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Dynamically create list of jpanels swing/java

I am attempting to create panel, PluginListPanel (extending JPanel), which will show a list of plugin panels which will respect the preferred height of the plugin's panel, but will force the width. I have a solution, but it is slow and has a weird bug. In the screenshot, there are two such panels, one to the left and one to the right:
I don't know different layout manager systems very well, but I know that the TOP field in the BorderLayout does what I want. So, I came up with this 'recursive' solution:
public PluginListPanel(List<PanelContainer> items) {
JPanel body = this;
for (PanelContainer item : items) {
body.setLayout(new BorderLayout(0, 0));
JPanel panel = new PluginOnePanel(item);
body.add(panel, BorderLayout.NORTH);
JPanel newBody = new JPanel();
body.add(newBody, BorderLayout.CENTER);
body = newBody;
}
}
The problem I encounter is when I scroll, the system responds somewhat slowly, and the colour of the SamplePluginPanels is different (see picture below), even if the number of SamplePluginPanels is as low as 8.
The question is, how can I make this more elegant, not slow down the program and not miscolour the panels?
Any insights are highly appreciated.

I think a vertical Box is the answer (actually 2, on both columns):
Box leftBox = Box.createVerticalBox();
Box rightBox = Box.createVerticalBox();
/* put them together */
setLayout(new GridLayout(2,1));
add(leftBox);
add(rightBox);
Also make sure, that the content of the scroll pane implements Scrollable and returns true, to scrollableTracksViewportWidth(). This will force equal widths.

Java Swing component interaction (BoxLayout and Label)

OK, several questions about the test code below... I don't have the full working program to post, but I'm hoping people know Swing well enough to take a stab at it. This is a JLabel inside of a JPanel(BoxLayout), and I'm working on the sizing of the label in the lower right.
What I get with the code as shown is a status box 300 width by 30 height. I have fiddled with the preferred size and the label minimum size, and it does not seem to behave in any rational way.
Why does the JPanel Preferred Size affect the height but not the
width? If I change the x dimension in setPreferredSize() to 0 or
500, it still comes out 300 from the label.
Why does the JLabel Minimum Size affect the width but not the
height? If I comment the setPreferredSize() call and increase the
label height to 30, nothing happens.
I started out with JPanel setMinimumSize (commented), but it no longer has any
effect - why does the JPanel require setPreferredSize()?
If I change the label text from "" to " ", this increases the height
of the label. Since the label is not controlling the height here,
why does this have any effect at all?
By the way, the createRigidArea() call is to force the separator to the right, rather than sticking to the left hand side of the screen. If there are any less kludgy ideas for this, I'd be grateful.
private JComponent makeStatusBarTest() {
JPanel statusPanel = new JPanel();
statusPanel.setLayout(new BoxLayout(statusPanel, BoxLayout.LINE_AXIS));
statusPanel.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
// statusPanel.setMinimumSize(new Dimension(0, 30));
statusPanel.setPreferredSize(new Dimension(500, 30));
JLabel statusLabel = new JLabel();
Border emptyBorder = BorderFactory.createEmptyBorder(5, 10, 5, 10);
statusLabel.setBorder(emptyBorder);
statusLabel.setText("");
statusLabel.setMinimumSize(new Dimension(300, 20));
statusPanel.add(statusLabel);
statusPanel.add(new JSeparator(SwingConstants.VERTICAL));
statusPanel.add(Box.createRigidArea(new Dimension(5000,0)));
return statusPanel;
}

I can explain #1 and #2:
From the BoxLayout javadocs: "BoxLayout attempts to arrange components at their preferred widths (for horizontal layout) or heights (for vertical layout)."
In other words, BoxLayout uses the internal components (in your case, statusLabel) to decide the widths, but the JPanel itself (within reason) to decide the heights.
You can usually use Glue instead of RigidArea to move stuff around, but I agree that it takes some getting used to.
#4 is Swing being too efficient - if the JLabel is empty the text rectangle is 0x0. Ultimately determined in SwingUtilities.layoutCompoundLabelImpl().
I think #3 is because BoxLayout is trying to respect the preferred size of the internal components. Since setMinimumSize, arguably, overrides their preferred sizes.

Java Swing Panel Size

Hi I have been learning Java Swing for creating a chess game to practice my Java programming skills.
I've added a JPanel to the east of the JFrame with BorderLayout and I've used the setPrefferedSize(new Dimension(x,y)) method to set the width and height.
After that I have created 4 JPanel and added them with BoxLayout on the previously created panel.
I have tried to set the size of the 4 panels with the setSize(x,y) and setPreferredSize(new Dimension(x,y)) but it dosent work the 4 panels automaticly changed there size to fit the main JPanel and after adding a JLabel on one of them the size of it increased automaticly .
This is my code:
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
JPanel a = new JPanel();
a.setPreferredSize(new Dimension(50, 50)); //this dosent work
a.add(min);
a.setBackground(Color.red);
this.add;
JPanel b = new JPanel();
b.setBackground(Color.blue);
this.add(b);
JPanel c = new JPanel();
this.add(c);
JPanel d = new JPanel();
d.setBackground(Color.black);
this.add(d);
How can I change the size of each of these panels?

