Problems with JTable and JScrollpane size

I have a JScrollPane with a JTable in it. In the JTable I have initially 3 rows. Later on rows get added.

The default JTable with my 3 rows is ugly because JScrollPane calls getPreferredScrollableViewportSize from the client (JTable) and the return value is always the same. That's why my JTable/JScrollpane with 3 rows has this free space, JScrollpane andJTable do not have the same size.

My solution is to make a subclass JTable, override getPreferredScrollableViewportSize and return in this function getPreferredSize();. Now the whole JScrollPane has exactly the size of the 3 row `JTable!

When a row gets added I have the command ((JComponent) scrollPane.getParent()).revalidate();

The scrollpane grows with the table.

Everything works fine!

But now I want to set a certain layout for the container of the scrollpane (panel): myjpanel.setLayout (new BoxLayout(contentPane, BoxLayout.Y_AXIS));

When I add this command my whole solution doesn't work anymore. The scrollpane hasn't the size of the 3 row table, this free space is there again.

Why is this?

Does anybody have a solution?

CONTINUED

Thank you camickr for pointing me in the right direction. My solution is the following:

    scrollPane = new JScrollPane (table) {          
      public Dimension getMaximumSize () {
        double height = 0;

        double width = super.getMaximumSize().getWidth开发者_如何学编程();
        height += columnHeader.getViewSize().getHeight();           
        height += viewport.getView().getPreferredSize().getHeight();
        height += (getViewportBorderBounds().getHeight() * -1);
        Dimension returnValue = new Dimension ((int) width, (int) height);
        return returnValue;
      }
    };

It works now at the beginning. But when a row is added to the jtable and I call revalidate(); on the jpanel (parent container of the scrollpanel) the jscrollpanel shrinks in height to 1 row + header! Has anyone got an idea what is to do in this situation.

CONTINUED

Now I know the problem. It is the viewportBorder. In order to get the whole, exact height I have to total the height of the view (Jtable), the height of the column header and the height of the viewportBorder. The first time getViewportBorderBounds().getHeight() returns -3, next time - after a new row is inserted in the table model - the function returns 48. I do not understand why this function returns 48 now. Another point is that camickr says that changing the size of the jscrollpane defeats the purpose of the scrollpane. I do not understand this. How can anyone be satisfied with a default jscrollpane size of 450 x 400 (http://www.javalobby.org/java/forums/t19559.html) even when the jtable has only 3 lines at the beginning. This unfilled extra space does not look very professional in my eyes. Has anyone got a better solution for this.

Thank you very much for your answers

CONTINUED Now everything works! At the beginning I simply set the jscrollpane border to 0 ... sp.setBorder(createEmptyBorder()); In this way I avoid having these strange return values of getViewportBorderBounds().getHeight() Wolfgang

The BoxLayout allows the component to grow up to the maximum size of the component. I guess you need to override the getMaximumSize() of the scrollpane to return the preferred size.

When a row gets added I have the command "((JComponent) scrollPane.getParent()).revalidate();" The scrollpane grows with the jtable.

That kind of defeats the purpose of the scrollpane. The scrollbar is supposed to stay at a fixed size and then scrollbars will appear if necessary.

I had a similar problem - the basic upshot is that I wanted a JTable in a scroll pane that had a minimum and maximum size: when there was no data in the table, it should have a one-row-height pane background displayed (not a fake row, obviously), and when it was over 10 rows to limit the displayed table size to those 10 rows plus scrollbars. Any size between 1 and 10 should display the table at full height. The situation was a parent-child table, and this was the child table, so I had to trigger the child table resize depending on which parent table row was clicked. A fixed pane size looked ugly in that it took up unnecessary space to push other potentially viewable info under the child table out of view with just blank space.

Using the setPreferredScrollableViewportSize after updating the model with the child rows (and setFillsViewportHeight(true) of course) gave me almost everything I needed. Except that the viewport wouldn't redraw until I clicked on it, or took focus from the window then flicked back, it was most annoying.

The solution was super-simple after reading this post: I just had to call revalidate on the scrollpane's parent, as pointed out in the solution. Fixed it perfectly. Mostly I just wanted to share a use case where you want the scrollpane size to change dynamically up to a maximum size. Swing is so much simpler if everything is created at a fixed size forever... unlike pretty much every real-life use case I've ever encountered :-)