I want to add multiple jpanels to jpanel.So i added a root panel to jscrollpane.and then added all individual jpanels to this root panel.I made jscrollpane's scrolling policy as needed.i.e HORIZONTAL_SCROLLBAR_AS_NEEDED,VERTICAL_SCROLLBAR_AS_NEEDED.
But the problem is all individual panels are not shown inside root panel.
Code:
JScrollPane scPanel=new JScrollPane();
JPanel rootPanel=new JPanel();
rootPanel.setLayout(new FlowLayout());
JPanel indPanel = new JPanel();
rootPanel.add(indPanel);
JPanel indPanel2 = new JPanel();
rootPanel.add(indPanel2);
//.....like this added indPanals to rootPanel.
scPanel.setViewPortView(rootPanel);
//scPanel.setHorizontalScrollPolicy(HORIZONTAL_SCROLLBAR_AS_NEEDED);
And one more thing is, as i scroll the scrollbar the panels are going out of jscrollpane area.
I am not able to see all individual panels,
Please suggest me.
Edit: code snippet from double post:
MosaicFilesStatusBean mosaicFilesStatusBean = new MosaicFilesStatusBean();
DefaultTableModel tableModel = null;
tableModel = mosaicFilesStatusBean.getFilesStatusBetweenDates(startDate, endDate);
if (tableModel != null) {
rootPanel.removeAll();
rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS));
for (int tempRow = 0; tempRow < tableModel.getRowCount(); tempRow++) {
int fileIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 0).toString());
String dateFromTemp = tableModel.getValueAt(tempRow, 3).toString();
String dateToTemp = tableModel.getValueAt(tempRow, 4).toString();
int processIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 5).toString());
int statusIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 6).toString());
String operatingDateTemp = tableModel.getValueAt(tempRow, 7).toString();
MosaicPanel tempPanel =
new MosaicPanel(fileIdTemp, dateFromTemp, dateToTemp, processIdTemp, statusIdTemp, operatingDateTemp);
rootPanel.add(tempPanel);
}
rootPanel.revalidate();
}
The main reason, why you couldn't see your JPanel is that you are using FlowLayout as the LayoutManager for the rootPanel. And since your JPanel added to this rootPanel has nothing inside it, hence it will take it's size as 0, 0, for width and height respectively. Though using GridLayout such situation shouldn't come. Have a look at this code example attached :
import java.awt.*;
import javax.swing.*;
public class PanelAddition
{
private void createAndDisplayGUI()
{
JFrame frame = new JFrame("Panel Addition Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel contentPane = new JPanel();
contentPane.setLayout(new GridLayout(0, 1));
JScrollPane scroller = new JScrollPane();
CustomPanel panel = new CustomPanel(1);
contentPane.add(panel);
scroller.setViewportView(contentPane);
frame.getContentPane().add(scroller, BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
for (int i = 2; i < 20; i++)
{
CustomPanel pane = new CustomPanel(i);
contentPane.add(pane);
contentPane.revalidate();
contentPane.repaint();
}
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new PanelAddition().createAndDisplayGUI();
}
});
}
}
class CustomPanel extends JPanel
{
public CustomPanel(int num)
{
JLabel label = new JLabel("" + num);
add(label);
}
#Override
public Dimension getPreferredSize()
{
return (new Dimension(200, 50));
}
}
Don't use FlowLayout for the rootPanel. Instead consider using BoxLayout:
JPanel rootPanel=new JPanel();
// if you want to stack JPanels vertically:
rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS));
Edit 1
Here's an SSCCE that's loosely based on your latest code posted:
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.util.Random;
import javax.swing.*;
#SuppressWarnings("serial")
public class PanelsEg extends JPanel {
private static final int MAX_ROW_COUNT = 100;
private Random random = new Random();
private JPanel rootPanel = new JPanel();
public PanelsEg() {
rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS));
