Provide easier access to items of RefreshingView
------------------------------------------------
Key: WICKET-1227
URL: https://issues.apache.org/jira/browse/WICKET-1227
Project: Wicket
Issue Type: Improvement
Components: wicket
Reporter: Peter Ertl
Attachments: AccessItemsOfRefreshingView.patch
When trying to directly access items of a RefreshingView (or subclasses of it)
everything gets really complicated.
For Example:
When inserting a new, blank post into a guestbook the input focus should be set
to the input field 'author'.
public void onClick(final AjaxRequestTarget target)
{
// add new, blank entry to the guestbook posts model
posts.add(new Post());
//
// code that gets us the last item of the repeating view.
// however, the view first has to be rendered in order to contain the new
item
// as it's only in the model but will not appear in the RefreshingView
unless
// RefreshingView#onBeforeRender() is called
Item lastItem = ...???...
target.addComponent(/* container that contains the refreshing view */);
target.focusComponent(lastItem.get("author"));
}
Now what I did is attach a patch to provide methods for updating and getting
the items of the RefreshingView.
the above example would look like this:
public void onClick(final AjaxRequestTarget target)
{
posts.add(new Post());
guestbookView.refresh();
Item[] items = guestbookView.items();
Item lastItem = items[items.length() - 1];
target.addComponent(/* container that contains the refreshing view */);
target.focusComponent(lastItem.get("author")); // put focus on "author"
component where user can enter his name
}
Basically it works like this:
the refresh() method will invoke onBeforeRender() to populate the items of the
view (based on the current model). That way you can access the items before the
actual render occurs (using the iterator function MarkupContainer#getItems() ).
Once the render occurs it would be just too late...
In order to prevent unnecessary subsequent calls of onBeforeRender() a flag
will remember if the view needs refreshing, so onBeforeRender() is only called
once per render (unless you call refresh() for another time).
items() is a convenience method that collects the current items using
MarkupContainer#getItems() and returns a handy array of items and avoids
cumbersome code.
I also added firstItem() and lastItem() as I think these will be quite common
use cases for accessing that array.
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