public abstract class

Panel

extends Widget
implements HasWidgets.ForIsWidget

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

Known Direct Subclasses

ComplexPanel, HTMLTable, HorizontalSplitPanel, SimplePanel, VerticalSplitPanel

Known Indirect Subclasses

AbsolutePanel, CellPanel, DeckPanel, DecoratedPopupPanel, DecoratedStackPanel, DecoratorPanel, DialogBox, DockLayoutPanel, DockPanel, FlexTable, FlowPanel, FocusPanel, FormPanel, Grid, HTMLPanel, and 11 others.

AbsolutePanel	An absolute panel positions all of its children absolutely, allowing them to overlap.
CellPanel	A panel whose child widgets are contained within the cells of a table.
DeckPanel	A panel that displays all of its child widgets in a 'deck', where only one can be visible at a time.
DecoratedPopupPanel	A `PopupPanel` that wraps its content in a 3x3 grid, which allows users to add rounded corners.
DecoratedStackPanel	A `StackPanel` that wraps each item in a 2x3 grid (six box), which allows users to add rounded corners.
DecoratorPanel	A `SimplePanel` that wraps its contents in stylized boxes, which can be used to add rounded corners to a `Widget`.
DialogBox	A form of popup that has a caption area at the top and can be dragged by the user.
DockLayoutPanel	A panel that lays its child widgets out "docked" at its outer edges, and allows its last widget to take up the remaining space in its center.
DockPanel	This class is deprecated. Use `DockLayoutPanel` instead, but understand that it is not a drop in replacement for this class. It requires standards mode, and is most easily used under a `RootLayoutPanel` (as opposed to a `RootPanel`
FlexTable	A flexible table that creates cells on demand.
FlowPanel	A panel that formats its child widgets using the default HTML layout behavior.
FocusPanel	A simple panel that makes its contents focusable, and adds the ability to catch mouse and keyboard events.
FormPanel	A panel that wraps its contents in an HTML <FORM> element.
Grid	A rectangular grid that can contain text, html, or a child `Widget` within its cells.
HTMLPanel	A panel that contains HTML, and which can attach child widgets to identified elements within that HTML.
HorizontalPanel	A panel that lays all of its widgets out in a single horizontal column.
LayoutPanel	A panel that lays its children out in arbitrary `layers` using the `Layout` class.
LazyPanel	Convenience class to help lazy loading.
LoggingPopup	A simple popup to show log messages, which can be resized, minimized, and dragged to a different location.
PopupPanel	A panel that can "pop up" over other widgets.
RootLayoutPanel	A singleton implementation of `LayoutPanel` that always attaches itself to the document body (i.e.
RootPanel	The panel to which all other widgets must ultimately be added.
ScrollPanel	A simple panel that wraps its contents in a scrollable area.
SplitLayoutPanel	A panel that adds user-positioned splitters between each of its child widgets.
StackPanel	A panel that stacks its children vertically, displaying only one at a time, with a header for each child which the user can click to display.
VerticalPanel	A panel that lays all of its widgets out in a single vertical column.

Class Overview

Abstract base class for all panels, which are widgets that can contain other widgets.

Summary

[Expand]

Inherited Constants

From class com.google.gwt.user.client.ui.UIObject

Public Constructors
	Panel()

Public Methods
void	add(IsWidget child)
void	add(Widget child) Adds a child widget.
void	clear() Removes all child widgets.
abstract boolean	remove(Widget child) Removes a child widget.
boolean	remove(IsWidget child)

Protected Methods
final void	adopt(Widget child) Finalize the attachment of a Widget to this Panel.
void	adopt(Widget w, Element container) This method is deprecated. Use `adopt(Widget)`.
void	disown(Widget w) This method is deprecated. Use `orphan(Widget)`.
void	doAttachChildren() If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call `onAttach()` for each of its child widgets.
void	doDetachChildren() If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call `onDetach()` for each of its child widgets.
final void	orphan(Widget child) This method must be called as part of the remove method of any Panel.

