Added in API level 1

Summary: Nested Classes | Constants | Ctors | Methods | Inherited Methods

RemoteCallbackList

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Kotlin |Java

public class RemoteCallbackList
extends Object

java.lang.Object
↳	android.os.RemoteCallbackList<E extends android.os.IInterface>

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Takes care of the grunt work of maintaining a list of remote interfaces, typically for the use of performing callbacks from a Service to its clients. In particular, this:

• Keeps track of a set of registered IInterface objects, taking care to identify them through their underlying unique IBinder (by calling IInterface.asBinder().
• Attaches a IBinder.DeathRecipient to each registered interface, so that it can be cleaned out of the list if its process goes away.
• Performs locking of the underlying list of interfaces to deal with multithreaded incoming calls, and a thread-safe way to iterate over a snapshot of the list without holding its lock.

To use this class, simply create a single instance along with your service, and call its register(E) and unregister(E) methods as client register and unregister with your service. To call back on to the registered clients, use beginBroadcast(), getBroadcastItem(int), and finishBroadcast().

If a registered interface's process goes away, this class will take care of automatically removing it from the list. If you want to do additional work in this situation, you can create a subclass that implements the onCallbackDied(E) method.

Summary

Nested classes
class	RemoteCallbackList.Builder<E extends IInterface> Builder for RemoteCallbackList.

Constants
int	FROZEN_CALLEE_POLICY_DROP When the callback recipient's process is frozen, callbacks are suppressed as if they never happened.
int	FROZEN_CALLEE_POLICY_ENQUEUE_ALL When the callback recipient's process is frozen, callbacks are enqueued so they're invoked after the recipient is unfrozen.
int	FROZEN_CALLEE_POLICY_ENQUEUE_MOST_RECENT When the callback recipient's process is frozen, only the most recent callback is enqueued, which is later invoked after the recipient is unfrozen.
int	FROZEN_CALLEE_POLICY_UNSET Callbacks are invoked immediately regardless of the frozen state of the target process.

Public constructors
RemoteCallbackList() Creates a RemoteCallbackList with FROZEN_CALLEE_POLICY_UNSET.

Public methods
int	beginBroadcast() Use broadcast(java.util.function.Consumer) instead to ensure proper handling of frozen processes.
void	broadcast(Consumer<E> callback) Performs callback on each registered interface.
void	finishBroadcast() Clean up the state of a broadcast previously initiated by calling beginBroadcast().
Object	getBroadcastCookie(int index) Retrieve the cookie associated with the item returned by getBroadcastItem(int).
E	getBroadcastItem(int index) Retrieve an item in the active broadcast that was previously started with beginBroadcast().
Executor	getExecutor() Returns the executor used when invoking callbacks asynchronously.
int	getFrozenCalleePolicy() Returns the frozen callee policy.
int	getMaxQueueSize() Returns the max queue size.
Object	getRegisteredCallbackCookie(int index) Return any cookie associated with a currently registered interface.
int	getRegisteredCallbackCount() Returns the number of registered interfaces.
E	getRegisteredCallbackItem(int index) Return a currently registered interface.
void	kill() Disable this interface list.
void	onCallbackDied(E callbackInterface, Object cookie) Called when the process hosting an interface in the list has gone away.
void	onCallbackDied(E callbackInterface) Old version of onCallbackDied(E, java.lang.Object) that does not provide a cookie.
boolean	register(E callbackInterface, Object cookie) Add a new interface to the list.
boolean	register(E callbackInterface) Simple version of RemoteCallbackList.register(E, Object) that does not take a cookie object.
boolean	unregister(E callbackInterface) Remove from the list an interface that was previously added with register(E).

Inherited methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Constants

FROZEN_CALLEE_POLICY_DROP

Added in Android Baklava

public static final int FROZEN_CALLEE_POLICY_DROP

When the callback recipient's process is frozen, callbacks are suppressed as if they never happened. This could be useful in the case where the recipient wishes to react to callbacks only when they occur while the recipient is not frozen. For example, certain network events are only worth responding to if the response can be immediate. Another example is recipients having another way of getting the latest state once it's unfrozen. Therefore there is no need to save callbacks that happened while the recipient was frozen.

Constant Value: 3 (0x00000003)

FROZEN_CALLEE_POLICY_ENQUEUE_ALL

Added in Android Baklava

public static final int FROZEN_CALLEE_POLICY_ENQUEUE_ALL

When the callback recipient's process is frozen, callbacks are enqueued so they're invoked after the recipient is unfrozen. This is commonly used when the recipient wants to receive all callbacks without losing any history, e.g. the recipient maintains a running count of events that occurred. Queued callbacks are invoked in the order they were originally broadcasted.

