Join us on the livestream at Android Dev Summit on 7-8 November 2018, starting at 10AM PDT!

LifecycleRegistry

public class LifecycleRegistry
extends Lifecycle

java.lang.Object
   ↳ androidx.lifecycle.Lifecycle
     ↳ androidx.lifecycle.LifecycleRegistry


An implementation of Lifecycle that can handle multiple observers.

It is used by Fragments and Support Library Activities. You can also directly use it if you have a custom LifecycleOwner.

Summary

Public constructors

LifecycleRegistry(LifecycleOwner provider)

Creates a new LifecycleRegistry for the given provider.

Public methods

void addObserver(LifecycleObserver observer)

Adds a LifecycleObserver that will be notified when the LifecycleOwner changes state.

Lifecycle.State getCurrentState()

Returns the current state of the Lifecycle.

int getObserverCount()

The number of observers.

void handleLifecycleEvent(Lifecycle.Event event)

Sets the current state and notifies the observers.

void markState(Lifecycle.State state)

Moves the Lifecycle to the given state and dispatches necessary events to the observers.

void removeObserver(LifecycleObserver observer)

Removes the given observer from the observers list.

Inherited methods

Public constructors

LifecycleRegistry

public LifecycleRegistry (LifecycleOwner provider)

Creates a new LifecycleRegistry for the given provider.

You should usually create this inside your LifecycleOwner class's constructor and hold onto the same instance.

Parameters
provider LifecycleOwner: The owner LifecycleOwner

Public methods

addObserver

public void addObserver (LifecycleObserver observer)

Adds a LifecycleObserver that will be notified when the LifecycleOwner changes state.

The given observer will be brought to the current state of the LifecycleOwner. For example, if the LifecycleOwner is in Lifecycle.State.STARTED state, the given observer will receive Lifecycle.Event.ON_CREATE, Lifecycle.Event.ON_START events.

Parameters
observer LifecycleObserver: The observer to notify.

getCurrentState

public Lifecycle.State getCurrentState ()

Returns the current state of the Lifecycle.

Returns
Lifecycle.State The current state of the Lifecycle.

getObserverCount

public int getObserverCount ()

The number of observers.

Returns
int The number of observers.

handleLifecycleEvent

public void handleLifecycleEvent (Lifecycle.Event event)

Sets the current state and notifies the observers.

Note that if the currentState is the same state as the last call to this method, calling this method has no effect.

Parameters
event Lifecycle.Event: The event that was received

markState

public void markState (Lifecycle.State state)

Moves the Lifecycle to the given state and dispatches necessary events to the observers.

Parameters
state Lifecycle.State: new state

removeObserver

public void removeObserver (LifecycleObserver observer)

Removes the given observer from the observers list.

If this method is called while a state change is being dispatched,

  • If the given observer has not yet received that event, it will not receive it.
  • If the given observer has more than 1 method that observes the currently dispatched event and at least one of them received the event, all of them will receive the event and the removal will happen afterwards.

Parameters
observer LifecycleObserver: The observer to be removed.