Solved

Recognising changed data on a form

Posted on 2004-08-31
14
180 Views
Last Modified: 2010-03-31
I've got a JPanel with a number of different controls on it. The user can change data that is presented by these controls - is there a "normal" way of checking to see if any of the controls have changed on the forms rather than writing a monster IF statement?
0
Comment
Question by:howesd
  • 5
  • 4
  • 2
  • +1
14 Comments
 
LVL 35

Accepted Solution

by:
TimYates earned 25 total points
ID: 11942050
you can add listeners to the controls (after you set the default data into them), and if any of the listenerrs fire,  set a boolean flag to show that data (may) have changed....
0
 
LVL 18

Expert Comment

by:armoghan
ID: 11942111
add change listeners to all teh components like

addTextListener(new
                            TextListener() {
                            public void textValueChanged(TextEvent e) {
                                guiChangeEventHandler();
                            }
                        });
or some components will have this
itemStateChanged(ItemEvent e) {
                                guiChangeEventHandler();
                            }
                        });

in guiChangeEventHandler();
make a flag dirty to show that some change has occured
0
 
LVL 18

Expert Comment

by:armoghan
ID: 11942132
you can make a child class of JPanel and add the listener code into it

0
 
LVL 1

Author Comment

by:howesd
ID: 11942226
That's what I came up with ... is there a way to do that via a collection, or do I have to do it all manually?
0
 
LVL 86

Assisted Solution

by:CEHJ
CEHJ earned 25 total points
ID: 11945652
You can use the following class. Call

int initialValue = TextWatcher().rememberText(yourFrame);

when you want to 'start remembering' and once again when you want to see if changes have been made. Compare the two values:

class TextWatcher {


      private int textHashcode;


      /**
       *  Returns hash code of all text components
       *
       * @param  currentComponent  Description of the Parameter
       * @return                   Description of the Return Value
       */
      public int rememberText(Component currentComponent) {
            if (currentComponent instanceof Container) {
                  Component[] children = ((Container)currentComponent).getComponents();
                  for (int i = 0; i < children.length; i++) {
                        Component c = children[i];
                        rememberText(c);
                  }
            }
            if (currentComponent instanceof javax.swing.text.JTextComponent) {
                  textHashcode += ((JTextComponent) currentComponent).getText().hashCode();
            }
            return textHashcode;
      }

}
0
 
LVL 35

Expert Comment

by:TimYates
ID: 11949967
Will that work CEHJ?

what happens if I just swap 2 text values over?  ie:  if I have put the address in the name field, and vice-versa, and I just swap them over...

Won't that method show that as no change?
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 86

Expert Comment

by:CEHJ
ID: 11950550
That's probably unlikely, but true. There's probably a simple solution to that, but can't think of it at the moment
0
 
LVL 35

Expert Comment

by:TimYates
ID: 11950558
Just keeping you on your toes ;-)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 11950600
LOL
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 11950711
This'll fix it:

textHashcode = 31 * textHashcode + ((JTextComponent) currentComponent).getText().hashCode();
0
 
LVL 35

Expert Comment

by:TimYates
ID: 11950722
why 31?  Just asking...
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 11950913
Prime - they use it in String.hashCode
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

After being asked a question last year, I went into one of my moods where I did some research and code just for the fun and learning of it all.  Subsequently, from this journey, I put together this article on "Range Searching Using Visual Basic.NET …
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d…
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
Viewers will learn about the regular for loop in Java and how to use it. Definition: Break the for loop down into 3 parts: Syntax when using for loops: Example using a for loop:

914 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now