Develop Reference

Dynamically resize images linked to JLabels in a GridLayout layoutmanager

Current implementation layout:
((EDIT: added
Code: ))
private JPanel panelCenter;
private List<BufferedImage> listCreatedImages;
public ChooseCircuitPanel(List<BufferedImage> listCreatedImages) {
this.listCreatedImages = listCreatedImages;
initiate();
}
private void initiate() {
setLayout(new BorderLayout(50, 50));
panelCenter = new JPanel();
LayoutManager theLayout = new GridLayout(0, 3, 0, 0);
panelCenter.setLayout(theLayout);
panelCenter.setBorder(BorderFactory.createLineBorder(Color.BLACK));
for (BufferedImage bufferedImage : listCreatedImages) {
ImageIcon theImage = new ImageIcon(bufferedImage);
JLabel lblForImage = new JLabel(theImage);
lblForImage.setBorder(BorderFactory.createLineBorder(Color.BLACK));
panelCenter.add(lblForImage);
}
this.add(panelCenter, BorderLayout.CENTER);
}
Situation:
We want to display a race circuit here. A circuit should be displayed by placing standards tiles next to each other. It should be possible to resize the window, and with that, the circuit tiles should also resize.
((EDIT: bit more info: The race circuit data is stored on a server and the desktop application has to translate the data to a visual thing, by placing some standard tiles in the right order. ))
((EDIT: we are not allowed to use any external library. It should be doable by only using Java Swing code.))
I thought about placing the images in a JLabel and placing these JLabels in a panel with GridLayout as layout manager.
Using a GridLayout - I thought - it should be rather easy to get to a solution:
the components in the GridLayout (= JLabels) already scale and do exactly what I want.
Now, it would only be a matter of finding a way to resize the images so they fill the JLabels.
As you can see: right now, the images have a fixed size and don't scale at all.
I browsed a bit and saw lots of solutions that boil down to using Graphics2D and super.paintComponent, etc.
But most of these solutions had nothing to do with a GridLayout.
So conclusive question:
Is there an easier solution aside from using Graphics2D, etc. knowing that I use a GridLayout?
If not, I will of course use Graphics2D, etc. but I'm now just exploring my options. :)
((EDIT: SOLVED The tiles now neatly fit on each other. Don't mind the misalignments, that's our fault.))

There are no Swing components that do what you want so you will need to write your own code.
The easiest approach would be to use Darryl's Stretch Icon on your JLabel.
Or another approach is to create your own custom component that dynamically scales the image as it is painted. Something like the Background Panel which has code that allows you to scale or tile an image.

Given the nature of the view, I would recommend abandoning images altogether and instead implement the rendering in an Icon. Presuming you can make an icon scale with the label.

JScrollPane and sizing issues

I am having quite a problem in regards to a proper way to handle 'packing' a JPanel and allowing a scroll bar.
I left out a bit of the code, but I believe what is provided should suffice.
The issue, is that the JScrollBar either doesn't show up, or can't be interacted with (if I set the scroll bar to always have the vertical bar).
Here is an image depicting this:
![No Scroll Bar Present][1]
The ProjectPanel (extends JPanel) are of fixed size and, as you can see, extend farther than the visible view port. There is NO way of getting the calculated height of the JPanel (ProjectSelector), as the ProjectPanels can also be transitioned as so:
![They need to fill as a grid][2]
If anyone could help provide some insight on how to do this, that would be great. As of now, I would like at all costs not to use an external API, as that would cause more harm than good.
Question:
How can I set the height for the preferred size to be 'flexible', so as I add components it can expand? If that wouldn't be ideal / no possible, how could I properly allow the JScrollPane to show all components of the JPanel efficiently?

if I do not, then the Flow Layout organizes them horizontally
Maybe you should be using a GridLayout.
If not then you can try the Wrap Layout which is a FlowLayout that wraps to a new line as required.

