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

java.lang.Object
  com.google.gwt.user.client.ui.UIObject

Direct Known Subclasses:

MenuItem, TreeItem, Widget

public abstract class UIObject
extends java.lang.Object

The superclass for all user-interface objects. It simply wraps a DOM element, and cannot receive events. Most interesting user-interface classes derive from Widget.

Styling With CSS

All UIObject objects can be styled using CSS. Style names that are specified programmatically in Java source are implicitly associated with CSS style rules. In terms of HTML and CSS, a GWT style name is the element's CSS "class". By convention, GWT style names are of the form [project]-[widget].

For example, the Button widget has the style name gwt-Button, meaning that within the Button constructor, the following call occurs:

 setStyleName("gwt-Button");

A corresponding CSS style rule can then be written as follows:

 // Example of how you might choose to style a Button widget 
 .gwt-Button {
   background-color: yellow;
   color: black;
   font-size: 24pt;
 }

Note the dot prefix in the CSS style rule. This syntax is called a CSS class selector.

Style Name Specifics

Every UIObject has a primary style name that identifies the key CSS style rule that should always be applied to it. Use setStylePrimaryName(String) to specify an object's primary style name. In most cases, the primary style name is set in a widget's constructor and never changes again during execution. In the case that no primary style name is specified, it defaults to the first style name that is added.

More complex styling behavior can be achieved by manipulating an object's secondary style names. Secondary style names can be added and removed using addStyleName(String) and removeStyleName(String). The purpose of secondary style names is to associate a variety of CSS style rules over time as an object progresses through different visual states.

There is an important special formulation of secondary style names called dependent style names. A dependent style name is a secondary style name prefixed with the primary style name of the widget itself. See addStyleName(String) for details.

Constructor Summary

UIObject()

Method Summary

void	addStyleDependentName(java.lang.String styleSuffix) Adds a dependent style name by specifying the style name's suffix.
void	addStyleName(java.lang.String style) Adds a secondary or dependent style name to this object.
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.
protected Element	getStyleElement() Template method that returns the element to which style names will be applied.
java.lang.String	getStyleName() Gets all of the object's style names, as a space-separated list.
protected static java.lang.String	getStyleName(Element elem) Gets all of the element's style names, as a space-separated list.
java.lang.String	getStylePrimaryName() Gets the primary style name associated with the object.
protected static java.lang.String	getStylePrimaryName(Element elem) Gets the element's primary style name.
java.lang.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	removeStyleDependentName(java.lang.String styleSuffix) Removes a dependent style name by specifying the style name's suffix.
void	removeStyleName(java.lang.String style) Removes a style name.
protected void	setElement(Element elem) Sets this object's browser element.
void	setHeight(java.lang.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(java.lang.String width, java.lang.String height) Sets the object's size.
protected static void	setStyleName(Element elem, java.lang.String styleName) Clears all of the element's style names and sets it to the given style.
protected static void	setStyleName(Element elem, java.lang.String style, boolean add) This convenience method adds or removes a style name for a given element.
void	setStyleName(java.lang.String style) Clears all of the object's style names and sets it to the given style.
protected static void	setStylePrimaryName(Element elem, java.lang.String style) Sets the element's primary style name and updates all dependent style names.
void	setStylePrimaryName(java.lang.String style) Sets the object's primary style name and updates all dependent style names.
void	setTitle(java.lang.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(java.lang.String width) Sets the object's width.
void	sinkEvents(int eventBitsToAdd) Adds a set of events to be sunk by this object.
java.lang.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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

UIObject

public UIObject()

Method Detail

isVisible

public static boolean isVisible(Element elem)

setVisible

public static void setVisible(Element elem,
                              boolean visible)

getStyleName

protected static java.lang.String getStyleName(Element elem)

Gets all of the element's style names, as a space-separated list.

Parameters:

elem - the element whose style is to be retrieved

Returns:

the objects's space-separated style names

getStylePrimaryName

protected static java.lang.String getStylePrimaryName(Element elem)

Gets the element's primary style name.

