive that latest value, which is perfect for screen state. 📦

Because StateFlow caches one item, you can read its current value synchronously through the value property without collecting.

A StateFlow only emits when the value actually changes. Setting it to the same value again sends nothing to collectors.

A SharedFlow broadcasts events to many collectors but holds no required current value. It is built for things that happen, not state that is.

A SharedFlow can replay a few past emissions to late collectors. With replay zero, new collectors only see future events.

Unlike StateFlow, a SharedFlow emits every value you send, even repeats. Two identical taps fire two separate events.

The rule of thumb: use StateFlow for what the screen looks like, and SharedFlow for one-time things like a navigation or a toast.

Keep a private mutable flow inside the ViewModel and expose a read-only one. The UI observes but cannot mutate it.

A StateFlow must start with an initial value, so the UI always has something to show. A SharedFlow can start empty.

You turn either flow into Compose state with a collector. For a StateFlow the screen has data immediately on first frame.

Match each flow to its purpose.

Nice! StateFlow caches one current value for screen state, while SharedFlow broadcasts repeatable events with an optional replay buffer. 🎯