Keep focus in a control until certain conditions are met?

Question

Hello,
Is there a way to keep focus at a control until certain conditions are met?
For example, if I might want to keep the focus set to a text field inside a tab unless the text field contains something valid.
If user tries to switch to different tab without having valid text inside the text field, I would like to pop up a stage/dialog and abort the tab switching.
Please help!
Thanks.

Answer 1

Hi. Here is an example:
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.stage.WindowEvent;
public class SSNValidation extends Application {
    public static void main(String[] args) {
        launch(args);
    @Override
    public void start(final Stage primaryStage) {
        primaryStage.setTitle("SSN Validation");
        Button btn = new Button();
        final TextField tfSSN = new TextField();
        StackPane layout = new StackPane();
        Scene scenePopup = new Scene(layout, 424, 154, Color.TRANSPARENT);
        final Stage stage = new Stage();
        stage.initModality(Modality.APPLICATION_MODAL);
        stage.setScene(scenePopup);
        stage.setOnCloseRequest(new EventHandler<WindowEvent>() {
            @Override
            public void handle(WindowEvent event) {
                tfSSN.requestFocus();
        tfSSN.focusedProperty().addListener(new ChangeListener<Boolean>() {
            public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, final Boolean newValue) {
                if (!newValue) {
                    if (tfSSN.getText().length() < 9) {
                        stage.show();
        final TextField tf2 = new TextField();
        btn.setText("Submit");
        VBox root = new VBox();
        root.getChildren().addAll(tfSSN, tf2, btn);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
}