Added in API level 1

Summary: Inherited Constants | Fields | Ctors | Methods | Inherited Methods

Messenger

Kotlin |Java

public final class Messenger
extends Object implements Parcelable

java.lang.Object
↳	android.os.Messenger

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

Inherited constants

From interface android.os.Parcelable

`int`	`CONTENTS_FILE_DESCRIPTOR` Descriptor bit used with `describeContents()`: indicates that the Parcelable object's flattened representation includes a file descriptor.
`int`	`PARCELABLE_WRITE_RETURN_VALUE` Flag for use with `writeToParcel(Parcel, int)`: the object being written is a return value, that is the result of a function such as "`Parcelable someFunction()`", "`void someFunction(out Parcelable)`", or "`void someFunction(inout 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 instance's marshaled 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 a hash code value for the 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.

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.

From interface


        
          android.os.Parcelable

`abstract int`	`describeContents()` Describe the kinds of special objects contained in this Parcelable instance's marshaled representation.
`abstract void`	`writeToParcel(Parcel dest, int flags)` Flatten this object in to a Parcel.

Fields

CREATOR

Added in API level 1

public static final Creator<Messenger> CREATOR

Public constructors

Messenger

Added in API level 1

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`	`Handler`: The Handler that will receive sent messages.

Messenger

Added in API level 1

public Messenger (IBinder target)

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

describeContents

Added in API level 1

public int describeContents ()

Describe the kinds of special objects contained in this Parcelable instance's marshaled representation. For example, if the object will include a file descriptor in the output of writeToParcel(android.os.Parcel, int), the return value of this method must include the CONTENTS_FILE_DESCRIPTOR bit.

Returns
`int`	a bitmask indicating the set of special object types marshaled by this Parcelable object instance. Value is either `0` or `CONTENTS_FILE_DESCRIPTOR`

equals

Added in API level 1

public boolean equals (Object otherObj)

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

Parameters
`otherObj`	`Object`: This value may be `null`.

Returns
`boolean`	`true` if this object is the same as the obj argument; `false` otherwise.

getBinder

Added in API level 1

public IBinder getBinder ()

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

Returns
`IBinder`	Returns the IBinder backing this Messenger.

hashCode

Added in API level 1

public int hashCode ()

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

Returns
`int`	a hash code value for this object.

readMessengerOrNullFromParcel

Added in API level 1

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(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.

send

Added in API level 1

public void send (Message message)

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.

writeMessengerOrNullToParcel

Added in API level 1

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(Parcel) for later reading it.

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

writeToParcel

Added in API level 1

public void writeToParcel (Parcel out, 
                int flags)

Flatten this object in to a Parcel.

Parameters
`out`	`Parcel`: The Parcel in which the object should be written. This value cannot be `null`.
`flags`	`int`: Additional flags about how the object should be written. May be 0 or `Parcelable.PARCELABLE_WRITE_RETURN_VALUE`. Value is either `0` or a combination of `Parcelable.PARCELABLE_WRITE_RETURN_VALUE`, and android.os.Parcelable.PARCELABLE_ELIDE_DUPLICATES