android.os
Class Message

java.lang.Object
  android.os.Message

All Implemented Interfaces:

Parcelable

public final class Message
extends Object
implements Parcelable

Defines a message containing a description and arbitrary data object that can be sent to a Handler. This object contains two extra int fields and an extra object field that allow you to not do allocations in many cases.

While the constructor of Message is public, the best way to get one of these is to call Message.obtain() or one of the Handler.obtainMessage() methods, which will pull them from a pool of recycled objects.

Nested Class Summary

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

Parcelable.Creator<T>

Field Summary

int	arg1 arg1 and arg2 are lower-cost alternatives to using setData() if you only need to store a few integer values.
int	arg2 arg1 and arg2 are lower-cost alternatives to using setData() if you only need to store a few integer values.
(package private) Runnable	callback
static Parcelable.Creator<Message>	CREATOR
(package private) Bundle	data
(package private) Message	next
Object	obj An arbitrary object to send to the recipient.
Messenger	replyTo Optional Messenger where replies to this message can be sent.
(package private) Handler	target
int	what User-defined message code so that the recipient can identify what this message is about.
(package private) long	when

Fields inherited from interface android.os.Parcelable

CONTENTS_FILE_DESCRIPTOR, PARCELABLE_WRITE_RETURN_VALUE

Constructor Summary

Message()
Constructor (but the preferred way to get a Message is to call Message.obtain()).

Method Summary

(package private) void	clearForRecycle()
void	copyFrom(Message o) Make this message like o.
int	describeContents() Describe the kinds of special objects contained in this Parcelable's marshalled representation.
Runnable	getCallback() Retrieve callback object that will execute when this message is handled.
Bundle	getData() Obtains a Bundle of arbitrary data associated with this event, lazily creating it if necessary.
Handler	getTarget() Retrieve the a Handler implementation that will receive this message.
long	getWhen() Return the targeted delivery time of this message, in milliseconds.
static Message	obtain() Return a new Message instance from the global pool.
static Message	obtain(Handler h) Same as obtain(), but sets the value for the target member on the Message returned.
static Message	obtain(Handler h, int what) Same as obtain(), but sets the values for both target and what members on the Message.
static Message	obtain(Handler h, int what, int arg1, int arg2) Same as obtain(), but sets the values of the target, what, arg1, and arg2 members.
static Message	obtain(Handler h, int what, int arg1, int arg2, Object obj) Same as obtain(), but sets the values of the target, what, arg1, arg2, and obj members.
static Message	obtain(Handler h, int what, Object obj) Same as obtain(), but sets the values of the target, what, and obj members.
static Message	obtain(Handler h, Runnable callback) Same as obtain(Handler), but assigns a callback Runnable on the Message that is returned.
static Message	obtain(Message orig) Same as obtain(), but copies the values of an existing message (including its target) into the new one.
Bundle	peekData() Like getData(), but does not lazily create the Bundle.
void	recycle() Return a Message instance to the global pool.
void	sendToTarget() Sends this Message to the Handler specified by getTarget().
void	setData(Bundle data) Sets a Bundle of arbitrary data values.
void	setTarget(Handler target)
String	toString() Returns a string containing a concise, human-readable description of the receiver.
void	writeToParcel(Parcel dest, int flags) Flatten this object in to a Parcel.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

what

public int what

User-defined message code so that the recipient can identify what this message is about. Each Handler has its own name-space for message codes, so you do not need to worry about yours conflicting with other handlers.

arg1

public int arg1

arg1 and arg2 are lower-cost alternatives to using setData() if you only need to store a few integer values.

arg2

public int arg2

arg1 and arg2 are lower-cost alternatives to using setData() if you only need to store a few integer values.

obj

public Object obj

An arbitrary object to send to the recipient. This must be null when sending messages across processes.

replyTo

public Messenger replyTo

Optional Messenger where replies to this message can be sent.

when

long when

data

Bundle data

target

Handler target

callback

Runnable callback

next

Message next

CREATOR

public static final Parcelable.Creator<Message> CREATOR

Constructor Detail

Message

public Message()

Constructor (but the preferred way to get a Message is to call Message.obtain()).

