On 11/12/2010 3:44 AM, a wrote:
Hi
I have 2 classes. The CatContainer extends the HorizontalPanel. The
CatContainer should be updated when the CatWidget receives updated data
from
database by GWT RPC.
How can I implement the update of the CatContainer?
As mentioned, MVC will help you out here. The idea is to introduce a
third object, the controller, which knows about both objects and can
bind them at run time.
public class InitializationController {
public void init() {
CatContainer model = new CatContainer();
CatWidget view = new CatWidget();
model.addChangeListener( view );
...
}
}
class CatContainer extends HorizontalPanel{
private CatWidget catWidget=new CatWidget(1);
private ModelObserver view;
public void addChangeListener( ModelObserver obs ) {
view = obs;
}
//how can I implement the following to update the GUI?
catWidget.refresh( new CallBackFunc()
{
final CatContainer localModel = CatContainer.this;
onSuccess()
{
//Update GUI
if( localModel.view != null) {
localModel.view.refresh();
}
}
}
}
class CatWidget
implements ModelObserver
{
private data;
void refresh()
{
//Call GWT async to retrieve data from database, and update the data.
}
}
public interface ModelObserver {
void refersh();
}
Nothing here was compiled, double check my syntax.
I don't like the comment you have in "CatWidget". The view should not
know about any database. It should have a simple interface for a model
and that's it. Update the model from the database, then inform the view
that the model has changed. However, I'll leave design issues like that
one to you.
It is an event escalation question.