On 28 sep, 20:34, YoeZ <[EMAIL PROTECTED]> wrote:
> Hi,
> How can I access event from another widget?
> Or I want to implement an event from another widget.
> let say I have a three class:
> iCombo.java = contain listbox
> ComboParent.java = contain iCombo class
> MainMenu.java = contain ComboParent
>
> in the MainMenu.java class, I want to implement the event when the
> listbox (in iCombo class) has changed.
iCombo has to fire events on listbox's change event; and ComboParent
has to fire events on iCombo's event; then MainMenu can register as a
listener to the ComboParent instance.
> /****************
> * iCombo.java
> ****************/
> public class iCombo extends Composite implements ChangeListener {
The goal of a Composite is to mask the internal implementation
(encapsulation) and expose its own API. It doesn't matter to iCombo
users that it's made of three ListBoxes or a set or RadioButtons or
whatever other widget; what matters is that some events are fired in
response to changes (generally in response to user interaction).
(note: I wouldn't implement ChangeListener on iCombo, it's an
"implementation detail"; I would rather have a ChangeListener stored
in a private field: private ChangeListener listener = new
ChangeListener() { ... }; )
iCombo should implement SourcesChangeEvents:
private ChangeListenerCollection listeners = new
ChangeListenerCollection();
public void addChangeListener(ChangeListener listener) {
listeners.add(listener);
}
public void removeChangeListener(ChangeListener listener) {
listeners.remove(listener);
}
> private HorizontalPanel hPanel = new HorizontalPanel();
> private ListBox ListA = new ListBox();
> private ListBox ListB = new ListBox();
> private ListBox ListC = new ListBox();
>
> public iCombo () {
> hPanel.add(ListA);
> hPanel.add(ListB);
> hPanel.add(ListC);
>
> ListA.addChangeListener(this);
> ListB.addChangeListener(this);
> ListC.addChangeListener(this);
>
> initWidget(hPanel);
> }
> public void onChange(Widget sender) {
> // I want to implement this method from another class? :(
listeners.fireChange(this);
> }
>
> }
>
> /****************
> * ComboParent.java
> ****************/
> public class ComboParent extends Composite {
Same here.
> /****************
> * MainMenu.java
> ****************/
> public class MainMenu implements EntryPoint {
> private VerticalPanel vPanel = new VerticalPanel();
> private ComboParent cp = new ComboParent ();
>
> public void onModuleLoad() {
> vPanel.add(cp);
>
> RootPanel.get().add(cp);
cp.addChangeListener(new ChangeListener() {
public void onChange(Widget sender) {
// ComboParent fired a change event.
}
});
> }
>
> // How do I know when the ListBox has Changed From here..
>
> }
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