java.lang.Object | |||||
↳ | java.awt.Component | ||||
↳ | java.awt.Container | ||||
↳ | javax.swing.JComponent | ||||
↳ | javax.swing.text.JTextComponent | ||||
↳ | javax.swing.JTextArea |
A JTextArea
is a multi-line area that displays plain text.
It is intended to be a lightweight component that provides source
compatibility with the java.awt.TextArea
class where it can
reasonably do so.
You can find information and examples of using all the text components in
Using Text Components,
a section in The Java Tutorial.
This component has capabilities not found in the
java.awt.TextArea
class. The superclass should be
consulted for additional capabilities.
Alternative multi-line text classes with
more capabilities are JTextPane
and JEditorPane
.
The java.awt.TextArea
internally handles scrolling.
JTextArea
is different in that it doesn't manage scrolling,
but implements the swing Scrollable
interface. This allows it
to be placed inside a JScrollPane
if scrolling
behavior is desired, and used directly if scrolling is not desired.
The java.awt.TextArea
has the ability to do line wrapping.
This was controlled by the horizontal scrolling policy. Since
scrolling is not done by JTextArea
directly, backward
compatibility must be provided another way. JTextArea
has
a bound property for line wrapping that controls whether or
not it will wrap lines. By default, the line wrapping property
is set to false (not wrapped).
java.awt.TextArea
has two properties rows
and columns
that are used to determine the preferred size.
JTextArea
uses these properties to indicate the
preferred size of the viewport when placed inside a JScrollPane
to match the functionality provided by java.awt.TextArea
.
JTextArea
has a preferred size of what is needed to
display all of the text, so that it functions properly inside of
a JScrollPane
. If the value for rows
or columns
is equal to zero,
the preferred size along that axis is used for
the viewport preferred size along the same axis.
The java.awt.TextArea
could be monitored for changes by adding
a TextListener
for TextEvent
s.
In the JTextComponent
based
components, changes are broadcasted from the model via a
DocumentEvent
to DocumentListeners
.
The DocumentEvent
gives
the location of the change and the kind of change if desired.
The code fragment might look something like:
DocumentListener myListener = ??; JTextArea myArea = ??; myArea.getDocument().addDocumentListener(myListener);
Warning: Swing is not thread safe. For more information see Swing's Threading Policy.
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 XMLEncoder
.
Nested Classes | |||||||||||
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JTextArea.AccessibleJTextArea | This class implements accessibility support for the
JTextArea class. |
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Inherited Constants | |||||||||||
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Inherited Fields | |||||||||||
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Public Constructors | |||||||||||
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Constructs a new TextArea.
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Constructs a new TextArea with the specified text displayed.
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Constructs a new empty TextArea with the specified number of
rows and columns.
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Constructs a new TextArea with the specified text and number
of rows and columns.
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Constructs a new JTextArea with the given document model, and defaults
for all of the other arguments (null, 0, 0).
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Constructs a new JTextArea with the specified number of rows
and columns, and the given model.
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Public Methods | |||||||||||
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Appends the given text to the end of the document.
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Gets the AccessibleContext associated with this JTextArea.
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Returns the number of columns in the TextArea.
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Determines the number of lines contained in the area.
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Determines the offset of the end of the given line.
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Translates an offset into the components text to a
line number.
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Determines the offset of the start of the given line.
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Gets the line-wrapping policy of the text area.
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Returns the preferred size of the viewport if this component
is embedded in a JScrollPane.
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Returns the preferred size of the TextArea.
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Returns the number of rows in the TextArea.
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Returns true if a viewport should always force the width of this
Scrollable to match the width of the viewport.
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Components that display logical rows or columns should compute
the scroll increment that will completely expose one new row
or column, depending on the value of orientation.
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Gets the number of characters used to expand tabs.
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Returns the class ID for the UI.
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Gets the style of wrapping used if the text area is wrapping
lines.
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Inserts the specified text at the specified position.
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Replaces text from the indicated start to end position with the
new text specified.
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Sets the number of columns for this TextArea.
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Sets the current font.
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Sets the line-wrapping policy of the text area.
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Sets the number of rows for this TextArea.
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Sets the number of characters to expand tabs to.
| |||||||||||
Sets the style of wrapping used if the text area is wrapping
lines.
|
Protected Methods | |||||||||||
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Creates the default implementation of the model
to be used at construction if one isn't explicitly
given.
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Gets column width.
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Defines the meaning of the height of a row.
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Returns a string representation of this JTextArea.
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Constructs a new TextArea. A default model is set, the initial string is null, and rows/columns are set to 0.
Constructs a new TextArea with the specified text displayed. A default model is created and rows/columns are set to 0.
text | the text to be displayed, or null |
---|
Constructs a new empty TextArea with the specified number of rows and columns. A default model is created, and the initial string is null.
rows | the number of rows >= 0 |
---|---|
columns | the number of columns >= 0 |
IllegalArgumentException | if the rows or columns arguments are negative. |
---|
Constructs a new TextArea with the specified text and number of rows and columns. A default model is created.
text | the text to be displayed, or null |
---|---|
rows | the number of rows >= 0 |
columns | the number of columns >= 0 |
IllegalArgumentException | if the rows or columns arguments are negative. |
---|
Constructs a new JTextArea with the given document model, and defaults for all of the other arguments (null, 0, 0).
doc | the model to use |
---|
Constructs a new JTextArea with the specified number of rows and columns, and the given model. All of the constructors feed through this constructor.
doc | the model to use, or create a default one if null |
---|---|
text | the text to be displayed, null if none |
rows | the number of rows >= 0 |
columns | the number of columns >= 0 |
IllegalArgumentException | if the rows or columns arguments are negative. |
---|
Appends the given text to the end of the document. Does nothing if the model is null or the string is null or empty.
