CODEWITHSUNDEEP
javaswingjtextfielddocumentlistener
itro
itro

Reputation: 7228

How to make difference between textField.setText() and adding text to textField manually in java?

I have a textField in my application which will be initiated programmatically (textField.setText() ) when user clicked in an item in JList. later user will change this value manually. I get stuck with using document-listener to detect changes in this text field. When changes happens programmatically it must do nothing but if manually happens, it should change the background to red.

How to detect whether textField has been filled out manually or by textField.setText()?

txtMode.getDocument().addDocumentListener(new DocumentListener() {
        public void insertUpdate(DocumentEvent e) {
            if (!mode.equals(e.getDocument()))
            txtMode.setBackground(Color.red);
        }

        public void removeUpdate(DocumentEvent e) {
            if (mode.equals(e.getDocument()))
            txtMode.setBackground(Color.white);              
        }

        public void changedUpdate(DocumentEvent e) {
            //To change body of implemented methods
        }
    });

Upvotes: 10

Views: 3812

Answers (3)

fragorl
fragorl

Reputation: 1736

This doesn't solve the issue that user Hakanai mentioned about being unable to detect external, programmatic calls to setText. However, if only being able to guard against calls made from within your own code is satisfactory, then one solution could be to create a specific lock object within your class, synchronize on it during the block of code that calls setText, and then call Thread.holdsLock() to detect if you're executing in this block, and if so bail out.

public class SomeGuiClass {

    private final Object txtModeSetTextLock = new Object();

    public SomeGuiClass() {
        // ...
        txtMode.getDocument().addDocumentListener(
            new DocumentListener() {
                public void insertUpdate(DocumentEvent e) {
                    if (!isProgrammaticUpdate()){
                        txtMode.setBackground(Color.red);
                    }
                }

                public void removeUpdate(DocumentEvent e) {
                    if (!isProgrammaticUpdate()){
                        txtMode.setBackground(Color.white);
                    }
                }

                public void changedUpdate(DocumentEvent e) {
                }

                private boolean isProgrammaticUpdate() {
                    return Thread.holdsLock(txtModeSetTextLock);
                }
            }
        );
    }

    private void someOtherListenerInvocation() {
        synchronized(txtModeSetTextLock) {
            // ...
            txtMode.setText("...");
        }
    }

}

Upvotes: 0

Denis Tulskiy
Denis Tulskiy

Reputation: 19187

Keep in mind that all the event listeners are executed on the Swing Event Thread. So things might not go in the exact order as you want them to. In this situation, any solution will be hack-ish because you can not get total control over the swing thread and who posts events on it.

What I'm trying to say is this: suppose you chose to use some flag to let your listeners know that it's a programmatic change. Here's the possible scenario (I assume you're following the nice rule of doing any UI updates from the swing thread via invokeLater):

  1. set the flag to skip events
  2. setText
  3. set flag to false

if you do all of it in one invocation, the setText will trigger update events posted to the end of the event queue, thus, by the time they are executed, the flag will already be false.

So you should do step 1 and 2 in one invokeLater call, or even invokeAndWait, and then post another event with invokeLater to unset the flag. And pray that your user is not so fast as to make some changes between these two invocations, otherwise, they'de be considered a programmatic change as well.

Upvotes: 5

mKorbel
mKorbel

Reputation: 109823

there are two ways

  • remove DocumentListener before setText("...") add DocumentListener back if done

code 

public void attachDocumentListener(JComponent compo){
      compo.addDocumentListener(someDocumentListener);
}

//similair void for remove....
  • use boolean value for disabling "if needed", but you have to change contens of your DocumentListener

for example

 txtMode.getDocument().addDocumentListener(new DocumentListener() {
    public void insertUpdate(DocumentEvent e) {
        if (!mode.equals(e.getDocument()))

        if (!updateFromModel){
           txtMode.setBackground(Color.red);
        }  
    }

    public void removeUpdate(DocumentEvent e) {
        if (mode.equals(e.getDocument()))

        if (!updateFromModel){
           txtMode.setBackground(Color.white);
        }  
    }

    public void changedUpdate(DocumentEvent e) {
        //To change body of implemented methods
    }
});

Upvotes: 8

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