JScrollPane scrollPane = new JScrollPane(rootPanel);
scrollPane.setPreferredSize(new Dimension(400, 400)); // sorry kleopatra
add(scrollPane);
add(new JButton(new AbstractAction("Foo") {
#Override
public void actionPerformed(ActionEvent arg0) {
foo();
}
}));
}
public void foo() {
rootPanel.removeAll();
// rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS)); // only need to set layout once
int rowCount = random.nextInt(MAX_ROW_COUNT);
for (int tempRow = 0; tempRow < rowCount ; tempRow++) {
int fileIdTemp = tempRow;
String data = "Data " + (tempRow + 1);
MosaicPanel tempPanel =
new MosaicPanel(fileIdTemp, data);
rootPanel.add(tempPanel);
}
rootPanel.revalidate();
rootPanel.repaint(); // don't forget to repaint if removing
}
private class MosaicPanel extends JPanel {
public MosaicPanel(int fileIdTemp, String data) {
add(new JLabel(data));
}
}
private static void createAndShowGui() {
PanelsEg mainPanel = new PanelsEg();
JFrame frame = new JFrame("PanelsEg");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
This SSCCE works, in that it easily shows removing and adding JPanels to another JPanel that is held by a JScrollPane. If you're still having a problem, you should modify this SSCCE so that it shows your problem.
Related
I know this problem has probably already been solved before but I don't really know how to describe the problem well, so I have a hard time finding it.
The problem I have is that I have a canvas that is attached to a panel and that panel is attached to a main panel and that to the frame. When I run the code the canvas does nothing. However if I dont add the button panel it works.
this is my code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ColorFrame extends JFrame {
private static final int FRAMEWIDTH = 400;
private static final int FRAMEHEIGHT = 400;
private int aORec = 4;
private Canvas canvas;
private JPanel mainPanel;
private JPanel panel;
private JPanel buttonPanel;
private JButton lessButton;
private JButton moreButton;
public ColorFrame() {
mainPanel = new JPanel();
panel = new JPanel();
canvas = new painter();
panel.add(canvas);
mainPanel.add(panel, BorderLayout.CENTER);
createComponents();
add(mainPanel);
setSize(FRAMEWIDTH,FRAMEHEIGHT);
setDefaultCloseOperation(3);
}
private void createComponents() {
buttonPanel = new JPanel();
lessButton = new JButton("Less");
moreButton = new JButton("More");
ActionListener bL = new ButtonListener();
lessButton.addActionListener(bL);
moreButton.addActionListener(bL);
buttonPanel.add(moreButton);
buttonPanel.add(lessButton);
mainPanel.add(buttonPanel, BorderLayout.NORTH);
}
class painter extends Canvas {
#Override
public void paint(Graphics g) {
for (int i = 0; i < aORec; i++) {
int tempWidth = (int)(Math.random() * (FRAMEWIDTH-0));
int tempHeight = (int)(Math.random() * (FRAMEHEIGHT -0));
g.drawRect(tempWidth,tempHeight,20,20);
}
}
}
class ButtonListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == moreButton) {
aORec =+ aORec;
canvas.repaint();
} else {
if (aORec != 1) {
aORec -= (aORec*0.5);
canvas.repaint();
} else {
System.out.println("There are not enough rectangles to be drawn.");
}
}
}
}
}
Main panel is created by
mainPanel = new JPanel();
Components are being added to the main panel as
mainPanel.add(panel, BorderLayout.CENTER);
mainPanel.add(buttonPanel, BorderLayout.NORTH);
but no LayoutManager was set, so the default FlowLayout is used, not BorderLayout. Create the panel by
mainPanel = new JPanel(new BorderLayout());
or add the statement
mainPanel.setLayout(new BorderLayout());
This is also valid for panel (otherwise it will not be resized, that is, stay with size zero)
(BorderLayout is the default for JFrame(
Can somebody tell me why after calling method getContentPane().add(grid[i][j]) I am not able to display the matrix of JLabels. There's only one "e" label displayed.
