textarea.html

jsf、swing的官方指南

private final static String newline = "\n";
...
textArea.append(text + newline);
</pre></blockquote>

<p>
Unless the user has moved the caret (insertion point)
by clicking or dragging in the text area,
the text area automatically scrolls so that the appended text is visible.
You can force the text area to scroll to the bottom
by moving the caret to the end of the text area, like this,
after the call to <code>append</code>:


<blockquote><pre>
textArea.setCaretPosition(textArea.getDocument().getLength());
</pre></blockquote>


</blockquote>
<h3>
<a name="custom">Customizing Text Areas</a>
</h3>
<blockquote>

You can customize text areas in several ways.
For example, although a given text area 
can display text in only one font and color,
you can 
(as for any component)
set which font and color it uses.
You can also determine how the text area
wraps lines and the number of characters per tab.
Finally, you can use the methods <code>JTextArea</code> inherits
from <code>JTextComponent</code>
to set properties such as the caret,
support for dragging,
selection color, 
and so on.

<p>
The following code,
taken from 
<a class="SourceLink" target="_blank" href="examples/TextSamplerDemo.java"><code>TextSamplerDemo.java</code></a>, demonstrates
initializing an editable text area.
The text area uses the specified italic font,
and wraps lines between words.

<blockquote><pre>
JTextArea textArea = new JTextArea(
    "This is an editable JTextArea. " +
    "A text area is a \"plain\" text component, " +
    "which means that although it can display text " +
    "in any font, all of the text is in the same font."
);
textArea.setFont(new Font("Serif", Font.ITALIC, 16));
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
</pre></blockquote>

<p>
By default, a text area doesn't wrap lines
that are too long for the display area.
Instead it uses one line
for all the text between newline characters and
&#151;
if the text area is within a
<a href="scrollpane.html">scroll pane</a> &#151;
allows itself to be scrolled horizontally.
This example turns line wrapping on with
a call to <code>setLineWrap</code>
and then calls <code>setWrapStyleWord</code>
to indicate that the text area should wrap lines
at word boundaries rather than at character
boundaries.

<p>
To provide scrolling capability, the example
puts the text area in a scroll pane.

<blockquote><pre>
JScrollPane areaScrollPane = new JScrollPane(textArea);
areaScrollPane.setVerticalScrollBarPolicy(
		JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
areaScrollPane.setPreferredSize(new Dimension(250, 250));
</pre></blockquote>

You might have noticed 
that the <code>JTextArea</code> constructor
used in this example
does not specify the number of rows or columns.
Instead, the code limits the size of the text area
by setting the scroll pane's preferred size.


</blockquote>
<h3>
<a name="api">The Text Area API</a>
</h3>
<blockquote>
The following tables list the commonly used
<code>JTextArea</code> 
constructors and methods.
Other methods you are likely to call
are defined in <code>JTextComponent</code>,
and listed in
<a href="textapi.html">The Text Component API</a>.

<p>
You might also invoke methods on a
text area 
that it inherits from its other ancestors,
such as <code>setPreferredSize</code>,
<code>setForeground</code>, 
<code>setBackground</code>, 
<code>setFont</code>, and so on.
See
<a href="jcomponent.html">The JComponent Class</a>
for tables of commonly used inherited methods.

<p>
The API for using text areas 
falls into these categories:

<ul>
<li><a href="#contents">Setting or Getting Contents</a>
<li><a href="#looks">Fine Tuning Appearance</a>
<li><a href="#function">Implementing Functionality</a>
</ul>

<p>

<table border=1>
<caption><a name="contents">Setting or Getting Contents</a></caption>
<tr>
<th>Method or Constructor
</th>
<th>Purpose

</th>
</tr>
  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#JTextArea()">JTextArea()</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#JTextArea(java.lang.String)">JTextArea(String)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#JTextArea(java.lang.String, int, int)">JTextArea(String, int, int)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#JTextArea(int, int)">JTextArea(int, int)</a>    </td>
    <td>Create a text area.
        When present,
        the <code>String</code> argument contains the initial text.
        The <code>int</code> arguments specify the desired width
        in columns and height in rows, respectively.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/text/JTextComponent.html#setText(java.lang.String)">void setText(String)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/text/JTextComponent.html#getText()">String getText()</a><br>
<em>(defined in <code>JTextComponent</code>)</em>
    </td>
    <td>Set or get the text displayed by the text area.
    </td>
  </tr>
</table>

