Issue relating to JavaFX GUI event handling and updating - javafx

Question

apologies for the length of my code. I realized last night that I was on the wrong path and now have gotten stuck on an issue that I think relates to JavaFX event handling. Initially I had the logic functioning outside a GUI in a basic loop that depended on interaction through the console. Everything was working great. I've now tried to get this to work in a GUI with interaction from the user.
I have two main problems with the code below.
The first is that the text in textArea is not updating with additional text after the startButton executes the start of my main logic sequence. The first append starts right under the first while loop. I was hoping to have this show up in the GUI as the logic executes. I'm not sure if I need to tell the GUI to update at certain intervals or if there's something else wrong.
Second, I'm not sure how to get the program to wait for the user to type in something into textField before hitting the textButton I created to continue on. I used to have a scanner created which caused the program to wait in the console for input. I realize I need some way of telling it to wait for a button press when it's running inside JavaFX.
I chose not to include the rest of the code to make things easier to read, but I can add it on if it will help resolve this issue.
Thank you everyone for your help!
public class FxApp extends Application {
//Creates FileParser object with methods that alter the incoming Array of Strings into the format we need
FileParser fileParser = new FileParser();
Configure configure = new Configure();
private String text;
private String initialState;
private ArrayList<Machine> machines = new ArrayList<Machine>();
private Map<String, String> initialStates = new HashMap<String, String>();
private Map<String, String> states = new HashMap<String, String>();
private Map<String, ArrayDeque<String>> queues = new HashMap<String, ArrayDeque<String>>();
private Map<Integer, ArrayList<String>> parsedData = new HashMap<Integer, ArrayList<String>>();
#Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setTitle("File Chooser");
FileChooser fileChooser = new FileChooser();
fileChooser.getExtensionFilters().addAll(new ExtensionFilter("Text Files", "*.txt"));
Button startButton = new Button("Start");
Button openButton = new Button("Click to open a file...");
openButton.setPrefSize(200, 80);
Button textButton = new Button("Enter");
TextArea textArea = new TextArea();
textArea.setWrapText(true);
TextField textField = new TextField();
Label lbl = new Label();
VBox vbox = new VBox(lbl, openButton, startButton, textArea, textField, textButton);
vbox.setSpacing(10);
vbox.setPadding(new Insets(15));
lbl.setText("This tool creates virtual automata based \ron the file.");
Scene scene = new Scene(vbox, 640, 480);
primaryStage.setScene(scene);
primaryStage.show();
openButton.setOnAction(
new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
File file = fileChooser.showOpenDialog(primaryStage);
if (file != null) {
//Execute the method to convert to string array before sending to file parser
try {
fileParser.convertFile(file);
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
});
textButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
text = textField.getText();
}
});
startButton.setOnAction(new EventHandler <ActionEvent>()
{
public void handle(ActionEvent event)
{
machineCreation();
String exit = "no";
String nextLine = null;
ArrayList<String> listOfCurrentTransitions = new ArrayList<String>();
int nextInt = 0;
states = initialStates;
while(!(exit.toLowerCase().equals("yes"))) {
textArea.appendText("Choose a state to load");
//Print out the states possible for each machine
ArrayList<String> tempTrans = machines.get(nextInt).getTransitions();
//This loops through the list of transitions of the machine and pulls possible transitions from its current state
for(int i = 0; i < tempTrans.size(); i++) {
String pull = tempTrans.get(i);
String[] apart = pull.split(" ");
pull = apart[0];
if(states.get(Integer.toString(nextInt)).equals(pull)) {
listOfCurrentTransitions.add(tempTrans.get(i));
}
}
if(!(listOfCurrentTransitions.isEmpty())) {
textArea.appendText("The following transitions are possible. Choose one: " + listOfCurrentTransitions);
}
else {
textArea.appendText("No transitions for this machine exist from its current state");
}
//Tell GUI to wait for user input in textField and execute textButton which assigns to String text. Resume on button click.

Answer 1

The while loop blocks the JavaFX application thread which prevents updates of the GUI and handling of events.
You need to execute the logic of a single iteration of the loop on each "text commit" instead:
private TextArea textArea;
private void activateState(int nextInt) {
ArrayList<String> listOfCurrentTransitions = new ArrayList<String>();
textArea.appendText("Choose a state to load");
//Print out the states possible for each machine
ArrayList<String> tempTrans = machines.get(nextInt).getTransitions();
//This loops through the list of transitions of the machine and pulls possible transitions from its current state
for(int i = 0; i < tempTrans.size(); i++) {
String pull = tempTrans.get(i);
String[] apart = pull.split(" ");
pull = apart[0];
if(states.get(Integer.toString(nextInt)).equals(pull)) {
listOfCurrentTransitions.add(tempTrans.get(i));
}
}
if(listOfCurrentTransitions.isEmpty()) {
textArea.appendText("No transitions for this machine exist from its current state");
} else {
textArea.appendText("The following transitions are possible. Choose one: " + listOfCurrentTransitions);
}
}
#Override
public void start(Stage primaryStage) throws Exception {
...
textArea = new TextArea();
...
startButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
machineCreation();
activateState(0);
}
});
textButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
// read input and ask for more input...
int nextState = Integer.parseInt(textField.getText()); // TODO: deal with invalid input
activateState(nextState);
}
});
You probably need to fix the logic a bit to verify a transition is valid, change the values of some fields ect...