public class SudokuFrame extends JFrame implements ActionListener {
JButton generateButton;
JLabel[][] grid;
public SudokuFrame(){
setSize(300, 300);
setTitle("Sudoku");
setLayout(null);
generateButton = new JButton("Generate");
generateButton.setBounds(90, 220, 100, 30);
add(generateButton);
generateButton.addActionListener(this);
grid = new JLabel[9][9];
for (int i = 0; i < 9; i++) {
for (int j = 0; j < 9; j++) {
grid[i][j] = new JLabel("e");
grid[i][j].setBounds(100, 100, 30, 30);
getContentPane().add(grid[i][j]);
}
}
}
public static void main(String[] args){
SudokuFrame frame = new SudokuFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
You're giving every JLabel the exact same bounds -- same size and same position and so every new label is placed right smack dab on top of the previously added ones.
Solution: don't use null layout. Why use this when the problem is perfectly suited for a GridLayout? In general you want to avoid using null layouts and setBounds as the layout managers will make your coding and your GUI much easier to manage. Let the layouts do the heavy lifting for you.
e.g.,
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.GridLayout;
import javax.swing.*;
public class SimpleSudoku extends JPanel {
private static final int GAP = 1;
private static final Font LABEL_FONT = new Font(Font.DIALOG, Font.PLAIN, 24);
private JLabel[][] grid = new JLabel[9][9];
public SimpleSudoku() {
JPanel sudokuPanel = new JPanel(new GridLayout(9, 9, GAP, GAP));
sudokuPanel.setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
sudokuPanel.setBackground(Color.BLACK);
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[row].length; col++) {
grid[row][col] = new JLabel(" ", SwingConstants.CENTER);
grid[row][col].setFont(LABEL_FONT); // make it big
grid[row][col].setOpaque(true);
grid[row][col].setBackground(Color.WHITE);
sudokuPanel.add(grid[row][col]);
}
}
JPanel bottomPanel = new JPanel();
bottomPanel.add(new JButton("Regenerate"));
setLayout(new BorderLayout());
add(sudokuPanel, BorderLayout.CENTER);
add(bottomPanel, BorderLayout.PAGE_END);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
private static void createAndShowGui() {
SimpleSudoku mainPanel = new SimpleSudoku();
JFrame frame = new JFrame("SimpleSudoku");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
}
I'm creating a chess game where the main panel is using BorderLayout, there is a panel at NORTH for buttons, a panel at CENTER for the board itself (set to GridLayout) and a sidebar at East.
I have made the JFrame unresizable and I'd like the chessboard to fit the panels in so that the East panel is a lot wider (maybe 200 pixels) and the board remains a square. I can't figure out how to change the sizes of these components individually.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class GameWindow extends JFrame {
private final JPanel playArea = new JPanel(new BorderLayout(3,3));
private final JButton[][] boardSquares = new JButton[8][8];
private final JPanel board;
private final JPanel sidebar = new JPanel();
private final JLabel message = new JLabel("Game by ...");
public GameWindow() {
playArea.setBorder(new EmptyBorder(5, 5, 5, 5));
JToolBar tools = new JToolBar();
tools.setFloatable(false);
playArea.add(tools, BorderLayout.PAGE_START);
tools.add(new JButton("New Game"));
tools.add(new JButton("Save"));
tools.add(new JButton("Restore"));
tools.addSeparator();
tools.add(new JButton("Resign"))
tools.addSeparator();
tools.add(message);
board = new JPanel(new GridLayout(0, 8));
board.setBorder(new LineBorder(Color.BLACK));
playArea.add(board, BorderLayout.CENTER);
playArea.add(sidebar, BorderLayout.EAST);
Insets buttonMargin = new Insets(0,0,0,0);
for (int i = 0; i < boardSquares.length; i++) {
for (int j = 0; j < boardSquares[i].length; j++) {
JButton square = new JButton();
square.setMargin(buttonMargin);
if ((i+j)%2 == 0) {
square.setBackground(Color.WHITE);
}
else {
square.setBackground(Color.BLACK);
}
board.setSize(600, 600);
board.add(boardSquares[j][i] = square);
}
}
}
public final JComponent getChessBoard() {
return board;
}
public final JComponent getGui() {
return playArea;
}
public static void main(String[] args) {
GameWindow window = new GameWindow();
JFrame frame = new JFrame("Checkers");
frame.setResizable(false);
frame.add(window.getGui());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationByPlatform(true);
frame.setSize(800, 800);
frame.setVisible(true);
}
}
Firstly, since JDK 1.4, Java is encouraging the use of BorderLayout constants as BorderLayout.PAGE_START, BorderLayout.LINE_START, BorderLayout.CENTER, BorderLayout.LINE_END and BorderLayout.PAGE_END over the latter used by you.
