禁用移动JavaFX警报

Question

I have a problem with my "Do you want to quit" interface.

As of today I can move the alert box where I want, which I would like to change - preferably fixating the alert in a set position (in the middle of the screen).

The problem with this alert being able to move around is that on setups with more than one screen you could move it wherever you would like (out of the game interface fe).

    Button btExit = new Button("Exit Game");
    btExit.setMinWidth(100);
    buttonGrid.add(btExit, 0, 5);
    btExit.setOnAction(new EventHandler<ActionEvent>() 
    {
        @Override
        public void handle(ActionEvent event) 
        {
            Alert alert = new Alert(AlertType.CONFIRMATION);
            alert.setTitle("");
            alert.initModality(Modality.APPLICATION_MODAL);
            alert.initOwner(primaryStage);
            alert.setHeaderText("Quit Game");
            alert.setContentText("Are you sure?");

            Optional<ButtonType> result = alert.showAndWait();
            if (result.get() == ButtonType.OK){
                System.exit(1);
            }else 
            {
                alert.close();
            }

        }
    });

Answer 1

If you want to prevent the user from moving the dialog, simply set the style to UNDECORATED which removes the window border the user could use to move around the alert (as well as the x-button, but the user has a alternative way of closing the dialog):

@Override
public void start(Stage primaryStage) {
    Button btn = new Button("Show alert");
    btn.setOnAction((ActionEvent event) -> {
        Alert alert = new Alert(AlertType.CONFIRMATION);
        alert.getDialogPane().setStyle("-fx-border-color: black;");
        alert.initModality(Modality.APPLICATION_MODAL);

        alert.initStyle(StageStyle.UNDECORATED);

        alert.initOwner(primaryStage);
        alert.setHeaderText("Quit Game");
        alert.setContentText("Are you sure?");

        Optional<ButtonType> result = alert.showAndWait();
        if (result.orElse(null) == ButtonType.OK) {
            Platform.exit();
        }
    });

    StackPane root = new StackPane();
    root.getChildren().add(btn);

    Scene scene = new Scene(root, 600, 400);

    primaryStage.setScene(scene);
    primaryStage.show();
}

---

Some other modifications I did here:

• Replace

   System.exit(1); 

  with

   Platform.exit(); 

  To shut down the application more gracefully. After all a status code of 1 indicates abnormal termination .

• Remove

   else { alert.close(); } 

  this is never necessary, since showAndWait only returns after the Alert is closed anyways...

• Used

   result.orElse(null) 

  to retrieve the value without an error, even if the Optional is empty (not 100% sure this can happen in this case, but it does not hurt to do it like this).