MediaTracker class is a utility class to track
* the status of a number of media objects. Media objects could
* include audio clips as well as images, though currently only
* images are supported.
*
* To use a media tracker, create an instance of
* MediaTracker and call its addImage
* method for each image to be tracked. In addition, each image can
* be assigned a unique identifier. This identifier controls the
* priority order in which the images are fetched. It can also be used
* to identify unique subsets of the images that can be waited on
* independently. Images with a lower ID are loaded in preference to
* those with a higher ID number.
*
*
*
* Tracking an animated image
* might not always be useful
* due to the multi-part nature of animated image
* loading and painting,
* but it is supported.
* MediaTracker treats an animated image
* as completely loaded
* when the first frame is completely loaded.
* At that point, the MediaTracker
* signals any waiters
* that the image is completely loaded.
* If no ImageObservers are observing the image
* when the first frame has finished loading,
* the image might flush itself
* to conserve resources
* (see {@link Image#flush()}).
*
*
* Here is an example of using MediaTracker:
*
*
* import java.applet.Applet;
* import java.awt.Color;
* import java.awt.Image;
* import java.awt.Graphics;
* import java.awt.MediaTracker;
*
* public class ImageBlaster extends Applet implements Runnable {
* MediaTracker tracker;
* Image bg;
* Image anim[] = new Image[5];
* int index;
* Thread animator;
*
* // Get the images for the background (id == 0)
* // and the animation frames (id == 1)
* // and add them to the MediaTracker
* public void init() {
* tracker = new MediaTracker(this);
* bg = getImage(getDocumentBase(),
* "images/background.gif");
* tracker.addImage(bg, 0);
* for (int i = 0; i < 5; i++) {
* anim[i] = getImage(getDocumentBase(),
* "images/anim"+i+".gif");
* tracker.addImage(anim[i], 1);
* }
* }
*
* // Start the animation thread.
* public void start() {
* animator = new Thread(this);
* animator.start();
* }
*
* // Stop the animation thread.
* public void stop() {
* animator = null;
* }
*
* // Run the animation thread.
* // First wait for the background image to fully load
* // and paint. Then wait for all of the animation
* // frames to finish loading. Finally, loop and
* // increment the animation frame index.
* public void run() {
* try {
* tracker.waitForID(0);
* tracker.waitForID(1);
* } catch (InterruptedException e) {
* return;
* }
* Thread me = Thread.currentThread();
* while (animator == me) {
* try {
* Thread.sleep(100);
* } catch (InterruptedException e) {
* break;
* }
* synchronized (this) {
* index++;
* if (index >= anim.length) {
* index = 0;
* }
* }
* repaint();
* }
* }
*
* // The background image fills the frame so we
* // don't need to clear the applet on repaints.
* // Just call the paint method.
* public void update(Graphics g) {
* paint(g);
* }
*
* // Paint a large red rectangle if there are any errors
* // loading the images. Otherwise always paint the
* // background so that it appears incrementally as it
* // is loading. Finally, only paint the current animation
* // frame if all of the frames (id == 1) are done loading,
* // so that we don't get partial animations.
* public void paint(Graphics g) {
* if ((tracker.statusAll(false) & MediaTracker.ERRORED) != 0) {
* g.setColor(Color.red);
* g.fillRect(0, 0, size().width, size().height);
* return;
* }
* g.drawImage(bg, 0, 0, this);
* if (tracker.statusID(1, false) == MediaTracker.COMPLETE) {
* g.drawImage(anim[index], 10, 10, this);
* }
* }
* }
* Component that will be
* tracked by a media tracker where the image will
* eventually be drawn.
*
* @serial
* @see #MediaTracker(Component)
*/
Component target;
/**
* The head of the list of Images that is being
* tracked by the MediaTracker.
*
* @serial
* @see #addImage(Image, int)
* @see #removeImage(Image)
*/
MediaEntry head;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = -483174189758638095L;
/**
* Creates a media tracker to track images for a given component.
* @param comp the component on which the images
* will eventually be drawn
*/
public MediaTracker(Component comp) {
target = comp;
}
/**
* Adds an image to the list of images being tracked by this media
* tracker. The image will eventually be rendered at its default
* (unscaled) size.
* @param image the image to be tracked
* @param id an identifier used to track this image
*/
public void addImage(Image image, int id) {
addImage(image, id, -1, -1);
}
/**
* Adds a scaled image to the list of images being tracked
* by this media tracker. The image will eventually be
* rendered at the indicated width and height.
