Why do most animation APIs work pixel-based? and given the fact that units in Android are often give...

# compose

[Mehdi Haghgoo]

Why do most animation APIs work pixel-based? and given the fact that units in Android are often given in d.p, what is the best practice for creating accurate animations?

[Bryan Herbst]

Sounds like you are looking for animateDpAsState() 🙂

[Bryan Herbst]

Animations at some point need to work in pixels, because fundamentally that is what we are drawing on screen. There are helpers like animateDpAsState() that do some of that conversion for us though.

[Mehdi Haghgoo]

animateDpAsState is nice, but imagine the time we are working with gesture detection APIs like draggable or animateScrollTo, which take pixel parameters.

[Felix Schütz]

You can always use LocalDensity.current to convert between dp and px

[Felix Schütz]

https://developer.android.com/reference/kotlin/androidx/compose/ui/unit/Density

[Doris Liu]

Why do most animation APIs work pixel-based?

I'm assuming this is referring specifically to layout animations. Layout sizes can be defined with dp or pixel (for custom layouts). Therefore if we had to pick one unit to support, pixel would be more accurate.

and given the fact that units in Android are often given in d.p, what is the best practice for creating accurate animations?

Using LocalDensity.current for dp <-> px conversion would be my recommendation as well. 🙂

[Doris Liu]

For the non-layout animations, such as animate*AsState, Transition.animate* or Animatable, Dp is supported out of the box.