Re: GridBagLayout and changing constraints objects.

On Mar 25, 10:28 pm, Brandon McCombs <n...@xxxxxxxx> wrote:
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).
Actually, I have four objects which would only trade places, and they
are similar enough that the change shouldn't bother users. Have you
ever played a game on Yahoo games? notice when you sit at a table,
your side becomes the southern most side. I'm basically emulating
that effect.

It is easier to move the components around than to change which model
each component is looking at. Either way, the effect would be the
same.


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.

Hmm, I don't see how you think that my constraints object is unset. I
simply didn't copy the code that implemented getConstraints();

.

Relevant Pages

  • Re: GridBagLayout and changing constraints objects.
    ... myPanel.add, constaints); ... label, and re-add it with the new constraints? ...
    (comp.lang.java.gui)
  • Re: GridBagLayout and changing constraints objects.
    ... GridBagConstraints constaints = getConstraints; ... myPanel.add, constaints); ... Will this have the expected effect, or do I need to remove the old ... However I can't help noticing that the code you quoted can never have the expected effect since constaints!= constraints :-) ...
    (comp.lang.java.gui)