JavaFx: TextField KeyEvents are not triggered

Question

I am implmenting a cusom component where the user can type into a TextField and a TableView is pops up then the user can look for items in that table.

I have a problem with the standard KeyEvents of the TextFieldlike Ctrl+A or Home. After the pane with the TableView pops up, those key events are not working anymore. I have checked if the TextField lost the focus but it doesn't, and if I set an EventFilter to see what is happening, it shows that those events are triggered but I see no effect on UI. Even the popup's setHideOnEscape is not working.

Here is a simple code to verify it:

The fxml:

The controller:

public class Controller implements Initializable {

    @FXML
    private TextField textField;


    @Override
    public void initialize(URL location, ResourceBundle resources) {

        Popup popUp = new Popup();
        TableView

kleopatra · Accepted Answer

The reason that the textField doesn't react to some/all "standard function keys" is that their KEY_PRESSED type never reaches it - they are redirected to the table in the popup and most/all of them consumed by the table.

A naive first approximation would be to set the table's focusTraversable property to false: this effectively prevents all keys from being delivered to it. Real-world requirements might be a bit less simplistic, in that some of those should reach the table while others should bubble up to the textField.

This can be achieved by a custom EventDispatcher (on the table) which examines all keyEvents and decides which to deliver/not to the table's original dispatcher. A code snippet where interceptor is a predicate used for the decision (at the end there's complete working example for convenience):

private BasicEventDispatcher original;
private Predicate interceptor;

@Override
public Event dispatchEvent(Event event, EventDispatchChain tail) {
    if (!interceptor.test(event)) {
        event = original.dispatchCapturingEvent(event);
        if (event.isConsumed()) {
            return null;
        }
    }
    event = tail.dispatchEvent(event);
    if (event != null && !interceptor.test(event)) {
        event = original.dispatchBubblingEvent(event);
        if (event.isConsumed()) {
            return null;
        }
    }
    return event;
}

It's usage: if f.i. we want LEFT and RIGT be bubbled up to that textField, while all others should be handled normally by the table

List toIntercept = List.of(KeyCode.LEFT, KeyCode.RIGHT);
Predicate interceptor = e -> {
    if (e instanceof KeyEvent) {
        return toIntercept.contains(((KeyEvent) e).getCode());
    }
    return false;
};
table.setEventDispatcher(new InterceptingEventDispatcher(
        (BasicEventDispatcher) table.getEventDispatcher(), interceptor));

A complete example to play with:

public class ViewPopupApplication extends Application {

    public static class InterceptingEventDispatcher implements EventDispatcher {
        private BasicEventDispatcher original;
        private Predicate interceptor;

        public InterceptingEventDispatcher(BasicEventDispatcher original, Predicate interceptor) {
            this.original = original;
            this.interceptor = interceptor;
        }

        @Override
        public Event dispatchEvent(Event event, EventDispatchChain tail) {
            if (!interceptor.test(event)) {
                event = original.dispatchCapturingEvent(event);
                if (event.isConsumed()) {
                    return null;
                }
            }
            event = tail.dispatchEvent(event);
            if (event != null && !interceptor.test(event)) {
                event = original.dispatchBubblingEvent(event);
                if (event.isConsumed()) {
                    return null;
                }
            }
            return event;
        }

    }

    private Parent createContent() {
        TableView table = new TableView<>(FXCollections.observableArrayList(Locale.getAvailableLocales()));
        // just to see that right/left are intercepted while up/down are handled
        table.getSelectionModel().setCellSelectionEnabled(true);

        TableColumn country = new TableColumn<>("Country");
        country.setCellValueFactory(new PropertyValueFactory<>("displayCountry"));
        TableColumn language = new TableColumn<>("Language");
        language.setCellValueFactory(new PropertyValueFactory<>("displayLanguage"));
        table.getColumns().addAll(country, language);
        // disables default focus traversal
        //  table.setFocusTraversable(false);

        // decide which keys to intercept
        List toIntercept = List.of(KeyCode.LEFT, KeyCode.RIGHT);
        Predicate interceptor = e -> {
            if (e instanceof KeyEvent) {
                return toIntercept.contains(((KeyEvent) e).getCode());
            }
            return false;
        };
        table.setEventDispatcher(new InterceptingEventDispatcher(
                (BasicEventDispatcher) table.getEventDispatcher(), interceptor));

        TextField textField = new TextField("something to show");
        textField.setPrefColumnCount(20);
        textField.setText("something to see");

        table.prefWidthProperty().bind(textField.widthProperty());
        Popup popUp = new Popup();
        popUp.getContent().add(table);

        textField.setOnKeyTyped(event -> {
            if(!popUp.isShowing()){
                popUp.show(
                        textField.getScene().getWindow(),
                        textField.getScene().getWindow().getX()
                                + textField.localToScene(0, 0).getX()
                                + textField.getScene().getX(),
                        textField.getScene().getWindow().getY()
                                + textField.localToScene(0, 0).getY()
                                + textField.getScene().getY()
                                + textField.getHeight() - 1);
            }
        });

        BorderPane content = new BorderPane(textField);
        return content;
    }

    @Override
    public void start(Stage stage) throws Exception {
        stage.setScene(new Scene(createContent()));
        stage.show();
    }

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

}

JavaFx: TextField KeyEvents are not triggered

Answers (1)

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