How to set JavaFX-Alert into middle of actual monitor? - javafx

Question

I've got a static method in a class without knowing anything about the Application, Scene oder Stage. But I want to show an Alert in the middle of the actual used monitor.
For example: My tool is on the right screen. I want to see the alert also there and not on the main screen.
My method:
private static Alert createAlert(AlertType type, String title, String header, String content) {
Alert alert = new Alert(type);
alert.setTitle(title);
if (!header.isEmpty()) {
alert.setHeaderText(header);
}
alert.setContentText(content);
alert.setResizable(true);
alert.setX(0); // set this into the middle of used monitor
alert.setY(0); //
return alert;
}
How can I get the actual stage, scene or whatever to get its x- and y-position and use these information for setting x and y of the alert?

Answer 1

Assuming you have a reference to the current window, you can find the screen that contains it (e.g. contains its center point) with:
Window currentWindow = ... ;
Point2D windowCenter = new Point2D(currentWindow.getX() + currentWindow.getWidth()/2,
currentWindow.getY() + currentWindow.getHeight()/2);
Screen currentScreen = Screen.getScreens().stream()
.filter(screen -> screen.getBounds().contains(windowCenter))
.findAny().get();
And then you can do
Rectangle2D screenBounds = currentScreen.getBounds();
double screenCenterX = screenBounds.getMinX() + screenBounds.getWidth()/2 ;
double screenCenterY = screenBounds.getMinY() + screenBounds.getHeight()/2 ;
and position the Alert accordingly...
You need to know the current window though; it will be impossible to do this without that information. For example, your application might have multiple windows with different ones on different screens; the notion of "current screen" is simply not well defined in a case like that.