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Multiple custom JPanels inside JScrollPane - resizing/showing components on one resizes them all

So I've got a custom JPanel which I use multiple instances of to fill a wrapper Panel inside a JScrollPane. The number of custom JPanel elements I use is dependent on the size of a list. The problem I'm running across is a part of my Custom JPanel has another invisible JPanel which expands when I click on it's parent. The behavior I'm trying to mimic is that of an accordian UI element. Before I was on this project I was primarily a webdev and while I have worked with Java a lot, I'm still relatively new to Swing.
Here is an example of the behavior - the scroll pane with all elements closed. (forgive me for the quick paint-job comments. I tried to emphasize what I see going wrong).
Next, is the image of the first element expanded - which unexpectedly expands all other elements.
It must be noted that I'm only targeting the first panel and setting the visibility, yet all other repeating panels length grows when I do this, but obviously the components inside stay invisible.
Finally, here is my final deired result:
Is there some sort of constraint in the JScrollPane that resizes it's child JPanel's components to retain the same height at all times? I can't seem to figure a way around this and I've played with all sorts of different wrappers and layouts, all to no avail.
Please let me know if anyone wants to see code snippets, but they'll have to be heavily redacted and stripped down due to the nature of the project.
Thanks,
Marek
PS: yes, I absolutely must use Swing.
Edit: Here is a static, quick and dirty, stripped down implementation of my code as suggested by Roddy of the Frozen Peas
ExampleScrollPane:
public class ExampleSrollPane extends JPanel {
private static ExampleSrollPane instance = null;
private JScrollPane contentScrollPanel = new JScrollPane();
private Vector<ExamplePanel> exPanels;
private JPanel wrapPanel = new JPanel();
public ExampleSrollPane() {
super();
this.setLayout(new BorderLayout());
this.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED, Color.white,
Color.white, new Color(115, 114, 105), new Color(165, 163, 151)));
exPanels = new Vector<ExamplePanel>();
init();
}
private void init() {
contentScrollPanel.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
contentScrollPanel.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
contentScrollPanel.setBorder(new CompoundBorder(new EmptyBorder(5, 5, 5, 5), new SoftBevelBorder(BevelBorder.LOWERED)));
this.add(contentScrollPanel, BorderLayout.CENTER);
initPanels();
}
public void initPanels() {
int numUnits = 15;
// Init one empty panel at least
if (numUnits == 0) numUnits = 15;
wrapPanel.setLayout(new GridLayout(numUnits, 1));
for (int i = 0; i < numUnits; i++) {
ExamplePanel exPan = new ExamplePanel(i);
exPanels.add(i, exPan);
wrapPanel.add(exPan);
}
contentScrollPanel.setPreferredSize(new Dimension(575, 100));
contentScrollPanel.getViewport().add(wrapPanel);
}
/**
* Method: viewPanel()
*
*/
private static void viewPanel() {
JFrame frame = new JFrame();
frame.setLayout(new BorderLayout());
frame.setLocationRelativeTo(null);
frame.add(getInstance());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setSize(new Dimension(600, 350));
frame.setAlwaysOnTop(true);
frame.setVisible(true);
}
public static ExampleSrollPane getInstance() {
if (instance == null) {
instance = new ExampleSrollPane();
}
return instance;
}
/**
* The main method.
*
* #param args the arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
viewPanel();
}
});
}
}
It's here in the showHideTable method which creates the problem.
ExamplePanel (my custom JPanel):
public class ExamplePanel extends JPanel implements ActionListener {
private static final long serialVersionUID = 1L;
private static final Border STAT_BORDER = BorderFactory.createBevelBorder(BevelBorder.LOWERED, Color.white,
Color.white, new Color(115, 114, 105), new Color(165, 163, 151));
public static final EmptyBorder PAD_BORDER = new EmptyBorder(10, 10, 10, 10);
public int indx;
