How to resize an Alert window to match contents in JavaFX 8

Question

Is there any way to resize an Alert, to show a trace of an exception, in JavaFX 8. My code is :

Alert alert = new Alert(Alert.AlertType.ERROR);
alert.setResizable(true);
alert.setTitle(e.getLocalizedMessage());
alert.setHeaderText(e.toString());
alert.setContentText(message); // I previously made this using StackTraceElement[] java.lang.Exception.getStackTrace()

Then I've tried both :

alert.getDialogPane().getScene().getWindow().sizeToScene();

and

alert.getDialogPane().autosize();

and neither has worked.

Currently, I'm using my JRE is Java 8 update 144 and my JDK is Java 8 update 101 on Windows 10 Home 64-bit edition. Are there any ways for me to use the Alert framework as a replacement for JOptionPane seeing as Swing is essentially dead so that I can avoid having to code listeners and buttons and keep the cross icon which the Alert class "provides".

Answer 1

This code is pulled from Exception Dialog .

Alert alert = new Alert(AlertType.ERROR);
alert.setTitle("Exception Dialog");
alert.setHeaderText("Look, an Exception Dialog");
alert.setContentText("Could not find file blabla.txt!");

Exception ex = new FileNotFoundException("Could not find file blabla.txt");

// Create expandable Exception.
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
ex.printStackTrace(pw);
String exceptionText = sw.toString();

Label label = new Label("The exception stacktrace was:");

TextArea textArea = new TextArea(exceptionText);
textArea.setEditable(false);
textArea.setWrapText(true);

textArea.setMaxWidth(Double.MAX_VALUE);
textArea.setMaxHeight(Double.MAX_VALUE);
GridPane.setVgrow(textArea, Priority.ALWAYS);
GridPane.setHgrow(textArea, Priority.ALWAYS);

GridPane expContent = new GridPane();
expContent.setMaxWidth(Double.MAX_VALUE);
expContent.add(label, 0, 0);
expContent.add(textArea, 0, 1);

// Set expandable Exception into the dialog pane.
alert.getDialogPane().setExpandableContent(expContent);

alert.showAndWait();

Answer 2

I found a way to do this using Java reflection. First have to set ( comment of Ervin Szilagyi) alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);

and then use this method:

void sizeToScene(Alert alert) {
    try {
        final Field field = Dialog.class.getDeclaredField("dialog");
        field.setAccessible(true);
        final Object object = field.get(alert);
        final Method method = object.getClass().getMethod("sizeToScene");
        method.setAccessible(true);
        method.invoke(object);
    } catch (SecurityException | IllegalArgumentException | NoSuchFieldException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
            //  logger.catching(e);
    }
}

but it is better to use the Exception Dialog to display the trace of the exception.

Usage example:

MainThread

private static Alert alert;

public static Optional<Alert> getAlert(){
    return Optional.ofNullable(alert);
}

void alertMethod(){
    alert = new Alert(AlertType.ERROR);
    alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
    alert.setTitle("title");
    alert.setHeaderText(null);
    alert.setContentText("message");
    alert.showAndWait();
}

Another thread

//...
void addAlertText(String text){
    MainThread.getAlert()
    .ifPresent(
        al->Platform.runLater(()->{
            al.setContentText(al.getContentText() + '\n' + text);
            sizeToScene(al);
        }));
}
//...