[Compose Snippet]Neomorphic Button 🔘
Implementing Neomorphic views (hopefully I haven’t slaughtered the terminology here 😅) is explained to a greater clarity in this awesome article by gihub/fornewid.
As a TLDR; to the article, the impression of smooth elevation and subtle depression upon ‘pressing’ is achieved by animating two separate blur-edged shapes of two colors, a lighter shade and a darker shade of the general surface color.
Below is a demonstration of the same implementation above but, without the center gray circle at the top.
Basically, we diagonally displace the two blurred circles relative to the center one.
The diagonal displacement is achieved by animation frameworks provided in Compose. Another thing to notice here is that, the displacement animations are triggered only when we ‘touch’ the view or remove our ‘touch’. This calls for a little different approach than simply triggering the animation in onClick() callbacks.
Modifier.pressIndicatorGestureFilter()
With Compose we have a variety of GestureFilters at our disposal. In this particular case we’re going to usePressIndicatorGestureFilter , whose documentation reads,
This gesture detector has callbacks for when a press gesture starts and ends for the purposes of displaying visual feedback for those two states.fun Modifier.pressIndicatorGestureFilter(..)
Going through the above snippet,
[1] buttonState serves the purpose of triggering a recomposition of @Composable NeomorphButton() when its value is changed.
[2] Given a change in buttonState value, we need to trigger an animation from the previous state to the current value of buttonState, hence the toggle logic.
[3] For proper understanding of implementingtransition() in Compose, I would highly recommend this Raywenderlich tutorial. As a summary, transition() is Compose’s state-animation framework. In this case, transition from PRESSED to IDLE or vice versa, will alter buttonStateProgress value ‘using’ the predefined tween() animator.
[4] As we toggle the buttonState on interacting with @Composable NeomorphButton(), we have to toggle the ‘from’ & ‘to’ states of transition() This will ensure that the animation reverses on toggling buttonState.
[5] Implementing Modifier.pressIndicatorGestureFilter(), we listen to the onStart() and onStop() callbacks and alter buttonState value accordingly.
Pass the TransitionState
The TransitionState obtained from defining the transition() in @Composable NeomorphButton() is then passed on as a parameter to @Composable CircleNeomorph(). As per documentation, any child @Composable depending on a TransitionState will have their recomposition triggered whenever, theTransitionState value changes.
[transition] takes a transition definition, a target state and child composables.
These child composables will be receiving a [TransitionState] object as an argument, which captures all the current values of the animation. Child composables should read the animation values from the [TransitionState] object, and apply the value wherever necessary.@Composable
fun <T> transition(..): TransitionState
[1] From the TransitionState passed on, we obtain the buttonStateProgress (animated in its parent@Composable NeomorphButton()) which is used to calculate the x & y alignment biases of the blurred circles. As the value of buttonStateProgress animates from PRESSED to IDLE or vice versa, so do the alignment biases.
[2] This is the upper blurred circle with the lighter shade. I’m achieving blur here by using RadialGradient brush for Modifier.background().
[3] Since the upper circle will be displaced towards top-left, both of its alignment bias values should be negative & equal.
[4] This is the lower blurred circle with the darker shade.
[5] Since the lower circle will be displaced towards bottom-right, both of its alignment bias values should be positive & equal.
[6] This is the central circle whose color matches the overall surface color.
There you have it, a simple implementation of Neomorphic animation in Jetpack Compose. 😀
My implementation may not be the most optimised or perfect, but hopefully it could help you with few references to Compose implementations.
I’m documenting all my snippets at a single place. Check out Jetpack Compose over a Cup of Hot Chocolate ☕️
