Class LookAndFeel

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

ComponentUIs and defaults

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

JComponent c;
   Font font = c.getFont();
   if (font == null || (font instanceof UIResource)) {
       c.setFont(UIManager.getFont("fontKey"));
   }

Constructors

LookAndFeel

public LookAndFeel()

Methods

installColors

public static void installColors(JComponent c,
                                 String defaultBgName,
                                 String defaultFgName)

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 either null or a UIResource.

Parameters:

c - component to set the colors on

defaultBgName - key for the background

defaultFgName - key for the foreground

Throws:

NullPointerException - as described in exceptions

See Also:

installColorsAndFont(javax.swing.JComponent, java.lang.String, java.lang.String, java.lang.String), UIManager.getColor(java.lang.Object)

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 either null or a UIResource.

Parameters:

c - component set to the colors and font on

defaultBgName - key for the background

defaultFgName - key for the foreground

defaultFontName - key for the font

Throws:

NullPointerException - as described in exceptions

See Also:

installColors(javax.swing.JComponent, java.lang.String, java.lang.String), UIManager.getColor(java.lang.Object), UIManager.getFont(java.lang.Object)

installBorder

public static void installBorder(JComponent c,
                                 String defaultBorderName)

Convenience method for setting a component's border property with a value from the defaults. The border is only set if the border is null or an instance of UIResource.

Parameters:

c - component to set the border on

defaultBorderName - key specifying the border

Throws:

NullPointerException - as described in exceptions

uninstallBorder

public static void uninstallBorder(JComponent c)

Convenience method for uninstalling a border. If the border of the component is a UIResource, it is set to null.

Parameters:

c - component to uninstall the border on

Throws:

NullPointerException - if c is null

installProperty

public static void installProperty(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. 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 the UIResource marker, this method uses private state to determine whether the property has been set by the client.

Parameters:

c - target component to set the property on

propertyName - name of the property to set

propertyValue - value of the property

Throws:

IllegalArgumentException - if the specified property is not one which can be set using this method

ClassCastException - if the property value has not been set by the developer and the type does not match the property's type

NullPointerException - if c is null, or the named property has not been set by the developer and propertyValue is null

Since:

1.5

makeKeyBindings

public static JTextComponent.KeyBinding[] makeKeyBindings(Object[] keyBindingList)

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
  });

Parameters:

keyBindingList - an array of key-action pairs

Returns:

an array of KeyBindings

Throws:

NullPointerException - if keyBindingList is null

ClassCastException - if the key part of the pair is not a KeyStroke or String, or the action part of the pair is not a String

See Also:

ActionMap, InputMap, KeyStroke.getKeyStroke(char)

makeInputMap

public static InputMap makeInputMap(Object[] keys)

Creates a InputMapUIResource from keys. This is a convenience method for creating a new InputMapUIResource, invoking loadKeyBindings(map, keys), and returning the InputMapUIResource.

Parameters:

keys - alternating pairs of keystroke-action key pairs as described in loadKeyBindings(javax.swing.InputMap, java.lang.Object[])

Returns:

newly created and populated InputMapUIResource

Since:

1.3

See Also:

loadKeyBindings(javax.swing.InputMap, java.lang.Object[])

makeComponentInputMap

public static ComponentInputMap makeComponentInputMap(JComponent c,
                                                      Object[] keys)

Creates a ComponentInputMapUIResource from keys. This is a convenience method for creating a new ComponentInputMapUIResource, invoking loadKeyBindings(map, keys), and returning the ComponentInputMapUIResource.

Parameters:

c - component to create the ComponentInputMapUIResource with

keys - alternating pairs of keystroke-action key pairs as described in loadKeyBindings(javax.swing.InputMap, java.lang.Object[])

Returns:

newly created and populated InputMapUIResource

Throws:

IllegalArgumentException - if c is null

Since:

1.3

See Also:

loadKeyBindings(javax.swing.InputMap, java.lang.Object[]), ComponentInputMapUIResource

loadKeyBindings

public static void loadKeyBindings(InputMap retMap,
                                   Object[] keys)

LookAndFeel.loadKeyBindings(inputMap, new Object[] {
     "control X", "cut",
     "control V", "paste"
   });

Parameters:

retMap - InputMap to add the key-action pairs to

keys - bindings to add to retMap

Throws:

