statewaiter.java

FMJ（freedom media for java)是java视频开发的新选择

package net.sf.fmj.ejmf.toolkit.util;

import javax.media.Controller;
import javax.media.ControllerClosedEvent;
import javax.media.ControllerEvent;
import javax.media.ControllerListener;
import javax.media.Player;
import javax.media.Processor;
import javax.media.StopEvent;
import javax.media.Time;
import javax.media.TransitionEvent;

/**
 * The StateWaiter class provides routines to allow the current
 * thread to wait for a Controller to reach a particular state.  A
 * StateWaiter object will first register itself as a
 * ControllerListener on the given Controller object.  It will then
 * set the state to be waited for, and block the current thread
 * until either
 * <UL>
 * <LI>the Controller posts a TransitionEvent indicating that it
 * has moved to the desired state, or</LI>
 * <LI>the Controller posts a ControllerErrorEvent, indicating
 * that an error occurred andthe transition failed</LI>
 * </UL>
 *
 * From the book: Essential JMF, Gordon, Talley (ISBN 0130801046).  Used with permission.
 *
 * @author         Steve Talley and Rob Gordon
 */
public class StateWaiter implements ControllerListener {
    /**
     * The state to be waited for
     */
    private int state;

    /**
     * Indicates whether the desired state has been reached
     */
    private boolean stateReached = false;

    /**
     * Indicates whether this StateWaiter is already a
     * ControllerListener of its Controller.
     */
    private boolean listening = false;

    /**
     * The Controller on which to wait for the desired state
     */
    private Controller controller;

    /**
     * Construct a StateWaiter object for the given Controller
     *
     * @param          controller
     *                 the Controller on which to wait for the desired state
     */
    public StateWaiter(Controller controller) {
        this.controller = controller;
    }
    
    /**
     * Sets the state to wait for
     */
    private void setState(int state) {
        this.state = state;
        stateReached = false;
        addAsListener();
    }

    /**
     * Adds this StateWaiter as a ControllerListener of the Controller
     */
    private void addAsListener() {
        if( ! listening ) {
            controller.addControllerListener(this);
            listening = true;
        }
    }

    /**
     * Removes this StateWaiter as a ControllerListener of the Controller
     */
    private void removeAsListener() {
        controller.removeControllerListener(this);
        listening = false;
    }

    /**
     * Listens for a transition to the state that this
     * StateWaiter is waiting for.  Notifies the the waiting
     * thread and stops listening if any of the following occur:
     * <p>
     * <UL>
     * <LI>A TransitionEvent to the desired state is posted</LI>
     * <LI>A StopEvent is posted</LI>
     * <LI>A ControllerClosedEvent is posted (indicating
     * a failure)</LI>
     * </UL>
     *
     * @param          event
     *                 the media event
     */
    public synchronized void controllerUpdate(ControllerEvent event) {
        if( event.getSourceController() != controller ) {
            return;
        }

        if( event instanceof TransitionEvent ) {
            int currState =
                ((TransitionEvent)event).getCurrentState();

            stateReached = (currState >= state);
        }

        //  Is this a stop event or a Controller Error?
        if( event instanceof StopEvent ||
            event instanceof ControllerClosedEvent ||
            stateReached)
        {
            //  Stop listening
            removeAsListener();

            // Notify threads waiting for state change
            notifyAll();
        }
    }

    /**
     * Calls realize() on the Controller and blocks the current thread
     * until the Controller is Realized.
     *
     * @return     boolean indicating whether the transition was
     *             successful.
     */
    public boolean blockingRealize() {
        setState(Controller.Realized);
        controller.realize();
        return waitForState();
    }

    /**
     * Calls prefetch() on the Controller and blocks the current thread
     * until the Controller is Prefetched.
     *
     * @return     boolean indicating whether the transition was
     *             successful.
     */
    public boolean blockingPrefetch() {
        setState(Controller.Prefetched);
        controller.prefetch();
        return waitForState();
    }

    /**
     * Casts the Controller to a Player, calls start(), and
     * blocks the current thread until the player is Started.
     *
     * @return     boolean indicating whether the transition was
     *             successful.
     *
     * @exception  ClassCastException
     *             If the Controller is not a Player
     */
    public boolean blockingStart() {
        setState(Controller.Started);
        Player player = (Player)controller;
        player.start();
        return waitForState();
    }

    /**
     * Calls syncStart() on the Controller and blocks the current thread
     * until the Controller is Started.  This could throw a
     * ClockStartedError if the Controller is not in the Prefetched
     * state.
     *
     * @return     boolean indicating whether the transition was
     *             successful.
     */
    public boolean blockingSyncStart(Time t) {
        setState(Controller.Started);
        controller.syncStart(t);
        return waitForState();
    }

    
    public boolean blockingConfigure() {
        setState(Processor.Configured);
        ((Processor) controller).configure();
        return waitForState();
    }
    
    /**
     * Blocks the current thread until the Controller has reached the
     * previously specified state or an error has occurred.
     *
     * @return     boolean indicating whether the transition was
     *             successful.
     */
    private synchronized boolean waitForState() {
        while( listening ) {
            try {
                wait();
            } catch(InterruptedException e) {}
        }

        return stateReached;
    }
}