public class javax.swing.text
DefaultCaret


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Java SE 6
  
Extends: RectangularShape > Rectangle2D > Rectangle
Implements: Caret, FocusListener, MouseListener, MouseMotionListener
Extended by: BasicTextUI.BasicCaret
Details
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 JavaBeansTM has been added to the java.beans package. Please see java.beans.XMLEncoder.
version1.147 04/14/06
See also javax.swing.text.Caret


Fields
final public static int UPDATE_WHEN_ON_EDT Details
Indicates that the caret position is to be updated only when document changes are performed on the Event Dispatching Thread.
since1.5
See also setUpdatePolicy, getUpdatePolicy
final public static int NEVER_UPDATE Details
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.
since1.5
See also setUpdatePolicy, getUpdatePolicy
final public static int ALWAYS_UPDATE Details
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.
since1.5
See also setUpdatePolicy, getUpdatePolicy
protected EventListenerList listenerList
The event listener list.
protected 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".

Constructors
public DefaultCaret()
Constructs a default caret.

Methods
public void addChangeListener(ChangeListener l) Details
Adds a listener to track whenever the caret position has been changed.
lthe listener
See also addChangeListener
protected void adjustVisibility(Rectangle nloc) Details
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.
nlocthe new position to scroll to
protected void damage(Rectangle r) Details
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).
rthe current location of the caret
See also paint
public void deinstall(JTextComponent c) Details
Called when the UI is being removed from the interface of a JTextComponent. This is used to unregister any listeners that were attached.
cthe component
See also deinstall
public boolean equals(Object obj) Details
Compares this object to the specified object. The superclass behavior of comparing rectangles is not desired, so this is changed to the Object behavior.
objthe object to compare this font with
returntrue if the objects are equal; false otherwise
protected void fireStateChanged() Details
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 javax.swing.event.EventListenerList
public void focusGained(FocusEvent e) Details
Called when the component containing the caret gains focus. This is implemented to set the caret to visible if the component is editable.
ethe focus event
See also focusGained
public void focusLost(FocusEvent e) Details
Called when the component containing the caret loses focus. This is implemented to set the caret to visibility to false.
ethe focus event
See also focusLost
public void install(JTextComponent c) Details
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.
cthe component
See also install
public void mouseClicked(MouseEvent e) Details
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.
ethe mouse event
See also mouseClicked
public void mouseDragged(MouseEvent e) Details
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.
ethe mouse event
See also mouseDragged
public void mouseEntered(MouseEvent e) Details
Called when the mouse enters a region.
ethe mouse event
See also mouseEntered
public void mouseExited(MouseEvent e) Details
Called when the mouse exits a region.
ethe mouse event
See also mouseExited
public void mouseMoved(MouseEvent e) Details
Called when the mouse is moved.
ethe mouse event
See also mouseMoved
public void mousePressed(MouseEvent e) Details
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.
ethe mouse event
See also mousePressed
public void mouseReleased(MouseEvent e) Details
Called when the mouse is released.
ethe mouse event
See also mouseReleased
protected void moveCaret(MouseEvent e) Details
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.
ethe mouse event
public void moveDot(int dot) Details
Moves the caret position to the specified position, with a forward bias.
dotthe position >= 0
See also moveDot(int, javax.swing.text.Position.Bias), moveDot
public void moveDot(int dot, Position.Bias dotBias) Details
Moves the caret position to the specified position, with the specified bias.
dotthe position >= 0
dotBiasthe bias for this position, not null
ThrowsIllegalArgumentException: if the bias is null
since1.6
See also moveDot
public void paint(Graphics g) Details
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).
gthe graphics context
See also damage

protected void positionCaret(MouseEvent e) Details
Tries to set the position of the caret from the coordinates of a mouse event, using viewToModel().
ethe mouse event
public void removeChangeListener(ChangeListener l) Details
Removes a listener that was tracking caret position changes.
lthe listener
See also removeChangeListener
final protected 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 How to Use Threads for more information.

public String toString()

Properties
public boolean isActive() Details
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.
returntrue if active else false
since1.5
See also isVisible

public void setBlinkRate(int rate) Details
Sets the caret blink rate.
ratethe rate in milliseconds, 0 to stop blinking
See also setBlinkRate
public int getBlinkRate() Details
Gets the caret blink rate.
returnthe delay in milliseconds. If this is zero the caret will not blink.
See also getBlinkRate
public ChangeListener[] getChangeListeners() Details
Returns an array of all the change listeners registered on this caret.
returnall of this caret's ChangeListeners or an empty array if no change listeners are currently registered
since1.4
See also addChangeListener, removeChangeListener
final protected JTextComponent getComponent() Details
Gets the text editor component that this caret is is bound to.
returnthe component
public void setDot(int dot) Details
Sets the caret position and mark to the specified position, with a forward bias. This implicitly sets the selection range to zero.
dotthe position >= 0
See also setDot(int, Position.Bias), setDot
public void setDot(int dot, Position.Bias dotBias) Details
Sets the caret position and mark to the specified position, with the specified bias. This implicitly sets the selection range to zero.
dotthe position >= 0
dotBiasthe bias for this position, not null
ThrowsIllegalArgumentException: if the bias is null
since1.6
See also setDot
public int getDot() Details
Fetches the current position of the caret.
returnthe position >= 0
See also getDot
public Position.Bias getDotBias() Details
Returns the bias of the caret position.
returnthe bias of the caret position
since1.6
public EventListener[]<T> getListeners(Class listenerType) Details
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.
listenerTypethe type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener
returnan array of all objects registered as FooListeners on this component, or an empty array if no such listeners have been added
ThrowsClassCastException: if listenerType doesn't specify a class or interface that implements java.util.EventListener
since1.3
See also getChangeListeners
public void setMagicCaretPosition(Point p) Details
Saves the current caret position. This is used when caret up/down actions occur, moving between lines that have uneven end positions.
pthe position
See also getMagicCaretPosition
public Point getMagicCaretPosition() Details
Gets the saved caret position.
returnthe position see #setMagicCaretPosition
public int getMark() Details
Fetches the current position of the mark. If there is a selection, the dot and mark will not be the same.
returnthe position >= 0
See also getMark
public Position.Bias getMarkBias() Details
Returns the bias of the mark.
returnthe bias of the mark
since1.6
protected Highlighter.HighlightPainter getSelectionPainter() Details
Gets the painter for the Highlighter.
returnthe painter
public void setSelectionVisible(boolean vis) Details
Changes the selection visibility.
visthe new visibility
public boolean isSelectionVisible() Details
Checks whether the current selection is visible.
returntrue if the selection is visible
public void setUpdatePolicy(int policy) Details
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.
policyone of the following values : UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE
ThrowsIllegalArgumentException: if invalid value is passed
since1.5
See also getUpdatePolicy, adjustVisibility, UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE

public int getUpdatePolicy() Details
Gets the caret movement policy on document updates.
returnone of the following values : UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE
since1.5
See also setUpdatePolicy, UPDATE_WHEN_ON_EDT, NEVER_UPDATE, ALWAYS_UPDATE
public void setVisible(boolean e) Details
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
ethe visibility specifier
See also isActive, setVisible
public boolean isVisible() Details
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.
returntrue if visible else false
See also isVisible, isActive

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