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package javafx.animation;

import com.sun.javafx.tk.Toolkit;
import com.sun.scenario.animation.AbstractMasterTimer;
import com.sun.scenario.animation.shared.TimerReceiver;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;

The class AnimationTimer allows to create a timer, that is called in each frame while it is active. An extending class has to override the method handle(long) which will be called in every frame. The methods start() and stop() allow to start and stop the timer. 
Since:
JavaFX 2.0/**
 * The class {@code AnimationTimer} allows to create a timer, that is called in
 * each frame while it is active.
 *
 * An extending class has to override the method {@link #handle(long)} which
 * will be called in every frame.
 *
 * The methods {@link AnimationTimer#start()} and {@link #stop()} allow to start
 * and stop the timer.
 *
 *
 * @since JavaFX 2.0
 */
public abstract class AnimationTimer {

    private class AnimationTimerReceiver implements TimerReceiver {
        @Override public void handle(final long now) {
            if (accessCtrlCtx == null) {
                throw new IllegalStateException("Error: AccessControlContext not captured");
            }

            AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
                AnimationTimer.this.handle(now);
                return null;
            }, accessCtrlCtx);
        }
    }

    private final AbstractMasterTimer timer;
    private final AnimationTimerReceiver timerReceiver = new AnimationTimerReceiver();
    private boolean active;

    // Access control context, captured in start()
    private AccessControlContext accessCtrlCtx = null;

    
Creates a new timer.
/**
     * Creates a new timer.
     */
    public AnimationTimer() {
        timer = Toolkit.getToolkit().getMasterTimer();
    }

    // For testing only
    AnimationTimer(AbstractMasterTimer timer) {
        this.timer = timer;
    }

    
This method needs to be overridden by extending classes. It is going to be called in every frame while the AnimationTimer is active. 
Params:
now –  The timestamp of the current frame given in nanoseconds. This value will be the same for all AnimationTimers called during one frame./**
     * This method needs to be overridden by extending classes. It is going to
     * be called in every frame while the {@code AnimationTimer} is active.
     *
     * @param now
     *            The timestamp of the current frame given in nanoseconds. This
     *            value will be the same for all {@code AnimationTimers} called
     *            during one frame.
     */
    public abstract void handle(long now);

    
Starts the AnimationTimer. Once it is started, the handle(long) method of this AnimationTimer will be called in every frame. The AnimationTimer can be stopped by calling stop(). /**
     * Starts the {@code AnimationTimer}. Once it is started, the
     * {@link #handle(long)} method of this {@code AnimationTimer} will be
     * called in every frame.
     *
     * The {@code AnimationTimer} can be stopped by calling {@link #stop()}.
     */
    public void start() {
        if (!active) {
            // Capture the Access Control Context to be used during the animation pulse
            accessCtrlCtx = AccessController.getContext();
            timer.addAnimationTimer(timerReceiver);
            active = true;
        }
    }

    
Stops the AnimationTimer. It can be activated again by calling start(). /**
     * Stops the {@code AnimationTimer}. It can be activated again by calling
     * {@link #start()}.
     */
    public void stop() {
        if (active) {
            timer.removeAnimationTimer(timerReceiver);
            active = false;
        }
    }
}