BoxLayout is best for laying out components with varying sizes along a single axis. From the Javadocs:
"BoxLayout attempts to arrange components at their preferred widths (for horizontal layout) or heights (for vertical layout)."
The idea is that they may have different heights (for a horizontal layout) and it will take the maximum height. And, they definitely may have different widths. Also, BoxLayout works with some, er, "interesting" filler pieces like Box.createHorizontalGlue(). These are actually quite useful for flexible, resizeable layouts once you get the hang of it. But, all in all, BoxLayout is for flexible, resizable layout of items with differing sizes.
For simpler cases, especially if you want both preferred width and preferred height to be "respected", use GridLayout as everybody else has suggested.

Best Swing Layout for 2-dimensional grid of buttons?

I'm trying to create a JDialog like the Symbol dialog in Microsoft Word that you get by choosing Symbol... from the Insert menu. Basically, it's an n x m (n and m are not known until runtime) grid of small buttons. I've got a first version of this working nicely using a GridLayout. The problem is that when you resize the dialog (and there is a requirement that you should be able to resize it), the size of the buttons changes. I need the size of the buttons to remain constant.
But I want the dimensions of the grid containing the buttons to change. For example, if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
I've thought of a couple of ways to fix this:
When the dialog is resized, create a new GridLayout and repopulate it with the buttons. I'm going to try this and see how it looks, but it seems like a clumsy way of doing it.
Use some other type of layout such as a FlowLayout. I took a stab at this, but it put all n x m buttons in one row. I do not want to use horizontal scroll-bars and the buttons ran off the right edge. Anyway, it's supposed to be a 2-dimensional grid of buttons.
What is the best way to solve this layout problem?

Create a buttons panel with GridLayout and set a fixed size (could be calculated at runtime of course) to it. The buttons panel should be contained in a panel of BoxLayout.
Check out the BoxLayout Tutorial
Very Very basic example:
public static void main(String[] args) throws Exception
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel buttonPanel = new JPanel();
JPanel containerPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(2,2));
buttonPanel.add(new JButton("1"));
buttonPanel.add(new JButton("2"));
buttonPanel.add(new JButton("3"));
buttonPanel.add(new JButton("4"));
buttonPanel.setPreferredSize(new Dimension(300, 400));
containerPanel.add(buttonPanel);
frame.getContentPane().add(containerPanel);
frame.pack();
frame.setVisible(true);
}

if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
Wrap Layout might be what you are looking for.

I had a similar issue with a single column of buttons, and found that MiGLayout (third-party, available here) was simple and effective for this. It helped both with making a grid and with setting button sizes, although it took me a day or two to get used to its syntax.
But the key is really setting button sizes; GridLayout certainly seems like the way to go for a layout that is, well, a grid. I haven't tested, but I suspect that the built-in setXSize() methods would work just as well. The GridBagLayout tutorial has examples of some things you can do with sizing/positioning.

FlowLayout would be the way to go but you might have some configuration problems. What layout manager does the parent component use?

How to make JLabels start on the next line

JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.add(economy);
pMeasure.add(regularity);
...
When I run the code above I get this output:
Economy Regularity
How can I get this output, where each JLabel starts on a new line? Thanks
Economy
Regularity

You'll want to play around with layout managers to control the positioning and sizing of the controls in your JPanel. Layout managers are responsible for placing controls, determining where they go, how big they are, how much space is between them, what happens when you resize the window, etc.
There are oodles of different layout managers each of which allows you to layout controls in different ways. The default layout manager is FlowLayout, which as you've seen simply places components next to each other left to right. That's the simplest. Some other common layout managers are:
GridLayout - arranges components in a rectangular grid with equal-size rows and columns
BorderLayout - has one main component in the center and up to four surrounding components above, below, to the left, and to the right.
GridBagLayout - the Big Bertha of all the built-in layout managers, it is the most flexible but also the most complicated to use.
You could, for example, use a BoxLayout to layout the labels.
BoxLayout either stacks its components on top of each other or places them in a row — your choice. You might think of it as a version of FlowLayout, but with greater functionality. Here is a picture of an application that demonstrates using BoxLayout to display a centered column of components:
An example of code using BoxLayout would be:
JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));
pMeasure.add(economy);
pMeasure.add(regularity);
...

I read this piece of code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.VERTICAL));
It seems BoxLayout doesn't have VERTICAL. Upon searching, this will work using the following code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));

Here is what you need to use:
JLabel economy = new JLabel("<html>Economy<br>Regularity</html>");

A quick way is to use html within the JLabel.
For instance include the <br/> tag.
Otherwise, implement a BoxLayout.

Make a separate JPanel for each line, and set the dimensions to fit each word:
JLabel wordlabel = new JLabel("Word");
JPanel word1 = new JPanel();
word1.setPreferredSize(new Dimension(#,#);
This should work for each word. You can then add each of those JPanels to your main JPanel. This also allows you to add other components next to each word.