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jtextarea is showing character for a moment when character is masked which shouldn't

I have a requirement where I am entering input in JTextarea at run time and input should be masked. I am able to achieve this through below code snippet
if(encryptKeystroke == true) {
jTextArea.addKeyListener(new KeyListener() {
public void keyTyped(KeyEvent e) {
}
public void keyPressed(KeyEvent e) {
if (e.getExtendedKeyCode() == KeyEvent.VK_BACK_SPACE) {
if(text.length() > 0)
text = text.substring(0, text.length() - 1);
}
else {
text += String.valueOf(e.getKeyChar());
}
jTextArea.setText(text.replaceAll(".", "*"));
}
public void keyReleased(KeyEvent e) {
jTextArea.setText(text.replaceAll(".", "*"));
}
});
}
Issue is when I am running this, entered character is visible for a small moment and then getting masked(like it happened in Android).
I am using JTextarea because unable to achieve the scrollable & wrapstyle in Ttextfield.
Any suggestion how this can be achieved ?

Don't use a KeyListener for something like this. What if the user:
pastes text into the text area. The code won't handle multiple characters
moves the caret to the beginning of the text area. The code assumes text is always added at the end.
uses the Delete key
highlights a block of text and then enters a character
A KeyListener can't handle all these special situations. Swing has better and newer API's to use.
Instead you can use a DocumentFilter. The DocumentFilter allows you to filter the text BEFORE it is added to the Document of the JTextArea.
Basic example:
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class AsteriskFilter extends DocumentFilter
{
private StringBuilder realText = new StringBuilder();
#Override
public void insertString(FilterBypass fb, int offset, String text, AttributeSet attributes)
throws BadLocationException
{
replace(fb, offset, 0, text, attributes);
}
#Override
public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attributes)
throws BadLocationException
{
// Update the StringBuilder to contain the real text
Document doc = fb.getDocument();
realText.replace(offset, offset + length, text);
// Update the Document with asterisks
text = text.replaceAll(".", "*");
super.replace(fb, offset, length, text, attributes);
}
#Override
public void remove(DocumentFilter.FilterBypass fb, int offset, int length)
throws BadLocationException
{
realText.delete(offset, offset + length);
super.remove(fb, offset, length);
}
public String getRealText()
{
return realText.toString();
}
private static void createAndShowGUI()
{
JTextArea textArea = new JTextArea(3, 20);
AbstractDocument doc = (AbstractDocument) textArea.getDocument();
AsteriskFilter filter = new AsteriskFilter();
doc.setDocumentFilter( filter );
JButton button = new JButton("Display Text");
button.addActionListener(e -> JOptionPane.showMessageDialog(textArea, filter.getRealText()));
JFrame frame = new JFrame("Asterisk Filter");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(textArea, BorderLayout.CENTER);
frame.add(button, BorderLayout.PAGE_END);
frame.setSize(220, 200);
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args) throws Exception
{
EventQueue.invokeLater( () -> createAndShowGUI() );
/*
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
*/
}
}

How to change the background color of a JSpinner dependent on the current edited content of the field?

I have a GUI with a JSpinner using a SpinnerNumberModel using double values.
As soon as I change the content of the Editor of the JSpinner, I want the background to change to yellow (to show that the currently displayed value is not the one "saved" in the JSpinner respectively its Model.
If that content is not valid (e.g. out of the allowed range specified by my SpinnerNumberModel or a text as "abc") the background should change to red.
I tried to achieve what I want with a FocusListener already but yet have not been successful, also I am not sure if It could work anyway, as I need to check the content somewhere between focussing and defocussing.
I checked Tutorials for all Listeners that exist for Swing components, but could not find a right one that suits the job. (here I informed myself)
I am new to the concept of Listeners and would really appreciate any help that gets me closer to solving the problem but also helps generally understanding Listeners and how to use them in this context better!
My really basic code example with the mentioned poor attempt using a focus listener:
public class test implements FocusListener{
JFrame frame;
SpinnerNumberModel model;
JSpinner spinner;
JComponent comp;
JFormattedTextField field;
public test() {
JFrame frame = new JFrame("frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
model = new SpinnerNumberModel(0., 0., 100., 0.1);
spinner = new JSpinner(model);
comp = spinner.getEditor();
field = (JFormattedTextField) comp.getComponent(0);
field.addFocusListener(this);
frame.getContentPane().add(spinner);
frame.getContentPane().add(new JButton("defocus spinner")); //to have something to defocus when testing :)
frame.pack();
frame.setVisible(true);
}
#Override
public void focusGained(FocusEvent e) {
// TODO Auto-generated method stub
//when the values of the field and the spinner don't match, the field should get yellow
if(!field.getValue().equals(spinner.getModel().getValue())) {
field.setBackground(Color.YELLOW);
}
}
#Override
public void focusLost(FocusEvent e) {
// TODO Auto-generated method stub
//if they match again, reset to white
if(!field.getValue().equals(spinner.getModel().getValue())) {
field.setBackground(Color.RED);
}
}
}

