Android APIs
public class

WifiManager.MulticastLock

extends Object
java.lang.Object
   ↳ android.net.wifi.WifiManager.MulticastLock

Class Overview

Allows an application to receive Wifi Multicast packets. Normally the Wifi stack filters out packets not explicitly addressed to this device. Acquring a MulticastLock will cause the stack to receive packets addressed to multicast addresses. Processing these extra packets can cause a noticable battery drain and should be disabled when not needed.

Summary

Public Methods
void acquire()
Locks Wifi Multicast on until release() is called.
boolean isHeld()
Checks whether this MulticastLock is currently held.
void release()
Unlocks Wifi Multicast, restoring the filter of packets not addressed specifically to this device and saving power.
void setReferenceCounted(boolean refCounted)
Controls whether this is a reference-counted or non-reference- counted MulticastLock.
String toString()
Returns a string containing a concise, human-readable description of this object.
Protected Methods
void finalize()
Invoked when the garbage collector has detected that this instance is no longer reachable.
[Expand]
Inherited Methods
From class java.lang.Object

Public Methods

public void acquire ()

Added in API level 4

Locks Wifi Multicast on until release() is called. If this MulticastLock is reference-counted each call to acquire will increment the reference count, and the wifi interface will receive multicast packets as long as the reference count is above zero. If this MulticastLock is not reference-counted, the first call to acquire will turn on the multicast packets, but subsequent calls will be ignored. Only one call to release() will be required, regardless of the number of times that acquire is called. Note that other applications may also lock Wifi Multicast on. Only they can relinquish their lock. Also note that applications cannot leave Multicast locked on. When an app exits or crashes, any Multicast locks will be released.

public boolean isHeld ()

Added in API level 4

Checks whether this MulticastLock is currently held.

Returns
boolean true if this MulticastLock is held, false otherwise

public void release ()

Added in API level 4

Unlocks Wifi Multicast, restoring the filter of packets not addressed specifically to this device and saving power. If this MulticastLock is reference-counted, each call to release will decrement the reference count, and the multicast packets will only stop being received when the reference count reaches zero. If the reference count goes below zero (that is, if release is called a greater number of times than acquire()), an exception is thrown. If this MulticastLock is not reference-counted, the first call to release (after the radio was multicast locked using acquire()) will unlock the multicast, and subsequent calls will be ignored. Note that if any other Wifi Multicast Locks are still outstanding this release call will not have an immediate effect. Only when all applications have released all their Multicast Locks will the Multicast filter be turned back on. Also note that when an app exits or crashes all of its Multicast Locks will be automatically released.

public void setReferenceCounted (boolean refCounted)

Added in API level 4

Controls whether this is a reference-counted or non-reference- counted MulticastLock. Reference-counted MulticastLocks keep track of the number of calls to acquire() and release(), and only stop the reception of multicast packets when every call to acquire() has been balanced with a call to release(). Non-reference- counted MulticastLocks allow the reception of multicast packets whenever acquire() is called and stop accepting multicast packets whenever release() is called.

Parameters
refCounted boolean: true if this MulticastLock should keep a reference count

public String toString ()

Added in API level 4

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:

   getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Returns
String a printable representation of this object.

Protected Methods

protected void finalize ()

Added in API level 4

Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

Throws
Throwable