Question

The Following class DoStuff starts a thread and syncs to protect the listener object from being accessed when null.

Now when accessing the DoStuff class function setOnProgressListener() externally I’m having issues because the call is getting held for a long time before it exits the function call. I’m not sure why this happens? I seems as if the synchronization has queued up a lot of calls? Any input on this would help!

I’m essentially passing null to the listener because I no longer wish to get updated for this status. I do this as part of my process to kill the DoStuff Thread.

Thanks!

public class DoStuff extends Runnable
{
    Object MUTEX = new Object();
    private OnProgressListener mOnProgressListener  = null;

    public DoStuff()
    {
        new Thread(this).start();
    }

    public void setOnProgressListener( OnProgressListener onProgressListener )
    {
        synchronized (MUTEX) 
        {
            mOnProgressListener = onProgressListener;
        }
    }

    private void reportStatus( int statusId )
    {
        synchronized (MUTEX) 
        {
            if (null != mOnStatusListener)
            {
                mOnStatusListener.setStatusMessage(new OnStatusEvent(this, statusId));
            }
        }
    }

    // this is the run of a thread
    public void run()
    {
        int status = 0;
        do
        {
            // do some work and report the current work status
            status = doWork();
            reportStatus( status );
        } while(true);
    }
}

Answer 1

Thanks all for your help. I was able to determine why the indefinite lock. Something important and obvious is that once I run the reportStatus() function call it will hold the lock MUTEX until it is completely done executing the callback. My fault was that at the registered callback I was calling setOnProgressListener(null) by mistake. Yes, I admit didn’t post enough code, and most likely all of you would have catched the bug… So calling setOnProgressListener(null) would wait until the MUTEX object has been released, and the reportStatus() was held waiting to call setOnProgressListener(null), therefore I was in a deadlock!

Again the main point I learned is to remember that triggering a callback message will hold until the registered callback function is done processing it’s call.

Thanks all!