Alert box is not showing in the center of the application using JavaFX [duplicate] - javafx

Question

This question already has answers here:
Center stage on parent stage
(2 answers)
Closed 4 years ago.
I am trying to pop-up the box in the center of the application when I resize the application or move it.
I tried with css alignment and also using Java. Is it possible if I don't use pane and directly add box in the scene?
Here is my code:
public Boolean call(String question) {
final Stage dialogStage = new Stage(StageStyle.UNDECORATED);
dialogStage.initModality(Modality.WINDOW_MODAL);
dialogStage.initOwner(owner);
dialogStage.setTitle("ConfirmTitle"); // WIP, waiting for the strings&trans
final Button ok = new Button(
nmsGuiContainer.getI18nService().getMessage("com.mlnms.gui.fmwk.main.container.ok")); // WIP,
// waiting
// for
// the
// strings&trans
ok.getStyleClass().add(HTML_POPUP_BUTTON_STYLE);
final Button cancel = new Button(
nmsGuiContainer.getI18nService().getMessage("com.mlnms.gui.fmwk.main.container.cancel")); // WIP,
// waiting
// for the
// strings&trans
cancel.getStyleClass().add(HTML_POPUP_BUTTON_STYLE);
final Text text = new Text(question);
text.getStyleClass().add(HTML_POPUP_STYLE);
final Insets ins = new Insets(10);
final VBox box = new VBox();
box.setAlignment(Pos.BOTTOM_CENTER);
box.setSpacing(10);
box.setPadding(ins);
final HBox buttons = new HBox(10);
buttons.getChildren().addAll(ok, cancel);
buttons.setAlignment(Pos.CENTER);
buttons.setPadding(ins);
box.getChildren().addAll(text, buttons);
box.getStyleClass().add(HTML_POPUP_STYLE);
StackPane pane = new StackPane();
pane.setAlignment(box, Pos.CENTER);
pane.getChildren().add(box);
Scene scene = new Scene(pane);
try {
URL javafxCss = nmsGuiContainer.getBundleContext().getBundle()
.getResource(NmsGuiContainer.JAVAFX_CSS_URL);
scene.getStylesheets().add(javafxCss.toExternalForm());
} catch (Exception e) {
LOGGER.error("Cannot load the CSS file for JavaFX components ", e);
}
dialogStage.setScene(scene);
ok.setCancelButton(false);
final boolean[] res = new boolean[1];
ok.setOnAction(new CloseDialogHandler(dialogStage, res));
cancel.setCancelButton(true);
cancel.setOnAction(new CloseDialogHandler(dialogStage, null));
dialogStage.centerOnScreen();
nmsGuiContainer.fadeContainer();
dialogStage.showAndWait();
nmsGuiContainer.unfadeContainer();
return res[0];
}
Here is a screenshot of the alertbox:

Answer 1

The Stage.initOwner() method does exactly what you need. While you do call it in your example code, I do not know what owner you are passing to it.
Here is a sample that demonstrates how to do this.
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class Main extends Application {
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) {
VBox root = new VBox(10);
root.setAlignment(Pos.CENTER);
root.setPadding(new Insets(10));
Button btnShowAlert = new Button("Show Alert!");
// Set the action to show the alert
btnShowAlert.setOnAction(e -> {
Alert alert = new Alert(Alert.AlertType.WARNING);
alert.setHeaderText("This is centered over the main window!");
alert.setContentText("Move the main window and show the alert again!");
alert.initOwner(primaryStage);
alert.showAndWait();
});
root.getChildren().add(btnShowAlert);
primaryStage.setTitle("Centered Alerts");
primaryStage.setScene(new Scene(root));
primaryStage.setWidth(500);
primaryStage.setHeight(300);
primaryStage.show();
}
}