*
* @param image the image to be tracked
* @param id an identifier that can be used to track this image
* @param w the width at which the image is rendered
* @param h the height at which the image is rendered
*/
public synchronized void addImage(Image image, int id, int w, int h) {
head = MediaEntry.insert(head,
new ImageMediaEntry(this, image, id, w, h));
}
/**
* Flag indicating that media is currently being loaded.
* @see java.awt.MediaTracker#statusAll
* @see java.awt.MediaTracker#statusID
*/
public static final int LOADING = 1;
/**
* Flag indicating that the downloading of media was aborted.
* @see java.awt.MediaTracker#statusAll
* @see java.awt.MediaTracker#statusID
*/
public static final int ABORTED = 2;
/**
* Flag indicating that the downloading of media encountered
* an error.
* @see java.awt.MediaTracker#statusAll
* @see java.awt.MediaTracker#statusID
*/
public static final int ERRORED = 4;
/**
* Flag indicating that the downloading of media was completed
* successfully.
* @see java.awt.MediaTracker#statusAll
* @see java.awt.MediaTracker#statusID
*/
public static final int COMPLETE = 8;
static final int DONE = (ABORTED | ERRORED | COMPLETE);
/**
* Checks to see if all images being tracked by this media tracker
* have finished loading.
* * This method does not start loading the images if they are not * already loading. *
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* isErrorAny or isErrorID methods to
* check for errors.
* @return true if all images have finished loading,
* have been aborted, or have encountered
* an error; false otherwise
* @see java.awt.MediaTracker#checkAll(boolean)
* @see java.awt.MediaTracker#checkID
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#isErrorID
*/
public boolean checkAll() {
return checkAll(false, true);
}
/**
* Checks to see if all images being tracked by this media tracker
* have finished loading.
*
* If the value of the load flag is true,
* then this method starts loading any images that are not yet
* being loaded.
*
* If there is an error while loading or scaling an image, that
* image is considered to have finished loading. Use the
* isErrorAny and isErrorID methods to
* check for errors.
* @param load if true, start loading any
* images that are not yet being loaded
* @return true if all images have finished loading,
* have been aborted, or have encountered
* an error; false otherwise
* @see java.awt.MediaTracker#checkID
* @see java.awt.MediaTracker#checkAll()
* @see java.awt.MediaTracker#isErrorAny()
* @see java.awt.MediaTracker#isErrorID(int)
*/
public boolean checkAll(boolean load) {
return checkAll(load, true);
}
private synchronized boolean checkAll(boolean load, boolean verify) {
MediaEntry cur = head;
boolean done = true;
while (cur != null) {
if ((cur.getStatus(load, verify) & DONE) == 0) {
done = false;
}
cur = cur.next;
}
return done;
}
/**
* Checks the error status of all of the images.
* @return true if any of the images tracked
* by this media tracker had an error during
* loading; false otherwise
* @see java.awt.MediaTracker#isErrorID
* @see java.awt.MediaTracker#getErrorsAny
*/
public synchronized boolean isErrorAny() {
MediaEntry cur = head;
while (cur != null) {
if ((cur.getStatus(false, true) & ERRORED) != 0) {
return true;
}
cur = cur.next;
}
return false;
}
/**
* Returns a list of all media that have encountered an error.
* @return an array of media objects tracked by this
* media tracker that have encountered
* an error, or null if
* there are none with errors
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#getErrorsID
*/
public synchronized Object[] getErrorsAny() {
MediaEntry cur = head;
int numerrors = 0;
while (cur != null) {
if ((cur.getStatus(false, true) & ERRORED) != 0) {
numerrors++;
}
cur = cur.next;
}
if (numerrors == 0) {
return null;
}
Object errors[] = new Object[numerrors];
cur = head;
numerrors = 0;
while (cur != null) {
if ((cur.getStatus(false, false) & ERRORED) != 0) {
errors[numerrors++] = cur.getMedia();
}
cur = cur.next;
}
return errors;
}
/**
* Starts loading all images tracked by this media tracker. This
* method waits until all the images being tracked have finished
* loading.
*
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* isErrorAny or isErrorID methods to
* check for errors.
* @see java.awt.MediaTracker#waitForID(int)
* @see java.awt.MediaTracker#waitForAll(long)
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#isErrorID
* @exception InterruptedException if any thread has
* interrupted this thread
*/
public void waitForAll() throws InterruptedException {
waitForAll(0);
}
/**
* Starts loading all images tracked by this media tracker. This
* method waits until all the images being tracked have finished
* loading, or until the length of time specified in milliseconds
* by the ms argument has passed.
*
* If there is an error while loading or scaling an image, then
* that image is considered to have finished loading. Use the
* isErrorAny or isErrorID methods to
* check for errors.
