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Simple GUI - button not responding to clicks

John Deegan
Greenhorn

Joined: Nov 27, 2012
Posts: 4
Hello, all. This is my first post, and I am a bit new at this, as I am sure you will be able to tell soon. This code is loosely based on an example problem in Head First Java. It is a GUI with a button and a circle that should change color when the button is clicked. The code compiles and runs, but the problem is that nothing happens when I click on the button. I think it has to do with repaint(), but flipping through the API and looking online has not helped me much. Any ideas?

Paul Clapham
Bartender

Joined: Oct 14, 2005
Posts: 18882
    
    8

But you want to repaint the JPanel, not the JFrame, isn't that right?
Michael Dunn
Ranch Hand

Joined: Jun 09, 2003
Posts: 4632
> nothing happens when I click on the button. I think it has to do with repaint()

no, the color never changes (0,0,0)

gr = (int) Math.random() * 256;
is (int) Math.random() = < 1.00, so int value is 0
0 * 256 = 0

change to this
gr = (int) (Math.random() * 256);
ditto for the others
Ranganathan Kaliyur Mannar
Bartender

Joined: Oct 16, 2003
Posts: 1088
    
  10

and, Welcome to the Ranch!


Ranga.
SCJP 1.4, OCMJEA/SCEA 5.0.
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 39788
    
  28
Might be better to use a Random object, because that has a more specific method for getting pseudo‑random ints.
John Deegan
Greenhorn

Joined: Nov 27, 2012
Posts: 4
Michael's suggestion ended up fixing it. Thanks guys!
 
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subject: Simple GUI - button not responding to clicks