javax.swing.text
Class DefaultCaret

java.lang.Object
  |
  +--java.awt.geom.RectangularShape
        |
        +--java.awt.geom.Rectangle2D
              |
              +--java.awt.Rectangle
                    |
                    +--javax.swing.text.DefaultCaret

Direct Known Subclasses:

BasicTextUI.BasicCaret

public class DefaultCaret

extends Rectangle

implements Caret, FocusListener, MouseListener, MouseMotionListener

A default implementation of Caret. The caret is rendered as a vertical line in the color specified by the CaretColor property of the associated JTextComponent. It can blink at the rate specified by the BlinkRate property.

This implementation expects two sources of asynchronous notification. The timer thread fires asynchronously, and causes the caret to simply repaint the most recent bounding box. The caret also tracks change as the document is modified. Typically this will happen on the event thread as a result of some mouse or keyboard event. Updates can also occur from some other thread mutating the document. There is a property AsynchronousMovement that determines if the caret will move on asynchronous updates. The default behavior is to not update on asynchronous updates. If asynchronous updates are allowed, the update thread will fire the caret position change to listeners asynchronously. The repaint of the new caret location will occur on the event thread in any case, as calls to modelToView are only safe on the event thread.

The caret acts as a mouse and focus listener on the text component it has been installed in, and defines the caret semantics based upon those events. The listener methods can be reimplemented to change the semantics. By default, the first mouse button will be used to set focus and caret position. Dragging the mouse pointer with the first mouse button will sweep out a selection that is contiguous in the model. If the associated text component is editable, the caret will become visible when focus is gained, and invisible when focus is lost.

The Highlighter bound to the associated text component is used to render the selection by default. Selection appearance can be customized by supplying a painter to use for the highlights. By default a painter is used that will render a solid color as specified in the associated text component in the SelectionColor property. This can easily be changed by reimplementing the getSelectionHighlighter method.

A customized caret appearance can be achieved by reimplementing the paint method. If the paint method is changed, the damage method should also be reimplemented to cause a repaint for the area needed to render the caret. The caret extends the Rectangle class which is used to hold the bounding box for where the caret was last rendered. This enables the caret to repaint in a thread-safe manner when the caret moves without making a call to modelToView which is unstable between model updates and view repair (i.e. the order of delivery to DocumentListeners is not guaranteed).

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. A future release of Swing will provide support for long term persistence.

See Also:

Caret, Serialized Form

Inner classes inherited from class java.awt.geom.Rectangle2D

Rectangle2D.Double, Rectangle2D.Float

Field Summary

protected ChangeEvent	changeEvent The change event for the model.
protected EventListenerList	listenerList The event listener list.

Fields inherited from class java.awt.Rectangle

height, width, x, y

Fields inherited from class java.awt.geom.Rectangle2D

OUT_BOTTOM, OUT_LEFT, OUT_RIGHT, OUT_TOP

Constructor Summary

DefaultCaret()
Constructs a default caret.

