sending a looping thread a message java/android

Question

So I have the following thread:

  public class MyThread extends Thread
{
  Handler cHandler;
 private boolean looprunning = false;
  MyThread() {
  cHandler = new Handler();
          looprunning = true;

  }

  @Override
  public void run(){
      while (looprunning) {
          //do stuff here
        //update another system here or something else.
      }
  }

}

Inside the while loop of this thread, I want to run a Runnable that I pass to the thread while the thread is looping inside that while loop. How do I do this?

score 2 · Accepted Answer · answered May 16 '12 at 12:44

2

first please mark looprunning as volatile for proper thread visibility

you can use a queue

Queue<Runnable> taskQueue = new ConcurrentLinkedQueue<Runnable>();
@Override
public void run(){
   while (looprunning) {
       //do stuff here
     //update another system here or something else.
     Runnable r = taskQueue.poll();
     if(r!=null)r.run();
   }
}

you can use a (thread-safe) queue of your choice

answered May 16 '12 at 12:44

ratchet freak

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wait that's it? You mean to tell me that I don't need to use a handler to post messages to the thread? I can just send the runnable to this list, the one of which I'm assuming you're using is thread-safe, instead of something with a looper or doing handler.sendmessage() – Apothem Da Munster May 16 '12 at 14:00

score 1 · Answer 2 · answered May 16 '12 at 12:44

1

Android already provides a mechanism for creating threads that run in loops that execute Runnables. Have a look at HandlerThread

answered May 16 '12 at 12:44

David Wasser

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Is there a way to make that handlerthread actually have a loop of logic constantly going? Like in my example? I tried HandlerThread and from what I can tell, you dont want to override run(), but it processes messages one at a time. So I send a loop like in the example, the handler thread locks. – Apothem Da Munster May 16 '12 at 13:23
1

Sorry, I guess I misunderstood what you are trying to do. I didn;t realize that you wanted to have the thread looping constantly doing something else and then have it **additionally** run some Runnable that you send to it while it loops. In that case, the suggestion from @ratchetfreak seems reasonable. – David Wasser May 16 '12 at 13:55
Thank you very much for the verification on that. I made the same mistake myself when I first started trying to figure out how to do this. Hilariously enough, that was the same answer I got on my last question, and I thought that was it. http://stackoverflow.com/questions/10560166/pass-a-runnable-to-a-pre-existing-thread-to-be-run-in-android-java – Apothem Da Munster May 16 '12 at 14:05

Sachin Gurnani · Answer 3 · 2012-05-16T13:16:52.643

you do it like this whatever calculations you have write it inside that run method and when it done send message to handler and whatever UI Related thing like change the UI do it there like im doing progressdialog dismiss(); And one more thing if try to change the UI like thing in run you definitely get Leak Window Error because you are trying to change the UI in non UI thread.

final Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {


            dialog.dismiss();

        }

    };



            dialog = ProgressDialog.show(NewTransaction.this, "",
                    "Loading Meters...", false);

            new Thread() {

                public void run() {

                    while(Condition){

                                  do Something
                                 }
                    handler.sendEmptyMessage(0);

                }

            }.start();

sending a looping thread a message java/android

3 Answers3