Develop Reference

UI not aligning

I am using LibGDX and Scene2D to create a simple menu for my game.
Here is a simple example that works for me:
table.add(gameLogo).row();
table.add(button1).row();
table.add(button2).row();
table.add(button3).row();
I didn't include the irrelevant code(including the table into the stage for example).
If I don't include .row() to each object that I add to the table, then the menu isn't aligning to the center, which is very odd, for example:
table.add(gameLogo).row();
table.add(button1);
table.add(button2).row();
table.add(button3);
Why is the menu behaving like that? should I use more tables or add some HorizontalGroups perhaps?
If you need any additional information, or images I can provide, although it does the same for even the simplest menu implemention possible with LibGDX and Scene2d.

This is a colspan problem.
Looking at your code, this is what you are currently doing :
I assume that you would like to display your menu like that :
In order to do that, as you can see, you need to set the colspan size of your gamelogo to 2, so that it will take as much size as 2 regular cells.
So, to achieve this result, your code should be :
table.add(gameLogo).colspan(2).center().row();
table.add(button1);
table.add(button2).row();
table.add(button3);
The align(Align.center) or center() methods will not work alone, since these methods are only used to align the widget inside it's own cell.
If you experience more problems with libgdx ui table, remember that you can enable a debug renderer to display the cells border :
table.setDebug(true);

How to edit the Scroll Bar

I have a JTable in a JScrollPane but I'd like to change the look of the ScrollBar to something a bit better looking; a 'custom design'. Maybe put an image that a user can drag instead of the default thick blue bar. Is this even possible?
The main thing I'd like to do is change the thickness of the bar. My application uses a small window and the ScrollBar looks too thick.
Any help will be much appreciated.
Edit:
Thanks for the responses so far. I just found this; answers my answer, in part: java scrollbar thickness

Unfortunately I cannot provide a sample at the current moment, but you should definitely look into this
The BasicScrollBarUI class allows you to modify different features of a typical JScrollBar, such as various different colors, sizes, and shadow effects. This should be what you are looking for. Basically the idea is that you are supposed to override the installDefaults method and just modify the protected fields to your liking.
But, if you want to get fancy, I would highly suggest looking into JavaFX due to the amount of customizability it supports, one being CSS styling (which should be very helpful to you).

Dynamic JList implementation

I have a list of entities where each entity render into widget based on JPanel. Widgets have dynamic behaviour - once placed on panel it can be changed by underlying entity. This happens automaticaly. Moreover some widgets can be resized by different actions, on button click for example.
The question is how to organise them into something like JList but without rubber stamp technics. In other words I wanna JList where each item rendered with cellrenderer stay "alive".
Right now I have implemented quick-and-dirty component based on JPanel with vertical BoxLayout, it uses JList's renderer component and it's model... but my implementation is too dirty...
Um.. yeah, using JTable is not suitable too.
Do you have some ideas?

If you don't want rubber stamping to take place then you'll have to create your own JList implementation that uses actual components.
You could try and work around the rubber stamping effect by caching each component for each row in your renderer and bind values into it and return that instance when JList asks the renderer for it. This is pretty risky because if you have 20 rows being displayed you'll have to cache 20 instances in your renderer, and only when the row isn't visible can you reuse one. That would mean if you had 5 unique configurations (A,B,C,D,E) of components you might have 10 of type A, 5 of type B, 2 of type C, and 3 of type D, and 0 of type E being displayed. However, you can't simply reuse one of those components without knowing if its being displayed or not. So you'd have to take into account if the row is being displayed and if it's the right type for the row you are rendering. And you'll have to clean up after the row is hidden.
Another option is make a single component for the row that encapsulates all X variations you have and put those on a CardLayout. Then you can simply cache one per row being displayed, and simply swap the card being displayed upon rendering that row. I think that might be the simplest option for you.
The harder part is going to be routing events click mouse clicks, keyboard events, etc to those active components to have them respond like normal components. Re-rendering the buttons when the user clicks them, and so forth is going to be challenging. Not impossible, but tedious.
Finally, variable row height JList is a pain. Especially in your calculations to figure out if a row is displayed or not because you can't simply do easy math like: int rowHeight = jlist.getHeight / model.size(). It doesn't work. You have to calculate each row's height and them up to figure out if a row is visible or not.
Doing what you're talking about is a lot of work, and very tricky coding to work around some of the assumptions of JList to make it work. In the end you might find it easier just to implement your own List control that makes different design decisions. Either way its going to require you are good at Swing to get it to work.

Ok. I don't find any implementation of such component. Let it be first one.
https://github.com/wertlex/JActiveList
P.S. I don't think this is proper way implementation... but it works.

use JList and ActionListener XD

Is it possible to change the background of a jspinner using the nimbus laf?

I'm fairly confident that I have done my research before coming to you for help, but it's possible I have overlooked something.
I'm writing a java UI using the Nimbus l-a-f. I wish to change the background colour of a JSpinner on state-change, ie, when either the up or down button is pressed the background colour of the textfield within the jspinner changes colour to signify that the value has been altered.
I am aware this is possible using OTHER lookandfeels but not as easy with Nimbus, eg:
((JSpinner.NumberEditor)jSpinner1.getEditor()).getTextField().setBackground(color.yellow);
I have also looked into actually changing the colour theme of the UI manager, but I only want to change the colour when an action occurs, not just overall by default.
here or here
Is this at all possible and where do I start?
Failing this, I was hoping to just change a button's colour:
jButton.setBackground(Color.yellow);
This is easy enough but since the default colour is a painted gradient, how do I change it back to that?
Really hope someone out there knows or can help.
Much appreciated in advance!

Yes, it is possible. See this example (i.e. SpinnerDemo4) from The Java Tutorials for more detail. And yes, I did set the LaF to Nimbus when testing the code therein.

show the value of the graph when cursor is placed on the graph

I am using jfreechart to draw the graphs. I need to show the value when the cursor is placed on the graph.

Use the ToolTipManager. If you can register the graph as a component, you can assign a specific tooltip to it which will be displayed automatically.
If you cant use the default version it's also possible to write a custom ToolTipManager, which displays the tooltip when the cursor is over certain areas on the screen.

I've never used jfreechart tooltips before, but that maybe what you're looking for.
There a series of chart specific tooltip interface/classes in the org.jfreechart.labels package. For example, using a XyToolTipGenerator with an XYItemRenderer may do what your looking for.