:sparkles: Animation API As per my understanding, `MutableTransitionState` (MTS) with `updateTransi...

# compose

[theapache64]

✨ Animation API

As per my understanding, MutableTransitionState (MTS) with updateTransition is only useful if we want to update the state within the composable. If we simply want to access the MTS#currentState , MTS#targetState and MTS#isIdle , we can use Transition#currentState, Transition#targetState and Transition#isRunning respectively. Please correct me if am wrong.

[theapache64]

In other words, is it okay to use transition object inside animationSpec like this?

[Doris Liu]

Actually MutableTransitionState can be created and accessed from anywhere such as your ViewModel, whereas updateTransition can only be invoked from composition. Here's an example of creating & manipulating MutableTransitionState from outside of composition: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/[…]se/animation/demos/AnimatedVisiblilityLazyColumnDemo.kt;l=115

It's best to read initialState & targetState in transitionSpec from the receiver AnimatedContentScope (which is an impl of Transition.Segment), instead of from the Transition directly. When seeking Transitions (e.g. for animation tooling), we'll be creating new Transition.Segment for the specific initial/target required by seeking, and call Transition.Segment.transitionSpec() to obtain the animations used in that segment. There's no guarantee that the Segment.initialState is always the same as Transition.currentState.

[theapache64]

Understood 👍

[Doris Liu]

We should probably include that in the documentation. 🙂

BTW, aside from MTS allowing instantiation outside of composition, MTS#targetState/currentState are the same as Transition#targetState/currentState.