<p>

<table border=1>
<caption><a name="looks">Fine Tuning the Text Area's Appearance</a></caption>
<tr>
<th>Method
</th>
<th>Purpose
</th>
</tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/text/JTextComponent.html#setEditable(boolean)">void setEditable(boolean)</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/text/JTextComponent.html#isEditable()">boolean isEditable()</a><br>
<em>(defined in <code>JTextComponent</code>)</em>
    </td>
    <td>Set or get whether the user can edit the text in the text area.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#setColumns(int)">void setColumns(int);</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getColumns()">int getColumns()</a>    </td>
    <td>Set or get the number of columns displayed by the text area.
        This is really just a hint for computing the area's preferred width.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#setRows(int)">void setRows(int);</a>    <br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getRows()">int getRows()</a>    </td>
    <td>Set or get the number of rows displayed by the text area.
        This is a hint for computing the area's preferred width.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#setTabSize(int)">int setTabSize(int)</a>    </td>
    <td>Set the number of characters a tab is equivalent to.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#setLineWrap(boolean)">int setLineWrap(boolean)</a>    </td>
    <td>Set whether lines are wrapped if they are too long
	to fit within the allocated width.
	By default, this property is false
	and lines are not wrapped.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#setWrapStyleWord(boolean)">int setWrapStyleWord(boolean)</a>    </td>
    <td>Set whether lines can be wrapped at white space 
	(word boundaries) or
	at any character.
	By default, this property is false,
	and lines can be wrapped (if line wrapping is turned on)
	at any character.
    </td>
  </tr>
</table>

<p>

<table border=1>
<caption><a name="function">Implementing the Text Area's Functionality</a></caption>
<tr>
<th>Method
</th>
<th>Purpose
</th>
</tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/text/JTextComponent.html#selectAll()">void selectAll()</a><br>
<em>(defined in <code>JTextComponent</code>)</em>
    </td>
    <td>Select all characters in the text area.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#append(java.lang.String)">void append(String)</a>    </td>
    <td>Add the specified text to the end of the text area.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#insert(java.lang.String, int)">void insert(String, int)</a>    </td>
    <td>Insert the specified text at the specified position.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#replaceRange(java.lang.String, int, int)">void replaceRange(String, int, int)</a>    </td>
    <td>Replace the text between the indicated positions
	with the specified string.
    </td>
  </tr>

  <tr>
    <td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getLineCount()">int getLineCount()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getLineOfOffset(int)">int getLineOfOffset(int)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getLineStartOffset(int)">int getLineStartOffset(int)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/JTextArea.html#getLineEndOffset(int)">int getLineEndOffset(int)</a>    </td>
    <td>
    Utilities for finding a line number
    or the position of the beginning or end of the specified line.
    </td>
  </tr>
</table>
</blockquote>

<h3>
<a name="eg">Examples that Use Text Areas</a>
</h3>
<blockquote>
Many Tutorial examples use <code>JTextArea</code>,
typically to provide an area where 
events are logged.
Here's a partial list of the demos
that use text areas.

<p>
<table>
<tr>
<th align=left> Example
</th>
<th align=left> Where Described
</th>
<th align=left> Notes
</th>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#TextDemo">TextDemo</a>
</td>
<td valign=top> This section
</td>
<td valign=top> An application that appends user-entered text to a text area.
</td>
</tr>

<tr>
<td valign=top>
<a href="examples/index.html#TextSamplerDemo">TextSamplerDemo</a>
</td>
<td valign=top> 
<a href="text.html">Using Text Components</a>
</td>
<td valign=top> Uses one of each of Swing's text components.
</td>
</tr>

<tr>
<td valign=top>
<a href="examples/index.html#HtmlDemo">HtmlDemo</a>
</td>
<td valign=top> <a href="html.html">Using HTML in Swing Components</a>
</td>
<td valign=top> A text area lets the user enter
		HTML code to be displayed in a label.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../misc/examples/index.html#BasicDnD">BasicDnD</a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../dnd/intro.html">Introduction to Drag and Drop and Data Transfer</a></td>
<td valign=top> 
Demonstrates built-in drag-and-drop functionality
of several Swing components,
including text areas.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../misc/examples/index.html#ExtendedDnDDemo">ExtendedDnDDemo</a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../dnd/intro.html">Introduction to Drag and Drop and Data Transfer</a></td>
<td valign=top> 
Demonstrates dragging and dropping text
between a text area, 
a list, and a table.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../misc/examples/index.html#DragFileDemo">DragFileDemo</a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../dnd/intro.html">Introduction to Drag and Drop and Data Transfer</a></td>
<td valign=top> 
Demonstrates dragging file contents 
from a file chooser into a text area.
A tabbed pane lets you easily switch between files.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../misc/examples/index.html#FocusConceptsDemo">FocusConceptsDemo</a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../misc/focus.html">How to Use the Focus Subsystem</a></td>
<td valign=top> 
Demonstrates how focus works,
using a few components that include a text area.
</td>
</tr>

</table>



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