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JCheckBox centereing

I have been searching for a while now, but couldnt find a solution so I have decided to ask here.
I am using Java Swing for my gui implementation of calculator. I have custom made layout(which works correctly 100%). I have added all buttons and all buttons are positioned correctly, always. Last component I have inserted is "Inv" and it is checkbox which I cant find a way to center it inside its area. I have tried putting it in panel,in panel with borderlayout.center, setting the horizontal and vertical text alignment, but nothing works.
invert = new JCheckBox("Inv");
invert.setBackground(Color.decode("#8DA336"));
invert.addActionListener(new CommandListener(this,"invert"));
container.add(invert, new RCPosition(5, 7));
This RCPosition is nothing more than object which says in which row and column this component is (nothing wrong with that).

Checkbox is by default left-aligned. Try make it center-aligned:
invert = new JCheckBox("Inv");
invert.setHorizontalAlignment(SwingConstants.CENTER);
// styling and add to container
If it don't help, then you should publish your layout manager.

You could try putting it in a JPanel with BoxLayout, then add horizontal glue on the left and right.
final JFrame frame = new JFrame();
final JPanel jp = new JPanel();
jp.setLayout(new BoxLayout(jp, BoxLayout.X_AXIS));
jp.add(Box.createHorizontalGlue());
final JCheckBox jcb = new JCheckBox("inv");
jp.add(jcb);
jp.add(Box.createHorizontalGlue());
frame.getContentPane().add(jp);
frame.pack();
frame.setLocationRelativeTo(null);
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
frame.setVisible(true);
}
});
This is just one way to do it, setHorizontalAlignment should work as well.

JScrollPane drawing components under itself

I have a JScrollPane inside of a JTabbedPane tab. Into that JScrollPane I place a JPanel whose background is red and whose size is explicitly set.
This is what I get:
Note that in the second image, where the container frame has been resized, the component is being drawn under the scrollbar elements.
What's going on here? I've tried just about every combination of layout managers for all the components involved (as well as components besides JPanel - ultimately I want several JEditorPane here), and I cannot get anything to draw except under a big, blank, rectangle (is it a background? which?)
Code:
In main JFrame subclass:
// Called once on startup/layout.
public void refreshGUIState() {
for (int i = 0; i < client.getFrameStackLength(); i++) {
InferenceFrame frame = client.getFrame(i);
JScrollPane pane = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
JPanel wtf = new JPanel();
pane.setBackground(Color.YELLOW);
wtf.setBackground(Color.red);
wtf.setSize(100,100);
wtf.setPreferredSize(wtf.getSize());
pane.add(wtf);
workspace.addTab(Integer.toString(i), pane);
}
}
public GuiClient() throws CliException, ParticleSourceException {
super("L4 Interactive Prover");
setSize(800,600);
mainArea = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, true);
mainArea.setDividerSize(2);
mainArea.setBackground(Color.DARK_GRAY);
getContentPane().add(mainArea);
/* ... menu bar init ... */
toolspace = new JPanel();
workspace = new JTabbedPane();
mainArea.add(toolspace);
mainArea.add(workspace);
this.validate();
refreshGUIState();
}
Edit: under the suspicion that JScrollPane was somehow not creating a viewport when its first child was added, as expected, I also tried the three-argument constructor. Same behavior.
Re-edit: Except I erred and left in the add() call. Whoops. Looks like that's it.

Instead of
pane.add(wtf);
you need
pane.setViewportView(wtf);
You can also do it when initialising the JScrollPane:
JScrollPane pane = new JScrollPane(wtf);
Or, in your case:
JScollPane pane = new JScrollPane(wtf, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

Java Swing JTextArea not displaying correctly

I am trying to use Java Swing to create a simple GUI in which I have a drawing pad and some buttons it all works fine until I add this code for the JTextField:
String text = "hello";
JTextArea textArea = new JTextArea(text);
textArea.setPreferredSize(new Dimension(500, 50));
textArea.setEditable(false);
Before adding this code the drawpad displays on the left of the screen followed by the buttons, when I add this only the drawpad is displayed unless I resize the frame in which case the buttons and text field reappear although the text field is hidden behind the drawpad slightly. Here is the full code:
public class testGUI extends Frame{
public static void main(String[] args) {
JFrame frame = new JFrame("Neural Networks");
frame.setSize(700, 300); //set the size of the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true); //make it visible
Container content = frame.getContentPane();
content.setLayout(new BorderLayout());
JPanel mainPanel = new JPanel();
final PadDraw drawPad = new PadDraw();
drawPad.setSize(100, 100);
content.add(drawPad);
JButton clearButton = new JButton("Clear");
clearButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
drawPad.clear();
}
});
JButton loadButton = new JButton("Load");
loadButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
//Load something here
}
});
JButton testButton = new JButton("Test Draw Pad Image");
testButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
//
}
});
JButton loadImage = new JButton("Test image from file");
loadImage.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
//String filename = textField.getText();
}
});
String text = "hello";
JTextArea textArea = new JTextArea(text);
textArea.setPreferredSize(new Dimension(500, 50));
textArea.setEditable(false);
mainPanel.add(clearButton);
mainPanel.add(loadButton);
mainPanel.add(testButton);
mainPanel.add(loadImage);
mainPanel.add(textArea);
content.add(mainPanel);
}
}

