java.awt
Class TextComponent

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.TextComponent

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable

Direct Known Subclasses:

TextArea, TextField

public class TextComponent

extends Component

The TextComponent class is the superclass of any component that allows the editing of some text.

A text component embodies a string of text. The TextComponent class defines a set of methods that determine whether or not this text is editable. If the component is editable, it defines another set of methods that supports a text insertion caret.

In addition, the class defines methods that are used to maintain a current selection from the text. The text selection, a substring of the component's text, is the target of editing operations. It is also referred to as the selected text.

Since:

JDK1.0

See Also:

Serialized Form

Field Summary

protected TextListener

textListener

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Method Summary

void	addTextListener(TextListener l) Adds the specified text event listener to receive text events from this text component.
int	getCaretPosition() Gets the position of the text insertion caret for this text component.
String	getSelectedText() Gets the selected text from the text that is presented by this text component.
int	getSelectionEnd() Gets the end position of the selected text in this text component.
int	getSelectionStart() Gets the start position of the selected text in this text component.
String	getText() Gets the text that is presented by this text component.
boolean	isEditable() Indicates whether or not this text component is editable.
protected String	paramString() Returns the parameter string representing the state of this text component.
protected void	processEvent(AWTEvent e) Processes events on this text component.
protected void	processTextEvent(TextEvent e) Processes text events occurring on this text component by dispatching them to any registered TextListener objects.
void	removeTextListener(TextListener l) Removes the specified text event listener so that it no longer receives text events from this text component If l is null, no exception is thrown and no action is performed.
void	select(int selectionStart, int selectionEnd) Selects the text between the specified start and end positions.
void	selectAll() Selects all the text in this text component.
void	setCaretPosition(int position) Sets the position of the text insertion caret for this text component.
void	setEditable(boolean b) Sets the flag that determines whether or not this text component is editable.
void	setSelectionEnd(int selectionEnd) Sets the selection end for this text component to the specified position.
void	setSelectionStart(int selectionStart) Sets the selection start for this text component to the specified position.
void	setText(String t) Sets the text that is presented by this text component to be the specified text.

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addKeyListener, addMouseListener, addMouseMotionListener, addNotify, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, getAlignmentX, getAlignmentY, getBackground, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getCursor, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPreferredSize, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setCursor, setEnabled, setFont, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus, update, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

textListener

protected transient TextListener textListener

Method Detail

setText

public void setText(String t)

Sets the text that is presented by this text component to be the specified text.

Parameters:

t - the new text. If this parameter is null then the text is set to the empty string "".

See Also:

getText()

getText

public String getText()

Gets the text that is presented by this text component.

See Also:

setText(java.lang.String)

getSelectedText

public String getSelectedText()

Gets the selected text from the text that is presented by this text component.

Returns:

the selected text of this text component.

See Also:

select(int, int)

isEditable

public boolean isEditable()

Indicates whether or not this text component is editable.

Returns:

true if this text component is editable; false otherwise.

Since:

JDK1.0

See Also:

setEditable(boolean)

setEditable

public void setEditable(boolean b)

Sets the flag that determines whether or not this text component is editable.

If the flag is set to true, this text component becomes user editable. If the flag is set to false, the user cannot change the text of this text component. By default, non-editable text components have a background color of SystemColor.control. This default can be overridden by calling setBackground.

Parameters:

b - a flag indicating whether this text component is user editable.

Since:

JDK1.0

See Also:

isEditable()

getSelectionStart

public int getSelectionStart()

Gets the start position of the selected text in this text component.

Returns:

the start position of the selected text.

See Also:

setSelectionStart(int), getSelectionEnd()

setSelectionStart

public void setSelectionStart(int selectionStart)

Sets the selection start for this text component to the specified position. The new start point is constrained to be at or before the current selection end. It also cannot be set to less than zero, the beginning of the component's text. If the caller supplies a value for selectionStart that is out of bounds, the method enforces these constraints silently, and without failure.

Parameters:

selectionStart - the start position of the selected text.

Since:

JDK1.1

See Also:

getSelectionStart(), setSelectionEnd(int)

getSelectionEnd

public int getSelectionEnd()

Gets the end position of the selected text in this text component.

