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Class java.awt.MediaTracker

java.lang.Object
   |
   +----java.awt.MediaTracker

public class MediaTracker

extends Object

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.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 our 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() & 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) & MediaTracker.COMPLETE) != 0) {
		g.drawImage(anim[index], 10, 10, this);
	    }
	}
}

ABORTED

Flag indicating the download of some media was aborted.

COMPLETE

Flag indicating the download of media completed successfully.

ERRORED

Flag indicating the download of some media encountered an error.

LOADING

Flag indicating some media is currently being loaded.

MediaTracker(Component)

Create a Media tracker to track images for a given Component.

addImage(Image, int)

Add an image to the list of images being tracked.

addImage(Image, int, int, int)

Add a scaled image to the list of images being tracked.

checkAll()

Check to see if all images have finished loading, but do not start loading the images if they are not already loading.

checkAll(boolean)

Check to see if all images have finished loading and start loading any images that are not yet being loaded if load is true.

checkID(int)

Check to see if all images tagged with the indicated ID have finished loading, but do not start loading the images if they are not already loading.

checkID(int, boolean)

Check to see if all images tagged with the indicated ID have finished loading and start loading any images with that ID that are not yet being loaded if load is true.

getErrorsAny()

Return a list of all media that have encountered an error.

getErrorsID(int)

Return a list of media with the specified ID that have encountered an error.

isErrorAny()

Check the error status of all of the images.

isErrorID(int)

Check the error status of all of the images with the specified ID.

statusAll(boolean)

Return the boolean OR of the status of all of the media being tracked.

statusID(int, boolean)

Return the boolean OR of the status of all of the media with a given ID.

waitForAll()

Start loading all images and wait until they have finished loading, are aborted, or receive an error.

waitForAll(long)

Start loading all images and wait until they have finished loading, are aborted, receive an error, or until the specified timeout has elapsed.

waitForID(int)

Start loading all images with the specified ID and wait until they have finished loading or receive an error.

waitForID(int, long)

Start loading all images with the specified ID and wait until they have finished loading or receive an error, or until the specified timeout has elapsed.

  public final static int LOADING

Flag indicating some media is currently being loaded.

See Also:

statusAll, statusID

  public final static int ABORTED

Flag indicating the download of some media was aborted.

See Also:

statusAll, statusID

  public final static int ERRORED

Flag indicating the download of some media encountered an error.

See Also:

statusAll, statusID

  public final static int COMPLETE

Flag indicating the download of media completed successfully.

See Also:

statusAll, statusID

  public MediaTracker(Component comp)

Create a Media tracker to track images for a given Component.

Parameters:

comp - the component on which the images will eventually be drawn

  public void addImage(Image image,
                       int id)

Add an image to the list of images being tracked. The image will eventually be rendered at its default (unscaled) size.

Parameters:

image - the image to be tracked

id - the identifier used to later track this image

  public synchronized void addImage(Image image,
                                    int id,
                                    int w,
                                    int h)

Add a scaled image to the list of images being tracked. The image will eventually be rendered at the indicated size.

Parameters:

image - the image to be tracked

id - the identifier used to later track this image

w - the width that the image will be rendered at

h - the height that the image will be rendered at

  public boolean checkAll()

Check to see if all images have finished loading, but do 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 "complete". Use isErrorAny or isErrorID to check for errors.

Returns:

true if all images have finished loading, were aborted or encountered an error

See Also:

checkAll, checkID, isErrorAny, isErrorID

  public synchronized boolean checkAll(boolean load)

Check to see if all images have finished loading and start loading any images that are not yet being loaded if load is true. If there is an error while loading or scaling an image then that image is considered "complete". Use isErrorAny or isErrorID to check for errors.

Parameters:

load - start loading the images if this parameter is true

Returns:

true if all images have finished loading, were aborted or encountered an error

See Also:

isErrorAny, isErrorID, checkID, checkAll

  public synchronized boolean isErrorAny()

Check the error status of all of the images.

