"Go" Android Development Practice: Customizing worker threads with Message loops (Looper)

http://ticktick.blog.51cto.com/823160/1565272

The previous article mentions that the UI thread of an Android system is a thread with a message loop (Looper) mechanism, while Android also provides a Handlerthread class that encapsulates a message loop (Looper) that can bind handler () objects, A message is sent to the thread through the SendMessage () function of handler, and the message received by the thread is processed through the handlemessage () function. In this case, this article uses the underlying Java class library to implement a thread with a message loop (Looper) to help beginners understand how such a Looper works.

1. First, we complete a simple threading framework.

PublicClassLooperthread {   PrivateVolatileBoolean mislooperquit =False   Private Thread Mthread;  Publicvoid Start () {  if (mthread! =NULL) {   Return } Mislooperquit =False Mthread =New Thread (mlooperrunnable); Mthread.start ();}  Publicvoid Stop () {  if (Mthread = =NULL) {   Return }  Mislooperquit = true;  Mthread = null;}  protected Runnable mlooperrunnable = new Runnable ( ) {   @Override   public void run () {   while (!mislooperquit) { Span class= "indent" >    } }};}          

As shown in the code above, the Mlooperrunnable.run () loop executes the thread task, and Mislooperquit is the condition for the thread to exit the loop. Next, we'll add the sending and handling code for the message.

2. Add message sending and processing code for thread looping

(1) Define message structure, create message queue

Looperthread {    int what;}}

(2) Creating mutexes and condition variables

Looperthread {     private Condition mcondition = Mlock.newcondition ();}

(3) Create a function to send a message

Send message, called by external other module, send message to thread  void sendMessage (Message message) {  null) {return; } MLock. Lock (); //Add message to Message Queue mcondition.signal ();  Notifies the thread loop that there is a message coming, please immediately handle mlock.unlock ();}          

(4) Creating a function to process messages

Processing the message, called by the thread inside the  void handlemessage (Message message) {    //Here can be tuned back to listener through a callback} 

(5) Parsing messages in the Mlooperrunnable.run () loop

protected Runnable mlooperrunnable =New Runnable () {    @Override Publicvoid Run () {    while (!mislooperquit) {    MLock.Lock ();  Message message =Null     try {    while (!mislooperquit && mmessagequeue.isempty ()) {    Mcondition.await ();Hibernate if no message arrives   }   message = Mmessagequeue.poll ();  }   catch (interruptedexception e) {     E.printstacktrace ();   }   finally {    Mlock.unlock ();   }      Handlemessage (message);  }};}          

(6) Modify the thread's stop () function to wake the dormant message loop

void Stop () {  null) {return; } true; MLock. Lock (); mcondition.signal (); Mlock.unlock (); mmessagequeue.clear (); null;}         

Here, a basic thread class package with message loop is completed, I believe you should write this code in the process, understand how the system realizes the message loop. Complete code see the last attachment of the post, have any questions welcome message or letter [email protected] exchange.

"Go" Android Development Practice: Customizing worker threads with Message loops (Looper)