javax.swing

Class JComponent

public abstract class JComponent extends Container implements Serializable

The base class of all Swing components. It contains generic methods to manage events, properties and sizes. Actual drawing of the component is channeled to a look-and-feel class that is implemented elsewhere.

Nested Class Summary
abstract class	JComponent.AccessibleJComponent Basic accessibility support for `JComponent` derived widgets.

Field Summary
protected AccessibleContext	accessibleContext The accessible context of this `JComponent`.
protected EventListenerList	listenerList Listeners for events other than {@link PropertyChangeEvent} are handled by this listener list.
static String	TOOL_TIP_TEXT_KEY
protected ComponentUI	ui The user interface delegate for this component.
static int	UNDEFINED_CONDITION Constant used to indicate that no condition has been assigned to a particular action.
static int	WHEN_ANCESTOR_OF_FOCUSED_COMPONENT Constant used to indicate that an action should be performed only when the component is an ancestor of the component which has focus.
static int	WHEN_FOCUSED Constant used to indicate that an action should be performed only when the component has focus.
static int	WHEN_IN_FOCUSED_WINDOW Constant used to indicate that an action should be performed only when the component is in the window which has focus.

Constructor Summary
	JComponent() Creates a new `JComponent` instance.

Method Summary
void	addAncestorListener(AncestorListener listener) Register an `AncestorListener`.
void	addNotify() Receives notification if this component is added to a parent component.
void	addVetoableChangeListener(VetoableChangeListener listener) Register a `VetoableChangeListener`.
void	computeVisibleRect(Rectangle rect) Compute the component's visible rectangle, which is defined recursively as either the component's bounds, if it has no parent, or the intersection of the component's bounds with the visible rectangle of its parent.
boolean	contains(int x, int y) Returns `true` if the coordinates (x, y) lie within the bounds of this component and `false` otherwise. x and y are relative to the coordinate space of the component.
JToolTip	createToolTip() Return the `toolTip` property of this component, creating it and setting it if it is currently `null`.
void	disable() Disables this component.
void	enable() Enables this component.
void	firePropertyChange(String property, int oldValue, int newValue) Fires a property change for a primitive integer property.
void	firePropertyChange(String property, boolean oldValue, boolean newValue) Fires a property change for a primitive boolean property.
protected void	fireVetoableChange(String propertyName, Object oldValue, Object newValue) Call {@link VetoableChangeListener#vetoableChange} on all listeners registered to listen to a given property.
AccessibleContext	getAccessibleContext() Get the value of the accessibleContext property for this component.
ActionListener	getActionForKeyStroke(KeyStroke ks) Get the ActionListener (typically an {@link Action} object) which is associated with a particular keystroke.
ActionMap	getActionMap()
float	getAlignmentX() Get the value of the {@link #alignmentX} property.
float	getAlignmentY() Get the value of the {@link #alignmentY} property.
AncestorListener[]	getAncestorListeners() Return all registered `AncestorListener` objects.
boolean	getAutoscrolls() Get the current value of the {@link #autoscrolls} property.
Border	getBorder() Get the value of the {@link #border} property.
Rectangle	getBounds(Rectangle rv) Get the component's current bounding box.
Object	getClientProperty(Object key) Get a client property associated with this component and a particular key.
protected Graphics	getComponentGraphics(Graphics g) Prepares a graphics context for painting this object.
JPopupMenu	getComponentPopupMenu() Returns the popup menu for this component.
int	getConditionForKeyStroke(KeyStroke ks) Return the condition that determines whether a registered action occurs in response to the specified keystroke.
int	getDebugGraphicsOptions() Get the value of the {@link #debugGraphicsOptions} property.
static Locale	getDefaultLocale() Returns the locale used as the default for all new components.
Graphics	getGraphics() Returns the Graphics context for this component.
int	getHeight() Returns the height of this component.
boolean	getInheritsPopupMenu() Returns the flag that controls whether or not the component inherits its parent's popup menu when no popup menu is specified for this component.
InputMap	getInputMap(int condition) Returns the input map associated with this component for the given state/condition.
InputMap	getInputMap() Returns the input map associated with this component for the {@link #WHEN_FOCUSED} state.
InputVerifier	getInputVerifier() Returns the currently set input verifier for this component.