Secondly you can simply override, the getPreferredSize() of the said JPanel, in order for it to give, some size that you feel like will work for your use case. Use of setPreferredSize() is restricted, since, not all LayoutManagers use to respect the Dimension specified by it.
Hence you could do something like:
private final JPanel sidebar = new JPanel() {
#Override
public Dimension getPreferredSize() {
return new Dimension(100, 100);
}
};
You can try this modified code:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class GameWindow extends JFrame {
private final JPanel playArea = new CustomPanel(710, 710);
private final JButton[][] boardSquares = new JButton[8][8];
private final JPanel board;
private final JPanel sidebar = new CustomPanel(100, 100);
private final JLabel message = new JLabel("Game by ...");
public GameWindow() {
playArea.setLayout(new BorderLayout(3,3));
playArea.setBorder(new EmptyBorder(5, 5, 5, 5));
JToolBar tools = new JToolBar();
tools.setFloatable(false);
playArea.add(tools, BorderLayout.PAGE_START);
tools.add(new JButton("New Game"));
tools.add(new JButton("Save"));
tools.add(new JButton("Restore"));
tools.addSeparator();
tools.add(new JButton("Resign"));
tools.addSeparator();
tools.add(message);
board = new CustomPanel(600, 600);
board.setLayout(new GridLayout(0, 8));
board.setBorder(new LineBorder(Color.BLACK));
playArea.add(board, BorderLayout.CENTER);
playArea.add(sidebar, BorderLayout.LINE_START);
Insets buttonMargin = new Insets(0,0,0,0);
for (int i = 0; i < boardSquares.length; i++) {
for (int j = 0; j < boardSquares[i].length; j++) {
JButton square = new JButton();
square.setOpaque(true);
square.setMargin(buttonMargin);
if ((i+j)%2 == 0) {
square.setBackground(Color.WHITE);
}
else {
square.setBackground(Color.BLACK);
}
board.add(boardSquares[j][i] = square);
}
}
}
private class CustomPanel extends JPanel {
private int width;
private int height;
public CustomPanel(int width, int height) {
this.width = width;
this.height = height;
setOpaque(true);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(width, height);
}
}
public final JComponent getChessBoard() {
return board;
}
public final JComponent getGui() {
return playArea;
}
public static void main(String[] args) {
GameWindow window = new GameWindow();
JFrame frame = new JFrame("Checkers");
frame.setResizable(false);
frame.setContentPane(window.getGui());
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setLocationByPlatform(true);
frame.pack();
frame.setVisible(true);
}
}
Moreover, before setting the background of JButton, it would be wise to call button.setOpaque(true) property.
It's not difficult to set the size of a JPanel. Just call setPreferredSize(). In your case to resize your East JPanel, call:
sidebar.setPreferredSize(new Dimension(200, 200));
After that, your LayoutManager will set the size of your JPanel to 200,200.