private JLabel unitLabel;
private JLabel statLabel;
private JLabel invLabel;
private JLabel targetLabel;
private JLabel timeLabel;
// Custom BasicArrowButton to expand/hide the "table"
private UnitToggleButton unitToggleButton;
// The expandable JPanel
public ExpanableTable elementTable;
private String id;
private String unitStatusString;
private String invStatusString;
private String targetString;
private String timeString;
public Color componentColor;
private JPanel topPanel = new JPanel();
public JPanel tablePanel = new JPanel();
public ExamplePanel(int index) {
super();
this.indx = index;
id = "Unit # 00000";
id = "Unit #00000";
unitStatusString = "PENDING";
invStatusString = "PENDING";
elementTable = new ExpanableTable();
targetString = "AZ501";
timeString = "11:18:27";
componentColor = this.getBackground();
init();
}
private void init() {
topPanel.setLayout(new GridBagLayout());
topPanel.setBorder(PAD_BORDER);
unitLabel = new JLabel(id); // TODO unit.getID();
statLabel = new JLabel(unitStatusString); // TODO: unit.getStatus();
invLabel = new JLabel(invStatusString); // TODO: unit.getInventoryStatus();
targetLabel = new JLabel(targetString);
timeLabel = new JLabel(timeString);
buildLabel(statLabel);
buildLabel(invLabel);
buildLabel(targetLabel);
buildLabel(timeLabel);
unitToggleButton = new UnitToggleButton(BasicArrowButton.EAST, indx);
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.FIRST_LINE_START;
gbc.fill = GridBagConstraints.FIRST_LINE_END;
gbc.gridx = 0;
gbc.gridy = 0;
gbc.weightx = .1;
gbc.weighty = 1;
gbc.insets = new Insets(0, 0, 5, 0);
// Add toggle button far-left, row 1
topPanel.add(unitToggleButton, gbc);
// Add empty space far-left, row 2
gbc.gridy = 1;
topPanel.add(new JLabel(" "), gbc);
// Add unit label row 1 column 2
gbc.gridy = 0;
gbc.gridx = 1;
gbc.weightx = .3;
topPanel.add(unitLabel, gbc);
// Add Status label row 1 column 3
gbc.gridx = 2;
topPanel.add(statLabel, gbc);
// Add inventory label row 1 column 4
gbc.gridx = 3;
topPanel.add(invLabel, gbc);
// Add tasking label row 2 column 2
gbc.gridy = 1;
gbc.gridx = 1;
topPanel.add(new JLabel(" Tasking: "), gbc);
// Add target label row 2 column 3
gbc.gridx = 2;
topPanel.add(targetLabel, gbc);
// Add mission Label row 2 column 4
gbc.gridx = 3;
topPanel.add(timeLabel, gbc);
gbc.gridx = 0;
gbc.gridy = 2;
gbc.weighty = 1;
gbc.weightx = 1;
gbc.gridwidth = 4;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.insets = new Insets(0, 0, 0, 0);
JSeparator sep = new JSeparator(JSeparator.HORIZONTAL);
topPanel.add(sep, gbc);
gbc.gridy = 3;
topPanel.add(elementTable, gbc);
revalidate();
this.setLayout(new BorderLayout());
this.add(topPanel, BorderLayout.NORTH);
this.add(tablePanel, BorderLayout.CENTER);
HSIUtils.setColoredBorder(tablePanel, Color.RED);
tablePanel.add(elementTable);
// Do NOT show the table on initialization
tablePanel.setVisible(false);
unitToggleButton.addActionListener(this);
}
/**
* Method: buildLabel()
*
* #param label
*/
private void buildLabel(JLabel label) {
label.setBorder(STAT_BORDER);
label.setMinimumSize(new Dimension(80, 20));
label.setPreferredSize(new Dimension(100, 25));
label.setOpaque(true);
label.setHorizontalAlignment(SwingConstants.CENTER);
label.setHorizontalTextPosition(SwingConstants.CENTER);
label.setBackground(componentColor);
}
private void showHideTable(boolean show) {
tablePanel.setVisible(!show);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == this.unitToggleButton) {
showHideTable(unitToggleButton.isExpanded());
}
}
}
ExpandableTable:
public class ExpanableTable extends JPanel {
public ExpanableTable () {
super();
this.setLayout(new BorderLayout());
add(new JButton("Test1"), BorderLayout.WEST);
add(new JButton("Test2"), BorderLayout.CENTER);
add(new JButton("Test3"), BorderLayout.EAST);
}
}
Basically I want to be able expand/show/resize each Panel inside the scroll pane independently of the others. As it currently stands, if I show a hidden Panel on one, the other panel's height grows to match but does not show the component. Very strange to me but could be my ignorance of certain Swing components and the constraints they contain.

