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ControllerPoller.java
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ControllerPoller.java
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package com.valkryst.VController;
import net.java.games.input.Controller;
import net.java.games.input.Event;
import java.util.Objects;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class ControllerPoller {
/** {@link Controller} to poll. */
private final Controller controller;
/** Name of the {@link Controller}. */
private final String controllerName;
/** {@link ControllerListener}s to notify when {@link Event}s occur. */
private final CopyOnWriteArrayList<ControllerListener> listeners = new CopyOnWriteArrayList<>();
/** {@link ScheduledExecutorService} used to poll the {@link Controller} and notify {@code listeners}. */
private ScheduledExecutorService executorService;
/**
* Constructs a new {@code ControllerPoller}.
*
* @param controller The {@link Controller} to poll.
*/
public ControllerPoller(final Controller controller) {
Objects.requireNonNull(controller);
this.controller = controller;
controllerName = controller.getName();
}
/**
* <p>Starts polling the {@link Controller}.</p>
*
* <p>See {@link ScheduledExecutorService#scheduleAtFixedRate(Runnable, long, long, TimeUnit)} for caveats.</p>
*
* @param pollingRate The polling rate, in milliseconds.
* @throws IllegalStateException If the {@code ControllerPoller} is already running or if the polling rate is less than 16 millisecond.
*/
public void start(final int pollingRate) {
if (pollingRate < 1) {
throw new IllegalArgumentException("The polling rate cannot be less than 1 millisecond.");
}
// todo Verify thread safety of this block and everything within.
synchronized (this) {
if (executorService != null) {
throw new IllegalStateException("ControllerPoller is already running for '" + controllerName + "'.");
}
executorService = Executors.newSingleThreadScheduledExecutor();
executorService.scheduleAtFixedRate(() -> {
if (!controller.poll()) {
System.err.println("The controller is no-longer valid. Stopping ControllerPoller for '" + controllerName + "'.");
this.stop();
}
final var eventQueue = controller.getEventQueue();
while (true) {
final var event = new Event();
eventQueue.getNextEvent(event);
if (event.getComponent() == null) {
break;
} else {
for (final var listener : listeners) {
listener.eventOccurred(event);
}
}
}
}, 0, pollingRate, TimeUnit.MILLISECONDS);
}
}
/**
* Stops polling the {@link Controller}.
*
* @throws IllegalStateException If the {@code ControllerPoller} is not running.
*/
public void stop() {
synchronized (this) {
if (executorService == null) {
throw new IllegalStateException("ControllerPoller is not running for '" + controllerName + "'.");
}
executorService.shutdown();
executorService = null;
}
}
/**
* Adds a {@link ControllerListener} to {@code listeners}.
*
* @param listener Listener to add.
* @throws NullPointerException If {@code listener} is {@code null}.
*/
public void addListener(final ControllerListener listener) {
Objects.requireNonNull(listener);
listeners.add(listener);
}
/**
* Removes a {@link ControllerListener} from {@code listeners}.
*
* @param listener Listener to remove.
* @throws NullPointerException If {@code listener} is {@code null}.
*/
public void removeListener(final ControllerListener listener) {
Objects.requireNonNull(listener);
listeners.remove(listener);
}
}