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java.lang.Objectorg.eclipse.jface.resource.DeviceResourceDescriptor
org.eclipse.jface.resource.ImageDescriptor
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.
There are two ways to get an Image from an ImageDescriptor. The method createImage will always return a new Image which must be disposed by the caller. Alternatively, createResource() returns a shared Image. When the caller is done with an image obtained from createResource, they must call destroyResource() rather than disposing the Image directly. The result of createResource() can be safely cast to an Image.
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 |
createFromImage(Image img)
Creates and returns a new image descriptor for the given image. |
static ImageDescriptor |
createFromImage(Image img,
Device theDevice)
Creates and returns a new image descriptor for the given image. |
static ImageDescriptor |
createFromImageData(ImageData data)
Creates and returns a new image descriptor given ImageData describing the image. |
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. |
Object |
createResource(Device device)
Creates the resource described by this descriptor |
static ImageDescriptor |
createWithFlags(ImageDescriptor originalImage,
int swtFlags)
Creates an ImageDescriptor based on the given original descriptor, but with additional SWT flags. |
void |
destroyResource(Object previouslyCreatedObject)
Undoes everything that was done by a previous call to create(...), given the object that was returned by create(...). |
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 |
protected static final ImageData DEFAULT_IMAGE_DATA
Constructor Detail |
protected ImageDescriptor()
Method Detail |
public static ImageDescriptor createFromFile(Class location, String filename)
new FileImageDescriptor(location,filename)
.
location
- the class whose resource directory contain the filefilename
- the file name
public static ImageDescriptor createFromImageData(ImageData data)
data
- contents of the image
public static ImageDescriptor createFromImage(Image img)
Performance note: If the device that created the Image is known, it is more efficient to use createFromImage(Image, Device). This method should only be used in those rare situations where the device is unknown.
img
- image to create
public static ImageDescriptor createWithFlags(ImageDescriptor originalImage, int swtFlags)
Note that this sort of ImageDescriptor is slower and consumes more resources than a regular image descriptor. It will also never generate results that look as nice as a hand-drawn image. Clients are encouraged to supply their own disabled/grayed/etc. images rather than using a default image and transforming it.
originalImage
- image to transformswtFlags
- any flag that can be passed to the flags argument of Image#Image(Device, Image, int)
Image.Image(Device, Image, int)
public static ImageDescriptor createFromImage(Image img, Device theDevice)
img
- image to createtheDevice
- the device that was used to create the Image
public static ImageDescriptor createFromURL(URL url)
url
- The URL of the image file.
public Object createResource(Device device) throws DeviceResourceException
DeviceResourceDescriptor
createResource
in class DeviceResourceDescriptor
device
- the Device on which to allocate the resource
DeviceResourceException
- if unable to allocate the resourcepublic void destroyResource(Object previouslyCreatedObject)
DeviceResourceDescriptor
destroyResource
in class DeviceResourceDescriptor
previouslyCreatedObject
- an object that was returned by an equal
descriptor in a previous call to createResource(...).public Image createImage()
Note: this method differs from createResource(Device) in that the returned image must be disposed directly, whereas an image obtained from createResource(...) must be disposed by calling destroyResource(...). It is not possible to mix-and-match. If you obtained the Image from this method, you must not dispose it by calling destroyResource. Clients are encouraged to use create/destroyResource and downcast the result to Image rather than using createImage.
Note: it is still possible for this method to return null
in extreme cases, for example if SWT runs out of image handles.
null
if the image could not be
createdpublic Image createImage(boolean returnMissingImageOnError)
returnMissingImageOnError
is true, otherwise
null
is returned.
Note: Even if returnMissingImageOnError
is true, it is
still possible for this method to return null
in extreme
cases, for example if SWT runs out of image handles.
returnMissingImageOnError
- flag that determines if a default image is returned on error
null
if the image could not be
createdpublic Image createImage(Device device)
Note: it is still possible for this method to return null
in extreme cases, for example if SWT runs out of image handles.
device
- the device on which to create the image
null
if the image could not be
createdpublic Image createImage(boolean returnMissingImageOnError, Device device)
returnMissingImageOnError
is true, otherwise
null
is returned.
Note: Even if returnMissingImageOnError
is true, it is
still possible for this method to return null
in extreme
cases, for example if SWT runs out of image handles.
returnMissingImageOnError
- flag that determines if a default image is returned on errordevice
- the device on which to create the image
null
if the image could not be
createdpublic abstract ImageData getImageData()
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 null
if the image data could not be created.
null
public static ImageDescriptor getMissingImageDescriptor()
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Guidelines for using Eclipse APIs.
Copyright (c) IBM Corp. and others 2000, 2005. All rights reserved.