Returns:

true if any of the images had an error during loading

See Also:

isErrorID, getErrorsAny

  public synchronized Object[] getErrorsAny()

Return a list of all media that have encountered an error.

Returns:

an array of media objects or null if there are no errors

See Also:

isErrorAny, getErrorsID

  public void waitForAll() throws InterruptedException

Start loading all images and wait until they have finished loading, are aborted, or receive an error. If there is an error while loading or scaling an image then that image is considered "complete". Use isErrorAny or statusAll to check for errors.

Throws: InterruptedException

Another thread has interrupted this thread.

See Also:

waitForID, waitForAll, isErrorAny, isErrorID

  public synchronized boolean waitForAll(long ms) throws InterruptedException

Start loading all images and wait until they have finished loading, are aborted, receive an error, or until the specified timeout has elapsed. If there is an error while loading or scaling an image then that image is considered "complete". Use isErrorAny or statusAll to check for errors.

Parameters:

ms - the length of time to wait for the loading to complete

Returns:

true if all images were successfully loaded

Throws: InterruptedException

Another thread has interrupted this thread.

See Also:

waitForID, waitForAll, isErrorAny, isErrorID

  public int statusAll(boolean load)

Return the boolean OR of the status of all of the media being tracked.

Parameters:

load - specifies whether to start the media loading

See Also:

statusID, LOADING, ABORTED, ERRORED, COMPLETE

  public boolean checkID(int id)

Check to see if all images tagged with the indicated ID have finished loading, but do 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 "complete". Use isErrorAny or isErrorID to check for errors.

Parameters:

id - the identifier used to determine which images to check

Returns:

true if all tagged images have finished loading, were aborted, or received an error

See Also:

checkID, checkAll, isErrorAny, isErrorID

  public synchronized boolean checkID(int id,
                                      boolean load)

Check to see if all images tagged with the indicated ID have finished loading and start loading any images with that ID that are not yet being loaded if load is true. If there is an error while loading or scaling an image then that image is considered "complete". Use isErrorAny or isErrorID to check for errors.

Parameters:

id - the identifier used to determine which images to check

load - start loading the images if this parameter is true

Returns:

true if all tagged images have finished loading, were aborted, or received an error

See Also:

checkID, checkAll, isErrorAny, isErrorID

  public synchronized boolean isErrorID(int id)

Check the error status of all of the images with the specified ID.

Parameters:

id - the identifier used to determine which images to check

Returns:

true if any of the tagged images had an error during loading

See Also:

isErrorAny, getErrorsID

  public synchronized Object[] getErrorsID(int id)

Return a list of media with the specified ID that have encountered an error.

Parameters:

id - the identifier used to determine which images to return

Returns:

an array of media objects or null if there are no errors

See Also:

isErrorID, getErrorsAny

  public void waitForID(int id) throws InterruptedException

Start loading all images with the specified ID and wait until they have finished loading or receive an error. If there is an error while loading or scaling an image then that image is considered "complete". Use statusID or isErrorID to check for errors.

Parameters:

id - the identifier used to determine which images to wait for

Throws: InterruptedException

Another thread has interrupted this thread.

See Also:

waitForAll, waitForID, isErrorAny, isErrorID

  public synchronized boolean waitForID(int id,
                                        long ms) throws InterruptedException

Start loading all images with the specified ID and wait until they have finished loading or receive an error, or until the specified timeout has elapsed. If there is an error while loading or scaling an image then that image is considered "complete". Use statusID or isErrorID to check for errors.

Parameters:

id - the identifier used to determine which images to wait for

ms - the length of time to wait for the loading to complete

Throws: InterruptedException

Another thread has interrupted this thread.

See Also:

waitForAll, waitForID, isErrorAny, isErrorID

  public int statusID(int id,
                      boolean load)

Return the boolean OR of the status of all of the media with a given ID.

Parameters:

id - the identifier used to determine which images to check

load - specifies whether to start the media loading

See Also:

statusAll, LOADING, ABORTED, ERRORED, COMPLETE

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