Parameters:

elem - the element whose primary style name is to be retrieved

Returns:

the element's primary style name

setStyleName

protected static void setStyleName(Element elem,
                                   java.lang.String styleName)

Clears all of the element's style names and sets it to the given style.

Parameters:

elem - the element whose style is to be modified

styleName - the new style name

setStyleName

protected static void setStyleName(Element elem,
                                   java.lang.String style,
                                   boolean add)

This convenience method adds or removes a style name for a given element. This method is typically used to add and remove secondary style names, but it can be used to remove primary stylenames as well, but that is not recommended. See setStyleName(String) for a description of how primary and secondary style names are used.

Parameters:

elem - the element whose style is to be modified

style - the secondary style name to be added or removed

add - true to add the given style, false to remove it

setStylePrimaryName

protected static void setStylePrimaryName(Element elem,
                                          java.lang.String style)

Sets the element's primary style name and updates all dependent style names.

Parameters:

elem - the element whose style is to be reset

style - the new primary style name

See Also:

setStyleName(Element, String, boolean)

addStyleDependentName

public void addStyleDependentName(java.lang.String styleSuffix)

Adds a dependent style name by specifying the style name's suffix. The actual form of the style name that is added is:

 getStylePrimaryName() + '-' + styleSuffix
 

Parameters:

styleSuffix - the suffix of the dependent style to be added.

See Also:

setStylePrimaryName(String), removeStyleDependentName(String), addStyleName(String)

addStyleName

public void addStyleName(java.lang.String style)

Adds a secondary or dependent style name to this object. A secondary style name is an additional style name that is, in HTML/CSS terms, included as a space-separated token in the value of the CSS class attribute for this object's root element.

The most important use for this method is to add a special kind of secondary style name called a dependent style name. To add a dependent style name, use addStyleDependentName(String), which will prefix the 'style' argument with the result of getStylePrimaryName() (followed by a '-'). For example, suppose the primary style name is gwt-TextBox. If the following method is called as obj.setReadOnly(true):

 public void setReadOnly(boolean readOnly) {
   isReadOnlyMode = readOnly;
   
   // Create a dependent style name.
   String readOnlyStyle = "readonly";
    
   if (readOnly) {
     addStyleDependentName(readOnlyStyle);
   } else {
     removeStyleDependentName(readOnlyStyle);
   }
 }

then both of the CSS style rules below will be applied:

 // This rule is based on the primary style name and is always active.
 .gwt-TextBox {
   font-size: 12pt;
 }
 
 // This rule is based on a dependent style name that is only active
 // when the widget has called addStyleName(getStylePrimaryName() +
 // "-readonly").
 .gwt-TextBox-readonly {
   background-color: lightgrey;
   border: none;
 }

Dependent style names are powerful because they are automatically updated whenever the primary style name changes. Continuing with the example above, if the primary style name changed due to the following call:

setStylePrimaryName("my-TextThingy");

then the object would be re-associated with following style rules, removing those that were shown above.

 .my-TextThingy {
   font-size: 20pt;
 }
 
 .my-TextThingy-readonly {
   background-color: red;
   border: 2px solid yellow;
 }

Secondary style names that are not dependent style names are not automatically updated when the primary style name changes.

Parameters:

style - the secondary style name to be added

See Also:

UIObject, removeStyleName(String)

getAbsoluteLeft

public int getAbsoluteLeft()

Gets the object's absolute left position in pixels, as measured from the browser window's client area.

Returns:

the object's absolute left position

getAbsoluteTop

public int getAbsoluteTop()

Gets the object's absolute top position in pixels, as measured from the browser window's client area.

Returns:

the object's absolute top position

getElement

public Element getElement()

Gets a handle to the object's underlying DOM element.

Returns:

the object's browser element

getOffsetHeight

public int getOffsetHeight()

Gets the object's offset height in pixels. This is the total height of the object, including decorations such as border, margin, and padding.

Returns:

the object's offset height

getOffsetWidth

public int getOffsetWidth()

Gets the object's offset width in pixels. This is the total width of the object, including decorations such as border, margin, and padding.

Returns:

the object's offset width

getStyleName

public java.lang.String getStyleName()

Gets all of the object's style names, as a space-separated list. If you wish to retrieve only the primary style name, call getStylePrimaryName().

