Javafx, TextArea caret doesn't move back to first line on clear - javafx

Question

I'm having a hard time by setting back the cursor to position 0 in the first line, after clearing the text from the textarea.
Problem Background
I have a textarea, which listens to keyevents. The textarea only listens to Enter key, if found, either submits the text or clears the text if there is a "\n" in the text area.
I tried all of the following, but none really worked out.
textArea.setText("")
textArea.clear()
textArea.getText().replace("\n", "")
Remove focus from it and put it back again.
Here is a test project that is runnable and demonstrates the problem.
The Main class:
public class Main extends Application {
Stage primaryStage;
AnchorPane pane;
public void start(Stage primaryStage){
this.primaryStage = primaryStage;
initMain();
}
public void initMain(){
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(Main.class.getResource("main.fxml"));
pane = loader.load();
Controller controller = loader.getController();
Scene scene = new Scene(pane);
primaryStage.setScene(scene);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String args[]){
launch();
}
}
The Controller class:
public class Controller {
#FXML
TextArea textArea;
public void initialize() {
textArea.setOnKeyPressed(new EventHandler<KeyEvent>() {
#Override
public void handle(KeyEvent keyEvent) {
if (keyEvent.getCode() == KeyCode.ENTER) {
if (!textArea.getText().equals("")
&& !textArea.getText().contains("\n")) {
handleSubmit();
}
if (textArea.getText().contains("\n")) {
handleAsk();
}
}
}
});
}
/**
* After the user gives in a short input, that has no \n, the user submits by hitting enter.
* This method will be called, and the cursor jumps over to the beginning of the next line.
*/
public void handleSubmit(){
System.out.println("Submitted");
}
/**
* When this method is calls, the cursor is not in the first line.
* This method should move the cursor to the first position in the first line in the completely
* cleared text area.
*/
public void handleAsk(){
System.out.println("Asking and clearing text area.");
textArea.setText("");
}
}
The fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="317.0" prefWidth="371.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Controller">
<children>
<TextArea fx:id="textArea" layoutX="78.0" layoutY="59.0" prefHeight="114.0" prefWidth="200.0" />
</children>
</AnchorPane>
My problem is, that the cursor won't jump back...

Answer 1

I found a short solution: after I called the desired method (handleAsk()), that should clear the text area when its finished, I call: keyEvent.consume();
This consumes the default effect of ENTER.
So: First, the event handler that you explicitly define does it's job, and then you can decide if you want to have as a "side effect" the default effect of the given key event, if not, you can consume it.

Answer 2

So, either your key handler will be invoked before the text is changed (due to something being typed), or it will be invoked after the text is changed.
You are presumably hoping it will be invoked before, since otherwise
textArea.getText().contains("\n")
would always evaluate to true (since the user just pressed the Enter key).
But in this case, on the second press of Enter, you will clear the text before the text is then modified. So you clear the text, then the new line is added (from the user pressing Enter). Hence the blank line in the text area.
You probably don't want to rely on the order of the events being processed anyway. It turns out that the text is modified on keyTyped events (I think), but that's not documented, and so there's really no guarantee of it. The safer way is to listen to changes in the text, and then to count the number of newlines:
textArea.textProperty().addListener((obs, oldText, newText) -> {
int oldNewlines = countNewlines(oldText); // note, can be more efficient by caching this
int numNewlines = countNewlines(newText);
if (numNewlines == 1 && oldNewlines != 1) {
// submit data
} else if (numNewlines == 2) {
textArea.clear();
}
});
With
private int countNewlines(String text) {
int newlines = 0 ;
while (text.indexOf("\n") >= 0) {
newlines++ ;
text = text.substring(text.indexOf("\n") + 1);
}
return newlines ;
}
(or some other implementation, eg using regex).