Java-ME Application in Freeze Mode

Question

I am developing a Java-ME Based Mobile Application. Now My Requirements are like whenever I am updating one of my RMS, I want my application to be stay in a Freeze kind of mode; which means no other action like clicking button or anything else should happen. My Method is already "Synchronized".

Kindly guide me regarding this question.

Thanks.

Answer 1

The best way to handle this is to "serialize" your tasks. You can do this with a message queue - a class that maintains a Vector of message objects (tasks) and runs code based on each message. The queue runs on a thread that processes each task (message) in series. You create a simple message class for the different tasks - read RMS etc. A message can be an Integer if you like that wraps a number. The operation of adding and retrieving messages is synchronized but the code than does the tasks is not and runs on a simple switch block. The benefit of serializing your tasks is you don't have to worry about concurrency. Here is some of the essential code from a class I use to do this.

class MessageQueue implements Runnable{
Vector messages;
Thread myThread;
volatile boolean stop;

public void start() {
stop=false;
myThread=new Thread(this);
myThread.start();
}

// add message to queue - this is public
public synchronized void addMessage(Message m) {
messages.addElement(m);
if(stop) {
    start();
} else {
    // wake the thread
notify();
    }
}

// get next message from queue - used by this thread
private synchronized Message nextMessage() {
if(stop) return null;
if(messages.isEmpty()) {
    return null;
    } else {
    Message m=(Message)messages.firstElement();
    messages.removeElementAt(0);
    return m;
   }
}

public void run() {
    while (!stop) {
        // make thread wait for messages
        if (messages.size() == 0) {
            synchronized (this) {
                try {
                    wait();
                } catch (Exception e) {

                }
            }
        }
        if (stop) {
            // catch a call to quit
            return;
        }
        processMessage();
    }
}
}

// all the tasks are in here
private void processMessage() {
    Message m = nextMessage();
    switch (m.getType()) {
        case Message.TASK1:
            // do stuff
            break;
        case Message.TASK2:
            // do other stuff
            break;
        case Message.TASK3:
            // do other other stuff
            break;
        default: //handle bad message
        }
    }
}