android.os

Class Messenger

java.lang.Object

android.os.Messenger

All Implemented Interfaces:

Parcelable

public final class Messenger
extends Object
implements Parcelable

Reference to a Handler, which others can use to send messages to it. This allows for the implementation of message-based communication across processes, by creating a Messenger pointing to a Handler in one process, and handing that Messenger to another process.

Note: the implementation underneath is just a simple wrapper around a Binder that is used to perform the communication. This means semantically you should treat it as such: this class does not impact process lifecycle management (you must be using some higher-level component to tell the system that your process needs to continue running), the connection will break if your process goes away for any reason, etc.

Nested Class Summary

Nested classes/interfaces inherited from interface android.os.Parcelable

Parcelable.ClassLoaderCreator<T>, Parcelable.Creator<T>

Field Summary

Fields

Modifier and Type	Field and Description
static Parcelable.Creator<Messenger>	CREATOR

Fields inherited from interface android.os.Parcelable

CONTENTS_FILE_DESCRIPTOR, PARCELABLE_WRITE_RETURN_VALUE

Constructor Summary

Constructors

Constructor and Description
Messenger(Handler target) Create a new Messenger pointing to the given Handler.
Messenger(IBinder target) Create a Messenger from a raw IBinder, which had previously been retrieved with getBinder().

Method Summary

Modifier and Type	Method and Description
int	describeContents() Describe the kinds of special objects contained in this Parcelable's marshalled representation.
boolean	equals(Object otherObj) Comparison operator on two Messenger objects, such that true is returned then they both point to the same Handler.
IBinder	getBinder() Retrieve the IBinder that this Messenger is using to communicate with its associated Handler.
int	hashCode() Returns an integer hash code for this object.
static Messenger	readMessengerOrNullFromParcel(Parcel in) Convenience function for reading either a Messenger or null pointer from a Parcel.
void	send(Message message) Send a Message to this Messenger's Handler.
static void	writeMessengerOrNullToParcel(Messenger messenger, Parcel out) Convenience function for writing either a Messenger or null pointer to a Parcel.
void	writeToParcel(Parcel out, int flags) Flatten this object in to a Parcel.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

CREATOR

public static final Parcelable.Creator<Messenger> CREATOR

Constructor Detail

Messenger

public Messenger(Handler target)

Create a new Messenger pointing to the given Handler. Any Message objects sent through this Messenger will appear in the Handler as if Handler.sendMessage(Message) had been called directly.

Parameters:

target - The Handler that will receive sent messages.

Messenger

public Messenger(IBinder target)

Create a Messenger from a raw IBinder, which had previously been retrieved with getBinder().

Parameters:

target - The IBinder this Messenger should communicate with.

Method Detail

send

public void send(Message message)
          throws RemoteException

Send a Message to this Messenger's Handler.

Parameters:

message - The Message to send. Usually retrieved through Message.obtain().

Throws:

RemoteException - Throws DeadObjectException if the target Handler no longer exists.

getBinder

public IBinder getBinder()

Retrieve the IBinder that this Messenger is using to communicate with its associated Handler.

Returns:

Returns the IBinder backing this Messenger.

equals

public boolean equals(Object otherObj)

Comparison operator on two Messenger objects, such that true is returned then they both point to the same Handler.

Overrides:

equals in class Object

Parameters:

otherObj - the object to compare this instance with.

Returns:

true if the specified object is equal to this Object; false otherwise.

See Also:

Object.hashCode()

hashCode

public int hashCode()

Description copied from class: Object

Returns an integer hash code for this object. By contract, any two objects for which Object.equals(java.lang.Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.

Note that hash values must not change over time unless information used in equals comparisons also changes.

See Writing a correct hashCode method if you intend implementing your own hashCode method.

Overrides:

hashCode in class Object

Returns:

this object's hash code.

See Also:

Object.equals(java.lang.Object)

describeContents

public int describeContents()

Description copied from interface: Parcelable

Describe the kinds of special objects contained in this Parcelable's marshalled representation.

Specified by:

describeContents in interface Parcelable

Returns:

a bitmask indicating the set of special object types marshalled by the Parcelable.

writeToParcel

public void writeToParcel(Parcel out,
                          int flags)

Description copied from interface: Parcelable

Flatten this object in to a Parcel.

Specified by:

writeToParcel in interface Parcelable

Parameters:

out - The Parcel in which the object should be written.

flags - Additional flags about how the object should be written. May be 0 or Parcelable.PARCELABLE_WRITE_RETURN_VALUE.

writeMessengerOrNullToParcel

public static void writeMessengerOrNullToParcel(Messenger messenger,
                                                Parcel out)

Convenience function for writing either a Messenger or null pointer to a Parcel. You must use this with readMessengerOrNullFromParcel(android.os.Parcel) for later reading it.

Parameters:

messenger - The Messenger to write, or null.

out - Where to write the Messenger.

readMessengerOrNullFromParcel

public static Messenger readMessengerOrNullFromParcel(Parcel in)

Convenience function for reading either a Messenger or null pointer from a Parcel. You must have previously written the Messenger with writeMessengerOrNullToParcel(android.os.Messenger, android.os.Parcel).

Parameters:

in - The Parcel containing the written Messenger.

Returns:

Returns the Messenger read from the Parcel, or null if null had been written.