With GWT, is there a way to not load widgets declared in uibinder xml files?

One common design I have with GWT is to create a widget which contains two children: A and B.

I declare these two widgets A and B in the uibinder file associated to my main widget.

What I want to do is to load or not widget A depending on an if statement.

Ideal approach is to set provided=true for widget A and to set widget A to null when I want to not load this widget. But GWT throws an error.

Is there a way to declare widgets in uibinder and then not loading them ?

thanks

EDIT: after a lot of discussions, an ideal approach is to declared a field "provided=true" and "optional=true" when optional=true, createAndBindUI must not throw an Excepti开发者_开发知识库on if the field is null. This is a clean approach.

If you think that this feature must exists in GWT, please star this issue: http://code.google.com/p/google-web-toolkit/issues/detail?id=5699

EDIT 2 : using the LazyPanel as described by Thomas seems to be a better way to handle this.

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I stumbled on the GWT issue, which led me here, so here's my take on it, 20 months later.

Use a LazyPanel and set it to visible="false" so that it's content is not built until you need it (simply call setVisible(true) to reveal it, triggerring the lazy-initialization of its content.

LazyPanel is fully integrated with UiBinder so that you declare its content in the same UiBinder template, as if it were a SimplePanel, without even bothering creating a subclass of LazyPanel. See https://developers.google.com/web-toolkit/doc/2.4/DevGuideUiBinder#Lazy

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I would revert the logic. If you don't need the widget remove it

widget.removeFromParent();

I think it's a cleaner approach, since the UIBinder automatically defines and creates them.

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Since conditionals are not allowed in a UiBinder XML I'd suggest you define placeholders (i.e., panels) in your ui.xml, have a reference to them in your view class and decide there whether a specific widget needs to be created and added or not.

This is a common approach when using MVP pattern with nested presenters.

EDIT:

Until your request has been implemented by the GWT developers you could extend the FlowPanel and overwrite the add(Widget) method to check for null as in:

public class ExtendedFlowPanel extends FlowPanel {

    public ExtendedFlowPanel() {
        super();
    }

    @Override
    public void add(Widget w) {
        if (w != null) {
            super.add(w);
        }
    }
}

This way you can use provided = true and pass null to the panel.