Develop Reference

GridBagLayout not filling JPanel

I am building a toolbar for a program using GridBagLayout, but even using weightx and fill, the components are not the sizes they should be and they are not filling the JPanel.
For instance, when the total size of jidest.x_size is 1920, the total size of the components is 1776
package jide.parts;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.BoxLayout;
import javax.swing.JLabel;
import javax.swing.JPanel;
import jide.jidest;
#SuppressWarnings("serial")
public class BottomBar extends JPanel implements MouseListener{
JPanel charCountPanel = new JPanel();
JPanel lineCountPanel = new JPanel();
JPanel cursorPositionPanel = new JPanel();
JPanel spacer1 = new JPanel();
JPanel spacer2 = new JPanel();
JPanel spacer3 = new JPanel();
JPanel morespace = new JPanel();
JLabel charCount = new JLabel("charcount");
JLabel lineCount = new JLabel("linecount");
JLabel cursorPosition = new JLabel("TEST:TEST");
public BottomBar(){
this.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
charCountPanel.setToolTipText("Click here for more complete stats");
lineCountPanel.setToolTipText("Click here for more complete stats");
setPreferredSize(new Dimension((int) jidest.x_size,20));
setBackground(Color.red);
cursorPositionPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
cursorPositionPanel.add(cursorPosition);
//cursorPositionPanel.setSize(50,20);
lineCountPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
lineCountPanel.add(lineCount);
//lineCountPanel.setSize(50,20);
charCountPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
charCountPanel.add(charCount);
//charCountPanel.setSize(50,20);
morespace.setSize((int) (jidest.x_size-156),20);
//add(cursorPositionPanel);
spacer1.setBackground(Color.BLACK);
//spacer1.setSize(1,20);
spacer2.setBackground(Color.BLACK);
//spacer2.setSize(1,20);
spacer3.setBackground(Color.BLACK);
//spacer3.setPreferredSize(new Dimension(1,20));
//size is 156, width is 7
gbc.fill=GridBagConstraints.BOTH;
gbc.weighty=1;
gbc.gridx = 1;
gbc.weightx=(1.0)/jidest.x_size;
add(spacer1,gbc);
gbc.gridx=2;
gbc.weightx=(50.0)/jidest.x_size;
add(cursorPositionPanel,gbc);
gbc.gridx=3;
gbc.weightx=(1.0)/jidest.x_size;
add(spacer2,gbc);
gbc.gridx=4;
gbc.weightx=(50.0)/jidest.x_size;
add(lineCountPanel,gbc);
gbc.gridx=5;
gbc.weightx=(1.0)/jidest.x_size;
add(spacer3,gbc);
gbc.gridx=6;
gbc.weightx=(50.0)/jidest.x_size;
add(charCountPanel,gbc);
gbc.gridy = 0;
gbc.gridx=0;
gbc.weightx=(jidest.x_size-153)/jidest.x_size;
add(morespace,gbc);
System.out.println((spacer1.getWidth()+cursorPositionPanel.getWidth()+spacer2.getWidth()+lineCountPanel.getWidth()+spacer3.getWidth()+morespace.getWidth())+" should be " + jidest.x_size);
}
#Override
public void mouseClicked(MouseEvent arg0) {
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mousePressed(MouseEvent arg0) {
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
}

In future, please post an MCVE. This works to spread the components across the width of the bar.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class BottomBarGUI {
private JComponent ui = null;
BottomBarGUI() {
initUI();
}
public void initUI() {
if (ui != null) {
return;
}
ui = new JPanel(new BorderLayout(4, 4));
ui.setBorder(new EmptyBorder(4, 4, 4, 4));
ui.add(new BottomBar());
}
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) {
}
BottomBarGUI o = new BottomBarGUI();
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);
}
}
class BottomBar extends JPanel {
JPanel charCountPanel = new JPanel();
JPanel lineCountPanel = new JPanel();
JPanel cursorPositionPanel = new JPanel();
JPanel spacer1 = new JPanel();
JPanel spacer2 = new JPanel();
JPanel spacer3 = new JPanel();
JPanel morespace = new JPanel();
JLabel charCount = new JLabel("charcount");
JLabel lineCount = new JLabel("linecount");
JLabel cursorPosition = new JLabel("TEST:TEST");
public BottomBar() {
this.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.BOTH;
gbc.gridy = 0;
gbc.weightx = .5;
charCountPanel.setToolTipText("Click here for more complete stats");
lineCountPanel.setToolTipText("Click here for more complete stats");
setBackground(Color.red);
cursorPositionPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
cursorPositionPanel.add(cursorPosition);
lineCountPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
lineCountPanel.add(lineCount);
charCountPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
charCountPanel.add(charCount);
spacer1.setBackground(Color.BLACK);
spacer2.setBackground(Color.BLACK);
spacer3.setBackground(Color.BLACK);
gbc.fill = GridBagConstraints.BOTH;
gbc.weighty = 1;
gbc.gridx = 0;
add(spacer1, gbc);
gbc.gridx = 1;
add(cursorPositionPanel, gbc);
gbc.gridx = 2;
add(spacer2, gbc);
gbc.gridx = 3;
add(lineCountPanel, gbc);
gbc.gridx = 4;
add(spacer3, gbc);
gbc.gridx = 5;
add(charCountPanel, gbc);
gbc.gridx = 0;
}
}

