Customize shared element transition

To customize how the shared element transition animation runs, there are a few parameters that can be used to change how the shared elements transition.

Animation spec

To change the animation spec used for the size and position movement, you can specify a different boundsTransform parameter on Modifier.sharedElement(). This provides the initial Rect position and target Rect position.

For example, to make the text in the preceding example to move with an arc motion, specify the boundsTransform parameter to use a keyframes spec:

val textBoundsTransform = BoundsTransform { initialBounds, targetBounds ->
    keyframes {
        durationMillis = boundsAnimationDurationMillis
        initialBounds at 0 using ArcMode.ArcBelow using FastOutSlowInEasing
        targetBounds at boundsAnimationDurationMillis
    }
}
Text(
    "Cupcake", fontSize = 28.sp,
    modifier = Modifier.sharedBounds(
        rememberSharedContentState(key = "title"),
        animatedVisibilityScope = animatedVisibilityScope,
        boundsTransform = textBoundsTransform
    )
)
CustomizeSharedElementsSnippets.kt

You can use any AnimationSpec. This example uses a keyframes spec.

Resize mode

When animating between two shared bounds, you can set the resizeMode parameter to either RemeasureToBounds or ScaleToBounds. This parameter determines how the shared element transitions between the two states. ScaleToBounds first measures the child layout with the lookahead (or target) constraints. Then the child's stable layout is scaled to fit in the shared bounds. ScaleToBounds can be thought of as a "graphical scale" between the states.

Whereas RemeasureToBounds re-measures and re-layouts the child layout of sharedBounds with animated fixed constraints based on the target size. The re-measurement is triggered by the bounds size change, which could potentially be every frame.

For Text composables, ScaleToBounds is recommended as it'll avoid relayout and reflowing of text onto different lines. For bounds that are different aspect ratios, and if you'd like fluid continuity between the two shared elements, RemeasureToBounds is recommended.

The difference between the two resize modes can be seen in the examples that follow:

Skip to final layout

By default, when transitioning between two layouts, the layout size animates between its start and final state. This may be undesirable behavior when animating content such as text.

The following example illustrates the description text "Lorem Ipsum" entering the screen in two different ways. The first example the text reflows as it enters as the container grows in size, the second example the text does not reflow as it grows. Adding Modifier.skipToLookaheadSize() prevents the reflow as it grows.

Clip and overlays

An important concept when creating shared elements in Compose is that in order for them to share between different composables, the rendering of the composable is elevated into a layer overlay when the transition is started to its match in the destination. The effect of this is that it'll escape the parent's bounds and its layer transformations (for example the alpha and scale).

It will render on top of other non-shared UI elements, once the transition is finished, the element will be dropped from the overlay to its own DrawScope.

To clip a shared element to a shape, use the standard Modifier.clip() function. Place it after the sharedElement():

Image(
    painter = painterResource(id = R.drawable.cupcake),
    contentDescription = "Cupcake",
    modifier = Modifier
        .size(100.dp)
        .sharedElement(
            rememberSharedContentState(key = "image"),
            animatedVisibilityScope = this@AnimatedContent
        )
        .clip(RoundedCornerShape(16.dp)),
    contentScale = ContentScale.Crop
)
CustomizeSharedElementsSnippets.kt

If you need to ensure that a shared element never renders outside of a parent container, you can set clipInOverlayDuringTransition on sharedElement(). By default, for nested shared bounds, clipInOverlayDuringTransition uses the clip path from the parent sharedBounds().

To support keeping specific UI elements, such as a bottom bar or floating action button, always on top during a shared element transition, use Modifier.renderInSharedTransitionScopeOverlay(). By default, this modifier keeps the content in the overlay during the time when the shared transition is active.

For example, in Jetsnack, the BottomAppBar needs to be placed on top of the shared element until such time as the screen is not visible. Adding the modifier onto the composable keeps it elevated.

Sometimes you might want your non-shared composable to animate away as well as remain on top of the other composables before the transition. In such cases, use renderInSharedTransitionScopeOverlay().animateEnterExit() to animate the composable out as the shared element transition runs:

JetsnackBottomBar(
    modifier = Modifier
        .renderInSharedTransitionScopeOverlay(
            zIndexInOverlay = 1f,
        )
        .animateEnterExit(
            enter = fadeIn() + slideInVertically {
                it
            },
            exit = fadeOut() + slideOutVertically {
                it
            }
        )
)
CustomizeSharedElementsSnippets.kt

In the rare case that you'd like your shared element to not render in an overlay, you can set the renderInOverlayDuringTransition on sharedElement() to false.

Notify sibling layouts of changes to shared element size

By default, sharedBounds() and sharedElement() don't notify the parent container of any size changes as the layout transitions.

In order to propagate size changes to the parent container as it transitions, change the placeHolderSize parameter to PlaceHolderSize.animatedSize. Doing so causes the item to grow or shrink. All other items in the layout respond to the change.