Is there some sort of constraint in the JScrollPane that resizes it's child JPanel's components to retain the same height at all times?
A scroll pane doesn't resize anything. It only displays the component added to the scroll panes and add scroll bars when the preferred size of the component added is greater than the size of the scroll pane.
wrapPanel.setLayout(new GridLayout(numUnits, 1));
On the other hand when you use a GridLayout, then yes all components added to the grid will be resized to the size of the largest component.
So you don't want to use a GridLayout for the wrapper panel.
I would suggest you could use a GridBagLayout or a BoxLayout. As the panel.
Then I would suggest that for your expandable panel you use a BorderLayout. You add the part that is always visible to the CENTER and the expandable part to the PAGE_END. Then when you want to make the panel expand you just change the visibility of the component in the PAGE_END.
Then the layout managers will do all the work recalculating the proper size of the all the panels.

Can not figure out a simple 4 box JPanel layout

I have been trying for hours to get JPanel in Java to contain these 4 other panels in this configuration (see picture)
The blue box should never change size.
The white box should never change height, can get wider though.
The dark grey box should never change widths, can get taller though.
The light grey box can get taller or wider.
Seems pretty simple to me, I did it in C# the other day and it was a breeze. Set the position, the width, height, and whether a certain side was anchored or not, boom done, I was starting to like java more than C until I ran into this.
I've tried countless combinations of GridBagLayout, multiple nested BoxLayout instances. They all seem to do very strange things, like make each panel a tiny 4 x 4 square, or there is crazy padding around them, or the ones that need to re-size with the window, don't.
Is there some kind of magic combination that can achieve this? Does the null layout do anchoring or percent dimensions.
The closest I've gotten is the bottom image with GridBagLayout, which looks good when it loads, but does that when you re-size the window.
Here is the code that got the above images
class MainPanel extends JPanel {
public MainPanel(){
this.setBackground(new Color(216,216,216));
this.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JPanel topTitle = new JPanel();
topTitle.setPreferredSize(new Dimension(140, 40));
topTitle.setMinimumSize(new Dimension(140, 40));
topTitle.setBackground(new Color(174, 216, 249));
c.weightx = 0.5;
c.gridx = 0;
c.gridy = 0;
this.add(topTitle,c);
JPanel mainHeader = new JPanel();
mainHeader.setPreferredSize(new Dimension(1060, 40));
mainHeader.setMinimumSize(new Dimension(1060, 40));
mainHeader.setBackground(Color.WHITE);
c.gridx = 1;
c.gridy = 0;
this.add(mainHeader,c);
JPanel sideNav = new JPanel();
sideNav.setPreferredSize(new Dimension(140, 760));
sideNav.setMinimumSize(new Dimension(140, 760));
sideNav.setBackground(new Color(110,110,110));
c.gridx = 0;
c.gridy = 1;
this.add(sideNav,c);
JPanel dataPanel = new JPanel();
dataPanel.setPreferredSize(new Dimension(1060, 760));
dataPanel.setMinimumSize(new Dimension(1060, 760));
dataPanel.setBackground(new Color(216,216,216));
c.gridx = 1;
c.gridy = 1;
this.add(dataPanel,c);
}
}