[Expand]

Inherited Methods

From class com.google.gwt.user.client.ui.Widget

HandlerRegistration	addAttachHandler(AttachEvent.Handler handler) Adds an `AttachEvent` handler.
final <H extends EventHandler> HandlerRegistration	addDomHandler(H handler, Type<H> type) Adds a native event handler to the widget and sinks the corresponding native event.
final <H extends EventHandler> HandlerRegistration	addHandler(H handler, Type<H> type) Adds this handler to the widget.
Widget	asWidget() Returns the `Widget` aspect of the receiver.
static Widget	asWidgetOrNull(IsWidget w) This convenience method makes a null-safe call to `asWidget()`.
HandlerManager	createHandlerManager() Creates the `HandlerManager` used by this Widget.
void	delegateEvent(Widget target, GwtEvent<?> event) Fires an event on a child widget.
void	doAttachChildren() If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call `onAttach()` for each of its child widgets.
void	doDetachChildren() If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call `onDetach()` for each of its child widgets.
void	fireEvent(GwtEvent<?> event) Fires the given event to the handlers listening to the event's type.
int	getHandlerCount(Type<?> type) Gets the number of handlers listening to the event type.
Object	getLayoutData() Gets the panel-defined layout data associated with this widget.
Widget	getParent() Gets this widget's parent panel.
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).
final boolean	isOrWasAttached() Has this widget ever been attached?
void	onAttach() This method is called when a widget is attached to the browser's document.
void	onBrowserEvent(Event event) Fired whenever a browser event is received.
void	onDetach() This method is called when a widget is detached from the browser's document.
void	onLoad() This method is called immediately after a widget becomes attached to the browser's document.
void	onUnload() This method is called immediately before a widget will be detached from the browser's document.
void	removeFromParent() Removes this widget from its parent widget, if one exists.
void	setLayoutData(Object layoutData) Sets the panel-defined layout data associated with this widget.
void	sinkEvents(int eventBitsToAdd) Overridden to defer the call to super.sinkEvents until the first time this widget is attached to the dom, as a performance enhancement.

From class com.google.gwt.user.client.ui.UIObject

void	addStyleDependentName(String styleSuffix) Adds a dependent style name by specifying the style name's suffix.
void	addStyleName(String style) Adds a secondary or dependent style name to this object.
static void	ensureDebugId(Element elem, String baseID, String id) Set the debug id of a specific element.
final void	ensureDebugId(String id) Ensure that the main `Element` for this `UIObject` has an ID property set, which allows it to integrate with third-party libraries and test tools.
static void	ensureDebugId(Element elem, String id) Ensure that elem has an ID property set, which allows it to integrate with third-party libraries and test tools.
int	getAbsoluteLeft() Gets the object's absolute left position in pixels, as measured from the browser window's client area.
int	getAbsoluteTop() Gets the object's absolute top position in pixels, as measured from the browser window's client area.
Element	getElement() Gets a handle to the object's underlying DOM element.
int	getOffsetHeight() Gets the object's offset height in pixels.
int	getOffsetWidth() Gets the object's offset width in pixels.
Element	getStyleElement() Template method that returns the element to which style names will be applied.
String	getStyleName() Gets all of the object's style names, as a space-separated list.
static String	getStyleName(Element elem) Gets all of the element's style names, as a space-separated list.
String	getStylePrimaryName() Gets the primary style name associated with the object.
static String	getStylePrimaryName(Element elem) Gets the element's primary style name.
String	getTitle() Gets the title associated with this object.
boolean	isVisible() Determines whether or not this object is visible.
static boolean	isVisible(Element elem)
void	onEnsureDebugId(String baseID) Called when the user sets the id using the `ensureDebugId(String)` method.
void	removeStyleDependentName(String styleSuffix) Removes a dependent style name by specifying the style name's suffix.
void	removeStyleName(String style) Removes a style name.
final void	setElement(Element elem) Sets this object's browser element.
void	setElement(Element elem) Sets this object's browser element.
void	setHeight(String height) Sets the object's height.
void	setPixelSize(int width, int height) Sets the object's size, in pixels, not including decorations such as border, margin, and padding.
void	setSize(String width, String height) Sets the object's size.
void	setStyleDependentName(String styleSuffix, boolean add) Adds or removes a dependent style name by specifying the style name's suffix.
static void	setStyleName(Element elem, String styleName) Clears all of the element's style names and sets it to the given style.
static void	setStyleName(Element elem, String style, boolean add) This convenience method adds or removes a style name for a given element.
void	setStyleName(String style) Clears all of the object's style names and sets it to the given style.
void	setStyleName(String style, boolean add) Adds or removes a style name.
void	setStylePrimaryName(String style) Sets the object's primary style name and updates all dependent style names.
static void	setStylePrimaryName(Element elem, String style) Sets the element's primary style name and updates all dependent style names.
void	setTitle(String title) Sets the title associated with this object.
void	setVisible(boolean visible) Sets whether this object is visible.
static void	setVisible(Element elem, boolean visible)
void	setWidth(String width) Sets the object's width.
void	sinkEvents(int eventBitsToAdd) Adds a set of events to be sunk by this object.
String	toString() This method is overridden so that any object can be viewed in the debugger as an HTML snippet.
void	unsinkEvents(int eventBitsToRemove) Removes a set of events from this object's event list.

