Android APIs
public final class

Messenger

extends Object
implements Parcelable
java.lang.Object
   ↳ android.os.Messenger

Class Overview

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.

Summary

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Inherited Constants
From interface android.os.Parcelable
Fields
public static final Creator<Messenger> CREATOR
Public Constructors
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().
Public Methods
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.
[Expand]
Inherited Methods
From class java.lang.Object
From interface android.os.Parcelable

Fields

public static final Creator<Messenger> CREATOR

Added in API level 1

Public Constructors

public Messenger (Handler target)

Added in API level 1

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 Handler: The Handler that will receive sent messages.

public Messenger (IBinder target)

Added in API level 1

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

Parameters
target IBinder: The IBinder this Messenger should communicate with.

Public Methods

public int describeContents ()

Added in API level 1

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

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

public boolean equals (Object otherObj)

Added in API level 1

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

Parameters
otherObj Object: the object to compare this instance with.
Returns
boolean true if the specified object is equal to this Object; false otherwise.

public IBinder getBinder ()

Added in API level 1

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

Returns
IBinder Returns the IBinder backing this Messenger.

public int hashCode ()

Added in API level 1

Returns an integer hash code for this object. By contract, any two objects for which equals(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.

Returns
int this object's hash code.

public static Messenger readMessengerOrNullFromParcel (Parcel in)

Added in API level 1

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

Parameters
in Parcel: The Parcel containing the written Messenger.
Returns
Messenger Returns the Messenger read from the Parcel, or null if null had been written.

public void send (Message message)

Added in API level 1

Send a Message to this Messenger's Handler.

Parameters
message Message: The Message to send. Usually retrieved through Message.obtain().
Throws
RemoteException Throws DeadObjectException if the target Handler no longer exists.

public static void writeMessengerOrNullToParcel (Messenger messenger, Parcel out)

Added in API level 1

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

Parameters
messenger Messenger: The Messenger to write, or null.
out Parcel: Where to write the Messenger.

public void writeToParcel (Parcel out, int flags)

Added in API level 1

Flatten this object in to a Parcel.

Parameters
out Parcel: The Parcel in which the object should be written.
flags int: Additional flags about how the object should be written. May be 0 or PARCELABLE_WRITE_RETURN_VALUE.