com.google.gwt.user.client.ui
Class SimplePanel

java.lang.Object
  com.google.gwt.user.client.ui.UIObject
      com.google.gwt.user.client.ui.Widget
          com.google.gwt.user.client.ui.Panel
              com.google.gwt.user.client.ui.SimplePanel

All Implemented Interfaces:

HasAttachHandlers, HasHandlers, EventListener, AcceptsOneWidget, HasOneWidget, HasVisibility, HasWidgets, HasWidgets.ForIsWidget, IsWidget, java.lang.Iterable<Widget>

Direct Known Subclasses:

DecoratorPanel, FocusPanel, FormPanel, LazyPanel, PopupPanel, ResizeLayoutPanel, ScrollPanel, SimpleLayoutPanel

public class SimplePanel
extends Panel
implements HasOneWidget

Base class for panels that contain only one widget.

widget

Widget widget

SimplePanel

public SimplePanel()

Creates an empty panel that uses a DIV for its contents.

SimplePanel

public SimplePanel(Widget child)

Create a panel with the specified child widget.

Parameters:

child - the child to add to the panel

SimplePanel

protected SimplePanel(Element elem)

Creates an empty panel that uses the specified browser element for its contents.

Parameters:

elem - the browser element to use

add

public void add(Widget w)

Adds a widget to this panel.

Specified by:

add in interface HasWidgets

Overrides:

add in class Panel

Parameters:

w - the child widget to be added

See Also:

HasWidgets.add(Widget)

getWidget

public Widget getWidget()

Gets the panel's child widget.

Specified by:

getWidget in interface HasOneWidget

Returns:

the child widget, or null if none is present

iterator

public java.util.Iterator<Widget> iterator()

Description copied from interface: HasWidgets

Gets an iterator for the contained widgets. This iterator is required to implement Iterator.remove().

Specified by:

iterator in interface HasWidgets

Specified by:

iterator in interface java.lang.Iterable<Widget>

remove

public boolean remove(Widget w)

Description copied from class: Panel

Removes a child widget.

How to Override this Method

There are several important things that must take place in the correct order to properly remove a Widget from a Panel. Not all of these steps will be relevant to every Panel, but all of the steps must be considered.

1. Validate: Make sure this Panel is actually the parent of the child Widget; return false if it is not.
2. Orphan: Call Panel.orphan(Widget) first while the child Widget is still attached.
3. Physical Detach: Adjust the DOM to account for the removal of the child Widget. The Widget's Element must be physically removed from the DOM.
4. Logical Detach: Update the Panel's state variables to reflect the removal of the child Widget. Example: the Widget is removed from the Panel's WidgetCollection.

Specified by:

remove in interface HasWidgets

Specified by:

remove in class Panel

Parameters:

w - the widget to be removed

Returns:

true if the child was present

setWidget

public void setWidget(IsWidget w)

Description copied from interface: AcceptsOneWidget

Set the only widget of the receiver, replacing the previous widget if there was one.

Specified by:

setWidget in interface AcceptsOneWidget

Parameters:

w - the widget, or null to remove the widget

See Also:

SimplePanel

setWidget

public void setWidget(Widget w)

Sets this panel's widget. Any existing child widget will be removed.

Specified by:

setWidget in interface HasOneWidget

Parameters:

w - the panel's new widget, or null to clear the panel

getContainerElement

protected Element getContainerElement()

Override this method to specify that an element other than the root element be the container for the panel's child widget. This can be useful when you want to create a simple panel that decorates its contents. Note that this method continues to return the Element class defined in the User module to maintain backwards compatibility.

Returns:

the element to be used as the panel's container