org.eclipse.jface.resource
Class ImageDescriptor

java.lang.Object
  |
  +--org.eclipse.jface.resource.ImageDescriptor

Direct Known Subclasses:

CompositeImageDescriptor

public abstract class ImageDescriptor

extends Object

An image descriptor is an object that knows how to create an SWT image. It does not hold onto images or cache them, but rather just creates them on demand. An image descriptor is intended to be a lightweight representation of an image that can be manipulated even when no SWT display exists.

This package defines a concrete image descriptor implementation which reads an image from a file (FileImageDescriptor). It also provides abstract framework classes (this one and CompositeImageDescriptor) which may be subclassed to define news kinds of image descriptors.

Using this abstract class involves defining a concrete subclass and providing an implementation for the getImageData method.

See Also:

Image

Field Summary

protected static ImageData

DEFAULT_IMAGE_DATA A small red square used to warn that an image cannot be created.

Constructor Summary

protected

ImageDescriptor() Constructs an image descriptor.

Method Summary

static ImageDescriptor	createFromFile(Class location, String filename) Creates and returns a new image descriptor from a file.
static ImageDescriptor	createFromURL(URL url) Creates and returns a new image descriptor from a URL.
Image	createImage() Creates and returns a new SWT image for this image descriptor.
Image	createImage(boolean returnMissingImageOnError) Creates and returns a new SWT image for this image descriptor.
Image	createImage(boolean returnMissingImageOnError, Device device) Creates and returns a new SWT image for this image descriptor.
Image	createImage(Device device) Creates and returns a new SWT image for this image descriptor.
abstract ImageData	getImageData() Creates and returns a new SWT ImageData object for this image descriptor.
static ImageDescriptor	getMissingImageDescriptor() Returns the shared image descriptor for a missing image.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_IMAGE_DATA

protected static final ImageData DEFAULT_IMAGE_DATA

A small red square used to warn that an image cannot be created.

Constructor Detail

ImageDescriptor

protected ImageDescriptor()

Constructs an image descriptor.

Method Detail

createFromFile

public static ImageDescriptor createFromFile(Class location,
                                             String filename)

Creates and returns a new image descriptor from a file. Convenience method for new FileImageDescriptor(location,filename).

Parameters:

location - the class whose resource directory contain the file

filename - the file name

Returns:

a new image descriptor

createFromURL

public static ImageDescriptor createFromURL(URL url)

Creates and returns a new image descriptor from a URL.

Parameters:

url - The URL of the image file.

Returns:

a new image descriptor

createImage

public Image createImage()

Creates and returns a new SWT image for this image descriptor. Note that each call returns a new SWT image object.

Returns:

a new image

createImage

public Image createImage(boolean returnMissingImageOnError)

Creates and returns a new SWT image for this image descriptor. Note that if returnMissingImageOnError is true a default image is returned

Parameters:

returnMissingImageOnError - The flag that determines if a default image is returned on error

Returns:

a new image or null if the image could not be created

createImage

public Image createImage(Device device)

Creates and returns a new SWT image for this image descriptor.

Parameters:

device - the device on which to create the image

Returns:

a new image or null if the image could not be created

Since:

2.0

createImage

public Image createImage(boolean returnMissingImageOnError,
                         Device device)

Creates and returns a new SWT image for this image descriptor. Note that if returnMissingImageOnError is true a default image is returned

Parameters:

returnMissingImageOnError - The flag that determines if a default image is returned on error

device - the device on which to create the image

Returns:

a new image or null if the image could not be created

Since:

2.0

getImageData

public abstract ImageData getImageData()

Creates and returns a new SWT ImageData object for this image descriptor. Note that each call returns a new SWT image data object.

This framework method is declared public so that it is possible to request an image descriptor's image data without creating an SWT image object.

Returns:

a new image data

getMissingImageDescriptor

public static ImageDescriptor getMissingImageDescriptor()

Returns the shared image descriptor for a missing image.

Returns:

the missing image descriptor