Hi,
This message was supposed to be an answer to the "Menu Item and MVP"
discussion. But it does not appear, I probably made a mistake, so I
put it here in a new discussion.
The initial message posted by "mic" was :
>> 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.
This is probably a late answer to the initial question.
Anyway, I've made a quite simple implementation that solves the lack
of something like a HasClickHandlers dedicated to MenuItem.
Here I give you the solution I've built.
First, we need something like a "HasCommandHandlers" interface instead
of HasClickHandler. This will allow the presenter to handle a click on
a MenuItem.
public interface HasCommandHandlers extends HasHandlers {
// equivalent to the addClickHandler in the HasClickHandlers
interface
public HandlerRegistration addCommandHandler(CommandHandler handler);
}
We create a CommandHandler interface only to stay in line with the
naming convetion for the handlers.
public interface CommandHandler extends Command {
// this interface is empty
}
The Presenter :
public interface Display {
HasCommandHandlers getMenu1();
HasCommandHandlers getMenu2();
...
}
public void build() {
view.gerMenu1().addCommandHandler(new CommandHandler() {
public void execute() {
// do what you need
}
});
}
...
}
So this is standard MVP implementation.
Now the View.
We have to create a subclass of MenuItem implementing
MenuPresenter.HasCommandHandlers, so we will have a MenuItem
implementing the HasCommandHandlers interface just like a PushButton
implements HasClickHandlers.
public class MyMenuItem extends MenuItem implements
HasCommandHandlers {
// ----------------
// extends MenuItem
// ----------------
public MyMenuItem(String text) {
super(text, (Command)null);
}
// ---------------------------
// implements HasCommandHandlers
// ---------------------------
@Override
public HandlerRegistration addCommandHandler(CommandHandler
handler)
{
// call MenuItem setCommand() as the CommandHandler is
a Command !
setCommand(handler);
return new HandlerRegistration() {
@Override
public void removeHandler() {
// remove the command
MyMenuItem.this.setCommand(null);
}
};
}
@Override
public void fireEvent(GwtEvent<?> event) {
// do nothing because we do not receive events
}
}
The view as usual implements MenuPresenter.Display.
This seems to me a quite simple and straight solution.
Your comments are welcome !
HTH
Yves
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