GUI at minimum size
GUI stretched wider & taller
It's all about getting appropriate resize weights & fill values..
import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class FourPanelLayout {
private JComponent ui = null;
FourPanelLayout() {
initUI();
}
public void initUI() {
if (ui!=null) return;
ui = new JPanel(new GridBagLayout());
// It appears you don't want space around the panels.
// If not, commment out or remove this line.
ui.setBorder(new EmptyBorder(4,4,4,4));
// create the panels, each with a transparent image to suggest a size
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.CYAN);
bluePanel.add(new JLabel(new ImageIcon(getTransparentImage(40, 20))));
JPanel darkGrayPanel = new JPanel();
darkGrayPanel.setBackground(Color.DARK_GRAY);
darkGrayPanel.add(new JLabel(new ImageIcon(getTransparentImage(40, 20))));
JPanel whitePanel = new JPanel();
whitePanel.setBackground(Color.WHITE);
whitePanel.add(new JLabel(new ImageIcon(getTransparentImage(40, 20))));
JPanel grayPanel = new JPanel();
grayPanel.setBackground(Color.GRAY);
grayPanel.add(new JLabel(new ImageIcon(getTransparentImage(360, 80))));
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.BOTH;
gbc.weightx = 0.0f;
gbc.weighty = 0.0f;
gbc.gridx = 0;
gbc.gridy = 0;
ui.add(bluePanel, gbc);
gbc.weightx = .5f;
gbc.gridx = 1;
ui.add(whitePanel, gbc);
gbc.weighty = .5f;
gbc.gridy = 1;
ui.add(grayPanel, gbc);
gbc.weightx = 0f;
gbc.gridx = 0;
//gbc.gridy
ui.add(darkGrayPanel, gbc);
}
/* We use transparent images to give panels a natural size. */
private Image getTransparentImage(int w, int h) {
return new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
}
public JComponent getUI() {
return ui;
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception useDefault) {
}
FourPanelLayout o = new FourPanelLayout();
JFrame f = new JFrame(o.getClass().getSimpleName());
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setContentPane(o.getUI());
f.pack();
f.setMinimumSize(f.getSize());
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}

To implement this, I recommended to use FormLayout.
FormLayout is a powerful, flexible and precise general purpose layout manager. It places components in a grid of columns and rows, allowing specified components to span multiple columns or rows. Not all columns/rows necessarily have the same width/height.
Note: It good to use Windowbuilder in Eclipse or GUI Form in Intellij to automatically place and set the components properties.

Swing layout border margins on fullscreen

I have Java Swing application with JFrame using BorderLayout and inside it is a JPanel using CardLayout. I am displaying 3 different cards.
If I manually set the size of the JFrame, then the content is displayed like I want it. Label with image is in south east corner.
But when I set it to full screen, there is to much margin:
Here is the code with which I set it to full screen:
Frame[] frames = Frame.getFrames();
JFrame frame = (JFrame) frames[0];
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
//frame.getContentPane().setPreferredSize( Toolkit.getDefaultToolkit().getScreenSize());
frame.setUndecorated(true);
//frame.setSize(600,500);
frame.setVisible(true);
frame.setLayout(new BorderLayout());
Cards are build with Netbeans GUI builder and for layout is set "Free Design".
Application will be whole time in full screen, where I would like that label with the image is SE corner, like it is on resized window(image example 1). Do I need to change layout for this or is it something else?

