Question

I’m trying to use observable in my code and there is this problem giving me hard time.

public class observeState extends Observable
{
    public void setSelectedTransaction(int idx)
    {
        if (selectedTransaction != idx)
        {
            this.selectedTransaction = idx;
            setChanged();
            notifyObservers("setSelectedTransaction");
            System.out.println("Observers : "+this.countObservers());
        }
    }

    public void setLog(Log log)
    {
        if(theLog != log) {
            theLog = log;
            System.out.println(theLog.getLogTransactions().size() + "setLog");
            setChanged();
            notifyObservers("setLog");
            System.out.println("Observers : "+this.countObservers());
        }
    }

There are two observers observing this observable class and it does send out notifyObservers when the setSelectedTransaction method is called with the test line “Observers : 2”. However the next method setLog does not seem to have observers giving “Observers : 0”. I don’t think I can only use observable method once.

Answer 1

The mostly likely cause of this issue is that you are not calling the method on the same object. It is a common mistake to assume two objects are the same because they have the same name or some other confusion. I would print out the hashCode of each object or use a debugger to ensure you really are calling the same object.

BTW you can try making the calls in the opposite order, or more than once
to test your theory.