Handler

Handler

public Handler ()

This constructor is deprecated.
Implicitly choosing a Looper during Handler construction can lead to bugs where operations are silently lost (if the Handler is not expecting new tasks and quits), crashes (if a handler is sometimes created on a thread without a Looper active), or race conditions, where the thread a handler is associated with is not what the author anticipated. Instead, use an Executor or specify the Looper explicitly, using Looper.getMainLooper, View.getHandler(), or similar. If the implicit thread local behavior is required for compatibility, use new Handler(Looper.myLooper()) to make it clear to readers.

Default constructor associates this handler with the Looper for the current thread. If this thread does not have a looper, this handler won't be able to receive messages so an exception is thrown.

Handler

public Handler (Handler.Callback callback)

This constructor is deprecated.
Implicitly choosing a Looper during Handler construction can lead to bugs where operations are silently lost (if the Handler is not expecting new tasks and quits), crashes (if a handler is sometimes created on a thread without a Looper active), or race conditions, where the thread a handler is associated with is not what the author anticipated. Instead, use an Executor or specify the Looper explicitly, using Looper.getMainLooper, View.getHandler(), or similar. If the implicit thread local behavior is required for compatibility, use new Handler(Looper.myLooper(), callback) to make it clear to readers.

Constructor associates this handler with the Looper for the current thread and takes a callback interface in which you can handle messages. If this thread does not have a looper, this handler won't be able to receive messages so an exception is thrown.

Handler

public Handler (Looper looper)

Use the provided Looper instead of the default one.

Handler

public Handler (Looper looper, 
                Handler.Callback callback)

Use the provided Looper instead of the default one and take a callback interface in which to handle messages.

createAsync

public static Handler createAsync (Looper looper, 
                Handler.Callback callback)

Create a new Handler whose posted messages and runnables are not subject to synchronization barriers such as display vsync.

Messages sent to an async handler are guaranteed to be ordered with respect to one another, but not necessarily with respect to messages from other Handlers.

createAsync

public static Handler createAsync (Looper looper)

Create a new Handler whose posted messages and runnables are not subject to synchronization barriers such as display vsync.

Messages sent to an async handler are guaranteed to be ordered with respect to one another, but not necessarily with respect to messages from other Handlers.

dispatchMessage

public void dispatchMessage (Message msg)

Handle system messages here.

dump

public final void dump (Printer pw, 
                String prefix)

getLooper

public final Looper getLooper ()

getMessageName

public String getMessageName (Message message)

Returns a string representing the name of the specified message. The default implementation will either return the class name of the message callback if any, or the hexadecimal representation of the message "what" field.

handleMessage

public void handleMessage (Message msg)

Subclasses must implement this to receive messages.

hasCallbacks

public final boolean hasCallbacks (Runnable r)

Check if there are any pending posts of messages with callback r in the message queue.

hasMessages

public final boolean hasMessages (int what)

Check if there are any pending posts of messages with code 'what' in the message queue.

hasMessages

public final boolean hasMessages (int what, 
                Object object)

Check if there are any pending posts of messages with code 'what' and whose obj is 'object' in the message queue.

obtainMessage

public final Message obtainMessage (int what, 
                Object obj)

Same as obtainMessage(), except that it also sets the what and obj members of the returned Message.

obtainMessage

public final Message obtainMessage ()

Returns a new Message from the global message pool. More efficient than creating and allocating new instances. The retrieved message has its handler set to this instance (Message.target == this). If you don't want that facility, just call Message.obtain() instead.

obtainMessage

public final Message obtainMessage (int what, 
                int arg1, 
                int arg2)

Same as obtainMessage(), except that it also sets the what, arg1 and arg2 members of the returned Message.

obtainMessage

public final Message obtainMessage (int what, 
                int arg1, 
                int arg2, 
                Object obj)

Same as obtainMessage(), except that it also sets the what, obj, arg1,and arg2 values on the returned Message.

obtainMessage

public final Message obtainMessage (int what)

Same as obtainMessage(), except that it also sets the what member of the returned Message.

post

public final boolean post (Runnable r)

Causes the Runnable r to be added to the message queue. The runnable will be run on the thread to which this handler is attached.

postAtFrontOfQueue

public final boolean postAtFrontOfQueue (Runnable r)

