Update TextArea while executing processes - user-interface

Question

i found out that my GUI starts to freeze after 3-4 seconds when I click the "start" button like "no response". When I keep on click the App, it's forced to shut down.
Now I want to prevent this but I got no clue how. Just as far as I know JavaFX runs in a Single Thread, therefore, to update my TextArea while the Methods are executing, I need to run these Methods in another Thread.
I hope someone can help me.
How does my project look like?
I got a FXML, a Controller, a Handler, a Transformer , also a Writer and a Reader class (which are used in the Handler class).
When I click the button, which is bind to a method in the Controller, an instance of Handler is created and this one calls the Reader to read in a text file, transformed to a List of Strings (line by line).
In addition, the lines are getting manipulated. After this, the Writer is used to creat a new file and write the new manipulated lines to this file.
It is also allowed to the user to refer to more than just one file.
What I want is that the textarea shows whenever the reader starts to read a file like "The file ... is being read".
Then append "The file ... is being manipulated" when Transformer comes to action and then
"The file ... is being written" when the new lines are written to the new file.
Here is some code..
Controller:
public class FXMLDocumentController implements Initializable {
#FXML
private TextArea console;
#FXML
private void handleButtonAction(ActionEvent event) {
System.out.println("You clicked me!");
Handler hand = new Handler();
hand.handle(files);
}
#Override
public void initialize(URL url, ResourceBundle rb) {
// TODO
}
}
Handler:
public class Handler {
public void handle(List<String> files) {
for (String s : files) {
List<String> ls = Reader.readFile(s);
Writer.writeFile(Transformer.transform(ls));
}
}
How should I change my code to update the TextArea whenever a file is read, manipulated or written?
Info: I know the class Handler won't compile as I erased the initialization of the List "files" which contains Strings of file paths.
If I left out relevant information, feel free to ask.
I thank you in advance!

Answer 1

You should execute the handle() method in a background thread:
#FXML
private void handleButtonAction(ActionEvent event) {
System.out.println("You clicked me!");
Thread thread = new Thread(() -> {
Handler hand = new Handler();
hand.handle(files);
});
// this line means the background thread will not prevent application exit:
thread.setDaemon(true);
thread.start();
}
If you want to update the text area with the current status, you need to schedule that back on the FX Application Thread using Platform.runLater(). Probably the cleanest way to do this is not to have Platform.runLater() in the Handler class, but define a field in Handler for "consuming" status messages:
public class Handler {
private final Consumer<String> statusMessageProcessor ;
public Handler(Consumer<String> statusMessageProcessor) {
this.statusMessageProcessor = statusMessageProcessor ;
}
// default processor does nothing:
public Handler() {
this(s -> {});
}
public void handle(List<String> files) {
for (String s : files) {
// similarly for other status updates:
statusMessageProcessor.accept("The file "+s+" is being read");
List<String> ls = Reader.readFile(s);
Writer.writeFile(Transformer.transform(ls));
}
}
}
and then
Handler hand = new Handler() ;
can become
Handler hand = new Handler(message ->
Platform.runLater(() -> console.appendText(message + "\n")));
in the button handler method.