javax.swing.text
Class DefaultCaret

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

All Implemented Interfaces:

FocusListener, MouseListener, MouseMotionListener, Shape, Serializable, Cloneable, EventListener, Caret

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 dispatch thread as a result of some mouse or keyboard event. The caret behavior on both synchronous and asynchronous documents updates is controlled by UpdatePolicy property. 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).

The magic caret position is set to null when the caret position changes. A timer is used to determine the new location (after the caret change). When the timer fires, if the magic caret position is still null it is reset to the current caret position. Any actions that change the caret position and want the magic caret position to remain the same, must remember the magic caret position, change the cursor, and then set the magic caret position to its original value. This has the benefit that only actions that want the magic caret position to persist (such as open/down) need to know about it.

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. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see XMLEncoder.

See Also:

Caret

Nested Class Summary

 

Nested classes/interfaces inherited from class java.awt.geom.Rectangle2D
Rectangle2D.Double, Rectangle2D.Float

 

Field Summary
static int	ALWAYS_UPDATE           Indicates that the caret position is to be always updated accordingly to the document changes regardless whether the document updates are performed on the Event Dispatching Thread or not.
protected  ChangeEvent	changeEvent           The change event for the model.
protected  EventListenerList	listenerList           The event listener list.
static int	NEVER_UPDATE           Indicates that the caret should remain at the same absolute position in the document regardless of any document updates, except when the document length becomes less than the current caret position due to removal.
static int	UPDATE_WHEN_ON_EDT           Indicates that the caret position is to be updated only when document changes are performed on the Event Dispatching Thread.

 

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.
boolean	equals(Object obj)           Compares this object to the specified object.
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.
ChangeListener[]	getChangeListeners()           Returns an array of all the change listeners registered on this caret.
protected  JTextComponent	getComponent()           Gets the text editor component that this caret is is bound to.
int	getDot()           Fetches the current position of the caret.
<T extends EventListener> T[]	getListeners(Class<T> listenerType)           Returns an array of all the objects currently registered as FooListeners upon this 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.
int	getUpdatePolicy()           Gets the caret movement policy on document updates.
void	install(JTextComponent c)           Called when the UI is being installed into the interface of a JTextComponent.
boolean	isActive()           Determines if the caret is currently active.
boolean	isSelectionVisible()           Checks whether the current selection is visible.
boolean	isVisible()           Indicates whether or not 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	setUpdatePolicy(int policy)           Sets the caret movement policy on the document updates.
void	setVisible(boolean e)           Sets the caret visibility, and repaints the caret.
String	toString()           Returns a String representing this Rectangle and its values.

 

Methods inherited from class java.awt.Rectangle
add, add, add, contains, contains, contains, contains, createIntersection, createUnion, 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

 

Methods inherited from interface java.awt.Shape
contains, contains, contains, contains, getPathIterator, getPathIterator, intersects, intersects

 

Field Detail

UPDATE_WHEN_ON_EDT

public static final int UPDATE_WHEN_ON_EDT

Indicates that the caret position is to be updated only when document changes are performed on the Event Dispatching Thread.

Since:

1.5

See Also:

setUpdatePolicy(int), getUpdatePolicy(), Constant Field Values

NEVER_UPDATE

public static final int NEVER_UPDATE

Indicates that the caret should remain at the same absolute position in the document regardless of any document updates, except when the document length becomes less than the current caret position due to removal. In that case the caret position is adjusted to the end of the document.

Since:

1.5

See Also:

setUpdatePolicy(int), getUpdatePolicy(), Constant Field Values

ALWAYS_UPDATE

public static final int ALWAYS_UPDATE

Indicates that the caret position is to be always updated accordingly to the document changes regardless whether the document updates are performed on the Event Dispatching Thread or not.

Since:

1.5

See Also:

setUpdatePolicy(int), getUpdatePolicy(), Constant Field Values

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".

DefaultCaret

public DefaultCaret()

Constructs a default caret.

setUpdatePolicy

public void setUpdatePolicy(int policy)

Sets the caret movement policy on the document updates. Normally the caret updates its absolute position within the document on insertions occurred before or at the caret position and on removals before the caret position. 'Absolute position' means here the position relative to the start of the document. For example if a character is typed within editable text component it is inserted at the caret position and the caret moves to the next absolute position within the document due to insertion and if BACKSPACE is typed then caret decreases its absolute position due to removal of a character before it. Sometimes it may be useful to turn off the caret position updates so that the caret stays at the same absolute position within the document position regardless of any document updates.