* @param ms the number of milliseconds to wait
* for the loading to complete
* @return true if all images were successfully
* loaded; false otherwise
* @see java.awt.MediaTracker#waitForID(int)
* @see java.awt.MediaTracker#waitForAll(long)
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#isErrorID
* @exception InterruptedException if any thread has
* interrupted this thread.
*/
public synchronized boolean waitForAll(long ms)
throws InterruptedException
{
long end = System.currentTimeMillis() + ms;
boolean first = true;
while (true) {
int status = statusAll(first, first);
if ((status & LOADING) == 0) {
return (status == COMPLETE);
}
first = false;
long timeout;
if (ms == 0) {
timeout = 0;
} else {
timeout = end - System.currentTimeMillis();
if (timeout <= 0) {
return false;
}
}
wait(timeout);
}
}
/**
* Calculates and returns the bitwise inclusive OR of the
* status of all media that are tracked by this media tracker.
*
* Possible flags defined by the
* MediaTracker class are LOADING,
* ABORTED, ERRORED, and
* COMPLETE. An image that hasn't started
* loading has zero as its status.
*
* If the value of load is true, then
* this method starts loading any images that are not yet being loaded.
*
* @param load if true, start loading
* any images that are not yet being loaded
* @return the bitwise inclusive OR of the status of
* all of the media being tracked
* @see java.awt.MediaTracker#statusID(int, boolean)
* @see java.awt.MediaTracker#LOADING
* @see java.awt.MediaTracker#ABORTED
* @see java.awt.MediaTracker#ERRORED
* @see java.awt.MediaTracker#COMPLETE
*/
public int statusAll(boolean load) {
return statusAll(load, true);
}
private synchronized int statusAll(boolean load, boolean verify) {
MediaEntry cur = head;
int status = 0;
while (cur != null) {
status = status | cur.getStatus(load, verify);
cur = cur.next;
}
return status;
}
/**
* Checks to see if all images tracked by this media tracker that
* are tagged with the specified identifier have finished loading.
*
* This method does not start loading the images if they are not * already loading. *
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* isErrorAny or isErrorID methods to
* check for errors.
* @param id the identifier of the images to check
* @return true if all images have finished loading,
* have been aborted, or have encountered
* an error; false otherwise
* @see java.awt.MediaTracker#checkID(int, boolean)
* @see java.awt.MediaTracker#checkAll()
* @see java.awt.MediaTracker#isErrorAny()
* @see java.awt.MediaTracker#isErrorID(int)
*/
public boolean checkID(int id) {
return checkID(id, false, true);
}
/**
* Checks to see if all images tracked by this media tracker that
* are tagged with the specified identifier have finished loading.
*
* If the value of the load flag is true,
* then this method starts loading any images that are not yet
* being loaded.
*
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* isErrorAny or isErrorID methods to
* check for errors.
* @param id the identifier of the images to check
* @param load if true, start loading any
* images that are not yet being loaded
* @return true if all images have finished loading,
* have been aborted, or have encountered
* an error; false otherwise
* @see java.awt.MediaTracker#checkID(int, boolean)
* @see java.awt.MediaTracker#checkAll()
* @see java.awt.MediaTracker#isErrorAny()
* @see java.awt.MediaTracker#isErrorID(int)
*/
public boolean checkID(int id, boolean load) {
return checkID(id, load, true);
}
private synchronized boolean checkID(int id, boolean load, boolean verify)
{
MediaEntry cur = head;
boolean done = true;
while (cur != null) {
if (cur.getID() == id
&& (cur.getStatus(load, verify) & DONE) == 0)
{
done = false;
}
cur = cur.next;
}
return done;
}
/**
* Checks the error status of all of the images tracked by this
* media tracker with the specified identifier.
* @param id the identifier of the images to check
* @return true if any of the images with the
* specified identifier had an error during
* loading; false otherwise
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#getErrorsID
*/
public synchronized boolean isErrorID(int id) {
MediaEntry cur = head;
while (cur != null) {
if (cur.getID() == id
&& (cur.getStatus(false, true) & ERRORED) != 0)
{
return true;
}
cur = cur.next;
}
return false;
}
/**
* Returns a list of media with the specified ID that
* have encountered an error.
