Where have my JTable headings gone?

Your issue has nothing to do with GridBagLayout.

By default, a JTable's header will not appear unless it is in a JScrollpane. If you simply don't want to do this (why?), there is a workaround. The JTable tutorial explains:

http://java.sun.com/docs/books/tutorial/uiswing/components/table.html#show

KelVarnsona at 2007-7-12 19:23:08 >

I can see the point totally. But these four tables are not used often in this application (I'm thinking this panel will just pop up from amenu, and then close after use), so some inconvenience with looking at them is not too much of a problem.

But thanks for the JScrollpane advice. I tried it and it almost works. The modified code below at least gives me the headings for the first table, but the JScrollpane is huge! So I need to changhe its size right,and I can't figure out what to do. Am I supposed to be changing the scrollpane size, or is it a layout manager thing? Ideally, I need to get the a size attributr from the table, and somehow using that to set the scrollpane size. Somehow. (Help?!)

public ScrollerTest() {

JTable table1 = new JTable(data, columnNames);

JTable table2 = new JTable(data, columnNames);

JTable table3 = new JTable(data, columnNames);

JTable table4 = new JTable(data, columnNames);

JLabel label1 = new JLabel("Table 1");

JLabel label2 = new JLabel("Table 2");

JLabel label3 = new JLabel("Table 3");

JLabel label4 = new JLabel("Table 4");

JPanel myPanel = new JPanel();

myPanel.setLayout(new GridBagLayout());

GridBagConstraints c = new GridBagConstraints();

c.insets = new Insets(0,0,10,1);

c.gridx = 0;

c.gridy = 0;

c.anchor = GridBagConstraints.WEST;

myPanel.add(label1,c);

c.insets = new Insets(0,0,30,0);

c.gridx = 0;

c.gridy = 1;

c.anchor = GridBagConstraints.CENTER;

JScrollPane tablePane = new JScrollPane(table1);

myPanel.add(tablePane,c);

c.insets = new Insets(0,0,10,0);

c.gridx = 0;

c.gridy = 2;

c.anchor = GridBagConstraints.WEST;

myPanel.add(label2,c);

c.insets = new Insets(0,0,30,0);

c.gridx = 0;

c.gridy = 3;

c.anchor = GridBagConstraints.CENTER;

myPanel.add(table2,c);

c.insets = new Insets(0,0,10,0);

c.gridx = 0;

c.gridy = 4;

c.anchor = GridBagConstraints.WEST;

myPanel.add(label3,c);

c.insets = new Insets(0,0,30,0);

c.gridx = 0;

c.gridy = 5;

c.anchor = GridBagConstraints.CENTER;

myPanel.add(table3,c);

c.insets = new Insets(0,0,10,0);

c.gridx = 0;

c.gridy = 6;

c.anchor = GridBagConstraints.WEST;

myPanel.add(label4,c);

c.insets = new Insets(0,0,30,0);

c.gridx = 0;

c.gridy = 7;

c.anchor = GridBagConstraints.CENTER;

myPanel.add(table4,c);

JScrollPane scroller = new JScrollPane();

scroller.getViewport().add(myPanel);

scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);

scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

this.getContentPane().setLayout(new BorderLayout());

this.getContentPane().add(scroller);

this.setSize(new Dimension(300, 300));

this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

this.setVisible(true);

}

[/code]

Arwela at 2007-7-12 19:23:08 >

> p.s.

> All the tables are always 5 colums wide, so theres never a problem of

> seeing row 58 of one and 2 of another, by the way.

I don't think you understood my point (or, perhaps I was unclear).

If you put each table into their own JScrollPane, and showed maybe only 5 rows of each table (or whatever number is appropriate), then the user could scroll each scroll pane to the appropriate row for that table, and be able to see the desired data for each table all at the same time (perhaps for comparison purposes), without having to scroll the page up and down constantly.

The amount of columns is irrelevant, by the way.

With your way, let's assume that each table has:

100 rows for table 1,

460 rows for table 2,

60 rows for table 3,

570 rows for table 4,

1100 rows for table 5.

Now lets consider that I want to compare the data in row 9 of table 1 with the data in 56 of table 3, and row 513 of table 5. It is impossible. They will never be on the screen at the same time (which is the point I was trying to make). I would have to "page scroll" up and down several times, which is undesirable in my opinion. If each table could scroll all by themselves, it suddenly becomes very do-able.

Trying to avoid page scrolling (if you can) seems to be a common, accepted idiom of UI design. Of course, there are times when you want that, but that is typically an exception, not the norm.

Just my 2c.

KelVarnsona at 2007-7-12 19:23:08 >

> No honest, I understand the point. Its just that in this application,

> these three tables in particular are never very big, and just because of

> the information that they contain there is never really much need to

> compare information between these three tables at the same time.

> The user will typically require information from just one of them, and

> not very often at that.

Fair enough.

In that case, you still need to put each table in a scroll pane in order to see the headers. Then set the horizontal and vertical scrollbar policies to NEVER.

KelVarnsona at 2007-7-12 19:23:08 >

I got ut!!! :o)

THis now works. Thanks for the help everyone....

c.insets = new Insets(0,0,30,0);

c.gridx = 0;

c.gridy = 1;

c.anchor = GridBagConstraints.CENTER;

JScrollPane tablePane = new JScrollPane(table1);

tablePane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER);

tablePane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

tablePane.setPreferredSize(table1.getPreferredSize());

myPanel.add(tablePane,c);

Arwela at 2007-7-12 19:23:08 >