ExpandHeader
ExpandHeader is a header that owns what is under it: pressing it - its arrow or
its title - folds that content away, pressing it again brings it back.
ExpandHeader header = new ExpandHeader("Sales history");
cp.add(header);
header.setContent(salesTable);
header.setExpanded(true); // it starts folded
The API
| Method | What it does |
|---|---|
new ExpandHeader(String title) |
a normal-sized header |
new ExpandHeader(Type, String) |
NORMAL or SMALL |
setContent(NodeBase) |
what the header shows and folds away; it is kept while folded |
setOnExpand(INotify<Div>) |
instead of setContent(): fills the content afresh every time the header is opened, and folding drops it |
setExpanded(boolean) / isExpanded() / toggleExpansion() |
open and close from code; a new header starts folded |
setCaption(String) / setCaptionNode(NodeBase) |
the title, as a text or as a node |
setActionList(List<IUIAction<?>>) / clearActions() |
a hamburger menu of actions at the right |
The difference with the other two headers is exactly that ownership: a
GenericHeader or a
Caption2 is a line above whatever happens to follow it,
while this one is given the content and shows or hides it.
What folding costs
Content given with setContent() stays on the page and is hidden, so folding is a
css change rather than a rebuild: the state of everything inside it - a half-filled
form, a table's scroll position - survives. It also means the content is built even
while it is closed. Where that is the expensive part, use setOnExpand() instead:
the content is then only made when the header is opened, and dropped again when it
is folded.