Insets	getInsets() Get the component's insets, which are calculated from the {@link #border} property.
Insets	getInsets(Insets insets) Get the component's insets, which are calculated from the {@link #border} property.
<T extends EventListener> T[]	getListeners(Class<T> listenerType) Returns all registered {@link EventListener}s of the given `listenerType`.
Point	getLocation(Point rv) Get the component's location.
Dimension	getMaximumSize() Get the component's maximum size.
Dimension	getMinimumSize() Get the component's minimum size.
Component	getNextFocusableComponent() Return the value of the `nextFocusableComponent` property.
Dimension	getPreferredSize() Get the component's preferred size.
KeyStroke[]	getRegisteredKeyStrokes() Return the set of {@link KeyStroke} objects which are registered to initiate actions on this component.
JRootPane	getRootPane() Returns the first ancestor of this component which is a {@link JRootPane}.
Dimension	getSize(Dimension rv) Get the component's size.
Point	getToolTipLocation(MouseEvent event) Return the location at which the `toolTipText` property should be displayed, when triggered by a particular mouse event.
String	getToolTipText() Returns the current tooltip text for this component, or `null` if none has been set.
String	getToolTipText(MouseEvent event) Returns the tooltip text for this component for a particular mouse event.
Container	getTopLevelAncestor() Return the top level ancestral container (usually a {@link java.awt.Window} or {@link java.applet.Applet}) which this component is contained within, or `null` if no ancestors exist.
TransferHandler	getTransferHandler() Get the value of the {@link #transferHandler} property.
String	getUIClassID() Get the value of the UIClassID property.
boolean	getVerifyInputWhenFocusTarget()
VetoableChangeListener[]	getVetoableChangeListeners() Return all registered `VetoableChangeListener` objects.
Rectangle	getVisibleRect() Return the component's visible rectangle in a new {@link Rectangle}, rather than via a return slot.
int	getWidth() Returns the width of this component.
int	getX() Returns the X coordinate of the upper left corner of this component.
int	getY() Returns the Y coordinate of the upper left corner of this component.
void	grabFocus() Requests that this component receive input focus, giving window focus to the top level ancestor of this component.
boolean	isDoubleBuffered() Get the value of the {@link #doubleBuffered} property.
static boolean	isLightweightComponent(Component c) Return `true` if the provided component has no native peer; in other words, if it is a "lightweight component".
boolean	isManagingFocus() Return `true` if you wish this component to manage its own focus.
boolean	isOpaque() Return the current value of the {@link #opaque} property.
boolean	isOptimizedDrawingEnabled() Return `true` if the component can guarantee that none of its children will overlap in Z-order.
boolean	isPaintingTile() Return `true` if this component is currently painting a tile, this means that paint() is called again on another child component.
boolean	isRequestFocusEnabled() Get the value of the {@link #requestFocusEnabled} property.
boolean	isValidateRoot() Return `true` if this component is a validation root; this will cause calls to {@link #invalidate()} in this component's children to be "captured" at this component, and not propagate to its parents.
void	paint(Graphics g) Paint the component.
protected void	paintBorder(Graphics g) Paint the component's border.
protected void	paintChildren(Graphics g) Paint the component's children.
protected void	paintComponent(Graphics g) Paint the component's body.
void	paintImmediately(int x, int y, int w, int h) A variant of {@link #paintImmediately(Rectangle)} which takes integer parameters.
void	paintImmediately(Rectangle r) Transform the provided dirty rectangle for this component into the appropriate ancestral {@link JRootPane} and call {@link #paint} on that root pane.
protected String	paramString() Return a string representation for this component, for use in debugging.
void	print(Graphics g) Prints this component to the given Graphics context.
void	printAll(Graphics g) Prints this component to the given Graphics context.
protected void	printBorder(Graphics g) Print this component's border to the specified Graphics context.
protected void	printChildren(Graphics g) Print this component's children to the specified Graphics context.
protected void	printComponent(Graphics g) Prints this component to the specified Graphics context.
protected void	processComponentKeyEvent(KeyEvent e) A hook for subclasses which want to customize event processing.
protected boolean	processKeyBinding(KeyStroke ks, KeyEvent e, int condition, boolean pressed)
