Callback interface for discovering when a thread is going to block waiting for more messages.
Called when the message queue has run out of messages and will now wait for more.
boolean queueIdle ()
Called when the message queue has run out of messages and will now wait for more. Return true to keep your idle handler active, false to have it removed. This may be called if there are still messages pending in the queue, but they are all scheduled to be dispatched after the current time.