Value Change Listener to JTextField

Question

I want the message box to appear immediately after the user changes the value in the textfield. Currently, I need to hit the enter key to get the message box to pop out. Is there anything wrong with my code?

textField.addActionListener(new java.awt.event.ActionListener() {
    public void actionPerformed(java.awt.event.ActionEvent e) {

        if (Integer.parseInt(textField.getText())<=0){
            JOptionPane.showMessageDialog(null,
                    "Error: Please enter number bigger than 0", "Error Message",
                    JOptionPane.ERROR_MESSAGE);
        }       
    }
}

Any help would be appreciated!

Evin

Answer 1

Add a listener to the underlying Document, which is automatically created for you.

// Listen for changes in the text
textField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    warn();
  }
  public void removeUpdate(DocumentEvent e) {
    warn();
  }
  public void insertUpdate(DocumentEvent e) {
    warn();
  }

  public void warn() {
     if (Integer.parseInt(textField.getText())<=0){
       JOptionPane.showMessageDialog(null,
          "Error: Please enter number bigger than 0", "Error Message",
          JOptionPane.ERROR_MESSAGE);
     }
  }
});

Phiphenomenon

good format for the warning/type cast. Same pattern will be useful for handling double amounts (sales figures/prices entered or displayed) – Bug

it's working fine but i have a query that, when i insert some text in textfield then i want to call a method. i do not have much idea about how it is done.. – Olmstead

I was having issues with a JTable not getting text box updates from an editable JComboBox when clicking another table cell, and the insertUpdate function here was the only way to make it work properly. – Simper

"Error Massage" – Hallucinosis

expect NumberFormatExceptions, even if the user just deletes everything to reenter – Tice

Answer 2

The usual answer to this is "use a DocumentListener". However, I always find that interface cumbersome. Truthfully the interface is over-engineered. It has three methods, for insertion, removal, and replacement of text, when it only needs one method: replacement. (An insertion can be viewed as a replacement of no text with some text, and a removal can be viewed as a replacement of some text with no text.)

Usually all you want is to know is when the text in the box has changed, so a typical DocumentListener implementation has the three methods calling one method.

Therefore I made the following utility method, which lets you use a simpler ChangeListener rather than a DocumentListener. (It uses Java 8's lambda syntax, but you can adapt it for old Java if needed.)

/**
 * Installs a listener to receive notification when the text of any
 * {@code JTextComponent} is changed. Internally, it installs a
 * {@link DocumentListener} on the text component's {@link Document},
 * and a {@link PropertyChangeListener} on the text component to detect
 * if the {@code Document} itself is replaced.
 * 
 * @param text any text component, such as a {@link JTextField}
 *        or {@link JTextArea}
 * @param changeListener a listener to receieve {@link ChangeEvent}s
 *        when the text is changed; the source object for the events
 *        will be the text component
 * @throws NullPointerException if either parameter is null
 */
public static void addChangeListener(JTextComponent text, ChangeListener changeListener) {
    Objects.requireNonNull(text);
    Objects.requireNonNull(changeListener);
    DocumentListener dl = new DocumentListener() {
        private int lastChange = 0, lastNotifiedChange = 0;

        @Override
        public void insertUpdate(DocumentEvent e) {
            changedUpdate(e);
        }

        @Override
        public void removeUpdate(DocumentEvent e) {
            changedUpdate(e);
        }

        @Override
        public void changedUpdate(DocumentEvent e) {
            lastChange++;
            SwingUtilities.invokeLater(() -> {
                if (lastNotifiedChange != lastChange) {
                    lastNotifiedChange = lastChange;
                    changeListener.stateChanged(new ChangeEvent(text));
                }
            });
        }
    };
    text.addPropertyChangeListener("document", (PropertyChangeEvent e) -> {
        Document d1 = (Document)e.getOldValue();
        Document d2 = (Document)e.getNewValue();
        if (d1 != null) d1.removeDocumentListener(dl);
        if (d2 != null) d2.addDocumentListener(dl);
        dl.changedUpdate(null);
    });
    Document d = text.getDocument();
    if (d != null) d.addDocumentListener(dl);
}

Unlike with adding a listener directly to the document, this handles the (uncommon) case that you install a new document object on a text component. Additionally, it works around the problem mentioned in Jean-Marc Astesana's answer, where the document sometimes fires more events than it needs to.

Anyway, this method lets you replace annoying code which looks like this:

someTextBox.getDocument().addDocumentListener(new DocumentListener() {
    @Override
    public void insertUpdate(DocumentEvent e) {
        doSomething();
    }

    @Override
    public void removeUpdate(DocumentEvent e) {
        doSomething();
    }

    @Override
    public void changedUpdate(DocumentEvent e) {
        doSomething();
    }
});

With:

addChangeListener(someTextBox, e -> doSomething());

Code released to public domain. Have fun!

