- Direct Known Subclasses:
BasicLookAndFeel,MultiLookAndFeel
LookAndFeel, as the name implies, encapsulates a look and
feel. Beyond installing a look and feel most developers never need to
interact directly with LookAndFeel. In general only developers
creating a custom look and feel need to concern themselves with this class.
Swing is built upon the foundation that each JComponent
subclass has an implementation of a specific ComponentUI
subclass. The ComponentUI is often referred to as "the ui",
"component ui", or "look and feel delegate". The ComponentUI
subclass is responsible for providing the look and feel specific
functionality of the component. For example, JTree requires
an implementation of the ComponentUI subclass
TreeUI. The implementation of the specific
ComponentUI subclass is provided by the LookAndFeel. Each
JComponent subclass identifies the ComponentUI
subclass it requires by way of the JComponent method
getUIClassID.
Each LookAndFeel implementation must provide
an implementation of the appropriate ComponentUI subclass by
specifying a value for each of Swing's ui class ids in the
UIDefaults object returned from getDefaults. For example,
BasicLookAndFeel uses BasicTreeUI as the concrete
implementation for TreeUI. This is accomplished by
BasicLookAndFeel providing the key-value pair
"TreeUI"-"javax.swing.plaf.basic.BasicTreeUI", in the
UIDefaults returned from getDefaults. Refer to
UIDefaults.getUI(JComponent) for details on how the implementation
of the ComponentUI subclass is obtained.
When a LookAndFeel is installed the UIManager does
not check that an entry exists for all ui class ids. As such,
random exceptions will occur if the current look and feel has not
provided a value for a particular ui class id and an instance of
the JComponent subclass is created.
Recommendations for Look and Feels
As noted inUIManager each LookAndFeel has the opportunity
to provide a set of defaults that are layered in with developer and
system defaults. Some of Swing's components require the look and feel
to provide a specific set of defaults. These are documented in the
classes that require the specific default.
ComponentUIs and defaults
AllComponentUIs typically need to set various properties
on the JComponent the ComponentUI is providing the
look and feel for. This is typically done when the
ComponentUI is installed on the JComponent. Setting a
property should only be done if the developer has not set the
property. For non-primitive values it is recommended that the
ComponentUI only change the property on the
JComponent if the current value is null or implements
UIResource. If the current value is null or
implements UIResource it indicates the property has not
been set by the developer, and the ui is free to change it. For
example, BasicButtonUI.installDefaults only changes the
font on the JButton if the return value from
button.getFont() is null or implements
UIResource. On the other hand if button.getFont() returned
a non-null value that did not implement UIResource
then BasicButtonUI.installDefaults would not change the
JButton's font.
For primitive values, such as opaque, the method
installProperty should be invoked. installProperty only changes
the corresponding property if the value has not been changed by the
developer.
ComponentUI implementations should use the various install methods
provided by this class as they handle the necessary checking and install
the property using the recommended guidelines.
Exceptions
All of the install methods provided byLookAndFeel need to
access the defaults if the value of the property being changed is
null or a UIResource. For example, installing the
font does the following:
JComponent c;
Font font = c.getFont();
if (font == null || (font instanceof UIResource)) {
c.setFont(UIManager.getFont("fontKey"));
}
If the font is null or a UIResource, the
defaults table is queried with the key fontKey. All of
UIDefault's get methods throw a
NullPointerException if passed in null. As such, unless
otherwise noted each of the various install methods of
LookAndFeel throw a NullPointerException if the current
value is null or a UIResource and the supplied
defaults key is null. In addition, unless otherwise specified
all of the install methods throw a NullPointerException if
a null component is passed in.- Since:
- 1.2
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionReturns the look and feel defaults.abstract StringReturn a one line description of this look and feel implementation, e.g.static ObjectgetDesktopPropertyValue(String systemPropertyName, Object fallbackValue) Returns the value of the specified system desktop property by invokingToolkit.getDefaultToolkit().getDesktopProperty().getDisabledIcon(JComponent component, Icon icon) Returns anIconwith a disabled appearance.getDisabledSelectedIcon(JComponent component, Icon icon) Returns anIconfor use by disabled components that are also selected.abstract StringgetID()Return a string that identifies this look and feel.Returns theLayoutStylefor this look and feel.abstract StringgetName()Return a short string that identifies this look and feel, e.g.booleanReturnstrueif theLookAndFeelreturnedRootPaneUIinstances support providingWindowdecorations in aJRootPane.voidInitializes the look and feel.static voidinstallBorder(JComponent c, String defaultBorderName) Convenience method for setting a component's