Method Summary

void	addChangeListener(ChangeListener l) Adds a listener to track whenever the caret position has been changed.
protected void	adjustVisibility(Rectangle nloc) Scrolls the associated view (if necessary) to make the caret visible.
protected void	damage(Rectangle r) Damages the area surrounding the caret to cause it to be repainted in a new location.
void	deinstall(JTextComponent c) Called when the UI is being removed from the interface of a JTextComponent.
protected void	fireStateChanged() Notifies all listeners that have registered interest for notification on this event type.
void	focusGained(FocusEvent e) Called when the component containing the caret gains focus.
void	focusLost(FocusEvent e) Called when the component containing the caret loses focus.
int	getBlinkRate() Gets the caret blink rate.
protected JTextComponent	getComponent() Gets the text editor component that this caret is is bound to.
int	getDot() Fetches the current position of the caret.
Point	getMagicCaretPosition() Gets the saved caret position.
int	getMark() Fetches the current position of the mark.
protected Highlighter.HighlightPainter	getSelectionPainter() Gets the painter for the Highlighter.
void	install(JTextComponent c) Called when the UI is being installed into the interface of a JTextComponent.
boolean	isSelectionVisible() Checks whether the current selection is visible.
boolean	isVisible() Determines if the caret is currently visible.
void	mouseClicked(MouseEvent e) Called when the mouse is clicked.
void	mouseDragged(MouseEvent e) Moves the caret position according to the mouse pointer's current location.
void	mouseEntered(MouseEvent e) Called when the mouse enters a region.
void	mouseExited(MouseEvent e) Called when the mouse exits a region.
void	mouseMoved(MouseEvent e) Called when the mouse is moved.
void	mousePressed(MouseEvent e) If button 1 is pressed, this is implemented to request focus on the associated text component, and to set the caret position.
void	mouseReleased(MouseEvent e) Called when the mouse is released.
protected void	moveCaret(MouseEvent e) Tries to move the position of the caret from the coordinates of a mouse event, using viewToModel().
void	moveDot(int dot) Moves the caret position to some other position.
void	paint(Graphics g) Renders the caret as a vertical line.
protected void	positionCaret(MouseEvent e) Tries to set the position of the caret from the coordinates of a mouse event, using viewToModel().
void	removeChangeListener(ChangeListener l) Removes a listener that was tracking caret position changes.
protected void	repaint() Cause the caret to be painted.
void	setBlinkRate(int rate) Sets the caret blink rate.
void	setDot(int dot) Sets the caret position and mark to some position.
void	setMagicCaretPosition(Point p) Saves the current caret position.
void	setSelectionVisible(boolean vis) Changes the selection visibility.
void	setVisible(boolean e) Sets the caret visibility, and repaints the caret.
String	toString()

Methods inherited from class java.awt.Rectangle

add, add, add, contains, contains, contains, contains, createIntersection, createUnion, equals, getBounds, getBounds2D, getHeight, getLocation, getSize, getWidth, getX, getY, grow, inside, intersection, intersects, isEmpty, move, outcode, reshape, resize, setBounds, setBounds, setLocation, setLocation, setRect, setSize, setSize, translate, union

Methods inherited from class java.awt.geom.Rectangle2D

add, add, add, contains, contains, getPathIterator, getPathIterator, hashCode, intersect, intersects, intersectsLine, intersectsLine, outcode, setFrame, setRect, union

Methods inherited from class java.awt.geom.RectangularShape

clone, contains, contains, getCenterX, getCenterY, getFrame, getMaxX, getMaxY, getMinX, getMinY, intersects, setFrame, setFrame, setFrameFromCenter, setFrameFromCenter, setFrameFromDiagonal, setFrameFromDiagonal

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

listenerList

protected EventListenerList listenerList

The event listener list.

changeEvent

protected transient ChangeEvent changeEvent

The change event for the model. Only one ChangeEvent is needed per model instance since the event's only (read-only) state is the source property. The source of events generated here is always "this".

Constructor Detail

DefaultCaret

public DefaultCaret()

Constructs a default caret.

Method Detail

getComponent

protected final JTextComponent getComponent()

Gets the text editor component that this caret is is bound to.

Returns:

the component

repaint

protected final void repaint()

Cause the caret to be painted. The repaint area is the bounding box of the caret (i.e. the caret rectangle or this).

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

damage

protected void damage(Rectangle r)

Damages the area surrounding the caret to cause it to be repainted in a new location. If paint() is reimplemented, this method should also be reimplemented. This method should update the caret bounds (x, y, width, and height).

Parameters:

r - the current location of the caret

See Also:

paint(java.awt.Graphics)

adjustVisibility

protected void adjustVisibility(Rectangle nloc)

Scrolls the associated view (if necessary) to make the caret visible. Since how this should be done is somewhat of a policy, this method can be reimplemented to change the behavior. By default the scrollRectToVisible method is called on the associated component.