Diglot

Similar solution: create an abstract class DocumentChangeListener implements DocumentListener with an extra abstract method change(DocumentEvent e) that you call from all 3 other methods. Seems more obvious to me since it uses more or less the same logic as the abstract *Adapter listeners. – Abscind

+1 as changedUpdate method shall be invoked explicitly through a call within each of insertUpdate and removeUpdate, in order to get it work .. – Elderly

@Abscind The main advantage of this is that you do not get multiple change events for the same thing (remove+insert for replacing). – Oates

Answer 3

Just create an interface that extends DocumentListener and implements all DocumentListener methods:

@FunctionalInterface
public interface SimpleDocumentListener extends DocumentListener {
    void update(DocumentEvent e);

    @Override
    default void insertUpdate(DocumentEvent e) {
        update(e);
    }
    @Override
    default void removeUpdate(DocumentEvent e) {
        update(e);
    }
    @Override
    default void changedUpdate(DocumentEvent e) {
        update(e);
    }
}

and then:

jTextField.getDocument().addDocumentListener(new SimpleDocumentListener() {
    @Override
    public void update(DocumentEvent e) {
        // Your code here
    }
});

or you can even use lambda expression:

jTextField.getDocument().addDocumentListener((SimpleDocumentListener) e -> {
    // Your code here
});

Ultimatum

Don't forget that this solution requires an abstract class instead of an interface in all versions prior to Java 8. – Gramophone

Answer 4

Be aware that when the user modify the field, the DocumentListener can, sometime, receive two events. For instance if the user selects the whole field content, then press a key, you'll receive a removeUpdate (all the content is remove) and an insertUpdate. In your case, I don't think it is a problem but, generally speaking, it is. Unfortunately, it seems there's no way to track the content of the textField without subclassing JTextField. Here is the code of a class that provide a "text" property :

package net.yapbam.gui.widget;

import javax.swing.JTextField;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

/** A JTextField with a property that maps its text.
 * <br>I've found no way to track efficiently the modifications of the text of a JTextField ... so I developed this widget.
 * <br>DocumentListeners are intended to do it, unfortunately, when a text is replace in a field, the listener receive two events:<ol>
 * <li>One when the replaced text is removed.</li>
 * <li>One when the replacing text is inserted</li>
 * </ul>
 * The first event is ... simply absolutely misleading, it corresponds to a value that the text never had.
 * <br>Anoter problem with DocumentListener is that you can't modify the text into it (it throws IllegalStateException).
 * <br><br>Another way was to use KeyListeners ... but some key events are throw a long time (probably the key auto-repeat interval)
 * after the key was released. And others events (for example a click on an OK button) may occurs before the listener is informed of the change.
 * <br><br>This widget guarantees that no "ghost" property change is thrown !
 * @author Jean-Marc Astesana
 * <BR>License : GPL v3
 */

public class CoolJTextField extends JTextField {
    private static final long serialVersionUID = 1L;

    public static final String TEXT_PROPERTY = "text";

    public CoolJTextField() {
        this(0);
    }

    public CoolJTextField(int nbColumns) {
        super("", nbColumns);
        this.setDocument(new MyDocument());
    }

    @SuppressWarnings("serial")
    private class MyDocument extends PlainDocument {
        private boolean ignoreEvents = false;

        @Override
        public void replace(int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
            String oldValue = CoolJTextField.this.getText();
            this.ignoreEvents = true;
            super.replace(offset, length, text, attrs);
            this.ignoreEvents = false;
            String newValue = CoolJTextField.this.getText();
            if (!oldValue.equals(newValue)) CoolJTextField.this.firePropertyChange(TEXT_PROPERTY, oldValue, newValue);
        }

        @Override
        public void remove(int offs, int len) throws BadLocationException {
            String oldValue = CoolJTextField.this.getText();
            super.remove(offs, len);
            String newValue = CoolJTextField.this.getText();
            if (!ignoreEvents && !oldValue.equals(newValue)) CoolJTextField.this.firePropertyChange(TEXT_PROPERTY, oldValue, newValue);
        }
    }

Stenson

Swing already has a type of textField that maps document changes to a property - it's called JFormattedTextField :-) – Deliberation

Answer 5

I know this relates to a really old problem, however, it caused me some problems too. As kleopatra responded in a comment above, I solved the problem with a JFormattedTextField. However, the solution requires a bit more work, but is neater.

The JFormattedTextField doesn't by default trigger a property change after every text changes in the field. The default constructor of JFormattedTextField does not create a formatter.