Constant Value: 1 (0x00000001)

FROZEN_CALLEE_POLICY_ENQUEUE_MOST_RECENT

Added in Android Baklava

public static final int FROZEN_CALLEE_POLICY_ENQUEUE_MOST_RECENT

When the callback recipient's process is frozen, only the most recent callback is enqueued, which is later invoked after the recipient is unfrozen. This can be used when only the most recent state matters, for instance when clients are listening to screen brightness changes.

Constant Value: 2 (0x00000002)

FROZEN_CALLEE_POLICY_UNSET

Added in Android Baklava

public static final int FROZEN_CALLEE_POLICY_UNSET

Callbacks are invoked immediately regardless of the frozen state of the target process. Not recommended. Only exists for backward-compatibility. This represents the behavior up to SDK 35. Starting with SDK 36, clients should set a policy to govern callback invocations when recipients are frozen.

Constant Value: 0 (0x00000000)

Public constructors

RemoteCallbackList

Added in API level 1

public RemoteCallbackList ()

Creates a RemoteCallbackList with FROZEN_CALLEE_POLICY_UNSET. This is equivalent to

 new RemoteCallbackList.Build(RemoteCallbackList.FROZEN_CALLEE_POLICY_UNSET).build()
 

Public methods

beginBroadcast

Added in API level 1

public int beginBroadcast ()

Use broadcast(java.util.function.Consumer) instead to ensure proper handling of frozen processes. Prepare to start making calls to the currently registered interfaces. This creates a copy of the interface list, which you can retrieve items from using getBroadcastItem(int). Note that only one broadcast can be active at a time, so you must be sure to always call this from the same thread (usually by scheduling with Handler) or do your own synchronization. You must call finishBroadcast() when done.

A typical loop delivering a broadcast looks like this:

 int i = interfaces.beginBroadcast();
 while (i > 0) {
     i--;
     try {
         interfaces.getBroadcastItem(i).somethingHappened();
     } catch (RemoteException e) {
         // The RemoteCallbackList will take care of removing
         // the dead object for us.
     }
 }
 interfaces.finishBroadcast();

Note that this method is only supported for FROZEN_CALLEE_POLICY_UNSET. For other policies use broadcast(java.util.function.Consumer) instead.

Returns
int	Returns the number of interfaces in the broadcast, to be used with getBroadcastItem(int) to determine the range of indices you can supply.

Throws
UnsupportedOperationException	if an frozen callee policy is set.

See also:

• getBroadcastItem(int)
• finishBroadcast()

broadcast

Added in Android Baklava

public void broadcast (Consumer<E> callback)

Performs callback on each registered interface. This is equivalent to #beginBroadcast, followed by iterating over the items using #getBroadcastItem and then @finishBroadcast, except that this method supports frozen callee policies.

Parameters
callback	Consumer: This value cannot be null.

finishBroadcast

Added in API level 1

public void finishBroadcast ()

Clean up the state of a broadcast previously initiated by calling beginBroadcast(). This must always be called when you are done with a broadcast.

See also:

• beginBroadcast()

getBroadcastCookie

Added in API level 4

public Object getBroadcastCookie (int index)

Retrieve the cookie associated with the item returned by getBroadcastItem(int).

Parameters
index	int

Returns
Object

See also:

• getBroadcastItem(int)

getBroadcastItem

Added in API level 1

public E getBroadcastItem (int index)

Retrieve an item in the active broadcast that was previously started with beginBroadcast(). This can only be called after the broadcast is started, and its data is no longer valid after calling finishBroadcast().

Note that it is possible for the process of one of the returned interfaces to go away before you call it, so you will need to catch RemoteException when calling on to the returned object. The interface list itself, however, will take care of unregistering these objects once it detects that it is no longer valid, so you can handle such an exception by simply ignoring it.

Parameters
index	int: Which of the registered interfaces you would like to retrieve. Ranges from 0 to beginBroadcast()-1, inclusive.

Returns
E	Returns the interface that you can call. This will always be non-null.

See also:

• beginBroadcast()

getExecutor

Added in Android Baklava

public Executor getExecutor ()

Returns the executor used when invoking callbacks asynchronously.

Returns
Executor	The executor. This value may be null.

getFrozenCalleePolicy

Added in Android Baklava

public int getFrozenCalleePolicy ()

Returns the frozen callee policy.