Note that these UIs have a small border around the entire UI. To remove it, comment out the line:
ui.setBorder(new EmptyBorder(4,4,4,4));
import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class ImageInSouthEast {
private JComponent ui = null;
ImageInSouthEast() {
initUI();
}
public void initUI() {
if (ui!=null) return;
ui = new JPanel(new GridBagLayout());
ui.setBorder(new EmptyBorder(4,4,4,4));
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.WEST;
gbc.gridwidth = 2;
gbc.weighty = .5;
gbc.weightx = .5;
gbc.gridx = 0;
gbc.gridy = 0;
// first add the labels
for (int ii=1; ii<5; ii++) {
gbc.gridy = ii;
if (ii==4) {
gbc.gridwidth = 1;
}
JLabel l = new JLabel("Label " + ii);
l.setFont(l.getFont().deriveFont(50f));
ui.add(l, gbc);
}
// now for the image!
BufferedImage bi = new BufferedImage(100, 50, BufferedImage.TYPE_INT_RGB);
JLabel l = new JLabel(new ImageIcon(bi));
gbc.anchor = GridBagConstraints.LAST_LINE_END;
gbc.gridx = 2;
gbc.weighty = 0;
ui.add(l, gbc);
}
public JComponent getUI() {
return ui;
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception useDefault) {
}
ImageInSouthEast o = new ImageInSouthEast();
JFrame f = new JFrame(o.getClass().getSimpleName());
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setContentPane(o.getUI());
f.pack();
f.setMinimumSize(f.getSize());
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}

If you just want to remove the gap between the text then you could just use BoxLayout.
Set the layout by doing this:
Container pane = frame.getContentPane();
pane.setLayout(new BoxLayout(pane, BoxLayout.Y_AXIS));
pane.add(Box.createHorizontalGlue());
Adding an element
public void add(Component comp, int gap){
//comp is the component that will be added
//gap is the extra space after the last component and this
pane.remove(pane.getComponents().length - 1);
pane.add(Box.createVerticalStrut(gap));
pane.add(comp);
//Obviously pane or frame need to be visible to use this method
}
Add Text by doing this:
add(new JLabel(text), 5);
Add the image by doing this:
JPanel panel = new JPanel();
panel.add(image, BorderLayout.EAST);
panel.setOpaque(false);
add(Box.createHorizontalGlue(),0);
add(panel,0);

How to place a panel containing three buttons in the upper left cell of a GridBagLayout?

I have a panel that contains three buttons. I want this panel to be placed in the upper left cell of a GridBagLayout.
My problem is that when I run the program the panel is not located in the upper left cell but it's in the middle of the layout. I have set both gridxand gridy to zero.
private JFrame frame;
private JMenuBar menuBar;
private JMenu menuFile;
private JMenuItem fileItem1;
private JMenuItem fileItem2;
private JPanel btnPanel;
private JButton btnRewind;
private JButton btnPlayPause;
private JButton btnFastForward;
private static boolean shouldFill = true;
private static boolean shouldWeightX = true;
private static boolean RIGHT_TO_LEFT = false;
public JPlayer() {
}
public void createAndShowGUI() {
frame = new JFrame();
frame.setTitle("JPlayer");
frame.setSize(500, 500);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentsToPane(frame.getContentPane());
frame.setVisible(true);
}
private void addComponentsToPane(Container pane) {
if(RIGHT_TO_LEFT) {
pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
}
pane.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
if(shouldFill) {
gbc.fill = GridBagConstraints.HORIZONTAL;
}
btnRewind = new JButton();
try {
Image imgRewind = ImageIO.read(getClass().getResource("../utils/images/rewind.png"));
btnRewind.setIcon(new ImageIcon(imgRewind));
btnRewind.setOpaque(true);
btnRewind.setContentAreaFilled(false);
btnRewind.setBorderPainted(false);
} catch(Exception e) {
e.printStackTrace();
}
btnPlayPause = new JButton();
try {
Image imgPlay = ImageIO.read(getClass().getResource("../utils/images/play.png"));
Image imgPause = ImageIO.read(getClass().getResource("../utils/images/pause.png"));
btnPlayPause.setIcon(new ImageIcon(imgPlay));
btnPlayPause.setOpaque(true);
btnPlayPause.setContentAreaFilled(false);
btnPlayPause.setBorderPainted(false);
} catch(Exception e) {
e.printStackTrace();
}
btnFastForward = new JButton();
try {
Image imgFastForward = ImageIO.read(getClass().getResource("../utils/images/fast_forward.png"));
btnFastForward.setIcon(new ImageIcon(imgFastForward));
btnFastForward.setOpaque(true);
btnFastForward.setContentAreaFilled(false);
btnFastForward.setBorderPainted(false);
} catch(Exception e) {
e.printStackTrace();
}
btnPanel = new JPanel();
btnPanel.add(btnRewind);
btnPanel.add(btnPlayPause);
btnPanel.add(btnFastForward);
btnPanel.setSize(new Dimension(40, 40));
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 0;
JButton btn = new JButton("Some Button");
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 1;
c.gridy = 0;
pane.add(btnPanel, gbc);
pane.add(btn, c);
}

