com.levigo.jadice.demo.util

Class LazyFileIcon

java.lang.Object

javax.swing.ImageIcon

com.levigo.jadice.demo.util.LazyFileIcon

All Implemented Interfaces:

Serializable, Accessible, Icon

public class LazyFileIcon
extends ImageIcon

An ImageIcon which lazily loads the file icon.

This type of image can be used to lazily load a file icon. This can be useful if files reside on a slow network drive which could impact the GUI performance if loading would be performed OnEDT.

To use this icon, simply create it via LazyFileIcon(File, ImageObserver) and use it like any other ImageIcon. Correct size and obviously the paintIcon-Method will only be available after successful loading.
After successful loading, the passed ImageObserver will be notified to update the icon.

Note
This class contains an internal cache to store Icons for specific file suffixes. In consequence, a file type (based on suffix) only has 1 possible icon.

Consider the following situation / example:

• 2 LazyFileIcons are used in a list to represent files
• Both are for example PDF files
• The first file resides on an unavailable network drive or has been deleted; the second file resides locally and is available

In consequence, the icon can not be loaded for the first file. But when the second file is loaded, the icon for the suffix becomes available and all entries for that suffix will get that icon.

Internally, this class remembers the processed error files for which no icon could be retrieved. This is to prevent loops when fetching icons for non-existent files. Entries for a specific suffix will be removed if possible as soon as at least one file with that suffix has been processed successfully.

Usage
See LazyFileIcon(File, ImageObserver)

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class javax.swing.ImageIcon

ImageIcon.AccessibleImageIcon

Field Summary

Fields inherited from class javax.swing.ImageIcon

component, tracker

Constructor Summary

Constructors

Constructor and Description
LazyFileIcon(File file, ImageObserver imageObserver) Creates a new LazyFileIcon for the given file.

Method Summary

Modifier and Type	Method and Description
int	getIconHeight() As long as the icon is not yet fully loaded, this will return 0.
int	getIconWidth() As long as the icon is not yet fully loaded, this will return 0.
void	paintIcon(Component component, Graphics graphics, int x, int y)

Methods inherited from class javax.swing.ImageIcon

getAccessibleContext, getDescription, getImage, getImageLoadStatus, getImageObserver, loadImage, setDescription, setImage, setImageObserver, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

LazyFileIcon

public LazyFileIcon(File file,
                    ImageObserver imageObserver)

Creates a new LazyFileIcon for the given file. This will first check if an icon for the file's suffix has already been loaded and uses that if present.

If no cached entry is present, the loading will be queued - as soon as loading is finished, ImageObserver.imageUpdate(java.awt.Image, int, int, int, int, int) will be called on the passed ImageObserver which updates the visual appearance to the loaded icon.

If multiple requests for the same suffix arrive, the ImageObservers for that type will be collected in a list and will be notified when the loading operation succeeds.

Parameters:

file - the file to obtain an icon for

imageObserver - the ImageObserver to be notified when deferred loading completes

Method Detail

paintIcon

public void paintIcon(Component component,
                      Graphics graphics,
                      int x,
                      int y)

Specified by:

paintIcon in interface Icon

Overrides:

paintIcon in class ImageIcon

getIconWidth

public int getIconWidth()

As long as the icon is not yet fully loaded, this will return 0.

Specified by:

getIconWidth in interface Icon

Overrides:

getIconWidth in class ImageIcon

getIconHeight

public int getIconHeight()

As long as the icon is not yet fully loaded, this will return 0.

Specified by:

getIconHeight in interface Icon

Overrides:

getIconHeight in class ImageIcon