android.os
Class Looper

java.lang.Object
  android.os.Looper

public class Looper
extends Object

Class used to run a message loop for a thread. Threads by default do not have a message loop associated with them; to create one, call prepare() in the thread that is to run the loop, and then loop() to have it process messages until the loop is stopped.

Most interaction with a message loop is through the Handler class.

This is a typical example of the implementation of a Looper thread, using the separation of prepare() and loop() to create an initial Handler to communicate with the Looper.

  class LooperThread extends Thread {
      public Handler mHandler;
      
      public void run() {
          Looper.prepare();
          
          mHandler = new Handler() {
              public void handleMessage(Message msg) {
                  // process incoming messages here
              }
          };
          
          Looper.loop();
      }
  }

Nested Class Summary

(package private) static class

Looper.HandlerException

Field Summary

(package private) MessageQueue	mQueue
(package private) boolean	mRun
(package private) Thread	mThread

Method Summary

void	dump(Printer pw, String prefix)
static Looper	getMainLooper() Returns the application's main looper, which lives in the main thread of the application.
static void	loop() Run the message queue in this thread.
static Looper	myLooper() Return the Looper object associated with the current thread.
static MessageQueue	myQueue() Return the MessageQueue object associated with the current thread.
static void	prepare() Initialize the current thread as a looper.
static void	prepareMainLooper() Initialize the current thread as a looper, marking it as an application's main looper.
void	quit()
void	setMessageLogging(Printer printer) Control logging of messages as they are processed by this Looper.
String	toString() Returns a string containing a concise, human-readable description of the receiver.

Methods inherited from class java.lang.Object

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

Field Detail

mQueue

final MessageQueue mQueue

mRun

volatile boolean mRun

mThread

Thread mThread

Method Detail

prepare

public static final void prepare()

Initialize the current thread as a looper. This gives you a chance to create handlers that then reference this looper, before actually starting the loop. Be sure to call loop() after calling this method, and end it by calling quit().

prepareMainLooper

public static final void prepareMainLooper()

Initialize the current thread as a looper, marking it as an application's main looper. The main looper for your application is created by the Android environment, so you should never need to call this function yourself. prepare()

getMainLooper

public static final Looper getMainLooper()

Returns the application's main looper, which lives in the main thread of the application.

loop

public static final void loop()

Run the message queue in this thread. Be sure to call quit() to end the loop.

myLooper

public static final Looper myLooper()

Return the Looper object associated with the current thread.

setMessageLogging

public void setMessageLogging(Printer printer)

Control logging of messages as they are processed by this Looper. If enabled, a log message will be written to printer at the beginning and ending of each message dispatch, identifying the target Handler and message contents.

Parameters:

printer - A Printer object that will receive log messages, or null to disable message logging.

myQueue

public static final MessageQueue myQueue()

Return the MessageQueue object associated with the current thread.

quit

public void quit()

dump

public void dump(Printer pw,
                 String prefix)

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.