You're adding the drawPad and the mainPanel to the content panel, which uses BorderLayout, without specifying any location. They thus end up both in the center position of the border layout, which is supposed to contain only one component.
See How to use BorderLayout in the Swing tutorial.
Also note that setting the preferred size is not something you should do. Instead, the preferred size is supposed to be automatically computed based on other sttings (the contained components, the number of rows and columns of a text area, etc.)
And a JTextArea should be enclosed into a JScrollPane to be good-looking and allow you to scroll.

JPanel mainPanel = new JPanel();
The default layout for a JPanel is a FlowLayout, so all the components flow on a single row. If there is not enough room on the row then the components wrap to the next row.
So when you add the JTextArea the flow is disturbed. The solution is to use a combination of layout managers to get your desired layout effect. Read the section from the Swing tutorial on Using Layout Managers for more information and examples.
JTextArea textArea = new JTextArea(text);
textArea.setPreferredSize(new Dimension(500, 50));
Also, you should NOT set the preferred size of the text area (or any Swing component for that matter). Instead you should do something like:
JTextArea textArea = new JTextArea(rows, columns);
and let the component determine its own preferred size. Also a text area is typically used with a JScrollPane and then you add the scroll pane to your panel:
JScrollPane scrollPane = new JScrollPane( textArea );
Edit:
Taking a second look at your code you have many more problems.
The point of using a layout manager is to have the layout manager set the size and location of the components. So your code should not have any logic related to the size/location of a component.
When you use the add(...) statement on a BorderLayout without a constraint, the component gets added to the CENTER. However only the last component added is managed by the BorderLayout. So only the "mainPanel" is given a size/location by the layout manager. That is why you need the setSize(...) statement on the drawPad to make the component visible. Although you now have the problem that two components are painted in the same space.
So to see the drawPad on the left you might want to use:
content.add(drawPad.BorderLayout.LINE_START);
However this still probably won't work because I'm guessing you are doing custom painting on the draw pad which means you will also need to override the getPreferredSize() method of the class so the layout manager can use the information to determine the size of the component. Read the section from the Swing tutorial on Custom Painting for more information and working examples.
Finally some other issues:.
The setVisible(...) statement should be invoked AFTER all the components have been added to the frame.
To follow Java standards, class names should start with an upper case character.
You should NOT be extending "Frame". There is no need to extend any class in your example.
Read the tutorial and download the demos for examples of better structured code.

How to fit a JTable to the size of JFrame?

I have a frame which is set to:
setExtendedState(JFrame.MAXIMIZED_BOTH);
Now I have a Jtable and on the Design phase of eclipse I have exactly fitted to the frame:
But when I run the program I have so much wasted space on the right side as this:
How can I extend this to fill up the empty space on the right side?

To make JTable fill the available space, put it inside a JPanel which has a BorderLayout layout manager.
JTable table = new JTable();
// Set up table, add data
yourFrame.getContentPane().add( new JScrollPane( table ), BorderLayout.CENTER );
UPDATE: as suggested by camickr
you don't need the getContentPane(). Since JDK4 you can just add components directly to the frame and then will be added to the content pane automatically.
yourFrame.add( new JScrollPane( table ), BorderLayout.CENTER

If you have just the JTable the following code should work for you:
JFrame jframe = new JFrame();
jframe.setExtendedState(JFrame.MAXIMIZED_BOTH);
JTable jtable = new JTable();
jtable.setBackground(Color.yellow);
jframe.getContentPane().add(jtable);
jframe.setVisible(true);
If you need to add more components to the JFrame I suggest you to use a layout in this way
JFrame jframe = new JFrame();
jframe.setExtendedState(JFrame.MAXIMIZED_BOTH);
GridLayout layout = new GridLayout(); //chose your favorite
JTable jtable = new JTable();
jtable.setBackground(Color.yellow);
Container contentPane = jframe.getContentPane();
contentPane.setLayout(layout);
contentPane.add(jtable);
jframe.setVisible(true);