protected void	processKeyEvent(KeyEvent e) Override the default key dispatch system from Component to hook into the swing {@link InputMap} / {@link ActionMap} system.
protected void	processMouseMotionEvent(MouseEvent ev) Processes mouse motion event, like dragging and moving.
void	putClientProperty(Object key, Object value) Add a client property `value` to this component, associated with `key`.
void	registerKeyboardAction(ActionListener act, KeyStroke stroke, int cond) A variant of {@link #registerKeyboardAction(ActionListener,String,KeyStroke,int)} which provides `null` for the command name.
void	registerKeyboardAction(ActionListener act, String cmd, KeyStroke stroke, int cond) An obsolete method to register a keyboard action on this component.
void	removeAncestorListener(AncestorListener listener) Unregister an `AncestorListener`.
void	removeNotify() Receives notification that this component no longer has a parent.
void	removeVetoableChangeListener(VetoableChangeListener listener) Unregister a `VetoableChangeChangeListener`.
void	repaint(long tm, int x, int y, int width, int height) Mark the described region of this component as dirty in the current {@link RepaintManager}.
void	repaint(Rectangle r) Mark the described region of this component as dirty in the current {@link RepaintManager}.
boolean	requestDefaultFocus() Request focus on the default component of this component's {@link FocusTraversalPolicy}.
void	requestFocus() Requests that this component gets the input focus if the requestFocusEnabled property is set to `true`.
boolean	requestFocus(boolean temporary) This method is overridden to make it public so that it can be used by look and feel implementations.
boolean	requestFocusInWindow() Requests that this component gets the input focus if the top level window that contains this component has the focus and the requestFocusEnabled property is set to `true`.
protected boolean	requestFocusInWindow(boolean temporary) This method is overridden to make it public so that it can be used by look and feel implementations.
void	resetKeyboardActions() Reset all keyboard action registries.
void	reshape(int x, int y, int w, int h) Moves and resizes the component.
void	revalidate() Queue a an invalidation and revalidation of this component, using {@link RepaintManager#addInvalidComponent}.
void	scrollRectToVisible(Rectangle r) Calls `scrollRectToVisible` on the component's parent.
void	setActionMap(ActionMap map)
void	setAlignmentX(float a) Set the value of the {@link #alignmentX} property.
void	setAlignmentY(float a) Set the value of the {@link #alignmentY} property.
void	setAutoscrolls(boolean a) Set the value of the {@link #autoscrolls} property.
void	setBackground(Color bg) Set the value of the `background` property.
void	setBorder(Border newBorder) Set the value of the {@link #border} property.
void	setComponentPopupMenu(JPopupMenu popup) Sets the popup menu for this component (this is a bound property with the property name 'componentPopupMenu').
void	setDebugGraphicsOptions(int debugOptions) Set the value of the {@link #debugGraphicsOptions} property.
static void	setDefaultLocale(Locale l) Sets the locale to be used as the default for all new components.
void	setDoubleBuffered(boolean db) Set the value of the {@link #doubleBuffered} property.
void	setEnabled(boolean enable) Set the value of the `enabled` property.
void	setFont(Font f) Set the value of the `font` property.
void	setForeground(Color fg) Set the value of the `foreground` property.
void	setInheritsPopupMenu(boolean inherit) Sets the flag that controls whether or not the component inherits its parent's popup menu when no popup menu is specified for this component.
void	setInputMap(int condition, InputMap map) Sets the input map for the given condition.
void	setInputVerifier(InputVerifier verifier) Sets the input verifier to use by this component.
void	setNextFocusableComponent(Component aComponent) Set the specified component to be the next component in the focus cycle, overriding the {@link FocusTraversalPolicy} for this component.
void	setOpaque(boolean isOpaque) Set if the component should paint all pixels withing its bounds.
void	setRequestFocusEnabled(boolean e) Set the value of the {@link #requestFocusEnabled} property.
void	setToolTipText(String text) Set the tooltip text for this component.
void	setTransferHandler(TransferHandler newHandler) Set the value of the {@link #transferHandler} property.
protected void	setUI(ComponentUI newUI) Install a new UI delegate as the component's {@link #ui} property.
void	setVerifyInputWhenFocusTarget(boolean verifyInputWhenFocusTarget)
void	setVisible(boolean v) Set the value of the visible property.
void	unregisterKeyboardAction(KeyStroke aKeyStroke) Remove a keyboard action registry.
void	update(Graphics g) Call {@link #paint}.
void	updateUI() This method should be overridden in subclasses.