Posts a message to an object that implements Runnable. Causes the Runnable r to executed on the next iteration through the message queue. The runnable will be run on the thread to which this handler is attached. This method is only for use in very special circumstances -- it can easily starve the message queue, cause ordering problems, or have other unexpected side-effects.

postAtTime

public final boolean postAtTime (Runnable r, 
                long uptimeMillis)

Causes the Runnable r to be added to the message queue, to be run at a specific time given by uptimeMillis. The time-base is SystemClock.uptimeMillis(). Time spent in deep sleep will add an additional delay to execution. The runnable will be run on the thread to which this handler is attached.

postAtTime

public final boolean postAtTime (Runnable r, 
                Object token, 
                long uptimeMillis)

Causes the Runnable r to be added to the message queue, to be run at a specific time given by uptimeMillis. The time-base is SystemClock.uptimeMillis(). Time spent in deep sleep will add an additional delay to execution. The runnable will be run on the thread to which this handler is attached.

postDelayed

public final boolean postDelayed (Runnable r, 
                long delayMillis)

Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses. The runnable will be run on the thread to which this handler is attached. The time-base is SystemClock.uptimeMillis(). Time spent in deep sleep will add an additional delay to execution.

postDelayed

public final boolean postDelayed (Runnable r, 
                Object token, 
                long delayMillis)

Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses. The runnable will be run on the thread to which this handler is attached. The time-base is SystemClock.uptimeMillis(). Time spent in deep sleep will add an additional delay to execution.

removeCallbacks

public final void removeCallbacks (Runnable r)

Remove any pending posts of Runnable r that are in the message queue.

removeCallbacks

public final void removeCallbacks (Runnable r, 
                Object token)

Remove any pending posts of Runnable r with Object token that are in the message queue. If token is null, all callbacks will be removed.

removeCallbacksAndMessages

public final void removeCallbacksAndMessages (Object token)

Remove any pending posts of callbacks and sent messages whose obj is token. If token is null, all callbacks and messages will be removed.

removeMessages

public final void removeMessages (int what)

Remove any pending posts of messages with code 'what' that are in the message queue. Note that `Message#what` is 0 unless otherwise set. When calling `postMessage(Runnable)` or `postAtTime(Runnable, long)`, the `Runnable` is internally wrapped with a `Message` whose `what` is 0. Calling `removeMessages(0)` will remove all messages without a `what`, including posted `Runnable`s.

removeMessages

public final void removeMessages (int what, 
                Object object)

Remove any pending posts of messages with code 'what' and whose obj is 'object' that are in the message queue. If object is null, all messages will be removed.

sendEmptyMessage

public final boolean sendEmptyMessage (int what)

Sends a Message containing only the what value.

sendEmptyMessageAtTime

public final boolean sendEmptyMessageAtTime (int what, 
                long uptimeMillis)

Sends a Message containing only the what value, to be delivered at a specific time.

sendEmptyMessageDelayed

public final boolean sendEmptyMessageDelayed (int what, 
                long delayMillis)

Sends a Message containing only the what value, to be delivered after the specified amount of time elapses.

sendMessage

public final boolean sendMessage (Message msg)

Pushes a message onto the end of the message queue after all pending messages before the current time. It will be received in handleMessage(Message), in the thread attached to this handler.

sendMessageAtFrontOfQueue

public final boolean sendMessageAtFrontOfQueue (Message msg)

Enqueue a message at the front of the message queue, to be processed on the next iteration of the message loop. You will receive it in handleMessage(Message), in the thread attached to this handler. This method is only for use in very special circumstances -- it can easily starve the message queue, cause ordering problems, or have other unexpected side-effects.

sendMessageAtTime

public boolean sendMessageAtTime (Message msg, 
                long uptimeMillis)

Enqueue a message into the message queue after all pending messages before the absolute time (in milliseconds) uptimeMillis. The time-base is SystemClock.uptimeMillis(). Time spent in deep sleep will add an additional delay to execution. You will receive it in handleMessage(Message), in the thread attached to this handler.

sendMessageDelayed

public final boolean sendMessageDelayed (Message msg, 
                long delayMillis)

Enqueue a message into the message queue after all pending messages before (current time + delayMillis). You will receive it in handleMessage(Message), in the thread attached to this handler.

toString

public String toString ()

Returns a string representation of the object.