Returns:

the objects's space-separated style names

See Also:

getStylePrimaryName()

getStylePrimaryName

public java.lang.String getStylePrimaryName()

Gets the primary style name associated with the object.

Returns:

the object's primary style name

See Also:

setStyleName(String), addStyleName(String), removeStyleName(String)

getTitle

public java.lang.String getTitle()

Gets the title associated with this object. The title is the 'tool-tip' displayed to users when they hover over the object.

Returns:

the object's title

isVisible

public boolean isVisible()

Determines whether or not this object is visible.

Returns:

true if the object is visible

removeStyleDependentName

public void removeStyleDependentName(java.lang.String styleSuffix)

Removes a dependent style name by specifying the style name's suffix.

Parameters:

styleSuffix - the suffix of the dependent style to be removed

See Also:

setStylePrimaryName(Element, String), addStyleDependentName(String), addStyleName(String)

removeStyleName

public void removeStyleName(java.lang.String style)

Removes a style name. This method is typically used to remove secondary style names, but it can be used to remove primary stylenames as well. That use is not recommended.

Parameters:

style - the secondary style name to be removed

See Also:

addStyleName(String)

setHeight

public void setHeight(java.lang.String height)

Sets the object's height. This height does not include decorations such as border, margin, and padding.

Parameters:

height - the object's new height, in CSS units (e.g. "10px", "1em")

setPixelSize

public void setPixelSize(int width,
                         int height)

Sets the object's size, in pixels, not including decorations such as border, margin, and padding.

Parameters:

width - the object's new width, in pixels

height - the object's new height, in pixels

setSize

public void setSize(java.lang.String width,
                    java.lang.String height)

Sets the object's size. This size does not include decorations such as border, margin, and padding.

Parameters:

width - the object's new width, in CSS units (e.g. "10px", "1em")

height - the object's new height, in CSS units (e.g. "10px", "1em")

setStyleName

public void setStyleName(java.lang.String style)

Clears all of the object's style names and sets it to the given style. You should normally use setStylePrimaryName(String) unless you wish to explicitly remove all existing styles.

Parameters:

style - the new style name

See Also:

setStylePrimaryName(String)

setStylePrimaryName

public void setStylePrimaryName(java.lang.String style)

Sets the object's primary style name and updates all dependent style names.

Parameters:

style - the new primary style name

See Also:

addStyleName(String), removeStyleName(String)

setTitle

public void setTitle(java.lang.String title)

Sets the title associated with this object. The title is the 'tool-tip' displayed to users when they hover over the object.

Parameters:

title - the object's new title

setVisible

public void setVisible(boolean visible)

Sets whether this object is visible.

Parameters:

visible - true to show the object, false to hide it

setWidth

public void setWidth(java.lang.String width)

Sets the object's width. This width does not include decorations such as border, margin, and padding.

Parameters:

width - the object's new width, in CSS units (e.g. "10px", "1em")

sinkEvents

public void sinkEvents(int eventBitsToAdd)

Adds a set of events to be sunk by this object. Note that only widgets may actually receive events, but can receive events from all objects contained within them.

Parameters:

eventBitsToAdd - a bitfield representing the set of events to be added to this element's event set

See Also:

Event

toString

public java.lang.String toString()

This method is overridden so that any object can be viewed in the debugger as an HTML snippet.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of the object

unsinkEvents

public void unsinkEvents(int eventBitsToRemove)

Removes a set of events from this object's event list.

Parameters:

eventBitsToRemove - a bitfield representing the set of events to be removed from this element's event set

See Also:

sinkEvents(int), Event

getStyleElement

protected Element getStyleElement()

Template method that returns the element to which style names will be applied. By default it returns the root element, but this method may be overridden to apply styles to a child element.

Returns:

the element to which style names will be applied

setElement

protected void setElement(Element elem)

Sets this object's browser element. UIObject subclasses must call this method before attempting to call any other methods. If the browser element has already been set, then the current element's position is located in the DOM and removed. The new element is added into the previous element's position.

Parameters:

elem - the object's new element