Use or store serial data and access from other class-Java

Question

Hi i am new to serial programming.I am trying to return serial data from one class to another , This is my code(Using RXTX libraries)

class XXX implements SerialPortEventListener{

    final int[] val = new int[2];

    public synchronized void serialEvent(SerialPortEvent oEvent) {
        String storeId;
        String status; 

        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                String inputLine = input.readLine();
                String[] arrayValues = inputLine.split(" ");
                storeId=arrayValues[0];
                status=arrayValues[1];
                light=Integer.parseInt(storeId);
                lightstatus = Integer.parseInt(status);

                //System.out.println(light);
                //System.out.println(status);
                val[0] = light;
                val[1] = lightstatus;
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }  
    }

    public int send(){
        return val[0];
    }

    public int sendst(){
        return val[1];
    }
}

Reading and printing the data in this class is succesful, But accessing the value out of this returns null...any help would be appreciated..Thankyou

Answer 1

Reading and printing the data in this class is succesful, But accessing the value out of this returns null...

Based in your code I see you're following this example: Event Based Two Way Communication (if you are not then you should take a look). As its title says it's an event based way of read/write through serial port.

Having said this, I strongly suspect you're trying to do something like this:

XXX serialPortListener = new XXX();
int light = serialPortListener.send();
int lightStatus = serialPortListener.sendst();

It's most likely that send() and sendst() return null or 0 because no SerialPortEvent has happened yet when these methods are called. So if you're working in an event driven scenario then it makes sense keep in this framework. How? For instance implementing an Observer pattern:

1) Make XXX class extend from Observable and perform this little change:

public class XXX extends Observable implements SerialPortEventListener {

    int[] val = new int[2];

    public synchronized void serialEvent(SerialPortEvent oEvent) {
        String storeId;
        String status; 
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                // all your code here
                setChanged();
                notifyObservers();
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }  
    }

    ...
}

2) Another class has to implement Observer interface:

public class MyObserver implements Observer {

    @Override
    public void update(Observable o, Object arg) {
        if(o instanceof XXX){
            XXX observable = (XXX) o;
            System.out.println("Light: " + observable.send());
            System.out.println("Light status: " + observable.sendst());
        }
    }
}

3) Append a MyObserver object to XXX instance:

XXX serialPortListener = new XXX();
serialPortListener.addObserver(new MyObserver());

That's it. Every time a SerialPortEvent is processed the observer will be notified and it will successfuly read the values.