Author Archives: pedroduquevieira

While porting Modellus from javafx1.3 using  javafx script to javafx2.0 using java language I ended up creating a class with a few helper methods for converting swing objects to and from javafx objects:

• Converting from java.awt.color  to javafx.scene.paint.Color and vice versa
• Converting from java.awt.image.BufferedImage to javafx.scene.image.Image and vice versa

Nothing too fancy but I thought it might come in handy to other people so here’s the code:

public class SwingUtils {

    public static java.awt.Color toAWTColor(javafx.scene.paint.Color fxColor)
    {
        return new java.awt.Color((float)fxColor.getRed(), (float)fxColor.getGreen(), (float)fxColor.getBlue(), (float)fxColor.getOpacity());
    }

    public static javafx.scene.paint.Color fromAWTColor(java.awt.Color awtColor)
    {
        return ColorBuilder.create()
                            .red(awtColor.getRed() / 255.0)
                            .green(awtColor.getGreen() / 255.0)
                            .blue(awtColor.getBlue() / 255.0).build();
    }

    // There is a problem with this implementation: transparent pixels on the BufferedImage aren't converted to transparent pixels on the fxImage.
    public static javafx.scene.image.Image convertToFxImage(java.awt.image.BufferedImage awtImage) {
    	if (Image.impl_isExternalFormatSupported(BufferedImage.class)) {
    		return javafx.scene.image.Image.impl_fromExternalImage(awtImage);
    	} else {
    		return null;
    	}
    }

    public static java.awt.image.BufferedImage convertToAwtImage(javafx.scene.image.Image fxImage) {
    	if (Image.impl_isExternalFormatSupported(BufferedImage.class)) {
    		java.awt.image.BufferedImage awtImage = new BufferedImage((int)fxImage.getWidth(), (int)fxImage.getHeight(), BufferedImage.TYPE_INT_ARGB);
        	return (BufferedImage)fxImage.impl_toExternalImage(awtImage);
    	} else {
    		return null;
    	}
    }
}

This will probably be added on Lombard (next javafx version) as shown by this issue: http://javafx-jira.kenai.com/browse/RT-14038

JavaFX brings a new event handling approach, making an improvement over the Java use of the too verbose observer pattern.

Normally in javafx you’ll use binding to listen to state changes and update other objects as appropriate. However this approach is not adequate when you want to listen to something that doesn’t imply a state change, something like say pressing a button (not a two state button, that would involve state).

With this post I wanted to share an idea I had about how javafx could handle those cases not covered by binding.

In JavaFX functions are variables, you can have a sequence of functions with this:

var buttonPressedListeners: function(:MouseEvent)[];

Let’s say you have a button and every time the button is pressed you iterate through the sequence above and call the listener functions. If you want to expose this to any interested listener you can declare the above sequence public. Now lets say a listener wants to register for listening, he can do so by inserting a function on the listener sequence:

insert fooListener into button.buttonPressedListeners;

If he wants to unregister this simple call would do it:

delete fooListener from button.buttonPressedListeners;

There is however a problem with this, you can insert the same listener two times into the sequence. We could iterate through the sequence list and check for duplicates but that would imply writing the same boiler plate code over and over again. So I would propose a language feature to enable declaring a sequence which doesn’t allow repeating values. Something like:

var buttonPressedListeners:  function(:MouseEvent) unique [];

Every time you want to call the functions on the sequence you’ll have to write down a for each statement which iterates through the sequence of functions, to fix this I would propose a second language feature: the ability to call all the functions in a function sequence with a single method call.

And that’s my event handling proposal. 🙂