This method is thread safe, although most Swing methods are not. Please see How to Use Threads for more information.
str | the text to insert |
---|
Gets the AccessibleContext associated with this JTextArea. For JTextAreas, the AccessibleContext takes the form of an AccessibleJTextArea. A new AccessibleJTextArea instance is created if necessary.
Returns the number of columns in the TextArea.
Determines the number of lines contained in the area.
Determines the offset of the end of the given line.
line | the line >= 0 |
---|
BadLocationException | Thrown if the line is less than zero or greater or equal to the number of lines contained in the document (as reported by getLineCount). |
---|
Translates an offset into the components text to a line number.
offset | the offset >= 0 |
---|
BadLocationException | thrown if the offset is less than zero or greater than the document length. |
---|
Determines the offset of the start of the given line.
line | the line number to translate >= 0 |
---|
BadLocationException | thrown if the line is less than zero or greater or equal to the number of lines contained in the document (as reported by getLineCount). |
---|
Gets the line-wrapping policy of the text area. If set to true the lines will be wrapped if they are too long to fit within the allocated width. If set to false, the lines will always be unwrapped.
Returns the preferred size of the viewport if this component is embedded in a JScrollPane. This uses the desired column and row settings if they have been set, otherwise the superclass behavior is used.
Returns the preferred size of the TextArea. This is the maximum of the size needed to display the text and the size requested for the viewport.
Returns the number of rows in the TextArea.
Returns true if a viewport should always force the width of this Scrollable to match the width of the viewport. This is implemented to return true if the line wrapping policy is true, and false if lines are not being wrapped.
Components that display logical rows or columns should compute
the scroll increment that will completely expose one new row
or column, depending on the value of orientation. This is implemented
to use the values returned by the getRowHeight
and
getColumnWidth
methods.
Scrolling containers, like JScrollPane, will use this method each time the user requests a unit scroll.
visibleRect | the view area visible within the viewport |
---|---|
orientation | Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL. |
direction | Less than zero to scroll up/left, greater than zero for down/right. |
IllegalArgumentException | for an invalid orientation |
---|
Gets the number of characters used to expand tabs. If the document is null or doesn't have a tab setting, return a default of 8.
Returns the class ID for the UI.
Gets the style of wrapping used if the text area is wrapping lines. If set to true the lines will be wrapped at word boundaries (ie whitespace) if they are too long to fit within the allocated width. If set to false, the lines will be wrapped at character boundaries.
Inserts the specified text at the specified position. Does nothing if the model is null or if the text is null or empty.
This method is thread safe, although most Swing methods are not. Please see How to Use Threads for more information.
str | the text to insert |
---|---|
pos | the position at which to insert >= 0 |
IllegalArgumentException | if pos is an invalid position in the model |
---|
Replaces text from the indicated start to end position with the new text specified. Does nothing if the model is null. Simply does a delete if the new string is null or empty.
This method is thread safe, although most Swing methods are not. Please see How to Use Threads for more information.
str | the text to use as the replacement |
---|---|
start | the start position >= 0 |
end | the end position >= start |
IllegalArgumentException | if part of the range is an invalid position in the model |
---|
Sets the number of columns for this TextArea. Does an invalidate() after setting the new value.
columns | the number of columns >= 0 |
---|
IllegalArgumentException | if columns is less than 0 |
---|
Sets the current font. This removes cached row height and column width so the new font will be reflected, and calls revalidate().
f | the font to use as the current font |
---|
Sets the line-wrapping policy of the text area. If set
to true the lines will be wrapped if they are too long
to fit within the allocated width. If set to false,
the lines will always be unwrapped. A PropertyChange
event ("lineWrap") is fired when the policy is changed.
By default this property is false.
wrap | indicates if lines should be wrapped |
---|
Sets the number of rows for this TextArea. Calls invalidate() after setting the new value.
rows | the number of rows >= 0 |
---|
IllegalArgumentException | if rows is less than 0 |
---|
Sets the number of characters to expand tabs to. This will be multiplied by the maximum advance for variable width fonts. A PropertyChange event ("tabSize") is fired when the tab size changes.
size | number of characters to expand to |
---|
Sets the style of wrapping used if the text area is wrapping lines. If set to true the lines will be wrapped at word boundaries (whitespace) if they are too long to fit within the allocated width. If set to false, the lines will be wrapped at character boundaries. By default this property is false.
word | indicates if word boundaries should be used for line wrapping |
---|
Creates the default implementation of the model to be used at construction if one isn't explicitly given. A new instance of PlainDocument is returned.
Gets column width. The meaning of what a column is can be considered a fairly weak notion for some fonts. This method is used to define the width of a column. By default this is defined to be the width of the character m for the font used. This method can be redefined to be some alternative amount.
Defines the meaning of the height of a row. This defaults to the height of the font.
Returns a string representation of this JTextArea. This method
is intended to be used only for debugging purposes, and the
content and format of the returned string may vary between
implementations. The returned string may be empty but may not
be null
.