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<TITLE>Limiting the Capacity of a JTextComponent
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
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<h3>
e974.
Limiting the Capacity of a JTextComponent</h3>
Prior to J2SE 1.4, limiting the capacity of a text component involved
overriding the <code>insertString()</code> method of the component's
model. Here's an example:
<pre>
JTextComponent textComp = new <font color="#0066ff"><i>JTextField()</i></font>;
textComp.setDocument(new FixedSizePlainDocument(<font color="#0066ff"><i>10</i></font>));
class FixedSizePlainDocument extends PlainDocument {
int maxSize;
public FixedSizePlainDocument(int limit) {
maxSize = limit;
}
public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
if ((getLength() + str.length()) <= maxSize) {
super.insertString(offs, str, a);
} else {
throw new BadLocationException("Insertion exceeds max size of document", offs);
}
}
}
</pre>
J2SE 1.4 allows the ability to filter all editing operations on a text
component. Here's an example that uses the new filtering capability
to limit the capacity of the text component:
<pre>
JTextComponent textComponent = new JTextField();
AbstractDocument doc = (AbstractDocument)textComponent.getDocument();
doc.setDocumentFilter(new FixedSizeFilter(<font color="#0066ff"><i>10</i></font>));
class FixedSizeFilter extends DocumentFilter {
int maxSize;
// limit is the maximum number of characters allowed.
public FixedSizeFilter(int limit) {
maxSize = limit;
}
// This method is called when characters are inserted into the document
public void insertString(DocumentFilter.FilterBypass fb, int offset, String str,
AttributeSet attr) throws BadLocationException {
replace(fb, offset, 0, str, attr);
}
// This method is called when characters in the document are replace with other characters
public void replace(DocumentFilter.FilterBypass fb, int offset, int length,
String str, AttributeSet attrs) throws BadLocationException {
int newLength = fb.getDocument().getLength()-length+str.length();
if (newLength <= maxSize) {
fb.replace(offset, length, str, attrs);
} else {
throw new BadLocationException("New characters exceeds max size of document", offset);
}
}
}
</pre>
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Related Examples
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e967. <a class="eglink" href="GetText.html?l=rel">
Retrieving Text from a JTextComponent
</a>
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e968. <a class="eglink" href="PartialSeg.html?l=rel">
Retrieving All the Text from a JTextComponent Efficiently
</a>
<br>
e969. <a class="eglink" href="EditTextField.html?l=rel">
Modifying Text in a JTextComponent
</a>
<br>
e970. <a class="eglink" href="ConcurReadText.html?l=rel">
Asynchronously Reading the Contents of a Visible JTextComponent
</a>
<br>
e971. <a class="eglink" href="FindWord.html?l=rel">
Finding Word Boundaries in a JTextComponent
</a>
<br>
e972. <a class="eglink" href="GetWrappedLines.html?l=rel">
Retrieving the Visible Lines in a JTextComponent
</a>
<br>
e973. <a class="eglink" href="Pos.html?l=rel">
Using a Position in a JTextComponent
</a>
<br>
e975. <a class="eglink" href="DragEnabledTextArea.html?l=rel">
Enabling Text-Dragging on a JTextComponent
</a>
<br>
e976. <a class="eglink" href="ShareDoc.html?l=rel">
Sharing a Document Between JTextComponents
</a>
<br>
e977. <a class="eglink" href="WalkViews.html?l=rel">
Enumerating All the Views in a JTextComponent
</a>
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See also:
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#Actions%20and%20Key%20Bindings">
Actions and Key Bindings
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#Caret%20and%20Selection">
Caret and Selection
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#Events">
Events
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#JEditorPane">
JEditorPane
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#JFormattedTextField">
JFormattedTextField
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#JTextArea">
JTextArea
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#JTextField">
JTextField
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#JTextPane">
JTextPane
</a>
<a class="eglink" href="/egs/javax.swing.text/pkg.html?l=rel#Styles">
Styles
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