Returns
int	The frozen callee policy. Value is FROZEN_CALLEE_POLICY_UNSET, FROZEN_CALLEE_POLICY_ENQUEUE_ALL, FROZEN_CALLEE_POLICY_ENQUEUE_MOST_RECENT, or FROZEN_CALLEE_POLICY_DROP

getMaxQueueSize

Added in Android Baklava

public int getMaxQueueSize ()

Returns the max queue size.

Returns
int	The max queue size.

getRegisteredCallbackCookie

Added in API level 26

public Object getRegisteredCallbackCookie (int index)

Return any cookie associated with a currently registered interface. Note that this is not the same as getBroadcastCookie(int) and should not be used interchangeably with it. This method returns the current cookie registered at the given index, not the current broadcast state. This means that it is not itself thread-safe: any call to register(E) or unregister(E) will change these indices, so you must do your own thread safety between these to protect from such changes.

Parameters
index	int: Index of which registration cookie to return, from 0 to getRegisteredCallbackCount() - 1.

Returns
Object	Returns whatever cookie object is associated with this index, or null if kill() has been called.

getRegisteredCallbackCount

Added in API level 17

public int getRegisteredCallbackCount ()

Returns the number of registered interfaces. Note that the number of registered interfaces may differ from the value returned by beginBroadcast() since the former returns the number of interfaces registered at the time of the call and the second the number of interfaces to which the broadcast will be delivered.

This function is useful to decide whether to schedule a broadcast if this requires doing some work which otherwise would not be performed.

Returns
int	The size.

getRegisteredCallbackItem

Added in API level 26

public E getRegisteredCallbackItem (int index)

Return a currently registered interface. Note that this is not the same as getBroadcastItem(int) and should not be used interchangeably with it. This method returns the registered interface at the given index, not the current broadcast state. This means that it is not itself thread-safe: any call to register(E) or unregister(E) will change these indices, so you must do your own thread safety between these to protect from such changes.

Parameters
index	int: Index of which interface registration to return, from 0 to getRegisteredCallbackCount() - 1.

Returns
E	Returns whatever interface is associated with this index, or null if kill() has been called.

kill

Added in API level 1

public void kill ()

Disable this interface list. All registered interfaces are unregistered, and the list is disabled so that future calls to register(E) will fail. This should be used when a Service is stopping, to prevent clients from registering interfaces after it is stopped.

See also:

• register(E)

onCallbackDied

Added in API level 4

public void onCallbackDied (E callbackInterface, 
                Object cookie)

Called when the process hosting an interface in the list has gone away. The default implementation calls onCallbackDied(E) for backwards compatibility.

Parameters
callbackInterface	E: The interface whose process has died. Note that, since its process has died, you can not make any calls on to this interface. You can, however, retrieve its IBinder and compare it with another IBinder to see if it is the same object.
cookie	Object: The cookie object original provided to register(E, java.lang.Object).

See also:

• register(E)

onCallbackDied

Added in API level 1

public void onCallbackDied (E callbackInterface)

Old version of onCallbackDied(E, java.lang.Object) that does not provide a cookie.

Parameters
callbackInterface	E

register

Added in API level 4

public boolean register (E callbackInterface, 
                Object cookie)

Add a new interface to the list. This interface will remain in the list until a corresponding call to unregister(E) or its hosting process goes away. If the interface was already registered (determined by checking to see if the callbackInterface.asBinder() object is already in the list), then it will be replaced with the new interface. Registrations are not counted; a single call to unregister(E) will remove an interface after any number calls to register it.

Parameters
callbackInterface	E: The callback interface to be added to the list. Must not be null -- passing null here will cause a NullPointerException. Most services will want to check for null before calling this with an object given from a client, so that clients can't crash the service with bad data.
cookie	Object: Optional additional data to be associated with this interface.

Returns
boolean	Returns true if the interface was successfully added to the list. Returns false if it was not added, either because kill() had previously been called or the interface's process has gone away.

See also:

• unregister(E)
• kill()
• onCallbackDied(E)

register

Added in API level 1

public boolean register (E callbackInterface)

Simple version of RemoteCallbackList.register(E, Object) that does not take a cookie object.

Parameters
callbackInterface	E

Returns
boolean

unregister

Added in API level 1

public boolean unregister (E callbackInterface)

Remove from the list an interface that was previously added with register(E). This uses the callbackInterface.asBinder() object to correctly find the previous registration. Registrations are not counted; a single unregister call will remove an interface after any number calls to register(E) for it.

Parameters
callbackInterface	E: The interface to be removed from the list. Passing null here will cause a NullPointerException, so you will generally want to check for null before calling.

Returns
boolean	Returns true if the interface was found and unregistered. Returns false if the given interface was not found on the list.

See also:

• register(E)