JavaFX: scrolling and traversing focus using arrow keys

Question

I got a ScrollPane containing custom nodes.

Current default behavior:

• Shift + ← , ↑ , → , ↓ moves focus

• ← , ↑ , → , ↓ scrolls the view

I want everything to be the other way around. How can I do this or where to start?

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[EDIT] Well, there’s another fragile approach.

Instead of messing around with events, you can collect KeyBinding s.

  scrollPane.skinProperty().addListener(new ChangeListener<Skin<?>>() { @Override public void changed(ObservableValue<? extends Skin<?>> observable, Skin<?> oldValue, Skin<?> newValue) { ScrollPaneSkin scrollPaneSkin = (ScrollPaneSkin) scrollPane.getSkin(); ScrollPaneBehavior scrollPaneBehavior = scrollPaneSkin.getBehavior(); try { Field keyBindingsField = BehaviorBase.class.getDeclaredField("keyBindings"); keyBindingsField.setAccessible(true); List<KeyBinding> keyBindings = (List<KeyBinding>) keyBindingsField.get(scrollPaneBehavior); List<KeyBinding> newKeyBindings = new ArrayList<>(); for (KeyBinding keyBinding : keyBindings) { KeyCode code = keyBinding.getCode(); newKeyBindings.add(code == KeyCode.LEFT || code == KeyCode.RIGHT || code == KeyCode.UP || code == KeyCode.DOWN ? keyBinding.shift() : keyBinding); } keyBindingsField.set(scrollPaneBehavior, newKeyBindings); } catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) { LOGGER.warn("private api changed.", e); } } }); 

I think this could be a cleaner way if KeyBindings were more non-statistical, modifiable, and public.

Answer 1

Use the event filter to capture the corresponding key events and reassign them to different key events before the events start bubbling.

Re-matching keys by default is a complicated thing that:

• May confuse the user.
• May have unexpected side effects (for example, TextFields may not work as you expect).

Therefore, use with caution:

 import javafx.application.*; import javafx.event.*; import javafx.scene.Scene; import javafx.scene.control.*; import javafx.scene.input.KeyEvent; import javafx.scene.layout.TilePane; import javafx.stage.Stage; import java.util.*; public class ScrollInterceptor extends Application { @Override public void start(Stage stage) { ScrollPane scrollPane = new ScrollPane( createScrollableContent() ); Scene scene = new Scene( scrollPane, 300, 200 ); remapArrowKeys(scrollPane); stage.setScene(scene); stage.show(); hackToScrollToTopLeftCorner(scrollPane); } private void remapArrowKeys(ScrollPane scrollPane) { List<KeyEvent> mappedEvents = new ArrayList<>(); scrollPane.addEventFilter(KeyEvent.ANY, new EventHandler<KeyEvent>() { @Override public void handle(KeyEvent event) { if (mappedEvents.remove(event)) return; switch (event.getCode()) { case UP: case DOWN: case LEFT: case RIGHT: KeyEvent newEvent = remap(event); mappedEvents.add(newEvent); event.consume(); Event.fireEvent(event.getTarget(), newEvent); } } private KeyEvent remap(KeyEvent event) { KeyEvent newEvent = new KeyEvent( event.getEventType(), event.getCharacter(), event.getText(), event.getCode(), !event.isShiftDown(), event.isControlDown(), event.isAltDown(), event.isMetaDown() ); return newEvent.copyFor(event.getSource(), event.getTarget()); } }); } private TilePane createScrollableContent() { TilePane tiles = new TilePane(); tiles.setPrefColumns(10); tiles.setHgap(5); tiles.setVgap(5); for (int i = 0; i < 100; i++) { Button button = new Button(i + ""); button.setMaxWidth(Double.MAX_VALUE); button.setMaxHeight(Double.MAX_VALUE); tiles.getChildren().add(button); } return tiles; } private void hackToScrollToTopLeftCorner(final ScrollPane scrollPane) { Platform.runLater(new Runnable() { @Override public void run() { scrollPane.setHvalue(scrollPane.getHmin()); scrollPane.setVvalue(0); } }); } public static void main(String[] args) { launch(args); } }