We help IT Professionals succeed at work.

We've partnered with Certified Experts, Carl Webster and Richard Faulkner, to bring you a podcast all about Citrix Workspace, moving to the cloud, and analytics & intelligence. Episode 2 coming soon!Listen Now


mouse event handling...

Raydot asked
Medium Priority
Last Modified: 2010-04-16
I have a question about mouse event handling.  Why can the mouseDrag(), mouseMove(), mouseEnter(), and mouseExit() methods be used by simply entering commands, while the mouseUp() and mouseDown()methods have to be "checked," (i.e. "if(evt.modifiers == 0))."  I'm just wondering if there's something I don't understand about event handling.  
Watch Question


Oh, and why does the evt.modifiers evaluate to 0 when the mouse is clicked instead of to 1, which seems more logical?



There is no difference between the different methods
and how they go about handling events.

Most likely what you've seen is some inconsistent
programming style.  

The 0 vs. 1 thing is an old UNIX holdover.  


Not the solution you were looking for? Getting a personalized solution is easy.

Ask the Experts

OK, you're both right.  What I was looking at was a program that checks whether the left or right mouse buttons are clicked.  So as to Tony's comment, the programming snippet I gave, out of context, was "inconsistent" with the other mouse event methods in the program I was describing in that it utilized an if...else construct, like russgold suggests, to check which button had been clicked.  

Just to get my $$$'s worth, these methods (mouseDown, mouseUp, mouseDrag, etc.) are checked by Java automatically?  They handle all mouse events and I don't have to do anything else? (e. g. initialize, monitor, thread, etc.)




Russ is correct, I was only speaking to the fact that there
is no actual difference between the methods in terms of
what they are required to handle.  What you can do
with them are different.  

Events in 1.02 and 1.1 are completely different.  However,
since you're asking about 1.02 methods, we'll stick to

The events will get passed to the default event handler
for the container if you don't handle them.  There is
no need to initalize, monitor or anything if you don't
need to monitor those events.  

WHOA! (Record stops, bar clears out...) I'm talking about 1.02 events?  I'm reading a book on Visual J++ 1.1, so I thought I was dealing with Java 1.1.  How do you know these are 1.02 events, and if they are then how is it done in 1.1?



While mouseMove, mouseEnter, etc. all still work in 1.1,
they are 1.02 event handling methods and are deprecated.
Methods are handled using mouseListener() and mouseMotionListener() and adapter classes.  It's a
completely different model.

The code you are writing will still work now, but
probably not in the the next real release of Java (2.0 -
1.2 will still be fine).

So, the deal is that you can do things the way you are
or you can move to the new event model.  

Even with 1.1 though, there's no need to handle those
events if you don't need to do anything with them.

Mmmmm...this book I'm going through sucks.  That's like the third outdated method I've come across in it.  Maybe I'll e-mail the author...

Anyway, thanks Tony.




I review a lot of books, and I'd be happy to recommend
a good text for you.


Access more of Experts Exchange with a free account
Thanks for using Experts Exchange.

Create a free account to continue.

Limited access with a free account allows you to:

  • View three pieces of content (articles, solutions, posts, and videos)
  • Ask the experts questions (counted toward content limit)
  • Customize your dashboard and profile

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.