Custom TabLayoutPanel in GWT - gwt

Question

I'm trying to create my custom TabLayoutPanel extension, my code is following:
public class ExpandableTabLayoutPanel extends TabLayoutPanel {
#UiConstructor
public ExpandableTabLayoutPanel(double barHeight, Unit barUnit) {
super(barHeight, barUnit);
addExpandableBehaviour();
}
private addExpandableBehaviour(){
//...
}
}
And here I invoke it from UIBinder:
<a:ExpandableTabLayoutPanel barHeight="20" barUnit="PX">
<a:tab>
<a:header>header</a:header>
<a:AdvancedRichTextArea styleName="{style.area}" ui:field="area"/>
</a:tab>
</a:ExpandableTabLayoutPanel>
(I was forced by error messages to use a:tab/a:header instead of g:tab/g:header even if I don't have tab and header defined in my a: package/workspace, but that's probably not the issue)
If #UiConstructor annotation is present over ExpandableTabLayoutPanel like in the listing, I'm getting strange error:
[ERROR] [gwtreproduce] - <a:ExpandableTabLayoutPanel barHeight='20' barUnit='PX'> missing required attribute(s): arg1 barHeight Element <a:ExpandableTabLayoutPanel barHeight='20' barUnit='PX'> (:13)
When I disable #UiConstructor, I'm getting even stranger error:
[ERROR] [gwtreproduce] - Errors in 'generated://E6338B946DFB2D28988DA492134093C7/reproduce/client/TestView_TestViewUiBinderImpl.java' : [ERROR] [gwtreproduce] - Line 33: Type mismatch: cannot convert from TabLayoutPanel to ExpandableTabLayoutPanel
What am I doing wrong with extending TabLayoutPanel?
And side question: how it is possible that TabLayoutPanel constructor isn't annotated with #UiConstructor and can be used in UiBinder (how UiBinder knows which constructor to invoke)?

Answer 1

for you side question : you have to add (provided=true) to the UiField annotation of your widget. Then in the code, set the instance yourself, before createAndBindUi() call like this :
class Whaoo extends Composite{
/* with 'provided', UiBinder don't call any constructor */
#UiField(provided = true)
final Great foo;
interface WhaooUiBinder extends
UiBinder<Widget, Whaoo> {}
private static WhaooUiBinder uiBinder =
GWT.create(WhaooUiBinder.class);
public Whaoo() {
// initialize "provided" before createAndBindUi call
foo = new Great(String bar, int pouet);
initWidget(uiBinder.createAndBindUi(this));
}
}