Android Thread Communication

Summary

Andriod provides Handler and Looper to meet the communication between threads. For example, a sub-thread downloads a picture from the network and sends a message to the main thread when it is downloaded, and this message is passed by binding to the handler of the main thread.

Body

Graphic:

code example:

/** * @author Allin.dev * http://allin.cnblogs.com */public class Mainthread extends activity{private static F  inal String TAG = "Mainthread";  Private Handler Mmainhandler, Mchildhandler;  Private TextView info;    Private Button msgbtn;    @Override public void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate);        Setcontentview (R.layout.main);    info = (TextView) Findviewbyid (r.id.info);        MSGBTN = (Button) Findviewbyid (R.ID.MSGBTN);  Mmainhandler = new Handler () {@Override public void Handlemessage (Message msg) {LOG.I (        TAG, "Got an incoming message from the child thread-" + (String) msg.obj);      Receives the message Info.settext (String) msg.obj) of the child thread;        }          };        New Childthread (). Start ();                Msgbtn.setonclicklistener (New Onclicklistener () {@Override public void OnClick (View v) {    if (Mchildhandler! = null)    {//Send message to child thread message childmsg = Mchildhandler.obtainmessage ();          Childmsg.obj = Mmainhandler.getlooper (). GetThread (). GetName () + "says Hello";                    Mchildhandler.sendmessage (CHILDMSG);                  LOG.I (TAG, "Send a message to the child thread-" + (String) childmsg.obj);      }      }    } );    } public void OnDestroy () {Super.ondestroy ();    LOG.I (TAG, "Stop looping the child thread ' s Message queue");  Mchildhandler.getlooper (). Quit ();        } class Childthread extends Thread {private static final String Child_tag = "Childthread";            public void Run () {this.setname ("Childthread");            Initializes the message loop queue, which needs to be looper.prepare () before handler is created; Mchildhandler = new Handler () {@Override public void Handlemessage (Message msg) {L            OG.I (Child_tag, "Got a incoming message from the main thread-"  + (String) msg.obj);                        try {//can do some time-consuming work in a child thread sleep (100);            Message Tomain = Mmainhandler.obtainmessage ();  Tomain.obj = "This is" + this.getlooper (). GetThread (). GetName () + ".                        Did you send me \ "" + (String) msg.obj + "\"? ";                        Mmainhandler.sendmessage (Tomain);                      LOG.I (Child_tag, "Send a message to the main thread-" + (String) tomain.obj); } catch (Interruptedexception e) {//TODO auto-generated catch block E.printsta          Cktrace ();            }        }              };            LOG.I (Child_tag, "child handler was bound to-" + mchildhandler.getlooper (). GetThread (). GetName ());    Initiates a child thread message loop queue Looper.loop (); }  }}

Ps:

Using the Handlerthread Looper object to create the handler, if you use the default construction method, it is likely to block the UI thread, referring to http://www.cnblogs.com/ccdc/p/3837798.html. Improvement scheme A new thread will be used to replace the handler of the main course with the looper of the main thread looper, as below,

Reference

Shangdawei.android inter-thread communication [2014-07-11] (2013-03-26). http://www.cnblogs.com/shangdawei/archive/2013/03/26/2983217.html

Http://www.cnblogs.com/ccdc/p/3837883.html

Android Thread Communication