Method Detail

obtain

public static Message obtain()

Return a new Message instance from the global pool. Allows us to avoid allocating new objects in many cases.

obtain

public static Message obtain(Message orig)

Same as obtain(), but copies the values of an existing message (including its target) into the new one.

Parameters:

orig - Original message to copy.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h)

Same as obtain(), but sets the value for the target member on the Message returned.

Parameters:

h - Handler to assign to the returned Message object's target member.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h,
                             Runnable callback)

Same as obtain(Handler), but assigns a callback Runnable on the Message that is returned.

Parameters:

h - Handler to assign to the returned Message object's target member.

callback - Runnable that will execute when the message is handled.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h,
                             int what)

Same as obtain(), but sets the values for both target and what members on the Message.

Parameters:

h - Value to assign to the target member.

what - Value to assign to the what member.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h,
                             int what,
                             Object obj)

Same as obtain(), but sets the values of the target, what, and obj members.

Parameters:

h - The target value to set.

what - The what value to set.

obj - The object method to set.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h,
                             int what,
                             int arg1,
                             int arg2)

Same as obtain(), but sets the values of the target, what, arg1, and arg2 members.

Parameters:

h - The target value to set.

what - The what value to set.

arg1 - The arg1 value to set.

arg2 - The arg2 value to set.

Returns:

A Message object from the global pool.

obtain

public static Message obtain(Handler h,
                             int what,
                             int arg1,
                             int arg2,
                             Object obj)

Same as obtain(), but sets the values of the target, what, arg1, arg2, and obj members.

Parameters:

h - The target value to set.

what - The what value to set.

arg1 - The arg1 value to set.

arg2 - The arg2 value to set.

obj - The obj value to set.

Returns:

A Message object from the global pool.

recycle

public void recycle()

Return a Message instance to the global pool. You MUST NOT touch the Message after calling this function -- it has effectively been freed.

copyFrom

public void copyFrom(Message o)

Make this message like o. Performs a shallow copy of the data field. Does not copy the linked list fields, nor the timestamp or target/callback of the original message.

getWhen

public long getWhen()

Return the targeted delivery time of this message, in milliseconds.

setTarget

public void setTarget(Handler target)

getTarget

public Handler getTarget()

Retrieve the a Handler implementation that will receive this message. The object must implement Handler.handleMessage(). Each Handler has its own name-space for message codes, so you do not need to worry about yours conflicting with other handlers.

getCallback

public Runnable getCallback()

Retrieve callback object that will execute when this message is handled. This object must implement Runnable. This is called by the target Handler that is receiving this Message to dispatch it. If not set, the message will be dispatched to the receiving Handler's Handler.handleMessage(Message Handler.handleMessage()).

getData

public Bundle getData()

Obtains a Bundle of arbitrary data associated with this event, lazily creating it if necessary. Set this value by calling setData(Bundle).

peekData

public Bundle peekData()

Like getData(), but does not lazily create the Bundle. A null is returned if the Bundle does not already exist.

setData

public void setData(Bundle data)

Sets a Bundle of arbitrary data values. Use arg1 and arg1 members as a lower cost way to send a few simple integer values, if you can.

sendToTarget

public void sendToTarget()

Sends this Message to the Handler specified by getTarget(). Throws a null pointer exception if this field has not been set.

clearForRecycle

void clearForRecycle()

toString

public String toString()

Description copied from class: Object

Returns a string containing a concise, human-readable description of the receiver.

Overrides:

toString in class Object

Returns:

String a printable representation for the receiver.

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 dest,
                          int flags)

Description copied from interface: Parcelable

Flatten this object in to a Parcel.

Specified by:

writeToParcel in interface Parcelable

Parameters:

dest - 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.