A JSpinner uses a text field as the editor for the spinner
So, you can add a DocumentListener to the Document of the text field that is used as the editor.
Something like:
JTextField textField = ((JSpinner.DefaultEditor)spinner.getEditor()).getTextField());
textField.getDocument.addDocumentListener(...);
Then when text is added/removed a DocumentEvent will be generated and you can do your error checking. Read the section from the Swing tutorial on Listener For Changes on a Document for more information and working examples.

You can use CaretListener , here is a start:
import java.awt.Color;
import java.awt.Component;
import javax.swing.BoxLayout;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JSpinner;
import javax.swing.SpinnerNumberModel;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
public class SpinerTest{
JSpinner spinner;
public SpinerTest() {
JFrame frame = new JFrame("frame");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(300, 200);
frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
SpinnerNumberModel model = new SpinnerNumberModel(0., 0., 100., 0.1);
spinner = new JSpinner(model);
setCaretListener();
frame.getContentPane().add(spinner);
frame.pack();
frame.setVisible(true);
}
private void setCaretListener() {
for(Component c : spinner.getEditor().getComponents()) {
JFormattedTextField field =(JFormattedTextField) c;
field.addCaretListener(new CaretListener(){
#Override
public void caretUpdate(CaretEvent ce) {
if (field.isEditValid()) {
//add aditional test as needed
System.out.println("valid Edit Entered " + field.getText());
field.setBackground(Color.WHITE);
}
else {
System.out.println("Invalid Edit Entered" + field.getText());
field.setBackground(Color.PINK);
}
}
});
}
}
public static void main(String[] args) {
new SpinerTest();
}
}

I was able to fulfill the task with a combination of a KeyListener, a DocumentListener and a FocusListener. The solution might not be the easiest, but finally I coded sth. that works. Comments in the file appended should explain how I dealt with the problem.
I expanded the original task with a CommaReplacingNumericDocumentFilter expands DocumentFilter class that was not written by me, I got the code from my professor and edited it to my needs only. Now only digits, minus and e, E are accepted as entries in the JSpinner.
Commas are replaced with dots also.
Code:
import java.awt.*;
import java.awt.event.*;
import java.util.Locale;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
public class test implements DocumentListener, ChangeListener, KeyListener{
boolean keyPressed;
JFrame frame;
SpinnerNumberModel model;
JSpinner spinner;
JComponent comp;
JFormattedTextField field;
public test() {
JFrame frame = new JFrame("frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
model = new SpinnerNumberModel(0., 0., 100000., .1);
spinner = new JSpinner(model);
//disable grouping for spinner
JSpinner.NumberEditor editor = new JSpinner.NumberEditor(spinner);
editor.getFormat().setGroupingUsed(false);
spinner.setEditor(editor);
comp = spinner.getEditor();
field = (JFormattedTextField) comp.getComponent(0);
field.getDocument().addDocumentListener(this);
field.addKeyListener(this);
spinner.addChangeListener(this);
frame.getContentPane().add(spinner);
frame.pack();
frame.setVisible(true);
}
#Override
public void insertUpdate(DocumentEvent e) {
DocumentEventHandler(e);
}
#Override
public void removeUpdate(DocumentEvent e) {
DocumentEventHandler(e);
}
#Override
public void changedUpdate(DocumentEvent e) {
DocumentEventHandler(e);
}
public static boolean isNumeric(String str)
{
try
{
double d = Double.parseDouble(str);
}
catch(NumberFormatException nfe)
{
return false;
}
return true;
}
public static void main(String[] args) {
//to get the right format for double precision numbers
Locale.setDefault(Locale.US);
test test = new test();
}
#Override
public void stateChanged(ChangeEvent e) {
System.out.println("valuechanged: " + spinner.getValue().toString());
if(keyPressed) {
field.setBackground(Color.WHITE);
}
keyPressed = false;
}
public void DocumentEventHandler(DocumentEvent e) {
//as soon as update is inserted, set background to yellow
if (keyPressed) {
field.setBackground(Color.YELLOW);
//check if input is numeric and in bounds
String text = field.getText();
if (isNumeric(text)) {
double value = Double.parseDouble(text);
if (value < (Double)model.getMinimum() || value > (Double)model.getMaximum()) {
field.setBackground(Color.RED);
}
}
else { //set background to red
field.setBackground(Color.RED);
}
}
keyPressed = false;
//System.out.println(e.toString());
//System.out.println("Text: " + field.getText());
}
#Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
#Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}
/** If not done yet, replaces the DocumentFilter with one replacing commas by decimal points.
* This can't be done at the very beginning because the DocumentFilter would be changed to a
* javax.swing.text.DefaultFormatter$DefaultDocumentFilter when setting up the JSpinner GUI. */
public void keyPressed(KeyEvent e) {
PlainDocument document = (PlainDocument)(field.getDocument());
if(!(document.getDocumentFilter() instanceof CommaReplacingNumericDocumentFilter))
document.setDocumentFilter(new CommaReplacingNumericDocumentFilter());
/*Tell the other handlers that a key has been pressed and the change in the document does
* not come from using the JSpinner buttons or the MouseWheel.
*/
keyPressed = true;
}
}
/** A javax.swing.text.DocumentFilter that replaces commas to decimal points
* and ignores non-numeric characters except 'e' and 'E'. This is called before
* modi */
class CommaReplacingNumericDocumentFilter extends DocumentFilter {
#Override
public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr)
throws BadLocationException {
text = filter(text);
if (text.length() > 0)
super.insertString(fb, offset, text, attr);
}
#Override
public void replace(FilterBypass fb, int offset, int length, String text,
AttributeSet attrs) throws BadLocationException {
text = filter(text);
if (text.length() > 0)
super.replace(fb, offset, length, text, attrs);
}
String filter(String text) {
return text.replace(',', '.').replaceAll("[^0-9eE.-]","");
}
}