However, to do what the OP suggested, you need to use a formatter which will invoke the commitEdit() method after each valid edit of the field. The commitEdit() method is what triggers the property change from what I can see and without the formatter, this is triggered by default on a focus change or when the enter key is pressed.

See http://docs.oracle.com/javase/tutorial/uiswing/components/formattedtextfield.html#value for more details.

Create a default formatter (DefaultFormatter) object to be passed to the JFormattedTextField either via its constructor or a setter method. One method of the default formatter is setCommitsOnValidEdit(boolean commit), which sets the formatter to trigger the commitEdit() method every time the text is changed. This can then be picked up using a PropertyChangeListener and the propertyChange() method.

Zaria

Answer 6

An elegant way is to add the listener to the caret position, because it changes every time something is typed/deleted, then just compare old value with current one.

String oldVal = ""; // empty string or default value
JTextField tf = new JTextField(oldVal);

tf.addCaretListener(e -> {
    String currentVal = tf.getText();

    if(!currentVal.equals(oldVal)) {
        oldVal = currentVal;
        System.out.println("Change"); // do something
    }
});

(This event is also being triggered every time a user just clicks into a TextField).

Shearer

Answer 7

textBoxName.getDocument().addDocumentListener(new DocumentListener() {
   @Override
   public void insertUpdate(DocumentEvent e) {
       onChange();
   }

   @Override
   public void removeUpdate(DocumentEvent e) {
      onChange();
   }

   @Override
   public void changedUpdate(DocumentEvent e) {
      onChange();
   } 
});

But I would not just parse anything the user (maybe on accident) touches on his keyboard into an Integer. You should catch any Exceptions thrown and make sure the JTextField is not empty.

Demit

Answer 8

If we use runnable method SwingUtilities.invokeLater() while using Document listener application is getting stuck sometimes and taking time to update the result(As per my experiment). Instead of that we can also use KeyReleased event for text field change listener as mentioned here.

usernameTextField.addKeyListener(new KeyAdapter() {
    public void keyReleased(KeyEvent e) {
        JTextField textField = (JTextField) e.getSource();
        String text = textField.getText();
        textField.setText(text.toUpperCase());
    }
});

Fouquet

Answer 9

it was the update version of Codemwnci. his code is quite fine and works great except the error message. To avoid error you must change the condition statement.

  // Listen for changes in the text
textField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    warn();
  }
  public void removeUpdate(DocumentEvent e) {
    warn();
  }
  public void insertUpdate(DocumentEvent e) {
    warn();
  }

  public void warn() {
     if (textField.getText().length()>0){
       JOptionPane.showMessageDialog(null,
          "Error: Please enter number bigger than 0", "Error Massage",
          JOptionPane.ERROR_MESSAGE);
     }
  }
});

Thrower

Your adaptation fires the error message dialog whenever any string longer than length=0 is entered in the textfield. So that's basically any string other than an empty string. That's not the requested solution. – Gramophone

Answer 10

You can use even "MouseExited" to control. example:

 private void jtSoMauMouseExited(java.awt.event.MouseEvent evt) {                                    
        // TODO add your handling code here:
        try {
            if (Integer.parseInt(jtSoMau.getText()) > 1) {
                //auto update field
                SoMau = Integer.parseInt(jtSoMau.getText());
                int result = SoMau / 5;

                jtSoBlockQuan.setText(String.valueOf(result));
            }
        } catch (Exception e) {

        }

    }   

Krongold

not really: the requirement is doing something when the text is changed - that's unrelated to mouseEvents ;-) – Deliberation

Answer 11

Use a KeyListener (which triggers on any key) rather than the ActionListener (which triggers on enter)

Agripinaagrippa

This doesn't work because the value of the field isn't captured properly, field.getText() returns the initial value. and the event (arg0.getKeyChar()) returns the key pressed error checking is needed to determine if you should concatenate with field text. – Ruler

@glend, you can use keyReleased event instead of keyTyped event. It worked for me and getting the complete value. – Fouquet

Answer 12

I am brand new to WindowBuilder, and, in fact, just getting back into Java after a few years, but I implemented "something", then thought I'd look it up and came across this thread.

I'm in the middle of testing this, so, based on being new to all this, I'm sure I must be missing something.