The following update policies are allowed:

• NEVER_UPDATE: the caret stays at the same absolute position in the document regardless of any document updates, except when document length becomes less than the current caret position due to removal. In that case caret position is adjusted to the end of the document. The caret doesn't try to keep itself visible by scrolling the associated view when using this policy.
• ALWAYS_UPDATE: the caret always tracks document changes. For regular changes it increases its position if an insertion occurs before or at its current position, and decreases position if a removal occurs before its current position. For undo/redo updates it is always moved to the position where update occurred. The caret also tries to keep itself visible by calling adjustVisibility method.
• UPDATE_WHEN_ON_EDT: acts like ALWAYS_UPDATE if the document updates are performed on the Event Dispatching Thread and like NEVER_UPDATE if updates are performed on other thread.

The default property value is UPDATE_WHEN_ON_EDT.

Parameters:

policy - one of the following values : UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE

Throws:

IllegalArgumentException - if invalid value is passed

Since:

1.5

See Also:

getUpdatePolicy(), adjustVisibility(java.awt.Rectangle), UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE

getUpdatePolicy

public int getUpdatePolicy()

Gets the caret movement policy on document updates.

Returns:

one of the following values : UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE

Since:

1.5

See Also:

setUpdatePolicy(int), UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE

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 shift key is held down, the caret will be moved, potentially resulting in a selection, otherwise the caret position will be set to the new location. 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. By default, this is only done for mouse button 1.

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)

getChangeListeners

public ChangeListener[] getChangeListeners()

Returns an array of all the change listeners registered on this caret.

Returns:

all of this caret's ChangeListeners or an empty array if no change listeners are currently registered

Since:

1.4

See Also:

addChangeListener(javax.swing.event.ChangeListener), 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

getListeners

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

Returns an array of all the objects currently registered as FooListeners upon this caret. FooListeners are registered using the addFooListener method.

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a DefaultCaret c for its change listeners with the following code:

ChangeListener[] cls = (ChangeListener[])(c.getListeners(ChangeListener.class));

If no such listeners exist, this method returns an empty array.

Parameters:

listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener

Returns:

an array of all objects registered as FooListeners on this component, or an empty array if no such listeners have been added

Throws:

ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener

Since:

1.3

See Also:

getChangeListeners()

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

isActive

public boolean isActive()

Determines if the caret is currently active.

This method returns whether or not the Caret is currently in a blinking state. It does not provide information as to whether it is currently blinked on or off. To determine if the caret is currently painted use the isVisible method.

Returns:

true if active else false

Since:

1.5

See Also:

isVisible()

isVisible

public boolean isVisible()

Indicates whether or not the caret is currently visible. As the caret flashes on and off the return value of this will change between true, when the caret is painted, and false, when the caret is not painted. isActive indicates whether or not the caret is in a blinking state, such that it can be visible, and isVisible indicates whether or not the caret is actually visible.

Subclasses that wish to render a different flashing caret should override paint and only paint the caret if this method returns true.

Specified by:

isVisible in interface Caret

Returns:

true if visible else false

See Also:

Caret.isVisible(), isActive()

setVisible

public void setVisible(boolean e)

Sets the caret visibility, and repaints the caret. It is important to understand the relationship between this method, isVisible and isActive. Calling this method with a value of true activates the caret blinking. Setting it to false turns it completely off. To determine whether the blinking is active, you should call isActive. In effect, isActive is an appropriate corresponding "getter" method for this one. isVisible can be used to fetch the current visibility status of the caret, meaning whether or not it is currently painted. This status will change as the caret blinks on and off.

Here's a list showing the potential return values of both isActive and isVisible after calling this method:

setVisible(true):

• isActive(): true
• isVisible(): true or false depending on whether or not the caret is blinked on or off

setVisible(false):

• isActive(): false
• isVisible(): false

Specified by:

setVisible in interface Caret

Parameters:

e - the visibility specifier

See Also:

isActive(), 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

Returns:

the delay in milliseconds. If this is zero the caret will not blink.

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()

getMagicCaretPosition

public Point getMagicCaretPosition()

Gets the saved caret position.

Specified by:

getMagicCaretPosition in interface Caret

Returns:

the position see #setMagicCaretPosition

See Also:

Caret.setMagicCaretPosition(java.awt.Point)

equals

public boolean equals(Object obj)

Compares this object to the specified object. The superclass behavior of comparing rectangles is not desired, so this is changed to the Object behavior.

Overrides:

equals in class Rectangle

Parameters:

obj - the object to compare this font with

Returns:

true if the objects are equal; false otherwise

See Also:

Object.hashCode(), Hashtable

toString

public String toString()

Description copied from class: Rectangle

Returns a String representing this Rectangle and its values.

Overrides:

toString in class Rectangle

Returns:

a String representing this Rectangle object's coordinate and size values.