Java JTextField Converting to upper/lowercase while writing

I've got question regarding to typing in JTextField. My program search thru few csv files and look for specified in JTextField string. I have add to readLine function ".toLowerCase" to read all strings as lowercase. Is it possible to set JTextField to automatically convert uppercase to lower case while writing to JTextField?
if (line.toLowerCase().contains(searchedString))...

Yes, you can use the KeyListener and when a key is pressed in the textfield, you will make the input string lowerCase while keeping the cursor position where it was. Like the code below:
jTextField1.addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
int pos = jTextField1.getCaretPosition();
jTextField1.setText(jTextField1.getText().toLowerCase());
jTextField1.setCaretPosition(pos);
}
});
Source:
Value Change Listener to JTextField
Finding the cursor text position in JTextField

You can create a class that extends DocumentFilter class and override methods insertString and replace so that:
In insertString method it will call it's super, passing in one of the parameters string.toLowerCase()
In replace method it will call it's super, passing in one of the parameters text.toLowerCase()
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
class LowerCaseDocumentFilter extends DocumentFilter {
#Override
public void insertString(final FilterBypass fb, final int offset, final String string, final AttributeSet attr) throws BadLocationException {
super.insertString(fb, offset, string.toLowerCase(), attr);
}
#Override
public void replace(final FilterBypass fb, final int offset, final int length, final String text, final AttributeSet attrs) throws BadLocationException {
super.replace(fb, offset, length, text.toLowerCase(), attrs);
}
}
then adds an instance of this class so that the JTextField will automatically convert to lower case:
class Main {
public static void main(String[]args) {
JFrame jFrame = new JFrame("Example");
jFrame.setSize(500, 500);
jFrame.setVisible(true);
JPanel jPanel = new JPanel();
jFrame.add(jPanel);
JTextField jTextField = new JTextField("Example JTextField");
((AbstractDocument)jTextField.getDocument()).setDocumentFilter(new LowerCaseDocumentFilter());
jPanel.add(jTextField);
jFrame.pack();
}
}
Source:
https://stackoverflow.com/a/11573312

You can create your own class by extending the JTextfield and override constructor/setter method.

Restricting access to some lines in JTextArea?

