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MediaTracker

Name

MediaTracker

[Graphic: Figure from the text]

Description

The MediaTracker class assists in the loading of multimedia objects across the network. It can be used to wait until an object (or group of objects) has been loaded completely. Tracked objects are assigned to groups; if there is more than one object in a group, you can only track the behavior of the group as a whole (i.e., it isn't possible to track an individual object unless it is the only object in its group). Currently (1.0.2 and 1.1) MediaTracker only works for Image objects; future releases may extend MediaTracker to other multi-media types.

Class Definition

public abstract class java.awt.MediaTracker
    extends java.lang.Object
    implements java.io.Serializable {
  
  // Constants
  public static final int ABORTED;
  public static final int COMPLETE;
  public static final int ERRORED;
  public static final int LOADING;
  
  // Constructors
  public MediaTracker (Component component);
  
  // Instance Methods
  public void addImage (Image image, int id);
  public synchronized void addImage (Image image, int id, int width, int height);
  public boolean checkAll();
  public synchronized boolean checkAll (boolean load);
  public boolean checkID (int id);
  public synchronized boolean checkID (int id, boolean load);
  public synchronized Object[] getErrorsAny();
  public synchronized Object[] getErrorsID (int id);
  public synchronized boolean isErrorAny();
  public synchronized boolean isErrorID (int id);
  public synchronized void removeImage(Image image); (New)
  public synchronized void removeImage(Image image, int id); (New)
  public synchronized void removeImage(Image image, int id, int width, int height); (New)
  public synchronized int statusAll (boolean load);
  public synchronized int statusID (int id, boolean load);
  public void waitForAll() throws InterruptedException;
  public synchronized boolean waitForAll (long ms) throws InterruptedException;
  public void waitForID (int id) throws InterruptedException;
  public synchronized boolean waitForID (int id, long ms) throws InterruptedException;
}

Constants

ABORTED

public static final int ABORTED

Flag that indicates that the loading process aborted while loading a particular image.

COMPLETE

public static final int COMPLETE

Flag that indicates a particular image loaded successfully.

ERRORED

public static final int ERRORED

Flag that indicates an error occurred while a particular image was loading.

LOADING

public static final int LOADING

Flag that indicates a particular image is still loading.

Constructors

MediaTracker

public MediaTracker (Component component)

Parameters

component

Component that eventually renders objects being tracked.

Description

Constructs an MediaTracker object.

Instance Methods

addImage

public void addImage (Image image, int id)

Parameters

image

Image to track.

id

ID of a group.

Description

Tells a MediaTracker to track the loading of image, placing the image in the group identified by id.

public synchronized void addImage (Image image, int id, int width, int height)

Parameters

image

Image to track.

id

ID of a group.

width

Eventual rendering width.

height

Eventual rendering height.

Description

Tells a MediaTracker to track the loading of image, which will be scaled to the given height and width, placing the image in the group identified by id.

checkAll

public boolean checkAll()

Returns

true if images completed loading (successfully or unsuccessfully), false otherwise.

Description

Determines if all images have finished loading.

public synchronized boolean checkAll (boolean load)

Parameters

load

Flag to force image loading to start.

Returns

true if all images have completed loading (successfully or unsuccessfully), false otherwise.

Description

Determines if all images have finished loading; the load parameter may be used to force images to start loading.

checkID

public boolean checkID (int id)

Parameters

id

ID of a group.

Returns

true if all images have completed loading (successfully or unsuccessfully), false otherwise.

Description

Determines if all images with the given ID tag have finished loading.

public synchronized boolean checkID (int id, boolean load)

Parameters

id

ID of a group.

load

Flag to force image loading to start.

Returns

true if all images have completed loading (successfully or unsuccessfully), false otherwise.

Description

Determines if all images with the given ID tag have finished loading; the load parameter may be used to force images to start loading.

getErrorsAny

public synchronized Object[] getErrorsAny()

Returns

An array of objects managed by this media tracker that encountered a loading error.

Description

Checks to see if any media encountered an error while loading.

getErrorsID

public synchronized Object[] getErrorsID (int id)

Parameters

id

ID of a group.

Returns

An array of objects that encountered a loading error.

Description

Checks to see if any media with the given ID tag encountered an error while loading.

isErrorAny

public synchronized boolean isErrorAny()

Returns

true if an error occurred, false otherwise.

Description

Checks to see if any media monitored by this media tracker encountered an error while loading.

isErrorID

public synchronized boolean isErrorID (int id)

Parameters

id

ID of a group.

Returns

true if error happened, false otherwise.

Description

Checks to see if any media in the given group encountered an error while loading.

removeImage

public synchronized void removeImage (Image image) (New)

Parameters

image

The image to remove.

Description

Removes the specified image from this MediaTracker.

public synchronized void removeImage (Image image, int id) (New)

Parameters

image

The image to remove.

id

ID of a group.

Description

Removes the specified image from this MediaTracker. Only instances matching the given id will be removed.

public synchronized void removeImage (Image image, int id, int width, int height) (New)

Parameters

image

The image to remove.

id

ID of a group.

width

Width of the scaled image, or -1 for unscaled.

height

Height of the scaled image, or -1 for unscaled.

Description

Removes the specified image from this MediaTracker. Only instances matching the given id and scale sizes will be removed.

statusAll

public synchronized int statusAll (boolean load)

Parameters

load

Flag to force image loading to start.

Returns

MediaTracker status flags ORed together.

Description

Checks load status of all the images monitored by this media tracker; the load parameter may be used to force images to start loading.

statusID

public synchronized int statusID (int id, boolean load)

Parameters

id

ID of a group.

load

Flag to force image loading to start.

Returns

MediaTracker status flags ORed together.

Description

Checks load status of all the images in the given group; the load parameter may be used to force images to start loading.

waitForAll

public void waitForAll() throws InterruptedException

Throws

InterruptedException

If waiting interrupted.

Description

Waits for all the images monitored by this media tracker to load.

public synchronized boolean waitForAll (long ms) throws InterruptedException

Parameters

ms

Time to wait for loading.

Throws

InterruptedException

If waiting interrupted.

Returns

true if images fully loaded, false otherwise.

Description

Waits at most ms milliseconds for all images monitored by this media tracker to load.

waitForID

public void waitForID (int id) throws InterruptedException

Parameters

id

ID of a group.

Throws

InterruptedException

If waiting interrupted.

Description

Waits for images in the given group to load.

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

Parameters

id

ID of a group.

ms

Maximum time to wait for loading.

Throws

InterruptedException

If waiting interrupted.

Returns

true if images fully loaded, false otherwise.

Description

Waits at most ms milliseconds for the images in the given group to load.

See Also

Component, Image, Object


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