Module java.desktop
Package javax.swing.text

Interface Caret

All Known Implementing Classes:
BasicTextUI.BasicCaret, DefaultCaret
public interface Caret
A place within a document view that represents where things can be inserted into the document model. A caret has a position in the document referred to as a dot. The dot is where the caret is currently located in the model. There is a second position maintained by the caret that represents the other end of a selection called mark. If there is no selection the dot and mark will be equal. If a selection exists, the two values will be different.

The dot can be placed by either calling setDot or moveDot. Setting the dot has the effect of removing any selection that may have previously existed. The dot and mark will be equal. Moving the dot has the effect of creating a selection as the mark is left at whatever position it previously had.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addChangeListener(ChangeListener l)
    Adds a listener to track whenever the caret position has been changed.
    void
    deinstall(JTextComponent c)
    Called when the UI is being removed from the interface of a JTextComponent.
    int
    getBlinkRate()
    Gets the blink rate of the caret.
    int
    getDot()
    Fetches the current position of the caret.
    Point
    getMagicCaretPosition()
    Gets the current caret visual location.
    int
    getMark()
    Fetches the current position of the mark.
    void
    install(JTextComponent c)
    Called when the UI is being installed into the interface of a JTextComponent.
    boolean
    isSelectionVisible()
    Determines if the selection is currently visible.
    boolean
    isVisible()
    Determines if the caret is currently visible.
    void
    moveDot(int dot)
    Moves the caret position (dot) to some other position, leaving behind the mark.
    void
    paint(Graphics g)
    Renders the caret.
    void
    removeChangeListener(ChangeListener l)
    Removes a listener that was tracking caret position changes.
    void
    setBlinkRate(int rate)
    Sets the blink rate of the caret.
    void
    setDot(int dot)
    Sets the caret position to some position.
    void
    setMagicCaretPosition(Point p)
    Set the current caret visual location.
    void
    setSelectionVisible(boolean v)
    Sets the visibility of the selection
    void
    setVisible(boolean v)
    Sets the visibility of the caret.

  • Method Details

    • install

      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.
      Parameters:
      c - the JTextComponent

    • deinstall

      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.
      Parameters:
      c - the JTextComponent

    • paint

      void paint(Graphics g)
      Renders the caret. This method is called by UI classes.
      Parameters:
      g - the graphics context

    • addChangeListener

      void addChangeListener(ChangeListener l)
      Adds a listener to track whenever the caret position has been changed.
      Parameters:
      l - the change listener

    • removeChangeListener

      void removeChangeListener(ChangeListener l)
      Removes a listener that was tracking caret position changes.
      Parameters:
      l - the change listener

    • isVisible

      boolean isVisible()
      Determines if the caret is currently visible.
      Returns:
      true if the caret is visible else false

    • setVisible

      void setVisible(boolean v)
      Sets the visibility of the caret.
      Parameters:
      v - true if the caret should be shown, and false if the caret should be hidden

    • isSelectionVisible

      boolean isSelectionVisible()
      Determines if the selection is currently visible.
      Returns:
      true if the caret is visible else false

    • setSelectionVisible

      void setSelectionVisible(boolean v)
      Sets the visibility of the selection
      Parameters:
      v - true if the caret should be shown, and false if the caret should be hidden

    • setMagicCaretPosition

      void setMagicCaretPosition(Point p)
      Set the current caret visual location. This can be used when moving between lines that have uneven end positions (such as when caret up or down actions occur). If text flows left-to-right or right-to-left the x-coordinate will indicate the desired navigation location for vertical movement. If the text flow is top-to-bottom, the y-coordinate will indicate the desired navigation location for horizontal movement.
      Parameters:
      p - the Point to use for the saved position. This can be null to indicate there is no visual location.

    • getMagicCaretPosition

      Point getMagicCaretPosition()
      Gets the current caret visual location.
      Returns:
      the visual position.
      See Also:

    • setBlinkRate

      void setBlinkRate(int rate)
      Sets the blink rate of the caret. This determines if and how fast the caret blinks, commonly used as one way to attract attention to the caret.
      Parameters:
      rate - the delay in milliseconds >=0. If this is zero the caret will not blink.

    • getBlinkRate

      int getBlinkRate()
      Gets the blink rate of the caret. This determines if and how fast the caret blinks, commonly used as one way to attract attention to the caret.
      Returns:
      the delay in milliseconds >=0. If this is zero the caret will not blink.

    • getDot

      int getDot()
      Fetches the current position of the caret.
      Returns:
      the position >=0

    • getMark

      int getMark()
      Fetches the current position of the mark. If there is a selection, the mark will not be the same as the dot.
      Returns:
      the position >=0

    • setDot

      void setDot(int dot)
      Sets the caret position to some position. This causes the mark to become the same as the dot, effectively setting the selection range to zero.

      If the parameter is negative or beyond the length of the document, the caret is placed at the beginning or at the end, respectively.

      Parameters:
      dot - the new position to set the caret to

    • moveDot

      void moveDot(int dot)
      Moves the caret position (dot) to some other position, leaving behind the mark. This is useful for making selections.
      Parameters:
      dot - the new position to move the caret to >=0