border property with a value from the defaults.static voidinstallColors(JComponent c, String defaultBgName, String defaultFgName) Convenience method for setting a component's foreground and background color properties with values from the defaults.static voidinstallColorsAndFont(JComponent c, String defaultBgName, String defaultFgName, String defaultFontName) Convenience method for setting a component's foreground, background and font properties with values from the defaults.static voidinstallProperty(JComponent c, String propertyName, Object propertyValue) Convenience method for installing a property with the specified name and value on a component if that property has not already been set by the developer.abstract booleanIf the underlying platform has a "native" look and feel, and this is an implementation of it, returntrue.abstract booleanReturntrueif the underlying platform supports and or permits this look and feel.static voidloadKeyBindings(InputMap retMap, Object[] keys) Populates anInputMapwith the specified bindings.static ComponentInputMapmakeComponentInputMap(JComponent c, Object[] keys) Creates aComponentInputMapUIResourcefromkeys.static ObjectCreates and returns aUIDefault.LazyValuethat loads an image.static InputMapmakeInputMap(Object[] keys) Creates anInputMapUIResourcefromkeys.static JTextComponent.KeyBinding[]makeKeyBindings(Object[] keyBindingList) Convenience method for building an array ofKeyBindings.voidprovideErrorFeedback(Component component) Invoked when the user attempts an invalid operation, such as pasting into an uneditableJTextFieldthat has focus.toString()Returns a string that displays and identifies this object's properties.voidUninitializes the look and feel.static voidConvenience method for uninstalling a border.
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Constructor Details
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LookAndFeel
protected LookAndFeel()Constructor for subclasses to call.
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Method Details
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installColors
Convenience method for setting a component's foreground and background color properties with values from the defaults. The properties are only set if the current value is eithernullor aUIResource.- Parameters:
c- component to set the colors ondefaultBgName- key for the backgrounddefaultFgName- key for the foreground- Throws:
NullPointerException- as described in exceptions- See Also:
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installColorsAndFont
public static void installColorsAndFont(JComponent c, String defaultBgName, String defaultFgName, String defaultFontName) Convenience method for setting a component's foreground, background and font properties with values from the defaults. The properties are only set if the current value is eithernullor aUIResource.- Parameters:
c- component set to the colors and font ondefaultBgName- key for the backgrounddefaultFgName- key for the foregrounddefaultFontName- key for the font- Throws:
NullPointerException- as described in exceptions- See Also:
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installBorder
Convenience method for setting a component's border property with a value from the defaults. The border is only set if the border isnullor an instance ofUIResource.- Parameters:
c- component to set the border ondefaultBorderName- key specifying the border- Throws:
NullPointerException- as described in exceptions
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uninstallBorder
Convenience method for uninstalling a border. If the border of the component is aUIResource, it is set tonull.- Parameters:
c- component to uninstall the border on- Throws:
NullPointerException- ifcisnull
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installProperty
Convenience method for installing a property with the specified name and value on a component if that property has not already been set by the developer. This method is intended to be used by ui delegate instances that need to specify a default value for a property of primitive type (boolean, int, ..), but do not wish to override a value set by the client. Since primitive property values cannot be wrapped with theUIResourcemarker, this method uses private state to determine whether the property has been set by the client.- Parameters:
c- target component to set the property onpropertyName- name of the property to setpropertyValue- value of the property- Throws:
IllegalArgumentException- if the specified property is not one which can be set using this methodClassCastException- if the property value has not been set by the developer and the type does not match the property's typeNullPointerException- ifcisnull, or the named property has not been set by the developer andpropertyValueisnull- Since:
- 1.5
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makeKeyBindings
Convenience method for building an array ofKeyBindings. While this method is not deprecated, developers should instead useActionMapandInputMapfor supplying key bindings.This method returns an array of
KeyBindings, one for each alternatingkey-actionpair inkeyBindingList. Akeycan either be aStringin the format specified by theKeyStroke.getKeyStrokemethod, or aKeyStroke. Theactionpart of the pair is aStringthat corresponds to the name of theAction.The following example illustrates creating a
