Undecorated Alert will not close when requested - javafx

Question

I have a simple undecorated Alert that I am trying to display while a long-running task is being completed in the background.
However, when the task is finished, I want to close the alert. I can not, however, get the alert to close by calling either close() or hide().
This MCVE does not include the background Task, but even this refuses to close the alert:
import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.control.Alert;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
public class AlertClosing extends Application {
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
Alert simpleAlert = new Alert(Alert.AlertType.NONE);
simpleAlert.setContentText("Testing");
simpleAlert.initStyle(StageStyle.UNDECORATED);
simpleAlert.show();
// None of these seem to have any effect.
simpleAlert.close();
simpleAlert.hide();
Platform.runLater(simpleAlert::close);
}
}
I have found a few other answers here that deal with Alert and Dialog panes that have a cancel button, but my Alert has no buttons at all; it's simply meant to display a message while the background task is running.
Per the JavaDocs on Dialog closing rules:
JavaFX dialogs can only be closed 'abnormally' (as defined above) in
two situations:
When the dialog only has one button, or
When the dialog has multiple buttons, as long as one of them meets one of the following requirements:
The button has a ButtonType whose ButtonBar.ButtonData is of type ButtonBar.ButtonData.CANCEL_CLOSE.
The button has a ButtonType whose ButtonBar.ButtonData returns true when ButtonBar.ButtonData.isCancelButton() is called.
In all other situations, the dialog will refuse to respond to all
close requests, remaining open until the user clicks on one of the
available buttons in the DialogPane area of the dialog.
So this too suggests that a simple close() request should be honored since there are no qualifying buttons in an Alert(AlertStyle.NONE), right?

Answer 1

No according to the javadoc not honoring the close request: There's neither one nor multiple buttons.
You can assign one ButtonType as result make the Alert close properly.
Alert simpleAlert = new Alert(Alert.AlertType.NONE);
simpleAlert.setContentText("Testing");
simpleAlert.initStyle(StageStyle.UNDECORATED);
simpleAlert.show();
new Thread(() -> {
try {
Thread.sleep(5000);
} catch (InterruptedException ex) {
}
Platform.runLater(() -> {
simpleAlert.setResult(ButtonType.CANCEL);
simpleAlert.close();
});
}).start();