java - JTable 的页脚

Question

JTable 不支持显示包含每列聚合数据的页脚。受建议解决方案的启发 Oracle/Suns bug database这看起来很有希望，我开始采用在滚动 Pane 的边框上绘制页脚的方法。

现在一开始我只想要一个“概念证明”，看起来我快到了，每列都有一个页脚，宽度是同步的。等等 所以它似乎工作得很好，除了一件事，没有文字被绘制!我希望从 getFooterValueAt 返回的虚拟值绘制在每个“页脚单元格”上，但它们都是空白的，只绘制了背景(仅用于测试)。

为什么没有绘制任何文字？我在 paintFooter 中的位置/大小计算有问题吗？

import static java.awt.BorderLayout.CENTER;
import static java.awt.Color.BLUE;
import static java.awt.Color.CYAN;
import static java.awt.Color.GREEN;
import static java.awt.Color.LIGHT_GRAY;
import static java.awt.Color.MAGENTA;
import static java.awt.Color.ORANGE;
import static java.awt.Color.PINK;
import static java.awt.Color.RED;
import static java.awt.Color.WHITE;
import static java.awt.Color.YELLOW;
import static javax.swing.JTable.AUTO_RESIZE_OFF;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;

import javax.swing.CellRendererPane;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;
import javax.swing.border.Border;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.TableColumnModelEvent;
import javax.swing.event.TableColumnModelListener;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableCellRenderer;

/**
 * Demo application for JTable with footer.
 * 
 * @author Martin Uhlén
 */
public class TableFooterBorderDemo extends JFrame
{   
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new TableFooterBorderDemo().setVisible(true);
            }
        });
    }

    private TableFooterBorderDemo()
    {
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        setLayout(new BorderLayout());

        JTable table = createTable();
        JScrollPane scroll = new JScrollPane(table);
        add(scroll, CENTER);
        TableFooter.install(scroll, table);
        pack();
        positionAtMiddleOfScreen();
    }

    private void positionAtMiddleOfScreen()
    {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        setLocation((int) ((screenSize.getWidth() / 2) - (getWidth() / 2)), 
                    (int) ((screenSize.getHeight() / 2) - (getHeight() / 2)));
    }

    private JTable createTable()
    {
        Object[][] data = new Object[][]
        {
            { "A", "*", "*", "*", "*", "*" },
            { "*", "B", "*", "*", "*", "*" }, 
            { "*", "*", "C", "*", "*", "*" },
            { "*", "*", "*", "D", "*", "*" }, 
            { "*", "*", "*", "*", "E", "*" },
            { "*", "*", "*", "*", "*", "F" } 
        };
        Object[] columns = new Object[] { "A", "B", "C", "D", "E", "F" };
        DefaultTableModel model = new DefaultTableModel(data, columns);
        JTable table = new JTable(model);
        table.setAutoResizeMode(AUTO_RESIZE_OFF);
        return table;
    }

    /**
     * A Border for JScrollPane that paints a footer for JTable.
     */
    private static class TableFooter implements Border
    {
        private static final Color[] COLORS = {RED, GREEN, BLUE, YELLOW, PINK, CYAN, LIGHT_GRAY, MAGENTA, ORANGE, WHITE};

        private final JScrollPane scroll;
        private final JTable table;
        private final CellRendererPane cellRendererPane;

        TableFooter(JScrollPane scroll, JTable table)
        {
            this.scroll = scroll;
            this.table = table;
            cellRendererPane = new CellRendererPane();
        }

        public static TableFooter install(JScrollPane scroll, JTable table)
        {
            verify(scroll, table);
            TableFooter footer = new TableFooter(scroll, table);

            RepaintListener repainter = new RepaintListener(scroll);
            scroll.getViewport().addChangeListener(repainter);
            scroll.getHorizontalScrollBar().addAdjustmentListener(repainter);
            table.getColumnModel().addColumnModelListener(repainter);
            scroll.setViewportBorder(footer);
            return footer;
        }

        private static void verify(JScrollPane scroll, JTable table)
        {
            if (scroll.getViewport().getView() != table)
            {
                throw new IllegalArgumentException("Given table must be inside given scroll pane");
            }
        }

