Oto aplikacja (nieco zbyt skomplikowane) próbka demonstrując niektóre pojęcia, które eckig określa w swojej (doskonałej) odpowiedzi.
Próbka tworzy pole widzenia, które jest kafelkową szybą węzłów reaktora. Niestandardowe zdarzenie błyskawicy jest okresowo wysyłane do losowego węzła, który będzie migał na żółto po odebraniu zdarzenia. Filtry i procedury obsługi są dodawane do pola nadrzędnego, a ich wywołanie przekazywane do system.out, dzięki czemu można zobaczyć propagowanie zdarzeń i przechwytywanie faz w działaniu.
Kod samego LightningEvent został skopiowany bezpośrednio ze standardowego kodu ActionEvent ze źródła JavaFX, więc kod zdarzenia prawdopodobnie byłby nieco prostszy.
import javafx.animation.*;
import javafx.application.Application;
import javafx.event.*;
import javafx.scene.Scene;
import javafx.scene.layout.TilePane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
import javafx.util.Duration;
import java.util.Random;
public class LightningSimulator extends Application {
private static final int FIELD_SIZE = 10;
private static final Random random = new Random(42);
@Override
public void start(Stage stage) throws Exception {
TilePane field = generateField();
Scene scene = new Scene(field);
stage.setScene(scene);
stage.setResizable(false);
stage.show();
field.addEventFilter(
LightningEvent.PLASMA_STRIKE,
event -> System.out.println(
"Field filtered strike: " + event.getI() + ", " + event.getJ()
)
);
field.addEventHandler(
LightningEvent.PLASMA_STRIKE,
event -> System.out.println(
"Field handled strike: " + event.getI() + ", " + event.getJ()
)
);
periodicallyStrikeRandomNodes(field);
}
private void periodicallyStrikeRandomNodes(TilePane field) {
Timeline timeline = new Timeline(
new KeyFrame(
Duration.seconds(0),
event -> strikeRandomNode(field)
),
new KeyFrame(
Duration.seconds(2)
)
);
timeline.setCycleCount(Timeline.INDEFINITE);
timeline.play();
}
private void strikeRandomNode(TilePane field) {
LightningReactor struckNode = (LightningReactor)
field.getChildren()
.get(
random.nextInt(
FIELD_SIZE * FIELD_SIZE
)
);
LightningEvent lightningStrike = new LightningEvent(
this,
struckNode
);
struckNode.fireEvent(lightningStrike);
}
private TilePane generateField() {
TilePane field = new TilePane();
field.setPrefColumns(10);
field.setMinWidth(TilePane.USE_PREF_SIZE);
field.setMaxWidth(TilePane.USE_PREF_SIZE);
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 10; j++) {
field.getChildren().add(
new LightningReactor(
i, j,
new StrikeEventHandler()
)
);
}
}
return field;
}
private class LightningReactor extends Rectangle {
private static final int SIZE = 20;
private final int i;
private final int j;
private FillTransition fillTransition = new FillTransition(Duration.seconds(4));
public LightningReactor(int i, int j, EventHandler<? super LightningEvent> lightningEventHandler) {
super(SIZE, SIZE);
this.i = i;
this.j = j;
Color baseColor =
(i + j) % 2 == 0
? Color.RED
: Color.WHITE;
setFill(baseColor);
fillTransition.setFromValue(Color.YELLOW);
fillTransition.setToValue(baseColor);
fillTransition.setShape(this);
addEventHandler(
LightningEvent.PLASMA_STRIKE,
lightningEventHandler
);
}
public void strike() {
fillTransition.playFromStart();
}
public int getI() {
return i;
}
public int getJ() {
return j;
}
}
private class StrikeEventHandler implements EventHandler<LightningEvent> {
@Override
public void handle(LightningEvent event) {
LightningReactor reactor = (LightningReactor) event.getTarget();
reactor.strike();
System.out.println("Reactor received strike: " + reactor.getI() + ", " + reactor.getJ());
// event.consume(); if event is consumed the handler for the parent node will not be invoked.
}
}
static class LightningEvent extends Event {
private static final long serialVersionUID = 20121107L;
private int i, j;
public int getI() {
return i;
}
public int getJ() {
return j;
}
/**
* The only valid EventType for the CustomEvent.
*/
public static final EventType<LightningEvent> PLASMA_STRIKE =
new EventType<>(Event.ANY, "PLASMA_STRIKE");
/**
* Creates a new {@code LightningEvent} with an event type of {@code PLASMA_STRIKE}.
* The source and target of the event is set to {@code NULL_SOURCE_TARGET}.
*/
public LightningEvent() {
super(PLASMA_STRIKE);
}
/**
* Construct a new {@code LightningEvent} with the specified event source and target.
* If the source or target is set to {@code null}, it is replaced by the
* {@code NULL_SOURCE_TARGET} value. All LightningEvents have their type set to
* {@code PLASMA_STRIKE}.
*
* @param source the event source which sent the event
* @param target the event target to associate with the event
*/
public LightningEvent(Object source, EventTarget target) {
super(source, target, PLASMA_STRIKE);
this.i = ((LightningReactor) target).getI();
this.j = ((LightningReactor) target).getJ();
}
@Override
public LightningEvent copyFor(Object newSource, EventTarget newTarget) {
return (LightningEvent) super.copyFor(newSource, newTarget);
}
@Override
public EventType<? extends LightningEvent> getEventType() {
return (EventType<? extends LightningEvent>) super.getEventType();
}
}
}