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:

/** * @authorAllin.dev *http://allin.cnblogs.com */ Public classMainthreadextendsactivity{Private Static FinalString TAG = "Mainthread"; PrivateHandler Mmainhandler, Mchildhandler; PrivateTextView Info; PrivateButton msgbtn; @Override Public voidonCreate (Bundle savedinstancestate) {Super. OnCreate (savedinstancestate);        Setcontentview (R.layout.main); Info=(TextView) Findviewbyid (r.id.info); MSGBTN=(Button) Findviewbyid (R.ID.MSGBTN); Mmainhandler=NewHandler () {@Override Public voidhandlemessage (Message msg) {log.i (TAG,"Got an incoming message from the child thread-" +(String) msg.obj); //receive messages for child threadsInfo.settext ((String) msg.obj);        }          }; NewChildthread (). Start (); Msgbtn.setonclicklistener (NewOnclicklistener () {@Override Public voidOnClick (View v) {if(Mchildhandler! =NULL )        {                    //send a message to a child threadMessage 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 voidOnDestroy () {Super. OnDestroy (); LOG.I (TAG,"Stop Looping the child thread ' s message queue");  Mchildhandler.getlooper (). Quit (); }    classChildthreadextendsThread {Private Static FinalString Child_tag = "Childthread";  Public voidrun () { This. SetName ("Childthread" ); //Initialize the message loop queue before handler is createdLooper.prepare (); Mchildhandler=NewHandler () {@Override Public voidhandlemessage (Message msg) {log.i (Child_tag,"Got an incoming message from the main thread-" +(String) msg.obj); Try          {                        //you can do some time-consuming work in a child threadSleep (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 blockE.printstacktrace ();            }        }              }; LOG.I (Child_tag,"Child handler was bound to-" +mchildhandler.getlooper (). GetThread (). GetName ()); //Start a child thread message loop queueLooper.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