Parameters:

nloc - the new position to scroll to

getSelectionPainter

protected Highlighter.HighlightPainter getSelectionPainter()

Gets the painter for the Highlighter.

Returns:

the painter

positionCaret

protected void positionCaret(MouseEvent e)

Tries to set the position of the caret from the coordinates of a mouse event, using viewToModel().

Parameters:

e - the mouse event

moveCaret

protected void moveCaret(MouseEvent e)

Tries to move the position of the caret from the coordinates of a mouse event, using viewToModel(). This will cause a selection if the dot and mark are different.

Parameters:

e - the mouse event

focusGained

public void focusGained(FocusEvent e)

Called when the component containing the caret gains focus. This is implemented to set the caret to visible if the component is editable.

Specified by:

focusGained in interface FocusListener

Parameters:

e - the focus event

See Also:

FocusListener.focusGained(java.awt.event.FocusEvent)

focusLost

public void focusLost(FocusEvent e)

Called when the component containing the caret loses focus. This is implemented to set the caret to visibility to false.

Specified by:

focusLost in interface FocusListener

Parameters:

e - the focus event

See Also:

FocusListener.focusLost(java.awt.event.FocusEvent)

mouseClicked

public void mouseClicked(MouseEvent e)

Called when the mouse is clicked. If the click was generated from button1, a double click selects a word, and a triple click the current line.

Specified by:

mouseClicked in interface MouseListener

Parameters:

e - the mouse event

See Also:

MouseListener.mouseClicked(java.awt.event.MouseEvent)

mousePressed

public void mousePressed(MouseEvent e)

If button 1 is pressed, this is implemented to request focus on the associated text component, and to set the caret position. If the component is not enabled, there will be no request for focus.

Specified by:

mousePressed in interface MouseListener

Parameters:

e - the mouse event

See Also:

MouseListener.mousePressed(java.awt.event.MouseEvent)

mouseReleased

public void mouseReleased(MouseEvent e)

Called when the mouse is released.

Specified by:

mouseReleased in interface MouseListener

Parameters:

e - the mouse event

See Also:

MouseListener.mouseReleased(java.awt.event.MouseEvent)

mouseEntered

public void mouseEntered(MouseEvent e)

Called when the mouse enters a region.

Specified by:

mouseEntered in interface MouseListener

Parameters:

e - the mouse event

See Also:

MouseListener.mouseEntered(java.awt.event.MouseEvent)

mouseExited

public void mouseExited(MouseEvent e)

Called when the mouse exits a region.

Specified by:

mouseExited in interface MouseListener

Parameters:

e - the mouse event

See Also:

MouseListener.mouseExited(java.awt.event.MouseEvent)

mouseDragged

public void mouseDragged(MouseEvent e)

Moves the caret position according to the mouse pointer's current location. This effectively extends the selection.

Specified by:

mouseDragged in interface MouseMotionListener

Parameters:

e - the mouse event

See Also:

MouseMotionListener.mouseDragged(java.awt.event.MouseEvent)

mouseMoved

public void mouseMoved(MouseEvent e)

Called when the mouse is moved.

Specified by:

mouseMoved in interface MouseMotionListener

Parameters:

e - the mouse event

See Also:

MouseMotionListener.mouseMoved(java.awt.event.MouseEvent)

paint

public void paint(Graphics g)

Renders the caret as a vertical line. If this is reimplemented the damage method should also be reimplemented as it assumes the shape of the caret is a vertical line. Sets the caret color to the value returned by getCaretColor().

If there are multiple text directions present in the associated document, a flag indicating the caret bias will be rendered. This will occur only if the associated document is a subclass of AbstractDocument and there are multiple bidi levels present in the bidi element structure (i.e. the text has multiple directions associated with it).

Specified by:

paint in interface Caret

Parameters:

g - the graphics context

See Also:

damage(java.awt.Rectangle)

install

public void install(JTextComponent c)

Called when the UI is being installed into the interface of a JTextComponent. This can be used to gain access to the model that is being navigated by the implementation of this interface. Sets the dot and mark to 0, and establishes document, property change, focus, mouse, and mouse motion listeners.