Try GridBagConstraints.anchor constraint that has default value as CENTER positioned.
Directly from documentation on How to Use GridBagLayout
If a component's display area is larger than the component itself, then you can specify whereabouts in the display area the component will be displayed by using the GridBagConstraints.anchor constraint.
The anchor constraint's values can be absolute (north, south, east, west, and so on), or orientation-relative (at start of page, at end of line, at the start of the first line, and so on), or relative to the component's baseline.
Note:
You don't need to use multiple instances of GridBagConstraints. Just create one and update the constraints before adding the component in the panel. In this way you can reuse the existing constraints that is common for all.
Don't forget to set weightx and weighty to use anchor constraints properly.
Directly from same documentation
weightx, weighty
Specifying weights is an art that can have a significant impact on the appearance of the components a GridBagLayout controls. Weights are used to determine how to distribute space among columns (weightx) and among rows (weighty); this is important for specifying resizing behavior.
Unless you specify at least one non-zero value for weightx or weighty, all the components clump together in the center of their container. This is because when the weight is 0.0 (the default), the GridBagLayout puts any extra space between its grid of cells and the edges of the container.

Java Swing - JLabel width changed when icon or text added?

Same Question, different context
It seems I was too hasty in my accepting before, since the problem is still there. The problem? JLabel takes the liberty of expanding its parent panel when content is added to it.
It's time for reproducing it per "Hovercraft full of eels"-ses suggestion, and here it is:
import java.awt.*;
import javax.swing.*;
public class TestLabel {
public static void main(String[] args) {
// Var inits
JFrame frame;
JPanel panel;
JLabel label;
Container pane;
GridBagConstraints gbc = new GridBagConstraints();
// Frame, content pane, layout inits
frame = new JFrame("Label Tester");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pane = frame.getContentPane();
pane.setLayout(new GridBagLayout());
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
// Add panels (note gbc weighty and fill carries over all instances)
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.GREEN);
frame.add(panel,gbc);
label = new JLabel("THE PANEL IS NOW DISTORTED TO FIT THIS LABEL WHY IS THIS HAPPENING");
//label = new JLabel("");
label.setOpaque(true);
label.setBackground(Color.WHITE);
panel.add(label);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.RED);
frame.add(panel,gbc);
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.BLUE);
frame.add(panel,gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.YELLOW);
frame.add(panel,gbc);
frame.pack();
frame.setSize(800,600);
frame.setVisible(true);
}
}
Results:
As you can see, the green panel is forced wider and throws off my whole layout when text (or, in the original question, and icon) is added to it. I want my layout to remain the same weights, regardless of the content. The reason this came up is because I'm trying to add a scaled image as an icon to the label, as seen in the original question.
Incidentally, setPreferredSize() doesn't seem to work.
Is there a way to fix this?
Original Question
My JLabel element expands dramatically when I add an Icon to it. Why is this happening? Here's the applicable portion of the code:
// Show label and BG color
redLabel.setBackground(Color.RED);
redLabel.setOpaque(true);
// Grab stretched image (already loaded elsewhere in the code) and turn to icon
Img = Img.getScaledInstance(redLabel.getWidth(),12,Image.SCALE_REPLICATE);
ImageIcon icon = new ImageIcon(Img);
// This line throws everything off!
//It's commented out in the first pic, and included in the second.
redLabel.setIcon(icon);
As you can see from the first pic, I've got a label (in red) of width W. What I'm trying to do is stretch my icon to width W and put it in the label.
When I do this, the label expands (by exactly 50 pixels, I think) and also squeezes over the left edge (green). Does anyone have any idea why this is happening?
I've tried several things that are too verbose to explain but can't find the problem :-/

