Bounded TextField
/*
Core SWING Advanced Programming
By Kim Topley
ISBN: 0 13 083292 8
Publisher: Prentice Hall
*/
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.PlainDocument;
public class BoundedTextField extends JTextField implements
BoundedPlainDocument.InsertErrorListener {
public BoundedTextField() {
this(null, 0, 0);
}
public BoundedTextField(String text, int columns, int maxLength) {
super(null, text, columns);
if (text != null && maxLength == 0) {
maxLength = text.length();
}
BoundedPlainDocument plainDoc = (BoundedPlainDocument) getDocument();
plainDoc.setMaxLength(maxLength);
plainDoc.addInsertErrorListener(this);
}
public BoundedTextField(int columns, int maxLength) {
this(null, columns, maxLength);
}
public BoundedTextField(String text, int maxLength) {
this(text, 0, maxLength);
}
public void setMaxLength(int maxLength) {
((BoundedPlainDocument) getDocument()).setMaxLength(maxLength);
}
public int getMaxLength() {
return ((BoundedPlainDocument) getDocument()).getMaxLength();
}
// Override to handle insertion error
public void insertFailed(BoundedPlainDocument doc, int offset, String str,
AttributeSet a) {
// By default, just beep
Toolkit.getDefaultToolkit().beep();
}
// Method to create default model
protected Document createDefaultModel() {
return new BoundedPlainDocument();
}
// Test code
public static void main(String[] args) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception evt) {}
JFrame f = new JFrame("Bounded Text Field Example");
BoundedTextField tf = new BoundedTextField(10, 32);
JLabel l = new JLabel("Type up to 32 characters: ");
f.getContentPane().add(tf, "East");
f.getContentPane().add(l, "West");
f.pack();
f.setVisible(true);
}
}
class BoundedPlainDocument extends PlainDocument {
public BoundedPlainDocument() {
// Default constructor - must use setMaxLength later
this.maxLength = 0;
}
public BoundedPlainDocument(int maxLength) {
this.maxLength = maxLength;
}
public BoundedPlainDocument(AbstractDocument.Content content, int maxLength) {
super(content);
if (content.length() > maxLength) {
throw new IllegalArgumentException(
"Initial content larger than maximum size");
}
this.maxLength = maxLength;
}
public void setMaxLength(int maxLength) {
if (getLength() > maxLength) {
throw new IllegalArgumentException(
"Current content larger than new maximum size");
}
this.maxLength = maxLength;
}
public int getMaxLength() {
return maxLength;
}
public void insertString(int offset, String str, AttributeSet a)
throws BadLocationException {
if (str == null) {
return;
}
// Note: be careful here - the content always has a
// trailing newline, which should not be counted!
int capacity = maxLength + 1 - getContent().length();
if (capacity >= str.length()) {
// It all fits
super.insertString(offset, str, a);
} else {
// It doesn't all fit. Add as much as we can.
if (capacity > 0) {
super.insertString(offset, str.substring(0, capacity), a);
}
// Finally, signal an error.
if (errorListener != null) {
errorListener.insertFailed(this, offset, str, a);
}
}
}
public void addInsertErrorListener(InsertErrorListener l) {
if (errorListener == null) {
errorListener = l;
return;
}
throw new IllegalArgumentException(
"InsertErrorListener already registered");
}
public void removeInsertErrorListener(InsertErrorListener l) {
if (errorListener == l) {
errorListener = null;
}
}
public interface InsertErrorListener {
public abstract void insertFailed(BoundedPlainDocument doc, int offset,
String str, AttributeSet a);
}
protected InsertErrorListener errorListener; // Unicast listener
protected int maxLength;
}
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