Field Detail

accessibleContext

protected AccessibleContext accessibleContext

The accessible context of this JComponent.

listenerList

protected EventListenerList listenerList

Listeners for events other than {@link PropertyChangeEvent} are handled by this listener list. PropertyChangeEvents are handled in {@link #changeSupport}.

TOOL_TIP_TEXT_KEY

public static final String TOOL_TIP_TEXT_KEY

ui

protected ComponentUI ui

The user interface delegate for this component. Event delivery and repainting of the component are usually delegated to this object.

UNDEFINED_CONDITION

public static final int UNDEFINED_CONDITION

Constant used to indicate that no condition has been assigned to a particular action.

See Also: JComponent

WHEN_ANCESTOR_OF_FOCUSED_COMPONENT

public static final int WHEN_ANCESTOR_OF_FOCUSED_COMPONENT

Constant used to indicate that an action should be performed only when the component is an ancestor of the component which has focus.

See Also: JComponent

WHEN_FOCUSED

public static final int WHEN_FOCUSED

Constant used to indicate that an action should be performed only when the component has focus.

See Also: JComponent

WHEN_IN_FOCUSED_WINDOW

public static final int WHEN_IN_FOCUSED_WINDOW

Constant used to indicate that an action should be performed only when the component is in the window which has focus.

See Also: JComponent

Constructor Detail

JComponent

public JComponent()

Creates a new JComponent instance.

Method Detail

addAncestorListener

public void addAncestorListener(AncestorListener listener)

Parameters: listener The listener to register

See Also: JComponent

addNotify

public void addNotify()

Receives notification if this component is added to a parent component. Notification is sent to all registered AncestorListeners about the new parent. This method sets up ActionListeners for all registered KeyStrokes of this component in the chain of parent components. A PropertyChange event is fired to indicate that the ancestor property has changed. This method is used internally and should not be used in applications.

addVetoableChangeListener

public void addVetoableChangeListener(VetoableChangeListener listener)

Parameters: listener The listener to register

computeVisibleRect

public void computeVisibleRect(Rectangle rect)

Compute the component's visible rectangle, which is defined recursively as either the component's bounds, if it has no parent, or the intersection of the component's bounds with the visible rectangle of its parent.

Parameters: rect The return value slot to place the visible rectangle in

contains

public boolean contains(int x, int y)

Returns true if the coordinates (x, y) lie within the bounds of this component and false otherwise. x and y are relative to the coordinate space of the component.

Parameters: x the X coordinate of the point to check y the Y coordinate of the point to check

Returns: true if the specified point lies within the bounds of this component, false otherwise

createToolTip

public JToolTip createToolTip()

Return the toolTip property of this component, creating it and setting it if it is currently null. This method can be overridden in subclasses which wish to control the exact form of tooltip created.

Returns: The current toolTip

disable

public void disable()

Deprecated: replaced by {@link #setEnabled(boolean)}

Disables this component.

enable

public void enable()

Deprecated: replaced by {@link #setEnabled(boolean)}

Enables this component.

firePropertyChange

public void firePropertyChange(String property, int oldValue, int newValue)

Fires a property change for a primitive integer property.