Your component expands because it allocates the necessary space for its Icon.
public class JLabelDemo {
private static BufferedImage bi;
public static void main(String[] args) throws IOException{
loadImage();
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run() {
createAndShowGUI();
}
});
}
private static void loadImage() throws IOException{
bi = ImageIO.read(JLabelDemo.class.getResource("../resource/forever-alone.jpg"));
}
private static void createAndShowGUI(){
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel panel = new JPanel();
panel.setBackground(Color.YELLOW);
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
final JLabel emptyLabel = new JLabel();
final JLabel textLabel = new JLabel("This label has text only");
final JLabel textAndImageLabel = new JLabel("This label has text and image");
textAndImageLabel.setIcon(new ImageIcon(bi));
panel.add(emptyLabel);
panel.add(textLabel);
panel.add(textAndImageLabel);
frame.add(panel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
System.out.println("Empty label dimensions - " + emptyLabel.getSize());
System.out.println("Text only label dimensions - " + textLabel.getSize());
System.out.println("Image width: " + bi.getWidth() + ", Image height: " + bi.getHeight());
System.out.println("Text and image label dimensions - " +textAndImageLabel.getSize());
}
}
The following is outputted to console:
Empty label dimensions - java.awt.Dimension[width=0,height=0]
Text only label dimensions - java.awt.Dimension[width=129,height=16]
Image width: 194, Image height: 180
Text and image label dimensions - java.awt.Dimension[width=363,height=180]

Consider using a JLayeredPane to add components in layers. There are trips and traps though when doing this in matters of opacity, size and position of components added.
For example,
import java.awt.*;
import javax.swing.*;
public class TestLabel {
private static final Dimension SIZE = new Dimension(800, 600);
public static void main(String[] args) {
GridBagConstraints gbc = new GridBagConstraints();
JPanel defaultPane = new JPanel();
defaultPane.setLayout(new GridBagLayout());
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
// Add panels (note gbc weighty and fill carries over all instances)
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 0;
JPanel panel = new JPanel();
panel.setBackground(Color.GREEN);
defaultPane.add(panel, gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.RED);
defaultPane.add(panel, gbc);
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.BLUE);
defaultPane.add(panel, gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.YELLOW);
defaultPane.add(panel, gbc);
defaultPane.setSize(SIZE);
JLabel label = new JLabel("THE PANEL IS NOW DISTORTED TO FIT THIS LABEL WHY IS THIS HAPPENING");
label.setOpaque(true);
label.setBackground(Color.WHITE);
JPanel northPalettePanel = new JPanel();
northPalettePanel.setOpaque(false);
northPalettePanel.add(label);
JPanel palettePanel = new JPanel(new BorderLayout());
palettePanel.setOpaque(false);
palettePanel.setSize(SIZE);
palettePanel.setLocation(0, 0);
palettePanel.add(northPalettePanel, BorderLayout.NORTH);
JLayeredPane layeredPane = new JLayeredPane();
layeredPane.setPreferredSize(SIZE);
layeredPane.add(defaultPane, JLayeredPane.DEFAULT_LAYER);
layeredPane.add(palettePanel, JLayeredPane.PALETTE_LAYER);
JFrame frame = new JFrame("Label Tester");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(layeredPane, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}

Java swing is pretty old for me but if I remember well, setting a preferred size (setPreferredSize()) sometime solve these kind of problem ... Also try top lay with setMaximumSize and setMinimumSize.
You can maybe find more information in java documentation:
http://download.oracle.com/javase/tutorial/uiswing/layout/using.html#sizealignment
Regards!