public
final
class
Looper
extends Object
| java.lang.Object | |
| ↳ | android.os.Looper |
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.
Developers
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();
}
}
Public methods | |
|---|---|
void
|
dump(Printer pw, String prefix)
Dumps the state of the looper for debugging purposes. |
static
Looper
|
getMainLooper()
Returns the application's main looper, which lives in the main thread of the application. |
MessageQueue
|
getQueue()
Gets this looper's message queue. |
Thread
|
getThread()
Gets the Thread associated with this Looper. |
boolean
|
isCurrentThread()
Returns true if the current thread is this looper's thread. |
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 |
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()
Quits the looper. |
void
|
quitSafely()
Quits the looper safely. |
void
|
setMessageLogging(Printer printer)
Control logging of messages as they are processed by this Looper. |
String
|
toString()
Returns a string representation of the object. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
void dump (Printer pw, String prefix)
Dumps the state of the looper for debugging purposes.
| Parameters | |
|---|---|
pw |
Printer:
A printer to receive the contents of the dump. |
prefix |
String:
A prefix to prepend to each line which is printed.
|
Looper getMainLooper ()
Returns the application's main looper, which lives in the main thread of the application.
| Returns | |
|---|---|
Looper |
|
MessageQueue getQueue ()
Gets this looper's message queue.
| Returns | |
|---|---|
MessageQueue |
The looper's message queue. |
Thread getThread ()
Gets the Thread associated with this Looper.
| Returns | |
|---|---|
Thread |
The looper's thread. |
boolean isCurrentThread ()
Returns true if the current thread is this looper's thread.
| Returns | |
|---|---|
boolean |
|
void loop ()
Run the message queue in this thread. Be sure to call
quit() to end the loop.
Looper myLooper ()
Return the Looper object associated with the current thread. Returns null if the calling thread is not associated with a Looper.
| Returns | |
|---|---|
Looper |
|
MessageQueue myQueue ()
Return the MessageQueue object associated with the current
thread. This must be called from a thread running a Looper, or a
NullPointerException will be thrown.
| Returns | |
|---|---|
MessageQueue |
|
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().
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. See also: prepare()
void quit ()
Quits the looper.
Causes the loop() method to terminate without processing any
more messages in the message queue.
Any attempt to post messages to the queue after the looper is asked to quit will fail.
For example, the sendMessage(Message) method will return false.
Using this method may be unsafe because some messages may not be delivered
before the looper terminates. Consider using quitSafely() instead to ensure
that all pending work is completed in an orderly manner.
See also:
void quitSafely ()
Quits the looper safely.
Causes the loop() method to terminate as soon as all remaining messages
in the message queue that are already due to be delivered have been handled.
However pending delayed messages with due times in the future will not be
delivered before the loop terminates.
Any attempt to post messages to the queue after the looper is asked to quit will fail.
For example, the sendMessage(Message) method will return false.
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 |
Printer:
A Printer object that will receive log messages, or
null to disable message logging.
|
String toString ()
Returns a string representation of the object. In general, the
toString method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the at-sign character `@', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
| Returns | |
|---|---|
String |
a string representation of the object. |