To your other JPanel, board: It's impossible to make a Component (like a JPanel) remaining a square. They always fit into rectangles. You would need to make your own subclass of JComponent and only paint everything in the square, and leave the rest transparent. Therefore, overwrite the method JComponent.paintComponent(Graphics).
I have a GUI that consists of multiple JList components on a panel, which is on a JScrollPane. The scroll pane makes it possible to scroll all of the lists at once. However, when I use MigLayout on the panel containing the lists I am unable to scroll past the first 1819 list elements. The limitation appears to be related to the height of the list, not the number of elements. If I use larger element sizes I can scroll less elements. I'm currently using MigLayout 4.2.
Here is a simplified example that exhibits this behavior.
import net.miginfocom.swing.MigLayout;
import javax.swing.*;
import java.awt.*;
public final class MigLayoutListTest {
public static void main(final String... args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
final String[] listData = new String[5000];
for (int i = 0; i < 5000; i++) {
listData[i] = "Index " + i;
}
final JPanel panel = new JPanel(new MigLayout());
panel.add(new JList(listData));
final JFrame frame = new JFrame();
frame.setContentPane(new JScrollPane(panel));
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setPreferredSize(new Dimension(600, 400));
frame.pack();
frame.setVisible(true);
}
});
}
}
If I eliminate the JPanel and put the JList directly on the JScrollPane then scrolling works correctly, but I cannot use this workaround since I need multiple lists on the same JScrollPane. If I use any layout other than MigLayout for the JPanel then scrolling works correctly.
Is this a bug or limitation of MigLayout? Is there some configuration option that needs to be applied to MigLayout in order to get it working correctly?
I think your approach is kludgy. Rather, use JLists in their own JScrollPane and synch up the scrolling:
import java.awt.*;
import java.util.*;
import javax.swing.*;
public class ScrollingDemo implements Runnable
{
public static void main(String args[])
{
SwingUtilities.invokeLater(new ScrollingDemo());
}
public void run()
{
JScrollPane sp1 = new JScrollPane(getJList(1));
sp1.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
JScrollPane sp2 = new JScrollPane(getJList(3));
sp2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
JScrollBar sBar1 = sp1.getVerticalScrollBar();
JScrollBar sBar2 = sp2.getVerticalScrollBar();
// synchronize:
sBar2.setModel(sBar1.getModel());
JPanel p = new JPanel(new GridLayout(1,2));
p.add(sp1);
p.add(sp2);
JFrame frame = new JFrame("Synch Scrolling");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(p, BorderLayout.CENTER);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public JList getJList(int factor)
{
Vector<String> items = new Vector<String>();
for(int i = 0; i < 5000; i++)
{
items.add(Integer.toString((i+1)*factor));
}
JList list = new JList(items);
list.setPrototypeCellValue("XXXXXXXXXX");
list.setVisibleRowCount(10);
return list;
}
}
If only want to see 1 vertical scrollbar, just set the scrollbar policy to JScrollPane.VERTICAL_SCROLLBAR_NEVER on the ones you want to hide.
NOTE: This assumes that each JList has the same number of elements. If you had multiple lists of varying length, you'd probably (instead) need to add an AdjustmentListener to the vertical scrollbars.