Parameters: property the name of the property oldValue the old value of the property newValue the new value of the property

UNKNOWN: This method is implemented in {@link Component#firePropertyChange(String, int, int)}. It is only here because it is specified to be public, whereas the Component method is protected.

firePropertyChange

public void firePropertyChange(String property, boolean oldValue, boolean newValue)

Fires a property change for a primitive boolean property.

Parameters: property the name of the property oldValue the old value of the property newValue the new value of the property

UNKNOWN: This method is implemented in {@link Component#firePropertyChange(String, boolean, boolean)}. It is only here because it is specified to be public, whereas the Component method is protected.

fireVetoableChange

protected void fireVetoableChange(String propertyName, Object oldValue, Object newValue)

Call {@link VetoableChangeListener#vetoableChange} on all listeners registered to listen to a given property. Any method which changes the specified property of this component should call this method.

Parameters: propertyName The property which changed oldValue The old value of the property newValue The new value of the property

Throws: PropertyVetoException if the change was vetoed by a listener

getAccessibleContext

public AccessibleContext getAccessibleContext()

Get the value of the accessibleContext property for this component.

Returns: the current value of the property

getActionForKeyStroke

public ActionListener getActionForKeyStroke(KeyStroke ks)

Get the ActionListener (typically an {@link Action} object) which is associated with a particular keystroke.

Parameters: ks The keystroke to retrieve the action of

Returns: The action associated with the specified keystroke

getActionMap

public final ActionMap getActionMap()

getAlignmentX

public float getAlignmentX()

Get the value of the {@link #alignmentX} property.

Returns: The current value of the property.

getAlignmentY

public float getAlignmentY()

Get the value of the {@link #alignmentY} property.

Returns: The current value of the property.

getAncestorListeners

public AncestorListener[] getAncestorListeners()

Return all registered AncestorListener objects.

Returns: The set of AncestorListener objects in {@link #listenerList}

getAutoscrolls

public boolean getAutoscrolls()

Get the current value of the {@link #autoscrolls} property.

Returns: The current value of the property

getBorder

public Border getBorder()

Get the value of the {@link #border} property.

Returns: The property's current value

See Also: JComponent

getBounds

public Rectangle getBounds(Rectangle rv)

Get the component's current bounding box. If a rectangle is provided, use this as the return value (adjusting its fields in place); otherwise (of null is provided) return a new {@link Rectangle}.

Parameters: rv Optional return value to use

Returns: A rectangle bounding the component

getClientProperty

public final Object getClientProperty(Object key)

Get a client property associated with this component and a particular key.

Parameters: key The key with which to look up the client property

Returns: A client property associated with this object and key

getComponentGraphics

protected Graphics getComponentGraphics(Graphics g)

Prepares a graphics context for painting this object. If {@link #debugGraphicsOptions} is not equal to {@link DebugGraphics#NONE_OPTION}, produce a new {@link DebugGraphics} object wrapping the parameter. Otherwise configure the parameter with this component's foreground color and font.

Parameters: g The graphics context to wrap or configure

Returns: A graphics context to paint this object with

getComponentPopupMenu

public JPopupMenu getComponentPopupMenu()

Returns the popup menu for this component. If the popup menu is null AND the {@link #getInheritsPopupMenu()} method returns true, this method will return the parent's popup menu (if it has one).

Returns: The popup menu (possibly null.

Since: 1.5

getConditionForKeyStroke

public int getConditionForKeyStroke(KeyStroke ks)

Return the condition that determines whether a registered action occurs in response to the specified keystroke. As of 1.3 KeyStrokes can be registered with multiple simultaneous conditions.

Parameters: ks The keystroke to return the condition of

Returns: One of the values {@link #UNDEFINED_CONDITION}, {@link #WHEN_ANCESTOR_OF_FOCUSED_COMPONENT}, {@link #WHEN_FOCUSED}, or {@link #WHEN_IN_FOCUSED_WINDOW}

getDebugGraphicsOptions

public int getDebugGraphicsOptions()

Get the value of the {@link #debugGraphicsOptions} property.

Returns: The current value of the property.

getDefaultLocale

public static Locale getDefaultLocale()

Returns the locale used as the default for all new components. The default value is {@link Locale#getDefault()} (that is, the platform default locale).

