ScrollingTableFix.java

package com.ibm.nmon.gui.util;

import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;

import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;

/**
 * Fix to allow tables to autosize columns yet still actually scroll when in a scroll pane. By
 * default tables never scroll, the columns just get smaller.
 */
public final class ScrollingTableFix implements ComponentListener {
    private final JTable table;

    public ScrollingTableFix(JTable table, JScrollPane scrollPane) {
        assert table != null;

        this.table = table;

        table.getModel().addTableModelListener(new ColumnAddFix(table, scrollPane));
    }

    public void componentHidden(final ComponentEvent event) {}

    public void componentMoved(final ComponentEvent event) {}

    public void componentResized(final ComponentEvent event) {
        // turn off resize and let the scroll bar appear once the component is smaller than the
        // table
        if (event.getComponent().getWidth() < table.getPreferredSize().getWidth()) {
            table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
        }
        // otherwise resize new columns in the table
        else {
            table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
        }
    }

    public void componentShown(final ComponentEvent event) {}

    // similar behavior is needed when columns are added to the table
    private static final class ColumnAddFix implements TableModelListener {
        private final JTable table;
        private final JScrollPane scrollPane;

        ColumnAddFix(JTable table, JScrollPane scrollPane) {
            this.table = table;
            this.scrollPane = scrollPane;
        }

        @Override
        public void tableChanged(TableModelEvent e) {
            if (e.getFirstRow() == TableModelEvent.HEADER_ROW) {
                if (scrollPane.getViewport().getWidth() < table.getPreferredSize().getWidth()) {
                    table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
                }
                else {
                    table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
                }
            }
        }
    }
}