I've been looking into this for a chapter in the new edition of GWT In
Action, here's where I'm at.
The Google I/O approach to MVP has never sat well with me because, apart
from the fact that the interface can get out of hand, it just seems wrong
that the interface specifies that the view must, say, have something
clickable and not leave the implementation to the view.
So what I'm playing about with right now is (for the example you gave).
There would be a couple of interfaces HasClose and HasSave which would be
along the lines of
public interface HasSave
{
void save();
}
There would be a couple of corresponding CloseHandler and SaveHandler
classes e.g.
class SaveHandler implements ClickHandler
{
private HasSave presenter;
public SaveHandler(HasSave presenter)
{
this.presenter = presenter;
}
@Override
public void onClick(ClickEvent event)
{
presenter.save();
}
}
The presenter looks like this
class Presenter implements HasSave, HasClose
{
View view;
public Presenter(View view)
{
this.view = view;
}
@Override
public void save()
{
view.setText("Save");
}
@Override
public void close()
{
view.setText("Close");
}
}
and the view like this
class View extends FlowPanel implements HasText
{
Label label = new Label();
public View()
{
Presenter presenter = new Presenter(this);
add(new Button("Open", new SaveHandler(presenter)));
add(new Button("Close", new CloseHandler(presenter)));
add(label);
}
@Override
public String getText()
{
return label.getText();
}
@Override
public void setText(String text)
{
label.setText(text);
}
}
in the AppController or onModuleLoad method, you'd just have the line
RootPanel.get().add(new View());
Does that make sense? Feel free to ask but I'm still not too far forward
with this approach yet.
For a tiny project, it's a bit of work (unless you have already written the
interfaces and handler classes for some other project) but it does keep
everything well organised in larger projects.
Ian
http://examples.roughian.com
On 1 April 2010 00:15, Nathan Wells <[email protected]> wrote:
> Thomas,
>
> I've heard of your approach before, but I'm not clear on the
> implementation... are you passing the presenter itself into the view?
> or are you passing instances of event handlers? The difference seems
> trivial, but in practice (as I imagine it, anyway) seems large:
>
> http://etherpad.com/sIAaiCfuiG
>
> Let me know what you think. I would assume the first way is what your
> referring to in your comment above, which implies that it is a View
> layer responsibility to deal with HandlerRegistrations and the like.
> Is that correct?
>
> On Mar 31, 8:14 am, Thomas Broyer <[email protected]> wrote:
> > On Mar 31, 8:07 am, mic <[email protected]> wrote:
> >
> > > Just sharing some thoughts....
> >
> > > Would the MenuItem class need to implement HasClickHandler so that
> > > when a MenuItem is clicked, the action can be handled in the
> > > presenter. At this time, the MenuItem needs an object that implements
> > > the Command interface, so the view seems to know about the presenter.
> >
> > > I would like to know what others think about this.
> >
> > I've recently migrated from views with many HasXxxHandlers getters to
> > views with a setListener method that the presenter "injects" into its
> > view. The listener defines "callback methods" such as save(), close(),
> > italicize(), bold(), delete(), etc.
> > It makes unit tests waaay easier to write (you don't have to mock each
> > HasXxxHandlers, capturing each added XxxHandler, eventually mocking
> > the XxxEvent, etc.) and in your case would make things easier: the
> > Command is an implementation detail of the view.
>
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