Specified by:

install in interface Caret

Parameters:

c - the component

See Also:

Caret.install(javax.swing.text.JTextComponent)

deinstall

public void deinstall(JTextComponent c)

Called when the UI is being removed from the interface of a JTextComponent. This is used to unregister any listeners that were attached.

Specified by:

deinstall in interface Caret

Parameters:

c - the component

See Also:

Caret.deinstall(javax.swing.text.JTextComponent)

addChangeListener

public void addChangeListener(ChangeListener l)

Adds a listener to track whenever the caret position has been changed.

Specified by:

addChangeListener in interface Caret

Parameters:

l - the listener

See Also:

Caret.addChangeListener(javax.swing.event.ChangeListener)

removeChangeListener

public void removeChangeListener(ChangeListener l)

Removes a listener that was tracking caret position changes.

Specified by:

removeChangeListener in interface Caret

Parameters:

l - the listener

See Also:

Caret.removeChangeListener(javax.swing.event.ChangeListener)

fireStateChanged

protected void fireStateChanged()

Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created using the parameters passed into the fire method. The listener list is processed last to first.

See Also:

EventListenerList

setSelectionVisible

public void setSelectionVisible(boolean vis)

Changes the selection visibility.

Specified by:

setSelectionVisible in interface Caret

Parameters:

vis - the new visibility

isSelectionVisible

public boolean isSelectionVisible()

Checks whether the current selection is visible.

Specified by:

isSelectionVisible in interface Caret

Returns:

true if the selection is visible

isVisible

public boolean isVisible()

Determines if the caret is currently visible.

Specified by:

isVisible in interface Caret

Returns:

true if visible else false

See Also:

Caret.isVisible()

setVisible

public void setVisible(boolean e)

Sets the caret visibility, and repaints the caret.

Specified by:

setVisible in interface Caret

Parameters:

e - the visibility specifier

See Also:

Caret.setVisible(boolean)

setBlinkRate

public void setBlinkRate(int rate)

Sets the caret blink rate.

Specified by:

setBlinkRate in interface Caret

Parameters:

rate - the rate in milliseconds, 0 to stop blinking

See Also:

Caret.setBlinkRate(int)

getBlinkRate

public int getBlinkRate()

Gets the caret blink rate.

Specified by:

getBlinkRate in interface Caret

See Also:

Caret.getBlinkRate()

getDot

public int getDot()

Fetches the current position of the caret.

Specified by:

getDot in interface Caret

Returns:

the position >= 0

See Also:

Caret.getDot()

getMark

public int getMark()

Fetches the current position of the mark. If there is a selection, the dot and mark will not be the same.

Specified by:

getMark in interface Caret

Returns:

the position >= 0

See Also:

Caret.getMark()

setDot

public void setDot(int dot)

Sets the caret position and mark to some position. This implicitly sets the selection range to zero.

Specified by:

setDot in interface Caret

Parameters:

dot - the position >= 0

See Also:

Caret.setDot(int)

moveDot

public void moveDot(int dot)

Moves the caret position to some other position.

Specified by:

moveDot in interface Caret

Parameters:

dot - the position >= 0

See Also:

Caret.moveDot(int)

setMagicCaretPosition

public void setMagicCaretPosition(Point p)

Saves the current caret position. This is used when caret up/down actions occur, moving between lines that have uneven end positions.

Specified by:

setMagicCaretPosition in interface Caret

Parameters:

p - the position

See Also:

getMagicCaretPosition(), UpAction, DownAction

getMagicCaretPosition

public Point getMagicCaretPosition()

Gets the saved caret position.

Specified by:

getMagicCaretPosition in interface Caret

Returns:

the position see #setMagicCaretPosition

toString

public String toString()

Overrides:

toString in class Rectangle