How to get source object from DocumentListener (DocumentEvent)?

Question

I have my class and I have implemented DocumentListener

public void removeUpdate( DocumentEvent arg0 ) {
   System.out.println( arg0.getDocument());
}

It would print javax.swing.text.PlainDocument@49ea903c

Is there any possible way I would get the object so I can get the value of the changed textfield? At the moment I have only one field so I do not need a check, but what if I use two or more, how do I know which JTextField has notified the listener?

score 5 · Accepted Answer · answered May 18 '13 at 16:11

5

I'm not sure it's possible to get the swing component from a Document. But the issue is easily solved: just add a different instance of the listener to every text field, and store the text field in the listener itself.

textField1.getDocument().addDocumentListener(new MyDocumentListener(textField1));
textField2.getDocument().addDocumentListener(new MyDocumentListener(textField2));
textField3.getDocument().addDocumentListener(new MyDocumentListener(textField3));

answered May 18 '13 at 16:11

JB Nizet

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Yeah I am aware of that, I was hoping I could make my code cleaner, like you can use event.getSource() on ActionListener.. Thank you for the answer. – Nikola May 18 '13 at 16:16
Found any nice alternatives yet? – Redoman Apr 29 '14 at 11:18

score 3 · Answer 2 · edited May 23 '17 at 12:18

3

One option is to use an inner class, which will provide you an opportunity to reference the text field.

final JTextField field = new JTextField();

field.getDocument().addDocumentListener(new DocumentListener() {
  // Here you can reference 'field' in your methods
});

If you need to perform the same action for each text field, JB Nizet's solution will be neater.

edited May 23 '17 at 12:18

Community

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answered May 18 '13 at 16:11

Duncan Jones

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score 0 · Answer 3 · answered May 18 '13 at 16:07

0

You actually are getting the PlainDocument object. Just store it in a variable instead of printing it.

For more info see docs.

answered May 18 '13 at 16:07

Mateusz

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score 0 · Answer 4 · answered May 18 '13 at 16:13

What you need to do is adding document listners to each component you need.If you really need to know which text fields text has changed then you can have a property in the DocumentListner as textFieldName or something and you can set it when you create the document listner for them.But I think you better change your approaching to situation.It doesn't sound good.

Aubin · Answer 5 · 2013-05-18T17:56:45.383

You may update the document without knowing the context.

Consult the documentation of javax.swing.event.DocumentEvent

javax.swing.event.DocumentEvent.getOffset() Returns the offset within the document of the start of the change.
javax.swing.event.DocumentEvent.getLength() Returns the length of the change.

These methods combined with the document retrieved by javax.swing.event.DocumentEvent.getDocument() allow you to update the document in a proper way. Later you may add other text field without any change.

To simply get the text of a JTextField after change:

JTextField myTf = new ...; // maybe an attribute definition
...
myTf.addActionListener(
   new ActionListener(){@Override public void actionPerformed( ActionEvent e ) {
      JTextField tf = (JTextField)e.getSource();
      System.out.println( tf.getText());
      if( tf == myTf ) { // == for reference comparison
         ... // do something dedicated to myTf
      }
   }});

I have gone through the documentation several times before I have asked my question here, but I do not see how getOffset() or getLenght() is helping me. I want to get the text in the field after the change, not the length as I will do a search based on that — Nikola, May 18 '13 at 16:18
DocumentListener is used for more complex action, see my edit — Aubin, May 18 '13 at 17:57

How to get source object from DocumentListener (DocumentEvent)?

5 Answers5