Added in API level 1

RemoteCallbackList

open class RemoteCallbackList<E : IInterface!>
kotlin.Any
   ↳ android.os.RemoteCallbackList

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

  • Keeps track of a set of registered IInterface callbacks, 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 and unregister methods as client register and unregister with your service. To call back on to the registered clients, use beginBroadcast, getBroadcastItem, and finishBroadcast.

If a registered callback'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 method.

Summary

Public constructors

Public methods
open Int

Prepare to start making calls to the currently registered callbacks.

open Unit

Clean up the state of a broadcast previously initiated by calling beginBroadcast.

open Any!

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

open E

Retrieve an item in the active broadcast that was previously started with beginBroadcast.

open Any!

Return any cookie associated with a currently registered callback.

open Int

Returns the number of registered callbacks.

open E

Return a currently registered callback.

open Unit

Disable this callback list.

open Unit
onCallbackDied(callback: E)

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

open Unit
onCallbackDied(callback: E, cookie: Any!)

Called when the process hosting a callback in the list has gone away.

open Boolean
register(callback: E)

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

open Boolean
register(callback: E, cookie: Any!)

Add a new callback to the list.

open Boolean
unregister(callback: E)

Remove from the list a callback that was previously added with #register.

Public constructors

RemoteCallbackList

RemoteCallbackList()

Public methods

beginBroadcast

Added in API level 1
open fun beginBroadcast(): Int

Prepare to start making calls to the currently registered callbacks. This creates a copy of the callback list, which you can retrieve items from using getBroadcastItem. 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 = callbacks.beginBroadcast();
  while (i > 0) {
      i--;
      try {
          callbacks.getBroadcastItem(i).somethingHappened();
      } catch (RemoteException e) {
          // The RemoteCallbackList will take care of removing
          // the dead object for us.
      }
  }
  callbacks.finishBroadcast();
Return
Int Returns the number of callbacks in the broadcast, to be used with getBroadcastItem to determine the range of indices you can supply.

finishBroadcast

Added in API level 1
open fun finishBroadcast(): Unit

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

getBroadcastCookie

Added in API level 4
open fun getBroadcastCookie(index: Int): Any!

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

getBroadcastItem

Added in API level 1
open fun getBroadcastItem(index: Int): E

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 callbacks to go away before you call it, so you will need to catch RemoteException when calling on to the returned object. The callback 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 callbacks you would like to retrieve. Ranges from 0 to beginBroadcast-1, inclusive.
Return
E Returns the callback interface that you can call. This will always be non-null.

See Also

getRegisteredCallbackCookie

Added in API level 26
open fun getRegisteredCallbackCookie(index: Int): Any!

Return any cookie associated with a currently registered callback. Note that this is not the same as getBroadcastCookie 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 or unregister 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.
Return
Any! Returns whatever cookie object is associated with this index, or null if kill() has been called.

getRegisteredCallbackCount

Added in API level 17
open fun getRegisteredCallbackCount(): Int

Returns the number of registered callbacks. Note that the number of registered callbacks may differ from the value returned by beginBroadcast() since the former returns the number of callbacks registered at the time of the call and the second the number of callback 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.

Return
Int The size.

getRegisteredCallbackItem

Added in API level 26
open fun getRegisteredCallbackItem(index: Int): E

Return a currently registered callback. Note that this is not the same as getBroadcastItem and should not be used interchangeably with it. This method returns the registered callback at the given index, not the current broadcast state. This means that it is not itself thread-safe: any call to #register or unregister 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 callback registration to return, from 0 to getRegisteredCallbackCount() - 1.
Return
E Returns whatever callback is associated with this index, or null if kill() has been called.

kill

Added in API level 1
open fun kill(): Unit

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

See Also

    onCallbackDied

    Added in API level 1
    open fun onCallbackDied(callback: E): Unit

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

    onCallbackDied

    Added in API level 4
    open fun onCallbackDied(
        callback: E,
        cookie: Any!
    ): Unit

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

    Parameters
    callback E: The callback 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 Any!: The cookie object original provided to register(E,java.lang.Object).

    See Also

      register

      Added in API level 1
      open fun register(callback: E): Boolean

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

      register

      Added in API level 4
      open fun register(
          callback: E,
          cookie: Any!
      ): Boolean

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

      Parameters
      callback 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 Any!: Optional additional data to be associated with this callback.
      Return
      Boolean Returns true if the callback was successfully added to the list. Returns false if it was not added, either because kill had previously been called or the callback's process has gone away.

      See Also

      unregister

      Added in API level 1
      open fun unregister(callback: E): Boolean

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

      Parameters
      callback E: The callback to be removed from the list. Passing null here will cause a NullPointerException, so you will generally want to check for null before calling.
      Return
      Boolean Returns true if the callback was found and unregistered. Returns false if the given callback was not found on the list.

      See Also