ViewStateCache

@WorkflowUiExperimentalApi

Handles persistence chores for container views that manage a set of Named renderings, showing a view for one at a time -- think back stacks or tab sets.

This class implements Parcelable so that it can be preserved from a container view's own View.saveHierarchyState method. A simple container can return SavedState from that method rather than creating its own persistence class.

Container views using this class must call attachToParentRegistry and detachFromParentRegistry when they are attached and detached, respectively.

Constructors

ViewStateCache

fun ViewStateCache()

Types

CREATOR

object CREATOR : Parcelable.Creator<ViewStateCache>

SavedState

class SavedState : View.BaseSavedState

Convenience for use in View.onSaveInstanceState and View.onRestoreInstanceState methods of container views that have no other state of their own to save.

Functions

attachToParentRegistry

fun attachToParentRegistry(key: String, parentOwner: SavedStateRegistryOwner)

Must be called whenever the owning view is attached to a window. Must eventually be matched with a call to detachFromParentRegistry.

describeContents

open override fun describeContents(): Int

detachFromParentRegistry

fun detachFromParentRegistry()

Must be called whenever the owning view is detached from a window. Must be matched with a call to attachToParentRegistry.

prune

fun prune(retaining: Collection<Named<*>>)

To be called when the set of hidden views changes but the visible view remains the same. Any cached view state held for renderings that are not compatible those in retaining will be dropped.

restore

fun restore(from: ViewStateCache)

Replaces the state of the receiver with that of from. Typical usage is to call this from a container view's View.onRestoreInstanceState.

update

fun update(retainedRenderings: Collection<Named<*>>, oldViewMaybe: View?, newView: View)

writeToParcel

open override fun writeToParcel(parcel: Parcel, flags: Int)