If you are looking for a different layout, why don't you try MiGLayout? It is a very powerful and flexible layout manager.
See a detailed example here.
From that link, rewrite the initUI method to see the behavoir interesting to your problem:
public void initUI() {
this.setPreferredSize(new Dimension(100, 100));
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setJMenuBar(initMenuBar());
this.getContentPane().add(new JScrollPane(mainPanel = initMainPanel()));
this.setLocationByPlatform(true);
this.pack();
}

Why will BoxLayout not allow me to change the width of a JButton but let me change the height?

I'm trying to get the Layout of a JDialog of mine to fit a particular look that a program in which I'm porting to Java has, I've used several LayoutManagers before with great success yet for some reason I cannot seem to get this working at all. My goal is to have the Right (East) side of the JDialog contain a "Find Next" and "Cancel" button in a top-down order and then any extra space below so that the two buttons are always at the top of the JDialog, yet for some reason BoxLayout is continously ignoring any attempts at changing (this is where I'm lost) the width of a JButton. Code follows.
JButton findNext = new JButton("Find Next");
JButton cancel = new JButton("Cancel");
cancel.setPreferredSize(new Dimension((int)findNext.getPreferredSize().getWidth(),
(int)cancel.getPreferredSize().getHeight()));
JPanel example = new JPanel();
example.setLayout(new BoxLayout(example, BoxLayout.Y_AXIS));
example.add(findNext);
example.add(cancel);
example.add(Box.createGlue());
No matter what I try, cancel always retains it's normal size. I've tried setMinimumSize() and setMaximumSize() with the same parameters as setPreferredSize with no luck. I've even tried cancel.setPreferredSize(new Dimension(500, 500)); and the buttons height was the only thing adjusted, it STILL retained the default width it was given.
To clear up any questions, here is what it looks like (now that I've finished it) and you'll see that the "Find Next" and "Cancel" buttons are not the same size.

I know this is an old question but I don't really see a good explanation. So for the sake of searchers that stumble upon this I will add my two cents.
There are three methods associated with sizing components in Swing: setPreferredSize(), setMinimumSize(), and setMaximumSize(). However, the important point is that it is up to the particular layout manager being used as to whether or not it honors any of these methods.
For BoxLayout (the layout the original poster is using):
setMinimumSize() -- BoxLayout honors this
setMaximumSize() -- BoxLayout honors this
setPreferredSize() -- if X_AXIS is being used width is honored, if Y_AXIS is being used height is honored
The OP is using a Y_AXIS BoxLayout which is why only his height was being changed.
Update: I put together a page with this same information for all of the layout managers. Hopefully it can help some searchers out: http://thebadprogrammer.com/swing-layout-manager-sizing/

You may not want Box.createGlue(), which "grows as necessary to absorb any extra space in its container." Instead, use Box.createVerticalStrut() between the buttons, as shown below and in the ControlPanel of this simulation.
example.setLayout(new BoxLayout(example, BoxLayout.Y_AXIS));
example.add(findNext);
Box.createVerticalStrut(10);
example.add(cancel);
Addendum:
adding in setMaximumSize() made it work.
This is the expected behavior for components having identical maximum widths in a vertical BoxLayout, as described in Box Layout Features. The preferred width of the container becomes that of the (equally wide) children, and the X alignment becomes irrelevant.
example.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
JButton findNext = new JButton("Find Next");
JButton cancel = new JButton("Cancel");
Dimension d = findNext.getMaximumSize();
cancel.setMaximumSize(new Dimension(d));
example.add(findNext);
example.add(cancel);

As mentioned in the comments on the question, you were able to fix it by switching to setMaximumSize(). However, as you noted, setPreferredSize() doesn't work. So, what's up with that?
With many things Swing, the properties used to determine the actual component size when using the BoxLayout are somewhat random (in my opinion). When determining how to render the components, Swing calls layoutComponent() on the layout manager, which is figures out where to position everything.
BoxLayout's implementation of layoutComponent() involves a call to a method that creates SizeRequirements objects for the width and height of each of the components you add to the JPanel, based on their getMinimum/Preferred/MaximumSize() methods.
Later, it calls SizeRequirements.calculateAlignedPositions() for determining the correct width values for each component, because your orientation is BoxLayout.Y_AXIS (The heights are calculated using a different method). Taking snippets from the source, the relevant implementation of this method is as follows:
for (int i = 0; i < children.length; i++) {
SizeRequirements req = children[i];
//...
int maxAscent = (int)(req.maximum * alignment);
int maxDescent = req.maximum - maxAscent;
//...
int descent = Math.min(totalDescent, maxDescent);
//...
spans[i] = (int)Math.min((long) ascent + (long)descent, Integer.MAX_VALUE);
}
Note that totalDescent is the available width, so descent is always set to maxDescent, which is based on SizeRequirements.maximum, which was taken from JButton.getMaximumSize(). The value of spans[i] is then used later in a call to JButton.setBounds() as the width. As you'll note, getPreferredSize() was never involved here, which is why setting it has no impact in this case.

