Re: knowing when images have been loaded. (mediatracker not suitable)

Mark Space <>
Sat, 22 Mar 2008 17:07:36 -0700
nntpman68 wrote:

In order to have a non blocking applet UI I'd like to load all images
from a separate thread.

As Knute alluded there are probably better ways of doing this.

First, all images are already loaded asynchronously. If you use
getImage() it returns immediately, and loads the image in the background.

URL myImageUrl = new URL( "http://myserver/images/myImage.jpg" );
Image myImage = java.awt.Toolkit.getImage( myImageUrl );

The java.awt.Component class implements the ImageObserver interface.
That means all your components (JButtons, Applets, JPanes, JPanels,
etc.) can act as their own image observer. The default behavior is to
call your components repaint() method if the image does not get fully
drawn. There's a default limit of 100 milliseconds in between calls so
that image loading doesn't completely consume all CPU cycles.

 From inside some random component that has a custom image,

public void paint( Graphics g ) {
   g.drawImage( myImage, x, y, this );

will automatically invoke this default behavior.

NOTE 1: Nothing syntax checked.

NOTE 2: From _Learning Java_ by O'Reilly, 3rd ed., pages 709 - 710. Get
it. Buy it. Love it.

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