Resize and placement of elements

public class InputURL {
public InputURL() {
input();
}
private static JFrame mainFrame = Launcher.returnFrame();
private static JPanel mainPanel;
private void input(){
//Defining a Panel on which everything will be set
mainPanel = new JPanel();
mainPanel.setLayout(new GridBagLayout());
//To put the GridBagLayout Constraints
GridBagConstraints c = new GridBagConstraints();
//Set Panel Size
mainPanel.setSize(Constants.windowWidth,Constants.windowHeight);
//Setting the Input Box
JTextField inputURL = new JTextField();
c.fill = GridBagConstraints.CENTER;
c.ipady = 50;
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 1;
mainPanel.add(inputURL, c);
//Adding the start button
JButton submitURL = new JButton(Constants.SUBMIT_URL_BUTTON);
submitURL.addActionListener(new ActionListener() {
//The action performed by the start button
public void actionPerformed(ActionEvent e)
{
//Execute when button is pressed
}
});
//The placement of the button
c.fill = GridBagConstraints.VERTICAL;
c.ipady = 50;
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 2;
mainPanel.add(submitURL, c);
//Adding the components on Panel to Frame
mainFrame.add(mainPanel);
}
}
The ouput and expected output can be viewed here. Need help regarding the Output. E.G.:
I've tried using GridBagConstraints and for some reason I cannot play much with the UI.

A lot will come down to you final needs, for example, this just makes use of some of the basic properties of GridBagConstraints
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestLayout {
public static void main(String[] args) {
new TestLayout();
}
public TestLayout() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextField inputURL;
private JButton submitURL ;
public TestPane() {
inputURL = new JTextField(20);
submitURL = new JButton("Submit the URL");
submitURL.setMargin(new Insets(10, 10, 10, 10));
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.insets = new Insets(10, 10, 10, 10);
add(new JLabel("Header"), gbc);
gbc.gridy++;
gbc.insets = new Insets(0, 10, 20, 10);
add(inputURL, gbc);
gbc.gridy++;
gbc.insets = new Insets(0, 0, 0, 0);
gbc.weighty = 1.0;
add(submitURL, gbc);
}
}
}
A more complex solution might make use of compound layouts, using a mixture of BorderLayout, GridLayout and GridBagLayout
For example...
public class TestPane extends JPanel {
private JTextField inputURL;
private JButton submitURL ;
public TestPane() {
setLayout(new BorderLayout());
JLabel header = new JLabel("Header");
header.setHorizontalAlignment(JLabel.CENTER);
header.setBorder(new EmptyBorder(10, 10, 10, 10));
add(header, BorderLayout.NORTH);
inputURL = new JTextField(20);
submitURL = new JButton("Submit the URL");
submitURL.setMargin(new Insets(10, 10, 10, 10));
JPanel content = new JPanel(new GridLayout(2, 1));
JPanel field = new JPanel(new GridBagLayout());
field.add(inputURL);
content.add(field);
JPanel actions = new JPanel(new GridBagLayout());
actions.add(submitURL);
content.add(actions);
add(content);
}
}
While it might sound stupid, spend more time focusing on the actual workflow of the user, this will lead you to the best layout decisions, rather then focus on the physical layout itself

