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SavedStateRegistry

class SavedStateRegistry
kotlin.Any
   ↳ androidx.savedstate.SavedStateRegistry

An interface for plugging components that consumes and contributes to the saved state.

This objects lifetime is bound to the lifecycle of owning component: when activity or fragment is recreated, new instance of the object is created as well.

Summary

Nested classes

abstract

Subclasses of this interface will be automatically recreated if they were previously registered via {runOnNextRecreation(Class)}.

abstract

This interface marks a component that contributes to saved state.

Public methods

Bundle?

Consumes saved state previously supplied by SavedStateProvider registered via registerSavedStateProvider(String, SavedStateProvider) with the given key.

Boolean

Returns if state was restored after creation and can be safely consumed with consumeRestoredStateForKey(String)

Unit

Registers a SavedStateProvider by the given key.

Unit

Executes the given class when the owning component restarted.

Unit

Unregisters a component previously registered by the given key

Public methods

consumeRestoredStateForKey

@MainThread @Nullable fun consumeRestoredStateForKey(@NonNull key: String): Bundle?

Consumes saved state previously supplied by SavedStateProvider registered via registerSavedStateProvider(String, SavedStateProvider) with the given key.

This call clears an internal reference to returned saved state, so if you call it second time in the row it will return null.

All unconsumed values will be saved during onSaveInstanceState(Bundle savedState)

This method can be called after super.onCreate(savedStateBundle) of the corresponding component. Calling it before that will result in IllegalArgumentException. Lifecycle.Event#ON_CREATE can be used as a signal that a saved state can be safely consumed.

Parameters
key String: a key with which SavedStateProvider was previously registered.
Return
Bundle?: S with the previously saved state or null

isRestored

@MainThread fun isRestored(): Boolean

Returns if state was restored after creation and can be safely consumed with consumeRestoredStateForKey(String)

Return
Boolean: true if state was restored.

registerSavedStateProvider

@MainThread fun registerSavedStateProvider(@NonNull key: String, @NonNull provider: SavedStateRegistry.SavedStateProvider): Unit

Registers a SavedStateProvider by the given key. This savedStateProvider will be called during state saving phase, returned object will be associated with the given key and can be used after the restoration via consumeRestoredStateForKey(String).

If there is unconsumed value with the same key, the value supplied by savedStateProvider will be override and will be written to resulting saved state.

if a provider was already registered with the given key, an implementation should throw an IllegalArgumentException

Parameters
key String: a key with which returned saved state will be associated
provider String: savedStateProvider to get saved state.

runOnNextRecreation

@MainThread fun runOnNextRecreation(@NonNull clazz: Class<out SavedStateRegistry.AutoRecreated!>): Unit

Executes the given class when the owning component restarted.

The given class will be automatically instantiated via default constructor and method AutoRecreated#onRecreated(SavedStateRegistryOwner) will be called. It is called as part of dispatching of androidx.lifecycle.Lifecycle.Event#ON_CREATE event.

Parameters
clazz Class<out SavedStateRegistry.AutoRecreated!>: that will need to be instantiated on the next component recreation
Exceptions
IllegalStateException if you try to call if after Lifecycle.Event#ON_STOP was dispatched

unregisterSavedStateProvider

@MainThread fun unregisterSavedStateProvider(@NonNull key: String): Unit

Unregisters a component previously registered by the given key

Parameters
key String: a key with which a component was previously registered.