> There's not a whole lot of help, even in the Javadoc, for knowing what
> a Renderer should look like.
You are right, this is a weak point in the documentation.
> I...found the subtle element that, I'm
> guessing, pretty much every Renderer needs to do if it's based on a
> Component:
>
> @Override
> public void setSize(int width, int height) {
> super.setSize(width, height);
>
> // Since this component doesn't have a parent, it won't be validated
> // via layout; ensure that it is valid here
> validate();
> }
Yes - if your renderer extends Component, you need to do this. Renderers in
Swing have a similar requirement.
> An item renderer for ListView is a Component* that implements a couple
> extra methods, of which "render" is the interesting one -- it gets
> called when the ListView wants to layout its items or paint them. The
> renderer's job is to modify itself to look exactly like what the
> ListView should paint in the space allocated for the item that was
> passed to render. There are some extra arguments to render to allow
> you to customize your look according to whether the item is selected,
> highlighted etc. The ListView all by itself is setting the background
> of each item according to that selection/highlight/whatever state, so
> the extra arguments are useful if you want to be harmonious with it,
> e.g., by making your text's foreground color be white (actually, the
> ListView's selectionColor style) when the item is selected. That last
> bit was really non-obvious to me for some while.
>
> (*Strictly speaking, it doesn't have to be a Component, merely
> something that implements ConstrainedVisual, but Component does
> implement ConstrainedVisual, and I expect nearly everyone would use
> some sort of Component to make the implementation tractable.)
>
> It looks like other renderers are similar, differing mainly in the
> nature of the extra arguments to render, which depend on the
> capabilities of the container.
I don't see any reason why something like this couldn't be included in the
documentation. Where do you think it should go?
G
