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This is a part of a sample code from a RXTX serial communication program.
I would like to know on how to extract the string variable that I have created to store the output so that I could use it in another class. The output is showing on the console but I want to display it in a JTextfield and I'm unable to extract it. I have done the GUI part.
First I will show the main part:
public class MainSerialGui {
public static void main(String[] args) {
SerialGui vimal = new SerialGui ();
vimal.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
vimal.setSize(250, 200);
vimal.setVisible(true);
}
}
This is the GUI part
public class SerialGui extends JFrame { //inherit all the stuff from JFrame and let us create a window
private JTextField item1;
private JButton readButton;
public SerialGui (){
setLayout(new FlowLayout());
item1 = new JTextField("Display Output");
add(item1);
readButton = new JButton("Read Data");
add(readButton);
thehandler handler = new thehandler();
readButton.addActionListener(handler);
}
private class thehandler implements ActionListener {
public void actionPerformed(ActionEvent event) {
if(event.getSource() == readButton){
String portName = "COM4";
try{
CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(portName);
if ( portIdentifier.isCurrentlyOwned() )
{
System.out.println("Error: Port is currently in use");
}
else
{
CommPort commPort = portIdentifier.open(this.getClass().getName(),2000);
if ( commPort instanceof SerialPort )
{
SerialPort serialPort = (SerialPort) commPort;
serialPort.setSerialPortParams(57600,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE); // Setting port parameters
InputStream in = serialPort.getInputStream();
OutputStream out = serialPort.getOutputStream();
(new Thread(new SerialReader(in))).start();
SerialReader comm = new SerialReader(null);
item1.setText(comm.str);
}
}
}
catch (Exception e){
e.printStackTrace();
System.out.println("Only serial ports please");
}
}
}
}
}
This is a separate class to read the data from the comm port.
public class SerialReader implements Runnable {
InputStream in;
public String str;
public SerialReader ( InputStream in )
{
this.in = in;
}
public void run ()
{
byte[] buffer = new byte[1024];
int len = -1;
try
{
while ( ( len = this.in.read(buffer)) > -1 )
{
str = new String(buffer,0,len); // I would like to take this String
System.out.print(str); // and use it to display in a
} // Jtextfield
}
catch ( IOException e )
{
e.printStackTrace();
}
}
}
This is how I initially extract it to display in the textfield however the results shows null. I declare str as public string so that it is visible in the GUI class. The data that being read can be shown in the console but no changes in the textfield. Is it because its taking the value even before the output is stored in str or because of the 'null' argument?
I was unable to replace it with any other argument.
SerialReader comm = new SerialReader(null);
item1.setText(comm.str);
http://rxtx.qbang.org/wiki/index.php/Two_way_communcation_with_the_serial_port

You are creating TWO SerialReader instances, and starting one of them while using output of the other.
Try replacing,
(new Thread(new SerialReader(in))).start();
SerialReader comm = new SerialReader(null);
item1.setText(comm.str);
with
SerialReader comm = new SerialReader(in);
Thread commThread = new Thread(comm);
commThread.start();
commThread.join();
item1.setText(comm.str);
Hope this helps.