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    lt  0               JOptionPane showMessageDialog null                       Error  Please enter number bigger than 0    Error Message                       JOptionPane ERROR MESSAGE                              Any help would be appreciated

User · Answer

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  amp  leave the textbox w o making a change   I think all you ve done is an unnecessary assignment

User · Answer

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 - gt           Your code here

User · Answer

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

User · Answer

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     gt  1                      auto update field                 SoMau   Integer parseInt jtSoMau getText                     int result   SoMau   5                   jtSoBlockQuan setText String valueOf result                            catch  Exception e

User · Answer

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   gt 0          JOptionPane showMessageDialog null             Error  Please enter number bigger than 0    Error Massage             JOptionPane ERROR MESSAGE

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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    - gt                    if  lastNotifiedChange    lastChange                        lastNotifiedChange   lastChange                      changeListener stateChanged new ChangeEvent text                                                           text addPropertyChangeListener  document    PropertyChangeEvent e  - gt            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 - gt  doSomething       Code released to public domain  Have fun

User · Answer

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      lt br gt I ve found no way to track efficiently the modifications of the text of a JTextField     so I developed this widget      lt br gt DocumentListeners are intended to do it  unfortunately  when a text is replace in a field  the listener receive two events  lt ol gt      lt li gt One when the replaced text is removed  lt  li gt      lt li gt One when the replacing text is inserted lt  li gt      lt  ul gt     The first event is     simply absolutely misleading  it corresponds to a value that the text never had      lt br gt Anoter problem with DocumentListener is that you can t modify the text into it  it throws IllegalStateException       lt br gt  lt br gt 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      lt br gt  lt br gt This widget guarantees that no  ghost  property change is thrown       author Jean-Marc Astesana     lt BR gt 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  amp  amp   oldValue equals newValue   CoolJTextField this firePropertyChange TEXT PROPERTY  oldValue  newValue

User · Answer

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    lt  0          JOptionPane showMessageDialog null             Error  Please enter number bigger than 0    Error Message             JOptionPane ERROR MESSAGE

[java] Value Change Listener to JTextField

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