Returns:

the end position of the selected text.

See Also:

setSelectionEnd(int), getSelectionStart()

setSelectionEnd

public void setSelectionEnd(int selectionEnd)

Sets the selection end for this text component to the specified position. The new end point is constrained to be at or after the current selection start. It also cannot be set beyond the end of the component's text. If the caller supplies a value for selectionEnd that is out of bounds, the method enforces these constraints silently, and without failure.

Parameters:

selectionEnd - the end position of the selected text.

Since:

JDK1.1

See Also:

getSelectionEnd(), setSelectionStart(int)

select

public void select(int selectionStart,
                   int selectionEnd)

Selects the text between the specified start and end positions.

This method sets the start and end positions of the selected text, enforcing the restriction that the start position must be greater than or equal to zero. The end position must be greater than or equal to the start position, and less than or equal to the length of the text component's text. The character positions are indexed starting with zero. The length of the selection is endPosition-startPosition, so the character at endPosition is not selected. If the start and end positions of the selected text are equal, all text is deselected.

If the caller supplies values that are inconsistent or out of bounds, the method enforces these constraints silently, and without failure. Specifically, if the start position or end position is greater than the length of the text, it is reset to equal the text length. If the start position is less than zero, it is reset to zero, and if the end position is less than the start position, it is reset to the start position.

Parameters:

selectionStart - the zero-based index of the first character to be selected.

selectionEnd - the zero-based end position of the text to be selected. The character at selectionEnd is not selected.

See Also:

setSelectionStart(int), setSelectionEnd(int), selectAll()

selectAll

public void selectAll()

Selects all the text in this text component.

See Also:

select(int, int)

setCaretPosition

public void setCaretPosition(int position)

Sets the position of the text insertion caret for this text component. The caret position is constrained to be at or before the current selection end. If the caller supplies a value for position that is greater than the end of the component's text, the caret position is set to the end of the component's text. This happens silently and without failure. The caret position also cannot be set to less than zero, the beginning of the component's text. If the caller supplies a value for position that is less than zero, an IllegalArgumentException is thrown.

Parameters:

position - the position of the text insertion caret.

Throws:

IllegalArgumentException - if the value supplied for position is less than zero.

Since:

JDK1.1

getCaretPosition

public int getCaretPosition()

Gets the position of the text insertion caret for this text component.

Returns:

the position of the text insertion caret.

Since:

JDK1.1

addTextListener

public void addTextListener(TextListener l)

Adds the specified text event listener to receive text events from this text component. If l is null, no exception is thrown and no action is performed.

Parameters:

l - the text event listener

removeTextListener

public void removeTextListener(TextListener l)

Removes the specified text event listener so that it no longer receives text events from this text component If l is null, no exception is thrown and no action is performed.

Parameters:

l - the text listener.

Since:

JDK1.1

See Also:

TextListener, addTextListener(java.awt.event.TextListener)

processEvent

protected void processEvent(AWTEvent e)

Processes events on this text component. If the event is a TextEvent, it invokes the processTextEvent method, else it invokes its superclass's processEvent.

Overrides:

processEvent in class Component

Parameters:

e - the event

See Also:

Component.processComponentEvent(java.awt.event.ComponentEvent), Component.processFocusEvent(java.awt.event.FocusEvent), Component.processKeyEvent(java.awt.event.KeyEvent), Component.processMouseEvent(java.awt.event.MouseEvent), Component.processMouseMotionEvent(java.awt.event.MouseEvent)

processTextEvent

protected void processTextEvent(TextEvent e)

Processes text events occurring on this text component by dispatching them to any registered TextListener objects. NOTE: This method will not be called unless text events are enabled for this component. This happens when one of the following occurs: a) A TextListener object is registered via addTextListener() b) Text events are enabled via enableEvents()

Parameters:

e - the text event

See Also:

Component.enableEvents(long)

paramString

protected String paramString()

Returns the parameter string representing the state of this text component. This string is useful for debugging.

Overrides:

paramString in class Component

Returns:

the parameter string of this text component.