JavaFX - how to know if cancel was pressed

If a result is present, then the user pressed OK. If no result is present, then the user probably pressed cancel, but they might have just closed the dialog window using the OS close window function.

Optional<String> result = new TextInputDialog().showAndWait();
if (result.isPresent()) {
    // ok was pressed.
} else {
    // cancel might have been pressed.
}

To really know if a button was pressed, you can use a filter as noted in the Dialog javadoc section "Dialog Validation / Intercepting Button Actions".

final Button cancel = (Button) dialog.getDialogPane().lookupButton(ButtonType.CANCEL);
cancel.addEventFilter(ActionEvent.ACTION, event ->
    System.out.println("Cancel was definitely pressed")
);

Sample code:

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.stage.Stage;

import java.util.Optional;

public class DialogSample extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        Button showButton = new Button("show");
        showButton.setOnAction(event -> showDialog(stage));
        showButton.setPrefWidth(100);
        stage.setScene(new Scene(showButton));
        stage.show();

        showButton.fire();
    }

    private void showDialog(Stage stage) {
        TextInputDialog dialog = new TextInputDialog();
        dialog.initOwner(stage);
        dialog.setTitle("Delimiter");
        dialog.setHeaderText("Enter the delimiter");

        final Button ok = (Button) dialog.getDialogPane().lookupButton(ButtonType.OK);
        ok.addEventFilter(ActionEvent.ACTION, event ->
            System.out.println("OK was definitely pressed")
        );

        final Button cancel = (Button) dialog.getDialogPane().lookupButton(ButtonType.CANCEL);
        cancel.addEventFilter(ActionEvent.ACTION, event ->
            System.out.println("Cancel was definitely pressed")
        );

        Optional<String> result = dialog.showAndWait();
        if (result.isPresent()) {
            System.out.println("Result present => OK was pressed");
            System.out.println("Result: " + result.get());
        } else {
            System.out.println("Result not present => Cancel might have been pressed");
        }    
    }

    public static void main(String[] args) {
        Application.launch();
    }
}

Ok, I found the answere here JavaFX Dialogs

The result.isPresent() will return false if the user cancelled the dialog.

You can use Optional<ButtonType> instead of Optional<String>. And basically use the below code.

 Optional<ButtonType> result = dialog.showAndWait();
    if (result.isPresent() &&  result.get()  == ButtonType.OK){
        System.out.println("Ok button is pressed");
    } else if(result.isPresent() &&  result.get()  == ButtonType.CANCEL){
        System.out.println("Cancel button was pressed");
    }

Hope it helps. Let me know if you need any further clarification.