        /**
         * @see javax.swing.border.Border#paintBorder(java.awt.Component, java.awt.Graphics, int, int, int, int)
         */
        @Override
        public void paintBorder(Component c, Graphics g, int x, int y, int width, int height)
        {
            System.out.println("x: " + x + ", y: " + y + ", width: " + width + ", height: " + height);
            System.out.println("viewRect: " + scroll.getViewport().getViewRect());
            paintFooter(g, x, y, width, height);
        }

        private void paintFooter(Graphics g, int x, int y, int width, int height)
        {
            Color oldColor = null;
            Component cellRendererComponent = null;
            int columnWidths = x - scroll.getViewport().getViewRect().x;
            for (int column = 0; column < table.getColumnCount(); column++)
            {
                TableCellRenderer cellRenderer = table.getCellRenderer(0, column);
                cellRendererComponent = cellRenderer.getTableCellRendererComponent(table, getFooterValueAt(column), false, false, 0, column);
                if (oldColor == null)
                {
                    oldColor = cellRendererComponent.getBackground();
                }
                int columnWidth = table.getColumnModel().getColumn(column).getWidth();
                cellRendererComponent.setBackground(COLORS[column % COLORS.length]);
                cellRendererPane.paintComponent(g, cellRendererComponent, scroll, columnWidths, y, columnWidth, height);
                columnWidths += columnWidth;
            }
            if (cellRendererComponent != null)
            {
                cellRendererComponent.setBackground(oldColor);
            }
        }

        private Object getFooterValueAt(int viewColumn)
        {
            return "Column " + viewColumn;
        }

        @Override
        public Insets getBorderInsets(Component c)
        {
            return new Insets(0, 0, table.getRowHeight(), 0);
        }

        @Override
        public boolean isBorderOpaque()
        {
            return true;
        }
    }

    /**
     * Repaints JScrollPane when needed.
     */
    private static class RepaintListener implements ChangeListener, AdjustmentListener, TableColumnModelListener
    {
        private final JScrollPane scroll;

        RepaintListener(JScrollPane scroll)
        {
            this.scroll = scroll;
        }

        @Override
        public void columnAdded(TableColumnModelEvent e)
        {
            repaint();
        }

        @Override
        public void columnRemoved(TableColumnModelEvent e)
        {
            repaint();
        }

        @Override
        public void columnMoved(TableColumnModelEvent e)
        {
            repaint();
        }

        @Override
        public void columnMarginChanged(ChangeEvent e)
        {
            repaint();
        }

        @Override
        public void columnSelectionChanged(ListSelectionEvent e)
        {
            repaint();
        }

        @Override
        public void adjustmentValueChanged(AdjustmentEvent e)
        {
            repaint();
        }

        @Override
        public void stateChanged(ChangeEvent e)
        {
            repaint();
        }

        private void repaint()
        {
            scroll.repaint();
        }   
    }
}

Answer 1

问题是 rendererPane 的位置:您的代码中发生的是标签位于 x/y，即靠近具有视口(viewport)矩形完整高度的上边界线，然后文本被绘制在某处视口(viewport)的中间，后来被视口(viewport)覆盖。要查看效果，请使用零行 tableModel 并使视口(viewport)不透明。

相反，您必须将它定位在边框的底部。一个非常脏(没有做任何事情来使其像素正确，在周末运行时:) 片段

        g.setColor(Color.RED);
        int scrollBottom = scroll.getInsets().bottom;
        int lowerBorderTop = height - scrollBottom;
        g.drawLine(x, height - scrollBottom - 1, width - 10,  height - scrollBottom - 1);
        g.drawRect(x + 1,  height - scrollBottom, width - 10, 10);
        Color oldColor = null;
        Component cellRendererComponent = null;
        int columnWidths = x ;//- scroll.getViewport().getViewRect().x;
        for (int column = 0; column < table.getColumnCount(); column++)
        {
            TableCellRenderer cellRenderer = table.getCellRenderer(0, column);
            cellRendererComponent = cellRenderer.getTableCellRendererComponent(table, 
                    getFooterValueAt(column), false, false, 0, column);
            if (oldColor == null)
            {
                oldColor = cellRendererComponent.getBackground();
            }
            int columnWidth = table.getColumnModel().getColumn(column).getWidth();
            cellRendererComponent.setForeground(Color.BLACK);
            cellRendererComponent.setBackground(COLORS[column % COLORS.length]);
            cellRendererPane.paintComponent(g, cellRendererComponent, scroll, columnWidths, 
                  lowerBorderTop , columnWidth, table.getRowHeight(), false);
            columnWidths += columnWidth;
        }
        if (cellRendererComponent != null)
        {
            cellRendererComponent.setBackground(oldColor);
        }

额外的线和矩形只是为了看看我们在哪里。顺便说一句，不错的方法:-)