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<TITLE>Creating a Custom Editing Command for a JTextComponent (Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
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<h1>The Java Developers Almanac 1.4</h1>
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<h3>e1002. Creating a Custom Editing Command for a JTextComponent</h3>
This example demonstrates how to implement an editing command.
There are two steps when creating a custom command.
The first is to create an action object that executes the
desired functionality and then installs the action object
in the component. The second is to bind a keystroke to the action
object using an inputmap.
<P> Text component actions should extend from <code>TextAction</code>.
<code>TextAction</code> has a convenience method for finding the appropriate
text component on which to operate.
<P> This example implements a <font color="#0066ff"><i>Lowercase</i></font> command that converts
characters to lowercase. If the selection is empty, the command
converts the character following the caret and then moves the caret
forward one space. If the selection is not empty, the command
converts the characters in the selection.
<pre> JTextArea comp = new JTextArea();
// Bind F2 to the lowercase action
String actionName = <font color="#0066ff"><i>"Lowercase"</i></font>;
comp.getInputMap().put(KeyStroke.getKeyStroke(<font color="#0066ff"><i>"F2"</i></font>), actionName);
// Install the action
comp.getActionMap().put(actionName,
new TextAction(actionName) {
public void actionPerformed(ActionEvent evt) {
lowercaseSelection(getTextComponent(evt));
}
}
);
public static void lowercaseSelection(JTextComponent comp) {
if (comp.getSelectionStart() == comp.getSelectionEnd()) {
// There is no selection, only a caret
if (comp.getCaretPosition() < comp.getDocument().getLength()) {
// The caret must be at least one position left of the end
try {
int pos = comp.getCaretPosition();
Document doc = comp.getDocument();
String str = doc.getText(pos, 1).toLowerCase();
doc.remove(pos, 1);
doc.insertString(pos, str, null);
comp.moveCaretPosition(pos+1);
} catch (BadLocationException e) {
}
}
} else {
// There is a selection
int s = comp.getSelectionStart();
int e = comp.getSelectionEnd();
comp.replaceSelection(comp.getSelectedText().toLowerCase());
comp.select(s, e);
}
}
</pre>
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<b>Related Examples</b></font></td>
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e1001. <a class="eglink" href="OverrideDefAction.html?l=rel">
Overriding the Default Action of a JTextComponent
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e1003. <a class="eglink" href="OverrideKey.html?l=rel">
Overriding a Few Default Typed Key Bindings in a JTextComponent
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e1004. <a class="eglink" href="OverrideKey2.html?l=rel">
Overriding Many Default Typed Key Bindings in a JTextComponent
</a>
<br>
e1005. <a class="eglink" href="ListTextKeys.html?l=rel">
Listing the Key Bindings in a JTextComponent Keymap
</a>
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See also:
<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#JTextComponent">
JTextComponent
</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
</a>
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