JPanel doesnt show components after the second button click

I want to put a JTextPane component in a JPanel with a GridBagLayout when I click on button.
My code works fine for the first button click, But after, the next components are not displayed.
Here is my code:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class RefreshPanel {
private JFrame frame = new JFrame();
private JPanel panel = new JPanel();
private JTextPane [] textPane;// = new JTextPane[1];
private JScrollPane scrollbar;
private ArrayList arrayList = new ArrayList();
private JButton newItem = new JButton("new");
private int counter=0;
private GridBagLayout gbl = new GridBagLayout();
RefreshPanel() {
scrollbar = new JScrollPane(panel);
panel.setBackground(Color.WHITE);
panel.setLayout(gbl);
addButtonListener();
createFrame();
} //constructor
public void addButtonListener() {
newItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
arrayList.add("data");
textPane = generateTextPane(arrayList.size(), arrayList);
System.out.println(textPane.length);
for(int i=0;i<textPane.length;i++) {
System.out.println(textPane[i].getText());
addComponent(panel, gbl, textPane[i], 0, counter, 1, 1,1,1);
panel.revalidate();
}
}
});
}
private JTextPane[] generateTextPane(int arraySize, ArrayList arrayList) {
JTextPane [] textPane = new JTextPane[arraySize];
for(int i=0;i<textPane.length;i++) {
textPane[i]=new JTextPane();
textPane[i].setText((String) arrayList.get(i));
}
return textPane;
}
public void addComponent(Container cont,
GridBagLayout gbl,
Component c,
int x, int y,
int width, int height,
double weightx, double weighty) {
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = x; gbc.gridy = y;
gbc.gridwidth = width; gbc.gridheight = height;
gbc.weightx = weightx; gbc.weighty = weighty;
gbl.setConstraints( c, gbc );
cont.add( c );
}
public void createFrame() {
//frame.getContentPane().setLayout(new FlowLayout());
frame.add(scrollbar, BorderLayout.CENTER);
frame.add(newItem, BorderLayout.EAST);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(new Dimension(300,300));
frame.setVisible(true);
}
public static void main(String [] args) {
new RefreshPanel();
}
}

Patrick: you are right! I really forgot to change the gridbagconstraints
addComponent(panel, gbl, textPane[i], 0, i, 1, 1, 1, 1);
instead of
addComponent(panel, gbl, textPane[i], 0, counter, 1, 1, 1, 1);

What's the best way to organize JPanels in a list?

I've found myself writing up quite a few programs recently which all need to display some collection of data. So far the best looking approach I've thought of is make small JPanels which contain data on each item in the collection and put them all in a big JPanel which I then put in a JScrollPane. It works and looks just as intended but there's one issue: I can't seem to get the smaller JPanels to start at the top of the bigger JPanel.
The problem is only apparent when I've got a small number of small JPanels (green) added into the bigger JPanel (red).
Described below is the method I used to produce the above and I'd like to know if there's a better way I could do it (where the list starts at the top like it should):
I created a class which extends JPanel and in it add all data I want to display. We'll call it "SmallPanel.java". I don't set the size of it (that comes later).
In my main window's class (which extends JFrame):
private JScrollPane scrollPane;
private JPanel panel;
...
scrollPane = new JScrollPane();
getContentPane().add(scrollPane);
panel = new JPanel();
panel.setLayout(new GridBagLayout());
scrollPane.setViewportView(panel);
...
private void addPanel()
{
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = panel.getComponentCount(); //The new JPanel's place in the list
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.anchor = GridBagConstraints.PAGE_START; //I thought this would do it
gbc.ipady = 130; //Set the panel's height, the width will get set to that of the container JPanel (which is what I want since I'd like my JFrames to be resizable)
gbc.insets = new Insets(2, 0, 2, 0); //Separation between JPanels in the list
gbc.weightx = 1.0;
SmallPanel smallPanel = new SmallPanel();
panel.add(smallPanel, gbc);
panel.revalidate();
panel.invalidate();
panel.repaint(); //Better safe than peeved
}
Call the addPanel() method every time I want to add a panel.
EDIT
Final solution (based on MadProgrammer's answer below):
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.BevelBorder;
public class ListPanel extends JPanel
{
private static final long serialVersionUID = 1L;
private JPanel fillerPanel;
private ArrayList<JPanel> panels;
public ListPanel(List<JPanel> panels, int height)
{
this(panels, height, new Insets(2, 0, 2, 0));
}
public ListPanel(List<JPanel> panels, int height, Insets insets)
{
this();
for (JPanel panel : panels)
addPanel(panel, height, insets);
}
public ListPanel()
{
super();
this.fillerPanel = new JPanel();
this.fillerPanel.setMinimumSize(new Dimension(0, 0));
this.panels = new ArrayList<JPanel>();
setLayout(new GridBagLayout());
}
public void addPanel(JPanel p, int height)
{
addPanel(p, height, new Insets(2, 0, 2, 0));
}
public void addPanel(JPanel p, int height, Insets insets)
{
super.remove(fillerPanel);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = getComponentCount();
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.anchor = GridBagConstraints.PAGE_START;
gbc.ipady = height;
gbc.insets = insets;
gbc.weightx = 1.0;
panels.add(p);
add(p, gbc);
gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = getComponentCount();
gbc.fill = GridBagConstraints.VERTICAL;
gbc.weighty = 1.0;
add(fillerPanel, gbc);
revalidate();
invalidate();
repaint();
}
public void removePanel(JPanel p)
{
removePanel(panels.indexOf(p));
}
public void removePanel(int i)
{
super.remove(i);
panels.remove(i);
revalidate();
invalidate();
repaint();
}
public ArrayList<JPanel> getPanels()
{
return this.panels;
}
public static void main(String[] args)
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setMinimumSize(new Dimension(500, 500));
f.setLocationRelativeTo(null);
f.getContentPane().setLayout(new BorderLayout());
final ListPanel listPanel = new ListPanel();
for (int i = 1; i <= 10; i++)
listPanel.addPanel(getRandomJPanel(), new Random().nextInt(50) + 50);
JButton btnAdd = new JButton("Add");
btnAdd.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent paramActionEvent)
{
listPanel.addPanel(getRandomJPanel(), new Random().nextInt(50) + 50);
}
});
JButton btnRemove = new JButton("Remove");
btnRemove.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent paramActionEvent)
{
listPanel.removePanel(0);
}
});
f.getContentPane().add(btnRemove, BorderLayout.NORTH);
f.getContentPane().add(btnAdd, BorderLayout.SOUTH);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
scrollPane.setViewportView(listPanel);
f.getContentPane().add(scrollPane, BorderLayout.CENTER);
f.setVisible(true);
}
public static JPanel getRandomJPanel()
{
JPanel panel = new JPanel();
panel.setBorder(new BevelBorder(BevelBorder.LOWERED, null, null, null, null));
panel.add(new JLabel("This is a randomly sized JPanel"));
panel.setBackground(new Color(new Random().nextFloat(), new Random().nextFloat(), new Random().nextFloat()));
return panel;
}
}

