FollowingSubspace
Android
```kotlin
@Composable
@ComposableOpenTarget(index = -1)
@ExperimentalFollowingSubspaceApi
public fun FollowingSubspace(
target: FollowTarget,
behavior: FollowBehavior,
modifier: SubspaceModifier = SubspaceModifier,
dimensions: TrackedDimensions = TrackedDimensions.All,
allowUnboundedSubspace: Boolean = false,
content: @Composable @SubspaceComposable SpatialBoxScope.() -> Unit,
)
```
Create a user-centric 3D space that is ideal for spatial UI content that follows a target.
Each call to `FollowingSubspace` creates a new, independent spatial UI hierarchy. It does **not**
inherit the spatial position, orientation, or scale of any parent `Subspace` it is nested within.
Its position in the world is determined solely by its `target` parameter. By default, this
Subspace is automatically bounded by the system's recommended content box, similar to [Subspace](/jetpack-compose/androidx.xr.compose/compose/composable-functions/Subspace).
When the target parameter is specified to be `FollowTarget.ArDevice`, the content will be
positioned relative the view of the AR device. This is sometimes referred to as head-locked
content. For this API, it is required for headtracking to not be disabled in the session
configuration. If it is disabled, this API will not return anything. The session configuration
should resemble `session.configure( config = session.config.copy(deviceTracking =
Config.DeviceTrackingMode.LAST_KNOWN) )` The `FollowTarget.ArDevice` is not compatible with
`FollowBehavior.Tight`. Combining these together will cause this composable to not be displayed.
For a near tight experience, use `FollowBehavior.Soft` with a low duration value such as
`FollowBehavior.Soft([FollowBehavior.Companion.MIN_SOFT_DURATION_MS])`
When the target parameter is specified to be `FollowTarget.Anchor`, the content will be
positioned around an anchor. This is useful for placing UI elements on real-world surfaces or at
specific spatial locations. The visual stability of the anchored content depends on the
underlying system's ability to track the `AnchorEntity`. For Creating, loading, and persisting
anchors, please check `androidx.xr.scenecore.AnchorEntity` for more information
This composable is a no-op in non-XR environments (i.e., Phone and Tablet).
## Managing Spatial Overlap
Because each call to any kind of Subspace function creates an independent 3D scene, these spaces
are not aware of one another. This can lead to a scenario where a moving `FollowingSubspace`
(like a head-locked menu) can intersect with content in another stationary Subspace. This overlap
can cause jarring visual artifacts and z-depth ordering issues (Z-fighting), creating a confusing
user experience. A Subspace does not perform automatic collision avoidance between these
independent Subspaces. It is the developer's responsibility to manage the layout and prevent
these intersections or to introduce custom hit handling.
### Guidelines for Preventing Overlap:
1. **Control Volume Size**: Carefully define the bounds of your Subspace instances. Instead of letting content fill the maximum recommended constraints, use sizing modifiers to create smaller, manageable content areas that are less likely to collide.
2. **Use Strategic Offsets**: Use `SubspaceModifier.offset` to position a Subspace. For example, a head-locked menu can be offset to appear in the user's peripheral vision, reducing the chance it will collide with central content.Also, consider placing different Subspace instances at different depths. This ensures that if they overlap, their z-depth ordering will be clear and predictable. Note, however, that while the visual ordering may be clear, Jetpack XR doesn't guarantee predictable interaction behaviors between UI elements in separate, overlapping Subspaces.
#### Parameters
| | |
| --- | --- |
| target | Specifies an area which the Subspace will move towards. |
| behavior | determines how the FollowingSubspace follows the target. It can be made to move faster and be more responsive. The default is FollowBehavior.Soft(). |
| modifier | The [SubspaceModifier](/jetpack-compose/androidx.xr.compose/compose/interfaces/SubspaceModifier) to be applied to the content of this Subspace. |
| dimensions | A set of boolean flags to determine the dimensions of movement that are tracked. Possible tracking dimensions are: translationX, translationY, translationZ, rotationX, rotationY, and rotationZ. By default, all dimensions are tracked. Any dimensions not listed will not be tracked. For example if translationY is not listed, this means the content will not move as the user moves vertically up and down. |
| allowUnboundedSubspace | If true, the default recommended content box constraints will not be applied, allowing the Subspace to be infinite. Defaults to false, providing a safe, bounded space. |
| content | The 3D content to render within this Subspace. |