* @param id the identifier of the images to check
* @return an array of media objects tracked by this media
* tracker with the specified identifier
* that have encountered an error, or
* null if there are none with errors
* @see java.awt.MediaTracker#isErrorID
* @see java.awt.MediaTracker#isErrorAny
* @see java.awt.MediaTracker#getErrorsAny
*/
public synchronized Object[] getErrorsID(int id) {
MediaEntry cur = head;
int numerrors = 0;
while (cur != null) {
if (cur.getID() == id
&& (cur.getStatus(false, true) & ERRORED) != 0)
{
numerrors++;
}
cur = cur.next;
}
if (numerrors == 0) {
return null;
}
Object errors[] = new Object[numerrors];
cur = head;
numerrors = 0;
while (cur != null) {
if (cur.getID() == id
&& (cur.getStatus(false, false) & ERRORED) != 0)
{
errors[numerrors++] = cur.getMedia();
}
cur = cur.next;
}
return errors;
}
/**
* Starts loading all images tracked by this media tracker with the
* specified identifier. This method waits until all the images with
* the specified identifier have finished loading.
*
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* isErrorAny and isErrorID methods to
* check for errors.
* @param id the identifier of the images to check
* @see java.awt.MediaTracker#waitForAll
* @see java.awt.MediaTracker#isErrorAny()
* @see java.awt.MediaTracker#isErrorID(int)
* @exception InterruptedException if any thread has
* interrupted this thread.
*/
public void waitForID(int id) throws InterruptedException {
waitForID(id, 0);
}
/**
* Starts loading all images tracked by this media tracker with the
* specified identifier. This method waits until all the images with
* the specified identifier have finished loading, or until the
* length of time specified in milliseconds by the ms
* argument has passed.
*
* If there is an error while loading or scaling an image, then that
* image is considered to have finished loading. Use the
* statusID, isErrorID, and
* isErrorAny methods to check for errors.
* @param id the identifier of the images to check
* @param ms the length of time, in milliseconds, to wait
* for the loading to complete
* @see java.awt.MediaTracker#waitForAll
* @see java.awt.MediaTracker#waitForID(int)
* @see java.awt.MediaTracker#statusID
* @see java.awt.MediaTracker#isErrorAny()
* @see java.awt.MediaTracker#isErrorID(int)
* @exception InterruptedException if any thread has
* interrupted this thread.
*/
public synchronized boolean waitForID(int id, long ms)
throws InterruptedException
{
long end = System.currentTimeMillis() + ms;
boolean first = true;
while (true) {
int status = statusID(id, first, first);
if ((status & LOADING) == 0) {
return (status == COMPLETE);
}
first = false;
long timeout;
if (ms == 0) {
timeout = 0;
} else {
timeout = end - System.currentTimeMillis();
if (timeout <= 0) {
return false;
}
}
wait(timeout);
}
}
/**
* Calculates and returns the bitwise inclusive OR of the
* status of all media with the specified identifier that are
* tracked by this media tracker.
*
* Possible flags defined by the
* MediaTracker class are LOADING,
* ABORTED, ERRORED, and
* COMPLETE. An image that hasn't started
* loading has zero as its status.
*
* If the value of load is true, then
* this method starts loading any images that are not yet being loaded.
* @param id the identifier of the images to check
* @param load if true, start loading
* any images that are not yet being loaded
* @return the bitwise inclusive OR of the status of
* all of the media with the specified
* identifier that are being tracked
* @see java.awt.MediaTracker#statusAll(boolean)
* @see java.awt.MediaTracker#LOADING
* @see java.awt.MediaTracker#ABORTED
* @see java.awt.MediaTracker#ERRORED
* @see java.awt.MediaTracker#COMPLETE
*/
public int statusID(int id, boolean load) {
return statusID(id, load, true);
}
private synchronized int statusID(int id, boolean load, boolean verify) {
MediaEntry cur = head;
int status = 0;
while (cur != null) {
if (cur.getID() == id) {
status = status | cur.getStatus(load, verify);
}
cur = cur.next;
}
return status;
}
/**
* Removes the specified image from this media tracker.
* All instances of the specified image are removed,
* regardless of scale or ID.
* @param image the image to be removed
* @see java.awt.MediaTracker#removeImage(java.awt.Image, int)
* @see java.awt.MediaTracker#removeImage(java.awt.Image, int, int, int)
* @since JDK1.1
*/
public synchronized void removeImage(Image image) {
MediaEntry cur = head;
MediaEntry prev = null;
while (cur != null) {
MediaEntry next = cur.next;
if (cur.getMedia() == image) {
if (prev == null) {
head = next;
} else {
prev.next = next;
}
cur.cancel();
} else {
prev = cur;
}
cur = next;
}
notifyAll(); // Notify in case remaining images are "done".
}
/**
* Removes the specified image from the specified tracking
* ID of this media tracker.
* All instances of Image being tracked
* under the specified ID are removed regardless of scale.