The best solution I've found is to use VerticalLayout from the SwingLabs SwingX (which can be downloaded from here) libraries.
You "could" use a GridBagLayout with an invisible component positioned at the end, whose weighty property is set to 1, but this is a lot more additional work to manage, as you need to keep updating the x/y positions of all the components to keep it in place...
Updated with GridBagLayout example
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class VerticalLayoutExample {
public static void main(String[] args) {
new VerticalLayoutExample();
}
public VerticalLayoutExample() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
final TestPane pane = new TestPane();
JButton add = new JButton("Add");
add.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
pane.addAnotherPane();
}
});
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new JScrollPane(pane));
frame.add(add, BorderLayout.SOUTH);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JPanel filler;
private int y = 0;
public TestPane() {
setBackground(Color.RED);
setLayout(new GridBagLayout());
filler = new JPanel();
filler.setOpaque(false);
GridBagConstraints gbc = new GridBagConstraints();
gbc.weighty = 1;
gbc.gridy = 0;
add(filler, gbc);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 400);
}
public void addAnotherPane() {
JPanel panel = new JPanel(new GridBagLayout());
panel.add(new JLabel("Hello"));
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridy = y++;
gbc.weightx = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.insets = new Insets(4, 4, 4, 4);
add(panel, gbc);
GridBagLayout gbl = ((GridBagLayout)getLayout());
gbc = gbl.getConstraints(filler);
gbc.gridy = y++;
gbl.setConstraints(filler, gbc);
revalidate();
repaint();
}
}
}
This is just a concept. As camickr has pointed out, so long as you know the last component, you can adjust the GridBagConstraints of the component so that the last component which is in the list has the weighty of 1 instead...
As you can, you can override some of the things GridBagLayout does, for example, instead of using the preferred size of the panel, I've asked GridBagLayout to make it fill the HORIZONTAL width of the parent container...

