Class Widget
public
class
Widget
extends
UIObject
implements
EventListener
// Superclass of
Composite,
FileUpload,
FocusWidget,
Frame,
Hidden,
Hyperlink,
Image,
Label,
MenuBar,
Panel,
Tree
The base class for the majority of user-interface objects. Widget adds
support for receiving events from the browser and being added directly to
panels.
Methods
| doAttachChildren() | If a widget implements HasWidgets, it must override this method and call
onAttach() for each of its child widgets. |
| doDetachChildren() | If a widget implements HasWidgets, it must override this method and call
onDetach() for each of its child widgets. |
| getParent() | Gets this widget's parent panel. |
| isAttached() | Determines whether this widget is currently attached to the browser's
document (i.e., there is an unbroken chain of widgets between this widget
and the underlying browser document). |
| onAttach() | This method is called when a widget is attached to the browser's document. |
| onBrowserEvent(Event) | Fired whenever a browser event is received. |
| onDetach() | This method is called when a widget is detached from the browser's
document. |
| onLoad() | This method is called immediately after a widget becomes attached to the
browser's document. |
| onUnload() | This method is called immediately before a widget will be detached from the
browser's document. |
| removeFromParent() | Removes this widget from its parent widget. |
| setElement(Element) | Sets this object's browser element. |
Method Detail
doAttachChildren
protected void doAttachChildren()
If a widget implements HasWidgets, it must override this method and call
onAttach() for each of its child widgets.
See Also
Panel.onAttach()
doDetachChildren
protected void doDetachChildren()
If a widget implements HasWidgets, it must override this method and call
onDetach() for each of its child widgets.
See Also
Panel.onDetach()
getParent
Gets this widget's parent panel.
Return Value
the widget's parent panel
isAttached
public boolean isAttached()
Determines whether this widget is currently attached to the browser's
document (i.e., there is an unbroken chain of widgets between this widget
and the underlying browser document).
Return Value
true if the widget is attached
onAttach
protected void onAttach()
This method is called when a widget is attached to the browser's document.
To receive notification after a Widget has been added to the document,
override the
onLoad method.
Subclasses that override this method must call
super.onAttach() to ensure that the Widget has been attached
to its underlying Element.
onBrowserEvent
public void
onBrowserEvent(
Event event)
Fired whenever a browser event is received.
Parameters
- event
- the event received
onDetach
protected void onDetach()
This method is called when a widget is detached from the browser's
document. To receive notification before a Widget is removed from the
document, override the
onUnload method.
Subclasses that override this method must call
super.onDetach() to ensure that the Widget has been detached
from the underlying Element. Failure to do so will result in application
memory leaks due to circular references between DOM Elements and JavaScript
objects.
onLoad
protected void onLoad()
This method is called immediately after a widget becomes attached to the
browser's document.
onUnload
protected void onUnload()
This method is called immediately before a widget will be detached from the
browser's document.
removeFromParent
public void removeFromParent()
Removes this widget from its parent widget. If it has no parent, this
method does nothing.
setElement
protected void
setElement(
Element elem)
Sets this object's browser element. Widget subclasses must call this method
before attempting to call any other methods.
If a browser element has already been attached, then it is replaced with
the new element. The old event listeners are removed from the old browser
element, and the event listeners are set up on the new browser element.
Parameters
- elem
- the object's new element