Returns: The locale (never null).

getGraphics

public Graphics getGraphics()

Returns the Graphics context for this component. This can be used to draw on a component.

Returns: the Graphics context for this component

getHeight

public int getHeight()

Returns the height of this component. Prefer this method over {@link #getBounds} or {@link #getSize} because it does not cause any heap allocation.

Returns: the height of the component

getInheritsPopupMenu

public boolean getInheritsPopupMenu()

Returns the flag that controls whether or not the component inherits its parent's popup menu when no popup menu is specified for this component.

Returns: A boolean.

Since: 1.5

See Also: JComponent

getInputMap

public final InputMap getInputMap(int condition)

Returns the input map associated with this component for the given state/condition.

Parameters: condition the state (one of {@link #WHEN_FOCUSED}, {@link #WHEN_ANCESTOR_OF_FOCUSED_COMPONENT} and {@link #WHEN_IN_FOCUSED_WINDOW}).

Returns: The input map.

Throws: IllegalArgumentException if condition is not one of the specified values.

Since: 1.3

getInputMap

public final InputMap getInputMap()

Returns the input map associated with this component for the {@link #WHEN_FOCUSED} state.

Returns: The input map.

Since: 1.3

See Also: JComponent

getInputVerifier

public InputVerifier getInputVerifier()

Returns the currently set input verifier for this component.

Returns: the input verifier, or null if none

getInsets

public Insets getInsets()

Get the component's insets, which are calculated from the {@link #border} property. If the border is null, calls {@link Container#getInsets}.

Returns: The component's current insets

getInsets

public Insets getInsets(Insets insets)

Get the component's insets, which are calculated from the {@link #border} property. If the border is null, calls {@link Container#getInsets}. The passed-in {@link Insets} value will be used as the return value, if possible.

Parameters: insets Return value object to reuse, if possible

Returns: The component's current insets

getListeners

public <T extends EventListener> T[] getListeners(Class<T> listenerType)

Returns all registered {@link EventListener}s of the given listenerType.

Parameters: listenerType the class of listeners to filter (null not permitted).

Returns: An array of registered listeners.

Throws: ClassCastException if listenerType does not implement the {@link EventListener} interface. NullPointerException if listenerType is null.

Since: 1.3

getLocation

public Point getLocation(Point rv)

Get the component's location. The passed-in {@link Point} value will be used as the return value, if possible.

Parameters: rv Return value object to reuse, if possible

Returns: The component's current location

getMaximumSize

public Dimension getMaximumSize()

Get the component's maximum size. If the maximumSize property has been explicitly set, it is returned. If the maximumSize property has not been set but the {@link #ui} property has been, the result of {@link ComponentUI#getMaximumSize} is returned. If neither property has been set, the result of {@link Container#getMaximumSize} is returned.

Returns: the maximum size of the component

getMinimumSize

public Dimension getMinimumSize()

Get the component's minimum size. If the minimumSize property has been explicitly set, it is returned. If the minimumSize property has not been set but the {@link #ui} property has been, the result of {@link ComponentUI#getMinimumSize} is returned. If neither property has been set, the result of {@link Container#getMinimumSize} is returned.

Returns: The minimum size of the component

getNextFocusableComponent

public Component getNextFocusableComponent()

Deprecated: See {@link java.awt.FocusTraversalPolicy}

Return the value of the nextFocusableComponent property.

Returns: The current value of the property, or null if none has been set.

getPreferredSize

public Dimension getPreferredSize()

Get the component's preferred size. If the preferredSize property has been explicitly set, it is returned. If the preferredSize property has not been set but the {@link #ui} property has been, the result of {@link ComponentUI#getPreferredSize} is returned. If neither property has been set, the result of {@link Container#getPreferredSize} is returned.

Returns: The preferred size of the component

getRegisteredKeyStrokes

public KeyStroke[] getRegisteredKeyStrokes()

Return the set of {@link KeyStroke} objects which are registered to initiate actions on this component.