KeyBindingarray from six alternatingkey-actionpairs:JTextComponent.KeyBinding[] multilineBindings = makeKeyBindings( new Object[] { "UP", DefaultEditorKit.upAction, "DOWN", DefaultEditorKit.downAction, "PAGE_UP", DefaultEditorKit.pageUpAction, "PAGE_DOWN", DefaultEditorKit.pageDownAction, "ENTER", DefaultEditorKit.insertBreakAction, "TAB", DefaultEditorKit.insertTabAction });IfkeyBindingList'slength is odd, the last element is ignored.Supplying a
nullvalue for either thekeyoractionpart of thekey-actionpair results in creating aKeyBindingwith the corresponding valuenull. As other parts of Swing's expectnon-nullvalues in aKeyBinding, you should avoid supplyingnullas either thekeyoractionpart of thekey-actionpair.- Parameters:
keyBindingList- an array ofkey-actionpairs- Returns:
- an array of
KeyBindings - Throws:
NullPointerException- ifkeyBindingListisnullClassCastException- if thekeypart of the pair is not aKeyStrokeorString, or theactionpart of the pair is not aString- See Also:
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makeInputMap
Creates anInputMapUIResourcefromkeys. This is a convenience method for creating a newInputMapUIResource, invokingloadKeyBindings(map, keys), and returning theInputMapUIResource.- Parameters:
keys- alternating pairs ofkeystroke-action keypairs as described inloadKeyBindings(javax.swing.InputMap, java.lang.Object[])- Returns:
- newly created and populated
InputMapUIResource - Since:
- 1.3
- See Also:
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makeComponentInputMap
Creates aComponentInputMapUIResourcefromkeys. This is a convenience method for creating a newComponentInputMapUIResource, invokingloadKeyBindings(map, keys), and returning theComponentInputMapUIResource.- Parameters:
c- component to create theComponentInputMapUIResourcewithkeys- alternating pairs ofkeystroke-action keypairs as described inloadKeyBindings(javax.swing.InputMap, java.lang.Object[])- Returns:
- newly created and populated
InputMapUIResource - Throws:
IllegalArgumentException- ifcisnull- Since:
- 1.3
- See Also:
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loadKeyBindings
Populates anInputMapwith the specified bindings. The bindings are supplied as a list of alternatingkeystroke-action keypairs. Thekeystrokeis either an instance ofKeyStroke, or aStringthat identifies theKeyStrokefor the binding. Refer toKeyStroke.getKeyStroke(String)for the specific format. Theaction keypart of the pair is the key registered in theInputMapfor theKeyStroke.The following illustrates loading an
InputMapwith twokey-actionpairs:LookAndFeel.loadKeyBindings(inputMap, new Object[] { "control X", "cut", "control V", "paste" });Supplying a
nulllist of bindings (keys) does not changeretMapin any way.Specifying a
nullaction keyresults in removing thekeystroke'sentry from theInputMap. Anullkeystrokeis ignored.- Parameters:
retMap-InputMapto add thekey-actionpairs tokeys- bindings to add toretMap- Throws:
NullPointerException- ifkeysisnon-null, not empty, andretMapisnull- Since:
- 1.3
- See Also:
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makeIcon
Creates and returns aUIDefault.LazyValuethat loads an image. The returned value is an implementation ofUIDefaults.LazyValue. WhencreateValueis invoked on the returned object, the image is loaded. If the image isnon-null, it is then wrapped in anIconthat implementsUIResource. The image is loaded usingClass.getResourceAsStream(gifFile).This method does not check the arguments in any way. It is strongly recommended that
non-nullvalues are supplied else exceptions may occur whencreateValueis invoked on the returned object.- Parameters:
baseClass-Classused to load the resourcegifFile- path to the image to load- Returns:
- a
UIDefaults.LazyValue; when resolved theLazyValueloads the specified image - See Also:
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getLayoutStyle
Returns theLayoutStylefor this look and feel. This never returnsnull.You generally don't use the
LayoutStylefrom the look and feel, instead use theLayoutStylemethodgetInstance.- Returns:
- the
LayoutStylefor this look and feel - Since:
- 1.6
- See Also:
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provideErrorFeedback
Invoked when the user attempts an invalid operation, such as pasting into an uneditableJTextFieldthat has focus. The default implementation beeps. Subclasses that wish different behavior should override this and provide the additional feedback.- Parameters:
component- theComponentthe error occurred in, may benullindicating the error condition is not directly associated with aComponent- Since:
- 1.4
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getDesktopPropertyValue
Returns the value of the specified system desktop property by invokingToolkit.getDefaultToolkit().getDesktopProperty(). If the value of the specified property isnull,fallbackValueis returned.- Parameters:
systemPropertyName- the name of the system desktop property being queriedfallbackValue- the object to be returned as the value if the system value is null- Returns:
- the current value of the desktop property
- Since:
- 1.4
- See Also:
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getDisabledIcon