Usually if want to ensure a size of the component in Swing you need to call setMinimumSize(), setMaximumSize(), and SetPrefferedSize() with the same value.

button.setMaximumSize(getMaximumSize());

If you put your buttons in a GridLayout panel they will be the same width.

Top alignment for FlowLayout

I'm using a FlowLayout JPanel. The panel looks ugly when child component heights are different. I'm looking for a solution to make them top-align (similar to valign="top" with table cells in HTML).

I realize this question was asked over a year ago, but like me, I thought many would stumble across this forum post and be left attempting to make a workaround like that one suggested in the bug report (failed to work for me just fyi).
Either way there is a better answer since JDK 1.6. Flowlayout has the following method:
public void setAlignOnBaseline(boolean alignOnBaseline)
If you use this method on your flowlayout and set it to true, then when flowlayout lays out the components it will check each component's baseline and align the component along this baseline.
But that's not all you need to do.
The component in question must override the following two methods in this way:
#Override
public Component.BaselineResizeBehavior getBaselineResizeBehavior() {
return Component.BaselineResizeBehavior.CONSTANT_ASCENT;
}
#Override
public int getBaseline(int width, int height) {
return 0;
}
They are methods in JComponent and layouts and layoutmanagers use these methods to determine how to layout the component.
If you take the steps mentioned above all the components will align themselves along the top of each row. Of course if you just want to use a component like JButton you will obviously have to extend it in order to achieve your desired goal... but it's not as much work as overriding layoutcontainer with a workaround that you have to debug. At least I think so.
Good luck,
-Asaf

Someone else has wished for this, in the form of a bug-report (which also lists a workaround).
Have a look at
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4295966

You should be able to use a BoxLayout. It supports vertical alignment. The only problem is you need to manually insert horizontal strut components.
Or you could try using the Relative Layout. In your case you would use:
RelativeLayout rl = new RelativeLayout(RelativeLayout.X_AXIS, 5);
rl.setBorderGap(5);
rl.setAlignment(RelativeLayout.LEADING);
JPanel panel = new JPanel( rl );
panel.add(...);

Resize JScrollPane client without scrollbars rolling

I have a JScrollpane which contains a scrollable client that changes its size dynamically while using the application. I want the JScrollPane to be aware of the changes without moving the viewport when the client size changes.
To clarify what I mean:
Refer to the Java Webstart example ScrollDemo2 from the article How to use scroll panes by Sun. When clicking at the bottom of the window, a circle appears partly outside the window and the scrollbars move. It's the latter behavior I want to avoid.
My guess is that it's just a matter of setting a simple flag in one of the many components that are involved in a scroll pane solution, but I just can't find where it is. Does anyone know?

I managed to solve this problem by overriding the standard behavior of the viewport in my JScrollPane. This might be a solution that is not suitable for all, but in my GUI this works like a charm.
JScrollPane pane = new JScrollPane();
pane.setViewport(
new JViewport(){
/**
* An empty override implementation to prevent undesired scrolling on
* size changes of the client.
*/
#Override
public void scrollRectToVisible(Rectangle rect){}
});

I would try something like:
Point p = scrollPane.getViewport().getViewportPosition();
revalidate();
scrollPane.getViewport().setViewportPosition(p);
You may need to wrap the last line of code in a SwingUtilities.invokeLater.
If that doesn't work then maybe you can disable/enable the viewport before and after the revalidate()?