Here's what I did, where "runTxt" is a textbox and "runName" is a data member of the class:

public void focusGained(FocusEvent e) {
    if (e.getSource() == runTxt) {
        System.out.println("runTxt got focus");
        runTxt.selectAll();
    }
}

public void focusLost(FocusEvent e) {
    if (e.getSource() == runTxt) {
        System.out.println("runTxt lost focus");
        if(!runTxt.getText().equals(runName))runName= runTxt.getText();
        System.out.println("runText.getText()= " + runTxt.getText() + "; runName= " + runName);
    }
}

Seems a lot simpler than what's here so far, and seems to be working, but, since I'm in the middle of writing this, I'd appreciate hearing of any overlooked gotchas. Is it an issue that the user could enter & leave the textbox w/o making a change? I think all you've done is an unnecessary assignment.

Autoeroticism

Answer 13

DocumentFilter ? It gives you the ability to manipulate.

[ http://www.java2s.com/Tutorial/Java/0240__Swing/FormatJTextFieldstexttouppercase.htm ]

Sorry. J am using Jython (Python in Java) - but easy to understand

# python style
# upper chars [ text.upper() ]

class myComboBoxEditorDocumentFilter( DocumentFilter ):
def __init__(self,jtext):
    self._jtext = jtext

def insertString(self,FilterBypass_fb, offset, text, AttributeSet_attrs):
    txt = self._jtext.getText()
    print('DocumentFilter-insertString:',offset,text,'old:',txt)
    FilterBypass_fb.insertString(offset, text.upper(), AttributeSet_attrs)

def replace(self,FilterBypass_fb, offset, length, text, AttributeSet_attrs):
    txt = self._jtext.getText()
    print('DocumentFilter-replace:',offset, length, text,'old:',txt)
    FilterBypass_fb.replace(offset, length, text.upper(), AttributeSet_attrs)

def remove(self,FilterBypass_fb, offset, length):
    txt = self._jtext.getText()
    print('DocumentFilter-remove:',offset, length, 'old:',txt)
    FilterBypass_fb.remove(offset, length)

// (java style ~example for ComboBox-jTextField)
cb = new ComboBox();
cb.setEditable( true );
cbEditor = cb.getEditor();
cbEditorComp = cbEditor.getEditorComponent();
cbEditorComp.getDocument().setDocumentFilter(new myComboBoxEditorDocumentFilter(cbEditorComp));

Alfonzoalford

Answer 14

Here is a Kotlin port of @Boann's answer, which is a great solution that has been working well for me.

import java.beans.*
import javax.swing.*
import javax.swing.event.*
import javax.swing.text.*

/**
 * Installs a listener to receive notification when the text of this
 * [JTextComponent] is changed. Internally, it installs a [DocumentListener] on the
 * text component's [Document], and a [PropertyChangeListener] on the text component
 * to detect if the `Document` itself is replaced.
 *
 * @param changeListener a listener to receive [ChangeEvent]s when the text is changed;
 * the source object for the events will be the text component
 */
fun JTextComponent.addChangeListener(changeListener: ChangeListener) {
    val dl: DocumentListener = object : DocumentListener {
        private var lastChange = 0
        private var lastNotifiedChange = 0
        override fun insertUpdate(e: DocumentEvent) = changedUpdate(e)
        override fun removeUpdate(e: DocumentEvent) = changedUpdate(e)
        override fun changedUpdate(e: DocumentEvent) {
            lastChange++
            SwingUtilities.invokeLater {
                if (lastNotifiedChange != lastChange) {
                    lastNotifiedChange = lastChange
                    changeListener.stateChanged(ChangeEvent(this))
                }
            }
        }
    }
    addPropertyChangeListener("document") { e: PropertyChangeEvent ->
        (e.oldValue as? Document)?.removeDocumentListener(dl)
        (e.newValue as? Document)?.addDocumentListener(dl)
        dl.changedUpdate(null)
    }
    document?.addDocumentListener(dl)
}

You can use it on any text component as follows:

myTextField.addChangeListener { event -> myEventHandler(event) }

Like his code, also public domain.

Peeper

Answer 15

This is how you can convert a single lambda into a DocumentListener:

interface DocumentChangeListener extends Consumer<DocumentEvent>, DocumentListener {
    @Override
    default void insertUpdate(DocumentEvent e) { accept(e); }
    @Override
    default void removeUpdate(DocumentEvent e) { accept(e); }
    @Override
    default void changedUpdate(DocumentEvent e) { accept(e); }
}

and its use is:

var textField = new JTextField();
textField.getDocument().addDocumentListener((DocumentChangeListener)
                e -> {
                    String s = documentText(e.getDocument());
                    // ....
                }
);

There is a gotcha: the document will end with a newline, while in ActionListener there will be no newline. I use trim() to get rid of that newline:

static String documentText(Document doc) {
    try {
        return doc.getText(0, doc.getEndPosition().getOffset()).trim();
    } catch (BadLocationException e) {
        throw new RuntimeException(e);
    }
}

Machos