From class java.lang.Object

From interface com.google.gwt.event.logical.shared.HasAttachHandlers

From interface com.google.gwt.event.shared.HasHandlers

From interface com.google.gwt.user.client.EventListener

From interface com.google.gwt.user.client.ui.HasWidgets

From interface com.google.gwt.user.client.ui.HasWidgets.ForIsWidget

From interface com.google.gwt.user.client.ui.IsWidget

From interface java.lang.Iterable

Public Constructors

public Panel ()

Public Methods

public void add (IsWidget child)

public void add (Widget child)

Adds a child widget.

How to Override this Method

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

Validate: Perform any sanity checks to ensure the Panel can accept a new Widget. Examples: checking for a valid index on insertion; checking that the Panel is not full if there is a max capacity.
Adjust for Reinsertion: Some Panels need to handle the case where the Widget is already a child of this Panel. Example: when performing a reinsert, the index might need to be adjusted to account for the Widget's removal. See adjustIndex(Widget, int).
Detach Child: Remove the Widget from its existing parent, if any. Most Panels will simply call removeFromParent() on the Widget.
Logical Attach: Any state variables of the Panel should be updated to reflect the addition of the new Widget. Example: the Widget is added to the Panel's WidgetCollection at the appropriate index.
Physical Attach: The Widget's Element must be physically attached to the Panel's Element, either directly or indirectly.
Adopt: Call adopt(Widget) to finalize the add as the very last step.

Parameters

child	the widget to be added

Throws

UnsupportedOperationException	if this method is not supported (most often this means that a specific overload must be called)

public void clear ()

Removes all child widgets.

public abstract boolean remove (Widget child)

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.

Validate: Make sure this Panel is actually the parent of the child Widget; return false if it is not.
Orphan: Call orphan(Widget) first while the child Widget is still attached.
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.
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.

Parameters

child	the widget to be removed

Returns

true if the child was present

public boolean remove (IsWidget child)

Protected Methods

protected final void adopt (Widget child)

Finalize the attachment of a Widget to this Panel. This method is the last step in adding or inserting a Widget into a Panel, and should be called after physical attachment in the DOM is complete. This Panel becomes the parent of the child Widget, and the child will now fire its onAttach() event if this Panel is currently attached.

Parameters

child	the widget to be adopted

protected void adopt (Widget w, Element container)

This method is deprecated.
Use adopt(Widget).

This method was formerly part of the process of adding a Widget to a Panel but has been deprecated in favor of adopt(Widget).

protected void disown (Widget w)

This method is deprecated.
Use orphan(Widget).

This method was formerly part of the process of removing a Widget from a Panel but has been deprecated in favor of orphan(Widget).

protected void doAttachChildren ()

If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call onAttach() for each of its child widgets.

protected void doDetachChildren ()

If a widget contains one or more child widgets that are not in the logical widget hierarchy (the child is physically connected only on the DOM level), it must override this method and call onDetach() for each of its child widgets.

protected final void orphan (Widget child)

This method must be called as part of the remove method of any Panel. It ensures that the Widget's parent is cleared. This method should be called after verifying that the child Widget is an existing child of the Panel, but before physically removing the child Widget from the DOM. The child will now fire its onDetach() event if this Panel is currently attached.

Calls to orphan(Widget) should be wrapped in a try/finally block to ensure that the widget is physically detached even if orphan throws an exception.

Parameters

child	the widget to be disowned

Interfaces

Classes

Annotations

Enums

Exceptions

Panel

Class Overview

Summary

Public Constructors

public Panel ()

Public Methods

public void add (IsWidget child)

public void add (Widget child)

Parameters

Throws

See Also

public void clear ()

public abstract boolean remove (Widget child)

Parameters

Returns

public boolean remove (IsWidget child)

Protected Methods

protected final void adopt (Widget child)

Parameters

See Also

protected void adopt (Widget w, Element container)

protected void disown (Widget w)

protected void doAttachChildren ()

protected void doDetachChildren ()

protected final void orphan (Widget child)

Parameters

See Also