Add a MotionLayout that animates between changing ConstraintSets

[bentrengrove]

This PR adds a MotionLayout that animates between changing ConstraintSets. This provides an easy way to animate layouts that change without having to worry about updating a progress variable yourself.

On recomposition if the constraint set has changed the changes will be animated using the animationSpec. On completion of the animation the finishListener will fire. This mimics the animateValueAsState API that already exists in Compose.

I changed MotionExample1 to use the new API and to provide an example of it's usage.

Happy to make changes and thanks for your help!

[camaelon]

Thanks! I think that makes sense, with one caveat, could we have it folded in the MotionLayout function that takes two constraintsets instead? with moving the 2nd constraintset parameter as optional. This way we ensure that API doesn't diverge too much (i.e not certain we should have animationSpec / finishedListener here)

[bentrengrove]

Folding it in to one would also involve making the progress parameter optional as well somehow which could be confusing.

Changing the animationSpec is also something I think that is quite useful, I almost didn't include the finishListener but just thought it would be good to match the other APIs for consistency. Happy to remove it if you don't think it's needed.

[camaelon]

Ok, after discussing with John, let's:

• let's name it as ConstraintLayout, not MotionLayout
• move it into the current ConstraintLayout function that takes a constraintset, and add an animate = false parameter

[bentrengrove]

Will do. And remove animationSpec and listener right?

…

On Fri, 30 July 2021, 11:17 am Nicolas Roard, ***@***.***> wrote: Ok, after discussing with John, let's: - let's name it as ConstraintLayout, not MotionLayout - move it into the current ConstraintLayout function that takes a constraintset, and add an animate = false parameter — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#359 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAEX5L4UOBUKP46MPOBW7LT2H4UNANCNFSM5BHKLO5Q> .

[camaelon]

I think if we merge it in that ConstraintLayout function, it's probably fine to have the animationspec and simple callback as optional parameters.