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[java] Static class - Load image (width/height problem)

Started by CodeMachine Sep 20, 2006 at 4:11 PM 5 replies 1k views

Original Post

Sep 20, 2006 at 4:11 PM

Hi I've problem finding the width/height of an image loaded within a static class of mine. A small example:


public class Text {
 private static Image[] _characters = null;
 
 private static void load() {
  _characters = new Image[26];
 
  // Load image (containing subimages a-z) from drive.
  Image img = Toolkit.getDefaultToolkit().getImage("characters.png");
 
  // Clip and save each character to '_characters'.
  // =====> How do I retrieve the width and height of "img" ?? <=====
  // I need somehow to wait for the loading above to finish.
  // MediaTracker can't be use within a static class, or am I wrong?
 }
 
 private static void drawString(Graphics g, String s, int x, int y) {
  if(_characters==null)
   load();
 
   // Draw string to screen.
   ...
  }
}

Kind Regards

CaptainJester

101

CaptainJester

Sep 20, 2006 at 8:45 PM

MediaTracker

Image img = Toolkit.getDefaultToolkit().getImage("picture.gif");try {    MediaTracker tracker = new MediaTracker(this);    tracker.addImage(img, 0);                tracker.waitForID(0);} catch (Exception e) {}int width = img.getWidth(this);int height = img.getHeight(this);

shmoove

Sep 21, 2006 at 1:37 AM

MediaTracker needs a Component instance for it's constructor. Maybe you can pass one as an argument to Text.load().

shmoove

CodeMachine

Author

CodeMachine

Sep 21, 2006 at 10:38 AM

Hi Captain and shmoove

Yes, I tried to use MediaTracker and as you say, shmoove, it doesn't work without a component instance.

It worked perfectly when I sent "this" (JPanel) as the component instance, but I needed to pass this reference in several steps. And that's ugly :)

I make the call within another class that also does not inherit a super-class.
And to pass this component reference through out the "whole" application is kind of ugly, isn't it? :)

So shmoove, it works. Thanks!

But couldn't it be solved another way?
Without having to pass a component reference as parameter through every call that indirectly call drawString(...)?

Kind Regards

CaptainJester

101

CaptainJester

Sep 21, 2006 at 11:33 AM

Two options.

1. Implement the ImageObserver interface and pass that into the MediaTracker.

2. Use javax.imageio.ImageIO.read(image file). It blocks until the image is loaded.

shmoove

Sep 21, 2006 at 11:39 AM

You could have a component that's statically available (like making your JPanel a singleton or something), or create a dummy Component in load() to use with the MediaTracker. But to be honest with you it sounds like you need to rethink your application's design.

shmoove

Disclaimer: Unless there's another class that can do what MediaTracker does. Standard Java isn't really my thing.

CodeMachine

Author

CodeMachine

Sep 21, 2006 at 1:05 PM

Thanks Captain, I will check out the alternatives...

Shmoove, how would you implement the functionality to draw userdefined (image) text?
I have several images (contains subimages a-z), and want to use these to draw text-strings to a Graphics object.

Should I create an instance of my "Text" class instead of having it static? If you do that, you may end up with A LOT of instances. Isn't a static solution better? With a static one you only read and construct the images (a-z) once.

Or should I make the class nonstatic and only having the internal a-z images static?

I think the best solution is to have it all public, then you can access it everywhere without having to create a instance each time...

Or am I wrong?

(
Im creating a game, and instead of having hundreds of lines of code in the paint-method, I've split up the drawing to several classes (that handles a unique thing (like menu, highscore, background etc)).

Within the main-paint I do:
_highscore.draw(g,...);
_background.draw(g,...);
etc...

And in several of these classes I use my "Text" class above (drawString(...))
)

Is this way of design bad?

Kind Regards

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