Updating GUI from another class which implements SerialPortEventListener (Java FX, FXML) - com

Question

I am making an application which uses serial communication. In SerialEvent method of that class, I am awaiting for a input from COM port, and then I want to pass it to the controller class of an .fxml screen.
Input will always be 8 bytes, and it works correctly inside that thread (I read the input and by printing it to the output, I see that the String is correct). However, when I try to pass it "in real time" to the controller class, I have a problem.
If I pass it directly, it does receieve it, but I can't invoke anything later (Not on FX Application Thread exception), I know that I can't do it that way, that I need to use Platform.runLater or similair solution, but if I use it that way, my controller class never receives that input, textField which I am trying to update stays blank.
I will copy part of the code here, and I am hoping that someone tell me what I'm doing wrong.
SERIALEVENT METHOD OF ANOTHER CLASS
#Override
public void serialEvent(SerialPortEvent spe) {
if (spe.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
byte singleData = (byte) input.read();
logText = new String(new byte[]{singleData});
bytes.add(logText);
if(bytes.size() == 8) {
for (int i = 0; i < bytes.size(); i++) {
inputText += bytes.get(i);
}
if(inputText.length() == 8) {
Platform.runLater(new Runnable() {
#Override
public void run() {
controller.getInputString(inputText);
}
});
}
bytes.clear();
inputText = "";
}
} catch (Exception e) {
logText = "Failed to read data. (" + e.toString() + ")";
controller.getInputString(logText);
}
}
}
GETINPUT METHOD OF THE CONTROLLER CLASS
#Override
public void getInputString(String input) {
firstSerialNumberField.setText(input);
}
When using it this way, my firstSerialNumberField never gets that input.
---EDIT---
SETCONTROLLER METHOD OF THE SERIALPORTLISTENER CLASS
public void setController(SerialController controller) {
this.controller = controller;
}
INITIALIZE SCREEN IN SCREEN HANDLER CLASS
serialCommunication = new SerialCommunication(this);
loader = new FXMLLoader();
loader.setLocation(getClass().getResource(path));
pane = loader.load(getClass().getResource(path).openStream());
serialController = (SerialController) loader.getController();
serialController.setScreenHandler(this);
serialController.setSerialCommunication(serialCommunication);
serialCommunication.setController(serialController);
parent = loader.getRoot();
stage = new Stage();
stage.setScene(new Scene(parent));
stage.setTitle(title);
stage.setResizable(false);
stage.sizeToScene();
stage.centerOnScreen();
stage.initModality(Modality.APPLICATION_MODAL);
stage.showAndWait();

Answer 1

You are passing a reference to inputText to the (inappropriately-named) getInputText() method in the controller. inputText is presumably a field in the class implementing the port listener. However, as soon as you pass it, you then set it back to an empty string:
if(inputText.length() == 8) {
Platform.runLater(new Runnable() {
#Override
public void run() {
controller.getInputString(inputText);
}
});
}
bytes.clear();
inputText = "";
Since inputText is being accessed from multiple threads, there is no guarantee as to which order things will happen: whether controller.getInputText(inputText) will execute first, or whether inputText = ""; will execute first. So you may end up setting the text field to an empty string.
What I think you intend to do is:
if(inputText.length() == 8) {
final String numberFieldText = inputText ;
Platform.runLater(new Runnable() {
#Override
public void run() {
controller.getInputString(numberFieldText);
}
});
}
or more succinctly:
if(inputText.length() == 8) {
final String numberFieldText = inputText ;
Platform.runLater(() -> controller.getInputString(numberFieldText));
}