Returns: An array of the registered keystrokes (possibly empty but never null).

getRootPane

public JRootPane getRootPane()

Returns the first ancestor of this component which is a {@link JRootPane}. Equivalent to calling SwingUtilities.getRootPane(this);.

Returns: An ancestral JRootPane, or null if none exists.

getSize

public Dimension getSize(Dimension rv)

Get the component's size. The passed-in {@link Dimension} value will be used as the return value, if possible.

Parameters: rv Return value object to reuse, if possible

Returns: The component's current size

getToolTipLocation

public Point getToolTipLocation(MouseEvent event)

Return the location at which the toolTipText property should be displayed, when triggered by a particular mouse event.

Parameters: event The event the tooltip is being presented in response to

Returns: The point at which to display a tooltip, or null if swing is to choose a default location.

getToolTipText

public String getToolTipText()

Returns the current tooltip text for this component, or null if none has been set.

Returns: the current tooltip text for this component, or null if none has been set

getToolTipText

public String getToolTipText(MouseEvent event)

Returns the tooltip text for this component for a particular mouse event. This can be used to support context sensitive tooltips that can change with the mouse location. By default this returns the static tooltip text returned by {@link #getToolTipText()}.

Parameters: event the mouse event which triggered the tooltip

Returns: the tooltip text for this component for a particular mouse event

getTopLevelAncestor

public Container getTopLevelAncestor()

Return the top level ancestral container (usually a {@link java.awt.Window} or {@link java.applet.Applet}) which this component is contained within, or null if no ancestors exist.

Returns: The top level container, if it exists

getTransferHandler

public TransferHandler getTransferHandler()

Get the value of the {@link #transferHandler} property.

Returns: The current value of the property

See Also: JComponent

getUIClassID

public String getUIClassID()

Get the value of the UIClassID property. This property should be a key in the {@link UIDefaults} table managed by {@link UIManager}, the value of which is the name of a class to load for the component's {@link #ui} property.

Returns: A "symbolic" name which will map to a class to use for the component's UI, such as "ComponentUI"

getVerifyInputWhenFocusTarget

public boolean getVerifyInputWhenFocusTarget()

Since: 1.3

getVetoableChangeListeners

public VetoableChangeListener[] getVetoableChangeListeners()

Return all registered VetoableChangeListener objects.

Returns: An array of the VetoableChangeListener objects registered with this component (possibly empty but never null).

Since: 1.4

getVisibleRect

public Rectangle getVisibleRect()

Return the component's visible rectangle in a new {@link Rectangle}, rather than via a return slot.

Returns: the component's visible rectangle

getWidth

public int getWidth()

Returns the width of this component. Prefer this method over {@link #getBounds} or {@link #getSize} because it does not cause any heap allocation.

Returns: the width of the component

getX

public int getX()

Returns the X coordinate of the upper left corner of this component. Prefer this method over {@link #getBounds} or {@link #getLocation} because it does not cause any heap allocation.

Returns: the X coordinate of the upper left corner of the component

getY

public int getY()

Returns the Y coordinate of the upper left corner of this component. Prefer this method over {@link #getBounds} or {@link #getLocation} because it does not cause any heap allocation.

Returns: the Y coordinate of the upper left corner of the component

grabFocus

public void grabFocus()

Requests that this component receive input focus, giving window focus to the top level ancestor of this component. Only works on displayable, focusable, visible components.

This method should not be called by clients; it is intended for focus implementations. Use {@link Component#requestFocus()} instead.

isDoubleBuffered

public boolean isDoubleBuffered()

Get the value of the {@link #doubleBuffered} property.

Returns: The property's current value

isLightweightComponent

public static boolean isLightweightComponent(Component c)

Return true if the provided component has no native peer; in other words, if it is a "lightweight component".

Parameters: c The component to test for lightweight-ness

Returns: Whether or not the component is lightweight

isManagingFocus

public boolean isManagingFocus()

Deprecated: 1.4 Use {@link Component#setFocusTraversalKeys(int, Set)} and {@link Container#setFocusCycleRoot(boolean)} instead

Return true if you wish this component to manage its own focus. In particular: if you want this component to be sent TAB and SHIFT+TAB key events, and to not have its children considered as focus transfer targets. If true, focus traversal around this component changes to CTRL+TAB and CTRL+SHIFT+TAB.

