FlexGanttFX Developer Manual : 3.5.2 Time Tracker

/**
 * Copyright (C) 2014 - 2016 Dirk Lemmermann Software & Consulting (dlsc.com)
 *
 * This file is part of FlexGanttFX.
 */
package com.flexganttfx.view.timeline;

import java.time.Instant;
import java.util.logging.Level;

import com.flexganttfx.core.LoggingDomain;
import com.flexganttfx.model.timeline.TimelineModel;

import javafx.application.Platform;
import javafx.beans.property.ReadOnlyObjectProperty;
import javafx.beans.property.ReadOnlyObjectWrapper;

/**
 * A time tracker can be used to update the property
 * {@link TimelineModel#nowProperty()}. In most cases the time "now" will be
 * equivalent to the system time but in simulations this might not be the case.
 * The time tracker can be used in combination with the {@link TimelineModel} by
 * binding the {@link TimelineModel#nowProperty()} to the
 * {@link TimeTracker#timeProperty()}.
 *
 * @since 1.0
 */
public class TimeTracker extends Thread {

   private boolean running = true;

   private long delay = 1000;

   private boolean stopped;

   /**
    * Constructs a new tracker.
    *
    * @since 1.0
    */
   public TimeTracker() {
      setName("Time Tracker");
      setDaemon(true);
   }

   private final ReadOnlyObjectWrapper<Instant> time = new ReadOnlyObjectWrapper<>(
         this, "time", Instant.now());

   public final ReadOnlyObjectProperty<Instant> timeProperty() {
      return time.getReadOnlyProperty();
   }

   public final Instant getTime() {
      return time.get();
   }

   /**
    * Returns the delay in milliseconds between updates of
    * {@link TimelineModel#nowProperty()}. The default is 1000 millis.
    *
    * @return the default delay between update calls
    * @since 1.0
    */
   public final long getDelay() {
      return delay;
   }

   /**
    * Sets the delay between updates of {@link TimelineModel#nowProperty()}.
    * The default is 1000 millis.
    *
    * @param millis
    *            the new delay
    * @throws IllegalArgumentException
    *             if the delay is zero or smaller
    * @since 1.0
    */
   public final void setDelay(long millis) {
      if (millis <= 0) {
         throw new IllegalArgumentException(
               "delay must be larger than zero but was" + millis); //$NON-NLS-1$
      }

      this.delay = millis;
   }

   /**
    * Starts the tracking of the time.
    *
    * @since 1.0
    */
   public final void startTracking() {
      if (stopped) {
         throw new IllegalStateException(
               "Time tracker has already been stopped and can not be started again.");
      } else {
         running = true;
         start();
      }
   }

   @Override
   public void run() {
      while (running) {
         Platform.runLater(() -> time.set(getNow()));
         try {
            Thread.sleep(delay);
         } catch (InterruptedException e) {
            LoggingDomain.CONFIG.log(Level.WARNING,
                  "problem in update thread", e); //$NON-NLS-1$
         }
      }
   }

   /**
    * Stops the tracking of the time.
    *
    * @since 1.0
    */
   public final void stopTracking() {
      stopped = true;
      running = false;
   }

   /**
    * Override to return the instant that will be set as "now" on the timeline
    * model. The default implementation uses {@link Instant#now()}.
    *
    * @see TimelineModel#setNow(Instant)
    *
    * @return the "now" instant
    */
   protected Instant getNow() {
      return Instant.now();
   }
}