I wanted to make a JTextArea where the user can't erase the previous line. Just like the Command Prompt in Windows and the terminal in Linux, you can't edit previous lines.
This is what I've come up with, but it doesn't seem to work, and I can only come up with one reason for this, but it appears to be more than just one reason.
if(commandArea.getCaretPosition() < commandArea.getText().lastIndexOf("\n")){
commandArea.setCaretPosition(commandArea.getText().lastIndexOf("\n"));
}
This block of code lives inside this method:
private void commandAreaKeyPressed(java.awt.event.KeyEvent evt)

You can use DocumentFilter for JTextArea's Document. Runnable working example that allows editing last line only in JTextArea:
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.text.DocumentFilter.FilterBypass;
public class MainClass {
public static void main(String[] args) {
JFrame frame = new JFrame("text area test");
JPanel panelContent = new JPanel(new BorderLayout());
frame.setContentPane(panelContent);
UIManager.getDefaults().put("TextArea.font", UIManager.getFont("TextField.font")); //let text area respect DPI
panelContent.add(createSpecialTextArea(), BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(800, 600);
frame.setLocationRelativeTo(null); //center screen
frame.setVisible(true);
}
private static JTextArea createSpecialTextArea() {
final JTextArea textArea = new JTextArea("first line\nsecond line\nthird line");
((AbstractDocument)textArea.getDocument()).setDocumentFilter(new DocumentFilter() {
private boolean allowChange(int offset) {
try {
int offsetLastLine = textArea.getLineCount() == 0 ? 0 : textArea.getLineStartOffset(textArea.getLineCount() - 1);
return offset >= offsetLastLine;
} catch (BadLocationException ex) {
throw new RuntimeException(ex); //should never happen anyway
}
}
#Override
public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
if (allowChange(offset)) {
super.remove(fb, offset, length);
}
}
#Override
public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
if (allowChange(offset)) {
super.replace(fb, offset, length, text, attrs);
}
}
#Override
public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
if (allowChange(offset)) {
super.insertString(fb, offset, string, attr);
}
}
});
return textArea;
}
}
How does it work? JTextArea is a text control, actual data has Document. Document allows listening for changes (DocumentListener), and some documents allow to set DocumentFilter to forbid changes. Both PlainDocument and DefaultStyledDocument extend from AbstractDocument, which allows setting a filter.
Be sure to read java doc:
JTextArea
AbstractDocument
DocumentFilter
I recommend also tutorials:
How to use text area
How to Write a Document Listener
Implementing a Document Filter

How to make a String not-deletable in JTextarea?

Basically, I have a dropdown menu containing templates. For example:
apple( )
banana( )
Once one of them is selected, it pastes onto a JTextArea. My problem is if "apple( )" is selected, I want "apple" and the two brackets non-deletable in the TextArea, and user can enter anything inside the brackets.
Can anyone give me any direction/ideas here? I have been searching on the internet and found very little about this.

Check out the Proctected Text Component. It allows you to mark individual pieces of text as protected so that it can't be changed or deleted.
It uses a DocumentFilter as well as a NavigationFilter.
For a simpler solution you might be able to just use a NavigationFilter. The example below shows how you can prevent the selection of text at the beginning of the Document. You should be able to customize it to also prevent selection of text at the end of the document as well.
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
public class NavigationFilterPrefixWithBackspace extends NavigationFilter
{
private int prefixLength;
private Action deletePrevious;
public NavigationFilterPrefixWithBackspace(int prefixLength, JTextComponent component)
{
this.prefixLength = prefixLength;
deletePrevious = component.getActionMap().get("delete-previous");
component.getActionMap().put("delete-previous", new BackspaceAction());
component.setCaretPosition(prefixLength);
}
#Override
public void setDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
{
fb.setDot(Math.max(dot, prefixLength), bias);
}
#Override
public void moveDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
{
fb.moveDot(Math.max(dot, prefixLength), bias);
}
class BackspaceAction extends AbstractAction
{
#Override
public void actionPerformed(ActionEvent e)
{
JTextComponent component = (JTextComponent)e.getSource();
if (component.getCaretPosition() > prefixLength)
{
deletePrevious.actionPerformed( null );
}
}
}
private static void createAndShowUI()
{
JTextField textField = new JTextField("Prefix_", 20);
textField.setNavigationFilter( new NavigationFilterPrefixWithBackspace(7, textField) );
JFrame frame = new JFrame("Navigation Filter Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(textField);
frame.pack();
frame.setLocationRelativeTo( null );
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}

You'll have to do this yourself. I'd suggest you to make an event handler that fires every time the text changes (Click here to find out how). And inside that handler check if the JTextArea still starts with "apple(" and ends with ")".