handler发送和接收message的各种方式 (1)Handler.SendEmptyMessage(what); (2)Handler.obtainMessage(int what, int arg1, int arg2, Object obj).sendYToTarget(); (3)Message.obtain(handler, MESSAGE_MSG, 0, 0, msg).sendToTarget(); (4)Message message = Message.obtain(); message.what = PROGRESS_MSG; message.arg1