Returns: true if you want this component to manage its own focus, otherwise (by default) false

isOpaque

public boolean isOpaque()

Return the current value of the {@link #opaque} property.

Returns: The current property value

isOptimizedDrawingEnabled

public boolean isOptimizedDrawingEnabled()

Return true if the component can guarantee that none of its children will overlap in Z-order. This is a hint to the painting system. The default is to return true, but some components such as {@link JLayeredPane} should override this to return false.

Returns: Whether the component tiles its children

isPaintingTile

public boolean isPaintingTile()

Return true if this component is currently painting a tile, this means that paint() is called again on another child component. This method returns false if this component does not paint a tile or if the last tile is currently painted.

Returns: whether the component is painting a tile

isRequestFocusEnabled

public boolean isRequestFocusEnabled()

Get the value of the {@link #requestFocusEnabled} property.

Returns: The current value of the property

isValidateRoot

public boolean isValidateRoot()

Return true if this component is a validation root; this will cause calls to {@link #invalidate()} in this component's children to be "captured" at this component, and not propagate to its parents. For most components this should return false, but some components such as {@link JViewport} will want to return true.

Returns: Whether this component is a validation root

paint

public void paint(Graphics g)

Paint the component. This is a delicate process, and should only be called from the repaint thread, under control of the {@link RepaintManager}. Client code should usually call {@link #repaint()} to trigger painting.

The body of the paint call involves calling {@link #paintComponent}, {@link #paintBorder}, and {@link #paintChildren} in order. If you want to customize painting behavior, you should override one of these methods rather than paint.

For more details on the painting sequence, see this article.

Parameters: g The graphics context to paint with

paintBorder

protected void paintBorder(Graphics g)

Paint the component's border. This usually means calling {@link Border#paintBorder} on the {@link #border} property, if it is non-null. You may override this if you wish to customize border painting behavior. The border is painted after the component's body, but before the component's children.

Parameters: g The graphics context with which to paint the border

paintChildren

protected void paintChildren(Graphics g)

Paint the component's children. This usually means calling {@link Container#paint}, which recursively calls {@link #paint} on any of the component's children, with appropriate changes to coordinate space and clipping region. You may override this if you wish to customize children painting behavior. The children are painted after the component's body and border.

Parameters: g The graphics context with which to paint the children

paintComponent

protected void paintComponent(Graphics g)

Paint the component's body. This usually means calling {@link ComponentUI#update} on the {@link #ui} property of the component, if it is non-null. You may override this if you wish to customize the component's body-painting behavior. The component's body is painted first, before the border and children.

Parameters: g The graphics context with which to paint the body

paintImmediately

public void paintImmediately(int x, int y, int w, int h)

A variant of {@link #paintImmediately(Rectangle)} which takes integer parameters.

Parameters: x The left x coordinate of the dirty region y The top y coordinate of the dirty region w The width of the dirty region h The height of the dirty region

paintImmediately

public void paintImmediately(Rectangle r)

Transform the provided dirty rectangle for this component into the appropriate ancestral {@link JRootPane} and call {@link #paint} on that root pane. This method is called from the {@link RepaintManager} and should always be called within the painting thread.

This method will acquire a double buffer from the {@link RepaintManager} if the component's {@link #doubleBuffered} property is true and the paint call is the first recursive paint call inside swing.

The method will also modify the provided {@link Graphics} context via the {@link #getComponentGraphics} method. If you want to customize the graphics object used for painting, you should override that method rather than paint.

Parameters: r The dirty rectangle to paint

paramString

protected String paramString()

Return a string representation for this component, for use in debugging.

Returns: A string describing this component.

print

public void print(Graphics g)

Prints this component to the given Graphics context. A call to this method results in calls to the methods {@link #printComponent}, {@link #printBorder} and {@link #printChildren} in this order. Double buffering is temporarily turned off so the painting goes directly to the supplied Graphics context.