我有一个简单的应用程序,可以限制用户的行数。已成功执行行数的计算。我使用documentListener来捕获用户的事件。
但是当用户的输入超过指定的行数时,我想禁止用户再次输入。但是,用户仍然可以删除他们输入的字符。
我已经尝试过使用setEditable(false),但这个方法导致JTextArea无法永久编辑。
这是我的密码。
....
public Demo2() {
initComponents();
textArea.getDocument().addDocumentListener(new DocumentListener() {
@Override
public void insertUpdate(DocumentEvent e) {
System.out.println("Current Line when method call : "+getLineCountAsSeen(textArea));
if (getLineCountAsSeen(textArea) > maxLine){
JOptionPane.showMessageDialog(null, "Max line : "+maxLine);
try {
textArea.getDocument().remove(textArea.getDocument().getLength()-2, 2);
} catch (BadLocationException ex) {
Logger.getLogger(Demo2.class.getName()).log(Level.SEVERE, null, ex.getMessage());
}
} else {
lblLineCount.setText(String.valueOf(currentLine));
}
}
@Override
public void removeUpdate(DocumentEvent e) {
System.out.println("Current Line when method call : "+getLineCountAsSeen(textArea));
if (getLineCountAsSeen(textArea) > maxLine){
JOptionPane.showMessageDialog(null, "Max line : "+maxLine);
try {
textArea.getDocument().remove(textArea.getDocument().getLength()-2, 2);
} catch (BadLocationException ex) {
Logger.getLogger(Demo2.class.getName()).log(Level.SEVERE, null, ex);
}
} else {
textArea.setEditable(true);
lblLineCount.setText(String.valueOf(getLineCountAsSeen(textArea)));
}
}
@Override
public void changedUpdate(DocumentEvent e) {
System.out.println("Current Line when method call : "+getLineCountAsSeen(textArea));
if (getLineCountAsSeen(textArea) > maxLine){
JOptionPane.showMessageDialog(null, "Max line : "+maxLine);
try {
textArea.getDocument().remove(textArea.getDocument().getLength()-2, 2);
} catch (BadLocationException ex) {
Logger.getLogger(Demo2.class.getName()).log(Level.SEVERE, null, ex);
}
} else {
textArea.setEditable(true);
lblLineCount.setText(String.valueOf(getLineCountAsSeen(textArea)));
}
}
});
}
public static int getLineCountAsSeen(JTextComponent txtComp) {
Font font = txtComp.getFont();
FontMetrics fontMetrics = txtComp.getFontMetrics(font);
int fontHeight = fontMetrics.getHeight();
int lineCount;
try {
int height = txtComp.modelToView(txtComp.getDocument().getEndPosition().getOffset() - 1).y;
lineCount = height / fontHeight + 1;
} catch (Exception e) {
lineCount = 0;
}
if (lineCount == 0) {
System.out.println("Not Set!");
return lineCount;
} else {
currentLine = lineCount;
System.out.println("currentLine : "+currentLine);
return currentLine;
}
}
....
尝试将DocumentFilter而不是DocumentListener放在类似的位置
final AbstractDocument abstractDocument = (AbstractDocument) textArea.getDocument();
abstractDocument.setDocumentFilter(new DocumentFilter()
{
@Override
public void remove(final FilterBypass fb, final int offset, final int length) throws BadLocationException
{
super.remove(fb, offset, length);
}
@Override
public void insertString(final FilterBypass fb,
final int offset,
final String string,
final AttributeSet attr) throws BadLocationException
{
if (getLineCountAsSeen(textArea) < 4)
{
super.insertString(fb, offset, string, attr);
}
}
@Override
public void replace(final FilterBypass fb,
final int offset,
final int length,
final String text,
final AttributeSet attrs) throws BadLocationException
{
if (getLineCountAsSeen(textArea) < 4)
{
super.replace(fb, offset, length, text, attrs);
}
}
});