com.google.gwt.user.client.ui
Class AbstractImagePrototype

java.lang.Object
  com.google.gwt.user.client.ui.AbstractImagePrototype

public abstract class AbstractImagePrototype
extends java.lang.Object

An opaque representation of a particular image such that the image can be accessed either as an HTML fragment or as an Image object. An image prototype can be thought of as an abstract image factory with additional capabilities.

The applyTo(Image) method provides an efficient way to replace the contents of an existing Image. This is useful in cases where an image changes its appearance based on a user's action. Instead of creating two Image objects then alternately hiding/showing them, one can use the applyTo(Image) method of two AbstractImagePrototype objects to transform a single Image object between two (or more) visual representations. The use of AbstractImagePrototypes results in an cleaner and more efficient implementation.

This class also provide methods for working with raw elements, using createElement() and applyTo(ImagePrototypeElement).

This class is also a useful way to encapsulate complex HTML that represents an image without actually instantiating Image objects. When constructing large HTML fragments, especially those that contain many images, getHTML() can be much more efficient.

AbstractImagePrototype

public AbstractImagePrototype()

create

public static AbstractImagePrototype create(ImageResource resource)

Create an AbstractImagePrototype backed by a ClientBundle ImageResource. This method provides an API compatibility mapping for the new ImageResource API.

Parameters:

resource - an ImageResource produced by a ClientBundle

Returns:

an AbstractImagePrototype that displays the contents of the ImageResource

applyTo

public abstract void applyTo(Image image)

Transforms an existing Image into the image represented by this prototype.

Parameters:

image - the instance to be transformed to match this prototype

applyTo

public void applyTo(AbstractImagePrototype.ImagePrototypeElement imageElement)

Transforms an existing AbstractImagePrototype.ImagePrototypeElement into the image represented by this prototype.

Parameters:

imageElement - an ImagePrototypeElement created by createElement()

createElement

public AbstractImagePrototype.ImagePrototypeElement createElement()

Creates a new AbstractImagePrototype.ImagePrototypeElement based on the image represented by this prototype. The DOM structure may not necessarily a simple <img> element. It may be a more complex structure that should be treated opaquely.

Returns:

the ImagePrototypeElement corresponding to the image represented by this prototype

createImage

public abstract Image createImage()

Creates a new Image instance based on the image represented by this prototype.

Returns:

a new Image based on this prototype

getHTML

public java.lang.String getHTML()

Gets an HTML fragment that displays the image represented by this prototype. The HTML returned is not necessarily a simple <img> element. It may be a more complex structure that should be treated opaquely.

The default implementation calls getSafeHtml().

Returns:

the HTML representation of this prototype

getSafeHtml

public SafeHtml getSafeHtml()

Gets an HTML fragment that displays the image represented by this prototype. The HTML returned is not necessarily a simple <img> element. It may be a more complex structure that should be treated opaquely.

The default implementation throws an UnsupportedOperationException.

Returns:

the HTML representation of this prototype