JTable selects wrong cell on click

I am working inside of a quite complex eclipse based application, and having a problem with a JTable based custom component inside of a JSplitPane. The part of the application that I actually have access to is a panel, within a tab, within a panel, within the actual application, so there are a lot of things that can go wrong.
The specific problem that I'm having right now is that the table component is selecting the wrong cell when I click on it. If I select a cell in row 0, column 0, the cell that actually gets selected is at row 2, column 0, which is about 20 pixels below the actual click. This only happens if the table is in a JSplitPane though: if I just add the table itself to a panel, cell selection is correct.
What it seems like to me is that because the table is in a JSplitPane, the boundaries of the table (or maybe the viewport of the scroll pane containing the table?) are off by about 20 pixels somewhere. Another problem that I had which can back this theory up, is that scrolling the table caused repaints above the table: so for example, as I scrolled down, instead of the table scrolling, it actually moved upwards (painting over the components above the table) about 20 pixels before scrolling. I was able to workaround this problem by adding
jscrollpane.getViewport().setScrollMode(JViewport.BACKINGSTORE_SCROLL_MODE);
to the scrollpane that contained the table.
Because of all the custom components involved, I can't actually get a small app that shows the problem, but I have the next best thing, which is an app that shows the layout that I have (of course, it doesn't actually have the same problems). Any ideas on what might be causing the problem?
//Test class showing layout of table/splitpane
import javax.swing.*;
import java.awt.*;
public class SplitTest
{
private static JFrame frame;
private static JPanel buildTable()
{
JPanel tblPanel = new JPanel();
tblPanel.setLayout(new BorderLayout());
String[] cols = new String[]{"one", "two", "three", "four", "five", "six", "seven"};
Object[][] data = new Object[30][7];
for(int x = 0;x < data.length;x++)
for(int y = 0;y < data[x].length;y++)
data[x][y] = x + ", " + y;
JTable tbl = new JTable(data, cols);
JScrollPane scrollPane = new JScrollPane(tbl);
tblPanel.add(scrollPane, BorderLayout.CENTER);
return tblPanel;
}
private static JPanel buildTab()
{
JPanel pnl = new JPanel();
pnl.setLayout(new BorderLayout());
JPanel menuPnl = new JPanel();
menuPnl.setLayout(new FlowLayout(FlowLayout.LEFT));
menuPnl.add(new JLabel("label"));
menuPnl.add(new JComboBox(new String[]{"one", "two"}));
menuPnl.add(new JButton("Button"));
pnl.add(menuPnl, BorderLayout.NORTH);
JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
splitPane.setLeftComponent(buildTable());
JPanel bottomPnl = new JPanel();
bottomPnl.setPreferredSize(new Dimension(800, 200));
bottomPnl.setBackground(Color.RED);
splitPane.setRightComponent(bottomPnl);
splitPane.setDividerLocation(.5);
pnl.add(splitPane, BorderLayout.CENTER);
return pnl;
}
private static JTabbedPane buildGUI()
{
JTabbedPane topLevelTabbedFrame = new JTabbedPane();
topLevelTabbedFrame.addTab("Tab 1", buildTab());
topLevelTabbedFrame.addTab("Tab 2", new JPanel());
topLevelTabbedFrame.addTab("Tab 3", new JPanel());
return topLevelTabbedFrame;
}
private static void createAndShowGUI()
{
frame = new JFrame("Split Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(buildGUI(), BorderLayout.CENTER);
// frame.setSize(new Dimension(800, 600));
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) throws Exception
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}

Because of all the custom components involved, I can't actually get a small app that shows the problem, but I have the next best thing, which is an app that shows the layout that I have (of course, it doesn't actually have the same problems).
I was about to tell you the posted code workd just fine, and the I read this.
Anyway, it seems the problem lies in all the custom components you added to the mix. For JTable and JSplitPane work fine alone.
What I would do is to remove components one by one until it works ( probably I will work when the code is similar to the one posted and there is nothing else there )
Or you can go the opposite way which is easier. Start with your sample code and then add more and more components until it fail.
You can take this opportunity to refactor and clean your code and move unneeded components. And even ( why not ) add test cases in the process.
Good luck.

Have you tries running it on a different box to check if its hardware related.
May be related to this bug
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4763448

As it turns out, the problem was with the order that the components were initialized and added to the split pane. So the eventual fix was to delay adding the table to the split pane until after the split pane was actually added to the panel, rather than adding the table to the split pane before adding the split pane to the panel. Making that small change fixed the issue.