NullPointerException - if keys is non-null, not empty, and retMap is null

Since:

1.3

See Also:

KeyStroke.getKeyStroke(String), InputMap

makeIcon

public static Object makeIcon(Class<?> baseClass,
                              String gifFile)

Parameters:

baseClass - Class used to load the resource

gifFile - path to the image to load

Returns:

a UIDefaults.LazyValue; when resolved the LazyValue loads the specified image

See Also:

UIDefaults.LazyValue, Icon, Class.getResourceAsStream(String)

getLayoutStyle

public LayoutStyle getLayoutStyle()

Returns:

the LayoutStyle for this look and feel

Since:

1.6

See Also:

LayoutStyle.getInstance()

provideErrorFeedback

public void provideErrorFeedback(Component component)

Invoked when the user attempts an invalid operation, such as pasting into an uneditable JTextField that has focus. The default implementation beeps. Subclasses that wish different behavior should override this and provide the additional feedback.

Parameters:

component - the Component the error occurred in, may be null indicating the error condition is not directly associated with a Component

Since:

1.4

getDesktopPropertyValue

public static Object getDesktopPropertyValue(String systemPropertyName,
                                             Object fallbackValue)

Returns the value of the specified system desktop property by invoking Toolkit.getDefaultToolkit().getDesktopProperty(). If the value of the specified property is null, fallbackValue is returned.

Parameters:

systemPropertyName - the name of the system desktop property being queried

fallbackValue - 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:

Toolkit.getDesktopProperty(java.lang.String)

getDisabledIcon

public Icon getDisabledIcon(JComponent component,
                            Icon icon)

Parameters:

component - JComponent that will display the Icon, may be null

icon - Icon to generate the disabled icon from

Returns:

disabled Icon, or null if a suitable Icon can not be generated

Since:

1.5

getDisabledSelectedIcon

public Icon getDisabledSelectedIcon(JComponent component,
                                    Icon icon)

Parameters:

component - JComponent that will display the Icon, may be null

icon - Icon to generate disabled and selected icon from

Returns:

disabled and selected icon, or null if a suitable Icon can not be generated.

Since:

1.5

getName

public abstract String 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

getID

public abstract String 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

getDescription

public abstract String 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

getSupportsWindowDecorations

public boolean getSupportsWindowDecorations()

Returns:

true if the RootPaneUI instances created by this look and feel support client side decorations

Since:

1.4

See Also:

JDialog.setDefaultLookAndFeelDecorated(boolean), JFrame.setDefaultLookAndFeelDecorated(boolean), JRootPane.setWindowDecorationStyle(int)

isNativeLookAndFeel

public abstract boolean isNativeLookAndFeel()

If the underlying platform has a "native" look and feel, and this is an implementation of it, return true. For example, when the underlying platform is Solaris running CDE a CDE/Motif look and feel implementation would return true.

Returns:

true if this look and feel represents the underlying platform look and feel

isSupportedLookAndFeel

public abstract boolean isSupportedLookAndFeel()

Return true if the underlying platform supports and or permits this look and feel. This method returns false if the look and feel depends on special resources or legal agreements that aren't defined for the current platform.

Returns:

true if this is a supported look and feel

See Also:

UIManager.setLookAndFeel(javax.swing.LookAndFeel)

initialize

public void initialize()

Initializes the look and feel. While this method is public, it should only be invoked by the UIManager when a look and feel is installed as the current look and feel. This method is invoked before the UIManager invokes getDefaults. 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 that isSupportedLookAndFeel() returns false.

See Also:

uninitialize(), UIManager.setLookAndFeel(javax.swing.LookAndFeel)

uninitialize

public void uninitialize()

See Also:

initialize(), UIManager.setLookAndFeel(javax.swing.LookAndFeel)

getDefaults

public UIDefaults getDefaults()

Returns the look and feel defaults. While this method is public, it should only be invoked by the UIManager when the look and feel is set as the current look and feel and after initialize has been invoked.

Returns:

the look and feel defaults

See Also:

initialize(), uninitialize(), UIManager.setLookAndFeel(javax.swing.LookAndFeel)

toString

public String toString()

Returns a string that displays and identifies this object's properties.

Overrides:

toString in class Object

Returns:

a String representation of this object