Making a JTable fill the view without extension

Ahhh, the old table-doesn’t-fill-the-view problem. Nothing says “this is a Swing app” more than a JTable that only fills up part of it’s parent JViewport. Apparently this behavior was not the original behavior (as I had once thought), but was introduced, presumably as a bug, back in Java 1.2 (see this bug report). This behavior has been fixed in Java 6, though not by default – you have to call JTable.setFillsViewportHeight(true).

Default fill behavior	Fixed fill behavior

Most work-arounds to this problem involve sub-classing JTable, and overriding getScrollableTracksViewportHeight() like this:

    @Override
    public boolean getScrollableTracksViewportHeight() {
        return getParent() instanceof JViewport
                && getPreferredSize().height < getParent().getHeight();
    }

This works great if you have control over the actual JTable. But if you’re crafting a UI delegate to be used with a table, your out of luck – at least with this technique.

There is, however, another way to make a table, or any other component that sits inside a JViewport, fill the view bounds. To do this, you can create an extension of ViewportLayout where you can add the corrected fill logic. You’ll also need to add a property listener to the ancestor property of the component sitting inside the JViewport. Listening to this property will give you a hook from which to install the custom layout on the containing JScrollPane‘s JViewport. The ancestor property is fired whenever the component is added as a child to another component.

Here’s a simple table UI delegate that paints row striping:

public class CustomTableUI extends BasicTableUI {

    private static final Color EVEN_ROW_COLOR = new Color(241, 245, 250);
    private PropertyChangeListener fAncestorPropertyChangeListener =
            createAncestorPropertyChangeListener();

    @Override
    public void installUI(JComponent c) {
        super.installUI(c);

        // TODO save defaults.

        table.setFont(MacFontUtils.ITUNES_FONT);
        table.setShowVerticalLines(true);
        table.setShowHorizontalLines(false);
        table.setShowGrid(false);
        table.setIntercellSpacing(new Dimension(0, 0));

        table.addPropertyChangeListener("ancestor", fAncestorPropertyChangeListener);
    }

    private PropertyChangeListener createAncestorPropertyChangeListener() {
        return new PropertyChangeListener() {
            public void propertyChange(PropertyChangeEvent evt) {
                // indicate that the parent of the JTable has changed.
                parentDidChange();
            }
        };
    }

    private void parentDidChange() {
        // if the parent of the table is an instance of JViewport, and that JViewport's parent is
        // a JScrollpane, then install the custom BugFixedViewportLayout.
        if (table.getParent() instanceof JViewport
                && table.getParent().getParent() instanceof JScrollPane) {
            JScrollPane scrollPane = (JScrollPane) table.getParent().getParent();
            scrollPane.getViewport().setLayout(new BugFixedViewportLayout());
        }
    }

    @Override
    public void paint(Graphics g, JComponent c) {
        // get the row index at the top of the clip bounds (the first row to paint).
        int rowAtPoint = table.rowAtPoint(g.getClipBounds().getLocation());
        // get the y coordinate of the first row to paint. if there are no rows in the table, start
        // painting at the top of the supplied clipping bounds.
        int topY = rowAtPoint < 0 ? g.getClipBounds().y : table.getCellRect(rowAtPoint,0,true).y;

        // create a counter variable to hold the current row. if there are no rows in the table,
        // start the counter at 0.
        int currentRow = rowAtPoint < 0 ? 0 : rowAtPoint;
        while (topY < g.getClipBounds().y + g.getClipBounds().height) {
            int bottomY = topY + table.getRowHeight();
            g.setColor(getRowColor(currentRow));
            g.fillRect(g.getClipBounds().x, topY, g.getClipBounds().width, bottomY);
            topY = bottomY;
            currentRow ++;
        }

        super.paint(g, c);
    }

    private Color getRowColor(int row) {
        return row % 2 == 0 ? EVEN_ROW_COLOR : table.getBackground();
    }

    // BugFixedViewportLayout implementation. /////////////////////////////////////////////////////

    /**
     * A modified ViewportLayout to fix the JFC bug where components that implement Scrollable do
     * not resize correctly, if their size is less than the viewport size.
     * This is a JDK1.2.2 bug (id 4310721). This used to work in Swing 1.0.3 and the fix is putting
     * the old logic back.
     * Copied from: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4310721
     */
    private class BugFixedViewportLayout extends ViewportLayout {
        public void layoutContainer(Container parent) {
            // note that the original code (at the link supplied in the comment above) contained the
            // following call to super.layoutContainer(parent). this call caused the table to
            // continuously paint itself when the table did not fill the view. thus, i've commented
            // it out for now, as doing so seems to have no ill effects.
            // super.layoutContainer(parent);

            JViewport vp = (JViewport)parent;
            Component view = vp.getView();

            if(view == null) {
                return;
            }

            Point viewPosition = vp.getViewPosition();
            Dimension viewPrefSize = view.getPreferredSize();
            Dimension vpSize = vp.getSize();
            Dimension viewSize = new Dimension(viewPrefSize);

            if ((viewPosition.x == 0) && (vpSize.width > viewPrefSize.width)) {
                viewSize.width = vpSize.width;
            }

            if ((viewPosition.y == 0) && (vpSize.height > viewPrefSize.height)) {
                viewSize.height = vpSize.height;
            }

            if (!viewSize.equals(viewPrefSize)) {
                vp.setViewSize(viewSize);
            }
        }
    }
}

Note that this is a simplistic example in that BugFixedLayout ignores JTables autoResize property – that is, if the JTable is set to use AUTO_RESIZE_OFF, the table will still fill the width of the view. Ultimately, the table’s background would still fill the width of the view, but the columns would not, as is the case with native tables on both Windows and Mac.

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