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Re: GridBagLayout and cha

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  To: comp.lang.java.gui
Daniel Pitts wrote:
> Say I have the following code:
> 
> JPanel myPanel = new JPanel(new GridBagLayout());
> GridBagConstraints constaints = getConstraints();
> myPanel.add(new JLabel("Hello world"), constaints);
> 
> And then later (as a result of an Event), I do something like
> constraints.gridx = 3;
> myPanel.revalidate();
> 
> Will this have the expected effect, or do I need to remove the old
> label, and re-add it with the new constraints?
> 

You will have to remove it and re-add it. How is Java to know which 
Object is supposed to have the new constraint if you don't re-add the 
Object with that constraint? It could assume to apply that new 
constraint property to the only Object in a JPanel if there is only one 
in it but that wouldn't work for more than 1 Object in container and it 
isn't a good way to do it anyway. It is bad design to need to 
relocate/resize an Object after an event occurs. You should rethink how 
you are presenting the interface to the user because the user should not 
normally see new things appear when they do something; all the Objects 
in the GUI should be visible, their sizes unchanging, and the unused 
ones disabled until they are needed (with the enabling trigger being 
your event).

As it is now, the line:
myPanel.add(new JLabel("Hello world"), constaints);

isn't going to do much because you aren't defining what your constraints 
are although some of the properties do have default values. The default 
for gridx is 'relative' which may not be what you want initially.

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GridBagLayout and changin "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Chris Smith" <chris.smith@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Knute Johnson" <knute.johnson@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Tom Hawtin" <tom.hawtin@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
    Re: GridBagLayout and cha "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "SadRed" <sadred@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
    Re: GridBagLayout and cha "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "SadRed" <sadred@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Brandon McCombs" <brandon.mccombs@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
    Re: GridBagLayout and cha "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Ian Wilson" <ian.wilson@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
    Re: GridBagLayout and cha "Daniel Pitts" <daniel.pitts@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Larry Barowski" <larry.barowski@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000
  Re: GridBagLayout and cha "Larry Barowski" <larry.barowski@THRWHITE.remove-dii-this> - 2011-04-27 15:32 +0000

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