You can use a vertical BoxLayout.
Just make sure the maximum size of the panel is equal to the preferred size so the panel doesn't grow.
Edit:
Since your class already has a custom panel all you need to do is override the getMaximumSize() method to return an appropriate value. Something like:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class VerticalLayoutExample2 {
public static void main(String[] args) {
new VerticalLayoutExample2();
}
public VerticalLayoutExample2() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
final TestPane pane = new TestPane();
JButton add = new JButton("Add");
add.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
pane.addAnotherPane();
}
});
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new JScrollPane(pane));
frame.add(add, BorderLayout.SOUTH);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JPanel filler;
private int y = 0;
public TestPane() {
setBackground(Color.RED);
setLayout(new GridBagLayout());
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
setBorder( new EmptyBorder(4, 4, 4, 4) );
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 400);
}
public void addAnotherPane() {
SmallPanel panel = new SmallPanel();
panel.setLayout( new GridBagLayout() );
panel.add(new JLabel("Hello"));
add(panel);
add(Box.createVerticalStrut(4));
revalidate();
repaint();
}
}
static class SmallPanel extends JPanel
{
#Override
public Dimension getMaximumSize()
{
Dimension preferred = super.getPreferredSize();
Dimension maximum = super.getMaximumSize();
maximum.height = preferred.height;
return maximum;
}
}
}
I know you mentioned you don't want to use a lib, but you can also look at Relative Layout. It is only a single class. It can easily mimic a BoxLayout but is easier to use because you don't need to override the getMaximumSize() method or add a Box component to the panel to give the vertical spacing.
You would set it as the layout of your panel as follow:
RelativeLayout rl = new RelativeLayout(RelativeLayout.Y_AXIS);
rl.setFill( true ); // fills components horizontally
rl.setGap(4); // vertical gap between panels
yourPanel.setLayout(rl);
yourPanel.add( new SmallPanel(...) );
yourPanel.add( new SmallPanel(...) );

BorderLayout doesn't show correctly

I want to have a JFrame, where on the left and the right there is a border that has the color black and a width of withfOfJFrame/10.
Now, my try at it looks like this:
JFrame f = new JFrame();
f.setSize(800, 600);
f.setLayout(new BorderLayout());
JPanel leftBorder = new JPanel();
JPanel rightBorder = new JPanel();
leftBorder.setBackground(Color.black);
rightBorder.setBackground(Color.black);
leftBorder.setSize(f.getWidth()/10, f.getHeight());
rightBorder.setSize(f.getWidth()/10, f.getHeight());
JPanel center = new JPanel();
center.setBackground(Color.red);
f.add(leftBorder, BorderLayout.WEST);
f.add(center, BorderLayout.CENTER);
f.add(rightBorder, BorderLayout.EAST);
f.setVisible(true);
This adds a black border on the left and the right, but that border has a fixed size and doesn't recalculate when resizing the window. The size isn't even 1/10 of 800 (the beginning width of the JFrame).
What am I doing wrong? Or is there even a better way to do this?

You may achieve the desired result with a GridBagLayout and appropriate weights:
public class Snippet {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel leftBorder = new JPanel();
JPanel rightBorder = new JPanel();
leftBorder.setBackground(Color.black);
rightBorder.setBackground(Color.black);
JPanel center = new JPanel();
center.setBackground(Color.red);
f.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.BOTH;
gbc.weighty = 1.0;
gbc.gridy = 0;
gbc.gridwidth = 1;
gbc.gridheight = 1;
gbc.gridx = 0;
gbc.weightx = 0.1;
f.add(leftBorder, gbc);
gbc.gridx = 1;
gbc.weightx = 0.8;
f.add(center, gbc);
gbc.gridx = 2;
gbc.weightx = 0.1;
f.add(rightBorder, gbc);
f.pack();
f.setVisible(true);
}
});
}
}

A ComponentListener works well for this.
Addendum: The Flank panel needs to revalidate() itself explicitly in response to any size change.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** #see http://stackoverflow.com/a/14588506/230513 */
public class Test {
private static final int W = 320;
private static final Center center = new Center();
private static class Center extends JPanel {
public Center() {
setBackground(Color.red);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(W, 3 * W / 4);
}
};
private static class Flank extends JPanel {
private Dimension d = new Dimension(W / 10, 0);
public Flank() {
setBackground(Color.black);
Test.center.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
d = new Dimension(e.getComponent().getWidth() / 10, 0);
revalidate();
}
});
}
#Override
public Dimension getPreferredSize() {
return d;
}
}
private void display() {
JFrame f = new JFrame("Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new Flank(), BorderLayout.WEST);
f.add(center, BorderLayout.CENTER);
f.add(new Flank(), BorderLayout.EAST);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Test().display();
}
});
}
}