EDIT: Example:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ScrollingDemo2 implements Runnable
{
public static void main(String args[])
{
SwingUtilities.invokeLater(new ScrollingDemo2());
}
public void run()
{
JScrollPane sp1 = new JScrollPane(getJList(100));
sp1.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
JScrollPane sp2 = new JScrollPane(getJList(200));
sp2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// synchronize:
sp2.getVerticalScrollBar().addAdjustmentListener(new Synchronizer(sp1, sp2));
JPanel p = new JPanel(new GridLayout(1,0));
p.add(sp1);
p.add(sp2);
JFrame frame = new JFrame("Synch Scrolling 2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(p, BorderLayout.CENTER);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public JList getJList(int count)
{
Vector<String> items = new Vector<String>();
for(int i = 0; i < count; i++)
{
items.add(Integer.toString(i+1));
}
JList list = new JList(items);
list.setPrototypeCellValue("XXXXXXXXXX");
list.setVisibleRowCount(10);
return list;
}
class Synchronizer implements AdjustmentListener
{
JScrollPane sp1, sp2;
public Synchronizer(JScrollPane sp1, JScrollPane sp2)
{
this.sp1 = sp1;
this.sp2 = sp2;
}
public void adjustmentValueChanged(AdjustmentEvent e)
{
if (! e.getValueIsAdjusting())
{
return;
}
JScrollBar vert1 = sp1.getVerticalScrollBar();
JScrollBar vert2 = sp2.getVerticalScrollBar();
int range1 = vert1.getMaximum() - vert1.getMinimum() -
vert1.getModel().getExtent();
int range2 = vert2.getMaximum() - vert2.getMinimum() -
vert2.getModel().getExtent();
float percent2 = (float) (vert2.getValue()) / range2;
int newVal1 = (int) (percent2 * range1);
vert1.setValue(newVal1);
}
}
}
I have been trying for hours to find a way to solve the issue, but I had no luck with that. Here is a sample code:
import java.awt.BorderLayout;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
public class Example extends JFrame
{
private static final long serialVersionUID = 1L;
public Example()
{
JPanel contentPane = (JPanel) getContentPane();
contentPane.setLayout(new BorderLayout());
JPanel panTop = new JPanel(new BorderLayout());
//JPanel panBottom = new JPanel(new BorderLayout());
JPanel panTopCenter = new JPanel();
//JPanel panTopLeft = new JPanel();
//JPanel panTopRight = new JPanel();
panTop.add(panTopCenter, BorderLayout.CENTER);
//panTop.add(panTopLeft, BorderLayout.WEST);
//panTop.add(panTopRight, BorderLayout.EAST);
contentPane.add(panTop, BorderLayout.CENTER);
//contentPane.add(panBottom, BorderLayout.SOUTH);
JPanel pan = new JPanel();
pan.setLayout(new BoxLayout(pan, BoxLayout.Y_AXIS));
for(int i = 0; i < 50; i++) pan.add(new JButton("Button " + i));
JScrollPane scrollPane = new JScrollPane(pan);
panTopCenter.add(scrollPane);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
new Example();
}
});
}
}
Snapshot:
I always have to set the viewport's preferred size like this.
import java.awt.*;
import javax.swing.*;
public class Example extends JFrame {
public Example() {
setDefaultCloseOperation(EXIT_ON_CLOSE);
Box box = new Box(BoxLayout.Y_AXIS);
for (int i = 0; i < 50; i++) {
box.add(new JButton("Button " + i));
}
JScrollPane sp = new JScrollPane(box);
Dimension d = new Dimension(box.getComponent(0).getPreferredSize());
sp.getVerticalScrollBar().setUnitIncrement(d.height);
d.height *= 10; // Show at least 10 buttons
sp.getViewport().setPreferredSize(d);
add(sp, BorderLayout.CENTER);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
Example e = new Example();
}
});
}
}
Don't set any sizes! The scroll-bar appears if this change is made.
JPanel panTopCenter = new JPanel(new GridLayout());
The basic problem is that FlowLayout will show components at the smallest size needed to display it, and for a scroll-pane, that is (decided to be) 0x0. By using a GridLayout with no arguments in the constructor and adding the scroll-pane as the only component, it will be forced to fill the available space.
You have to set the preferred-size, in the case that JScrollPane is single JComponent in the container or top-level container.
scrollPane.setPreferredSize(new Dimension(100,500));
Better would be to use GridLayout for the same type of JComponents.
The best solution, quick and easy, is using JXPanel from SwingX, which is quasi-standard and implements Scrollable.