* @param image the image to be removed
* @param id the tracking ID frrom which to remove the image
* @see java.awt.MediaTracker#removeImage(java.awt.Image)
* @see java.awt.MediaTracker#removeImage(java.awt.Image, int, int, int)
* @since JDK1.1
*/
public synchronized void removeImage(Image image, int id) {
MediaEntry cur = head;
MediaEntry prev = null;
while (cur != null) {
MediaEntry next = cur.next;
if (cur.getID() == id && cur.getMedia() == image) {
if (prev == null) {
head = next;
} else {
prev.next = next;
}
cur.cancel();
} else {
prev = cur;
}
cur = next;
}
notifyAll(); // Notify in case remaining images are "done".
}
/**
* Removes the specified image with the specified
* width, height, and ID from this media tracker.
* Only the specified instance (with any duplicates) is removed.
* @param image the image to be removed
* @param id the tracking ID from which to remove the image
* @param width the width to remove (-1 for unscaled)
* @param height the height to remove (-1 for unscaled)
* @see java.awt.MediaTracker#removeImage(java.awt.Image)
* @see java.awt.MediaTracker#removeImage(java.awt.Image, int)
* @since JDK1.1
*/
public synchronized void removeImage(Image image, int id,
int width, int height) {
MediaEntry cur = head;
MediaEntry prev = null;
while (cur != null) {
MediaEntry next = cur.next;
if (cur.getID() == id && cur instanceof ImageMediaEntry
&& ((ImageMediaEntry) cur).matches(image, width, height))
{
if (prev == null) {
head = next;
} else {
prev.next = next;
}
cur.cancel();
} else {
prev = cur;
}
cur = next;
}
notifyAll(); // Notify in case remaining images are "done".
}
synchronized void setDone() {
notifyAll();
}
}
abstract class MediaEntry {
MediaTracker tracker;
int ID;
MediaEntry next;
int status;
boolean cancelled;
MediaEntry(MediaTracker mt, int id) {
tracker = mt;
ID = id;
}
abstract Object getMedia();
static MediaEntry insert(MediaEntry head, MediaEntry me) {
MediaEntry cur = head;
MediaEntry prev = null;
while (cur != null) {
if (cur.ID > me.ID) {
break;
}
prev = cur;
cur = cur.next;
}
me.next = cur;
if (prev == null) {
head = me;
} else {
prev.next = me;
}
return head;
}
int getID() {
return ID;
}
abstract void startLoad();
void cancel() {
cancelled = true;
}
static final int LOADING = MediaTracker.LOADING;
static final int ABORTED = MediaTracker.ABORTED;
static final int ERRORED = MediaTracker.ERRORED;
static final int COMPLETE = MediaTracker.COMPLETE;
static final int LOADSTARTED = (LOADING | ERRORED | COMPLETE);
static final int DONE = (ABORTED | ERRORED | COMPLETE);
synchronized int getStatus(boolean doLoad, boolean doVerify) {
if (doLoad && ((status & LOADSTARTED) == 0)) {
status = (status & ~ABORTED) | LOADING;
startLoad();
}
return status;
}
void setStatus(int flag) {
synchronized (this) {
status = flag;
}
tracker.setDone();
}
}
class ImageMediaEntry extends MediaEntry implements ImageObserver,
java.io.Serializable {
Image image;
int width;
int height;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 4739377000350280650L;
ImageMediaEntry(MediaTracker mt, Image img, int c, int w, int h) {
super(mt, c);
image = img;
width = w;
height = h;
}
boolean matches(Image img, int w, int h) {
return (image == img && width == w && height == h);
}
Object getMedia() {
return image;
}
synchronized int getStatus(boolean doLoad, boolean doVerify) {
if (doVerify) {
int flags = tracker.target.checkImage(image, width, height, null);
int s = parseflags(flags);
if (s == 0) {
if ((status & (ERRORED | COMPLETE)) != 0) {
setStatus(ABORTED);
}
} else if (s != status) {
setStatus(s);
}
}
return super.getStatus(doLoad, doVerify);
}
void startLoad() {
if (tracker.target.prepareImage(image, width, height, this)) {
setStatus(COMPLETE);
}
}
int parseflags(int infoflags) {
if ((infoflags & ERROR) != 0) {
return ERRORED;
} else if ((infoflags & ABORT) != 0) {
return ABORTED;
} else if ((infoflags & (ALLBITS | FRAMEBITS)) != 0) {
return COMPLETE;
}
return 0;
}
public boolean imageUpdate(Image img, int infoflags,
int x, int y, int w, int h) {
if (cancelled) {
return false;
}
int s = parseflags(infoflags);
if (s != 0 && s != status) {
setStatus(s);
}
return ((status & LOADING) != 0);
}
}