# Messenger Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary:[Inherited Constants](https://developer.android.com/reference/android/os/Messenger#inhconstants)\|[Fields](https://developer.android.com/reference/android/os/Messenger#lfields)\|[Ctors](https://developer.android.com/reference/android/os/Messenger#pubctors)\|[Methods](https://developer.android.com/reference/android/os/Messenger#pubmethods)\|[Inherited Methods](https://developer.android.com/reference/android/os/Messenger#inhmethods) # Messenger *** ** * ** *** [Kotlin](https://developer.android.com/reference/kotlin/android/os/Messenger "View this page in Kotlin")\|Java ` public final class Messenger ` ` extends `[Object](https://developer.android.com/reference/java/lang/Object)` `` implements `[Parcelable](https://developer.android.com/reference/android/os/Parcelable)` ` |---|----------------------| | [java.lang.Object](https://developer.android.com/reference/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](https://developer.android.com/reference/android/os/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](https://developer.android.com/reference/android/os/Parcelable) |-------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | `int` | [CONTENTS_FILE_DESCRIPTOR](https://developer.android.com/reference/android/os/Parcelable#CONTENTS_FILE_DESCRIPTOR) Descriptor bit used with[describeContents()](https://developer.android.com/reference/android/os/Parcelable#describeContents()): indicates that the Parcelable object's flattened representation includes a file descriptor. | | `int` | [PARCELABLE_WRITE_RETURN_VALUE](https://developer.android.com/reference/android/os/Parcelable#PARCELABLE_WRITE_RETURN_VALUE) Flag for use with[writeToParcel(Parcel, int)](https://developer.android.com/reference/android/os/Parcelable#writeToParcel(android.os.Parcel,%20int)): 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](https://developer.android.com/reference/android/os/Parcelable.Creator)`<`[Messenger](https://developer.android.com/reference/android/os/Messenger)`>` | [CREATOR](https://developer.android.com/reference/android/os/Messenger#CREATOR)
| | ### Public constructors || |-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---| | ` `[Messenger](https://developer.android.com/reference/android/os/Messenger#Messenger(android.os.Handler))`(`[Handler](https://developer.android.com/reference/android/os/Handler)` target) ` Create a new Messenger pointing to the given Handler. | | ` `[Messenger](https://developer.android.com/reference/android/os/Messenger#Messenger(android.os.IBinder))`(`[IBinder](https://developer.android.com/reference/android/os/IBinder)` target) ` Create a Messenger from a raw IBinder, which had previously been retrieved with[getBinder()](https://developer.android.com/reference/android/os/Messenger#getBinder()). | | ### Public methods || |-------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` int` | ` `[describeContents](https://developer.android.com/reference/android/os/Messenger#describeContents())`() ` Describe the kinds of special objects contained in this Parcelable instance's marshaled representation. | | ` boolean` | ` `[equals](https://developer.android.com/reference/android/os/Messenger#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` otherObj) ` Comparison operator on two Messenger objects, such that true is returned then they both point to the same Handler. | | ` `[IBinder](https://developer.android.com/reference/android/os/IBinder) | ` `[getBinder](https://developer.android.com/reference/android/os/Messenger#getBinder())`() ` Retrieve the IBinder that this Messenger is using to communicate with its associated Handler. | | ` int` | ` `[hashCode](https://developer.android.com/reference/android/os/Messenger#hashCode())`() ` Returns a hash code value for the object. | | ` static `[Messenger](https://developer.android.com/reference/android/os/Messenger) | ` `[readMessengerOrNullFromParcel](https://developer.android.com/reference/android/os/Messenger#readMessengerOrNullFromParcel(android.os.Parcel))`(`[Parcel](https://developer.android.com/reference/android/os/Parcel)` in) ` Convenience function for reading either a Messenger or null pointer from a Parcel. | | ` void` | ` `[send](https://developer.android.com/reference/android/os/Messenger#send(android.os.Message))`(`[Message](https://developer.android.com/reference/android/os/Message)` message) ` Send a Message to this Messenger's Handler. | | ` static void` | ` `[writeMessengerOrNullToParcel](https://developer.android.com/reference/android/os/Messenger#writeMessengerOrNullToParcel(android.os.Messenger,%20android.os.Parcel))`(`[Messenger](https://developer.android.com/reference/android/os/Messenger)` messenger, `[Parcel](https://developer.android.com/reference/android/os/Parcel)` out) ` Convenience function for writing either a Messenger or null pointer to a Parcel. | | ` void` | ` `[writeToParcel](https://developer.android.com/reference/android/os/Messenger#writeToParcel(android.os.Parcel,%20int))`(`[Parcel](https://developer.android.com/reference/android/os/Parcel)` out, int flags) ` Flatten this object in to a Parcel. | | ### Inherited methods | |-----------------------|---| | From class` `[java.lang.Object](https://developer.android.com/reference/java/lang/Object)` ` |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/Object#clone())`() ` Creates and returns a copy of this object. | | ` boolean` | ` `[equals](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` `[finalize](https://developer.android.com/reference/java/lang/Object#finalize())`() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final `[Class](https://developer.android.com/reference/java/lang/Class)`` | ` `[getClass](https://developer.android.com/reference/java/lang/Object#getClass())`() ` Returns the runtime class of this`Object`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/java/lang/Object#hashCode())`() ` Returns a hash code value for the object. | | ` final void` | ` `[notify](https://developer.android.com/reference/java/lang/Object#notify())`() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` `[notifyAll](https://developer.android.com/reference/java/lang/Object#notifyAll())`() ` Wakes up all threads that are waiting on this object's monitor. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/lang/Object#toString())`() ` Returns a string representation of the object. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait(long,%20int))`(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](https://developer.android.com/reference/java/lang/Object#wait(long))`(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](https://developer.android.com/reference/java/lang/Object#wait())`() ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*. | || | From interface` `[android.os.Parcelable](https://developer.android.com/reference/android/os/Parcelable)` ` |------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract int` | ` `[describeContents](https://developer.android.com/reference/android/os/Parcelable#describeContents())`() ` Describe the kinds of special objects contained in this Parcelable instance's marshaled representation. | | ` abstract void` | ` `[writeToParcel](https://developer.android.com/reference/android/os/Parcelable#writeToParcel(android.os.Parcel,%20int))`(`[Parcel](https://developer.android.com/reference/android/os/Parcel)` dest, int flags) ` Flatten this object in to a Parcel. | || ## Fields ### CREATOR Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public static final Creator CREATOR ```

## Public constructors ### Messenger Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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)](https://developer.android.com/reference/android/os/Handler#sendMessage(android.os.Message))had been called directly.
| Parameters || |----------|----------------------------------------------------------------| | `target` | `Handler`: The Handler that will receive sent messages.
| ### Messenger Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public Messenger (IBinder target) ``` Create a Messenger from a raw IBinder, which had previously been retrieved with[getBinder()](https://developer.android.com/reference/android/os/Messenger#getBinder()).
| Parameters || |----------|-----------------------------------------------------------------------| | `target` | `IBinder`: The IBinder this Messenger should communicate with.
| ## Public methods ### describeContents Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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)](https://developer.android.com/reference/android/os/Parcelable#writeToParcel(android.os.Parcel,%20int)), the return value of this method must include the[CONTENTS_FILE_DESCRIPTOR](https://developer.android.com/reference/android/os/Parcelable#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](https://developer.android.com/reference/android/os/Parcelable#CONTENTS_FILE_DESCRIPTOR)
| ### equals Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public IBinder getBinder () ``` Retrieve the IBinder that this Messenger is using to communicate with its associated Handler.
| Returns || |-----------------------------------------------------------------------|----------------------------------------------------| | [IBinder](https://developer.android.com/reference/android/os/IBinder) | Returns the IBinder backing this Messenger.
| ### hashCode Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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](https://developer.android.com/reference/java/util/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](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))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](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))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](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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)](https://developer.android.com/reference/android/os/Messenger#writeMessengerOrNullToParcel(android.os.Messenger,%20android.os.Parcel)).
| Parameters || |------|---------------------------------------------------------------| | `in` | `Parcel`: The Parcel containing the written Messenger.
| | Returns || |---------------------------------------------------------------------------|--------------------------------------------------------------------------------------| | [Messenger](https://developer.android.com/reference/android/os/Messenger) | Returns the Messenger read from the Parcel, or null if null had been written.
| ### send Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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()](https://developer.android.com/reference/android/os/Message#obtain()).
| | Throws || |---------------------------------------------------------------------------------------|--------------------------------------------------------------------| | [RemoteException](https://developer.android.com/reference/android/os/RemoteException) | Throws DeadObjectException if the target Handler no longer exists. | ### writeMessengerOrNullToParcel Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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)](https://developer.android.com/reference/android/os/Messenger#readMessengerOrNullFromParcel(android.os.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](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` 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](https://developer.android.com/reference/android/os/Parcelable#PARCELABLE_WRITE_RETURN_VALUE). Value is either`0`or a combination of[Parcelable.PARCELABLE_WRITE_RETURN_VALUE](https://developer.android.com/reference/android/os/Parcelable#PARCELABLE_WRITE_RETURN_VALUE), and android.os.Parcelable.PARCELABLE_ELIDE_DUPLICATES
|