Returns anIconwith a disabled appearance. This method is used to generate a disabledIconwhen one has not been specified. For example, if you create aJButtonand only specify anIconviasetIconthis method will be called to generate the disabledIcon. Ifnullis passed asiconthis method returnsnull.Some look and feels might not render the disabled
Icon, in which case they will ignore this.- Parameters:
component-JComponentthat will display theIcon, may benullicon-Iconto generate the disabled icon from- Returns:
- disabled
Icon, ornullif a suitableIconcan not be generated - Since:
- 1.5
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getDisabledSelectedIcon
Returns anIconfor use by disabled components that are also selected. This method is used to generate anIconfor components that are in both the disabled and selected states but do not have a specificIconfor this state. For example, if you create aJButtonand only specify anIconviasetIconthis method will be called to generate the disabled and selectedIcon. Ifnullis passed asiconthis methods returnsnull.Some look and feels might not render the disabled and selected
Icon, in which case they will ignore this.- Parameters:
component-JComponentthat will display theIcon, may benullicon-Iconto generate disabled and selected icon from- Returns:
- disabled and selected icon, or
nullif a suitableIconcan not be generated. - Since:
- 1.5
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getName
Return a short string that identifies this look and feel, e.g. "CDE/Motif". This string should be appropriate for a menu item. Distinct look and feels should have different names, e.g. a subclass of MotifLookAndFeel that changes the way a few components are rendered should be called "CDE/Motif My Way"; something that would be useful to a user trying to select a L&F from a list of names.- Returns:
- short identifier for the look and feel
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getID
Return a string that identifies this look and feel. This string will be used by applications/services that want to recognize well known look and feel implementations. Presently the well known names are "Motif", "Windows", "Mac", "Metal". Note that a LookAndFeel derived from a well known superclass that doesn't make any fundamental changes to the look or feel shouldn't override this method.- Returns:
- identifier for the look and feel
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getDescription
Return a one line description of this look and feel implementation, e.g. "The CDE/Motif Look and Feel". This string is intended for the user, e.g. in the title of a window or in a ToolTip message.- Returns:
- short description for the look and feel
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getSupportsWindowDecorations
public boolean getSupportsWindowDecorations()Returnstrueif theLookAndFeelreturnedRootPaneUIinstances support providingWindowdecorations in aJRootPane.The default implementation returns
false, subclasses that supportWindowdecorations should override this and returntrue.- Returns:
trueif theRootPaneUIinstances created by this look and feel support client side decorations- Since:
- 1.4
- See Also:
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isNativeLookAndFeel
public abstract boolean isNativeLookAndFeel()If the underlying platform has a "native" look and feel, and this is an implementation of it, returntrue. For example, when the underlying platform is Solaris running CDE a CDE/Motif look and feel implementation would returntrue.- Returns:
trueif this look and feel represents the underlying platform look and feel
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isSupportedLookAndFeel
public abstract boolean isSupportedLookAndFeel()Returntrueif the underlying platform supports and or permits this look and feel. This method returnsfalseif the look and feel depends on special resources or legal agreements that aren't defined for the current platform.- Returns:
trueif this is a supported look and feel- See Also:
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initialize
public void initialize()Initializes the look and feel. While this method is public, it should only be invoked by theUIManagerwhen a look and feel is installed as the current look and feel. This method is invoked before theUIManagerinvokesgetDefaults. This method is intended to perform any initialization for the look and feel. Subclasses should do any one-time setup they need here, rather than in a static initializer, because look and feel class objects may be loaded just to discover thatisSupportedLookAndFeel()returnsfalse.- See Also:
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uninitialize
public void uninitialize()Uninitializes the look and feel. While this method is public, it should only be invoked by theUIManagerwhen the look and feel is uninstalled. For example,UIManager.setLookAndFeelinvokes this when the look and feel is changed.Subclasses may choose to free up some resources here.
- See Also:
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getDefaults
Returns the look and feel defaults. While this method is public, it should only be invoked by theUIManagerwhen the look and feel is set as the current look and feel and afterinitializehas been invoked.- Returns:
- the look and feel defaults
- See Also:
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toString
Returns a string that displays and identifies this object's properties.
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