JTable 连续调用自定义单元格渲染器方法...

Question

可以在以下位置找到可编译的源代码：http://www.splashcd.com/jtable.tar

我是该语言的新手，所以我不确定这是否是可接受的行为。

我创建了一个 JTable 来为收到的每条消息显示一行（它接收大约 每 20 秒一次）。其中一个表列可以包含大量 文本，所以我创建了一个自定义单元格渲染器，它自动换行并设置行 相应的高度。

一切都按预期工作，除了一旦表格显示第一行， 它每秒调用单元格渲染器大约十次......直到用户关闭 表。

一旦我在那里获得大约 20 行，表格就会变得相当缓慢，需要 2-8 秒来调整列的大小，向上或向下滑动，或使用 选定的背景颜色。

我在渲染器中插入了一个打印语句，所以我可以看到多少次 正在调用 getTableCellRendererComponent 方法。

我禁用了工具提示，并禁用了所有单元格编辑。我确实有一个听众 当添加新行或表格时，将视图滚动到最后一行 调整大小。

getTableCellRendererComponent 方法是否应该每秒调用多次 当我只是查看屏幕（不触摸鼠标或键盘）时？

TIA

Answer 1

• aaaaach

• 你需要doLayout()，

• 下一级 :-)，然后您也可以将Maximum visible rows 设置为JTextComponents，毫不费力

doLayout()

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.text.*;
//http://tips4java.wordpress.com/2008/10/26/text-utilities/
public class AutoWrapTest {

    public JComponent makeUI() {
        String[] columnNames = {" Text Area Cell Renderer "};
        Object[][] data = {
            {"123456789012345678901234567890"},
            {"dddddddddddddddddddddddddddddddddddddddddddddddddddddddddx"},
            {"----------------------------------------------0"},
            {">>>>>>>>>>>>>dddddddddddddddddddddddddddddddddddddddddddddddddd"
                + "dddddddxdddddddddddddddddddddddddddddddddddddddddddddd"
                + "dddddddddddx>>>>>>>>>>>>>>>>>>>>>>>>>|"},
            {">>>>>>>>>>>>ddddddddddddddddddddddddddddddddddddddddddddddddddd"
                + "ddddddx>>>>>>>>>>>>>>>>>>>>>>>>>>|"},
            {"a|"},
            {">>>>>>>>bbbb>>>>>>>>>>>>>>>>>>>|"},
            {">>>>>>>>>>>>>>>>>>|"},
            {">>>>>>>>>>>>>dddddddddddddddddddddddddddddddddddddddddddddddddd"
                + "dddddddxdddddddddddddd123456789012345678901234567890dddddd"
                + "dddddddddddddddddddddddddddddddddddddx>>>>>>>>>>>>>>>>>>>>"
                + ">>>>>|"},
            {">>>>>>>>>>>>>dddddddddddddd123456789012345678901234567890dddddd"
                + "dddddddddddddddddddddddddddddddddddddxdddddddddddddd123456"
                + "789012345678901234567890dddddddddddddddddddddddddddddddddd"
                + "ddddd123456789012345678901234567890ddddx>>>>>>>>>>>>>>>>>>"
                + ">>>>>>>|"},};
        TableModel model = new DefaultTableModel(data, columnNames) {

            private static final long serialVersionUID = 1L;

            @Override
            public boolean isCellEditable(int row, int column) {
                return false;
            }
        };
        JTable table = new JTable(model) {

            private static final long serialVersionUID = 1L;

            @Override
            public void doLayout() {
                TableColumn col = getColumnModel().getColumn(0);
                for (int row = 0; row < getRowCount(); row++) {
                    Component c = prepareRenderer(col.getCellRenderer(), row, 0);
                    if (c instanceof JTextArea) {
                        JTextArea a = (JTextArea) c;
                        int h = getPreferredHeight(a) + getIntercellSpacing().height;
                        if (getRowHeight(row) != h) {
                            setRowHeight(row, h);
                        }
                    }
                }
                super.doLayout();
            }

            private int getPreferredHeight(JTextComponent c) {
                Insets insets = c.getInsets();
                View view = c.getUI().getRootView(c).getView(0);
                int preferredHeight = (int) view.getPreferredSpan(View.Y_AXIS);
                return preferredHeight + insets.top + insets.bottom;
            }
        };
        table.setEnabled(false);
        table.setShowGrid(false);
        table.setTableHeader(null);
        table.getColumnModel().getColumn(0).setCellRenderer(new TextAreaCellRenderer());
        //table.setPreferredScrollableViewportSize(table.getPreferredSize());
        JScrollPane sp = new JScrollPane(table);
        sp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        sp.setPreferredSize(new Dimension(250, 533));
        JPanel p = new JPanel(new BorderLayout());
        p.add(sp);
        return p;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }

    public static void createAndShowGUI() {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        f.getContentPane().add(new AutoWrapTest().makeUI());
        f.setLocation(100, 100);
        f.pack();
        f.setVisible(true);
    }
}

class TextAreaCellRenderer extends JTextArea implements TableCellRenderer {

    private static final long serialVersionUID = 1L;
    private final Color evenColor = new Color(230, 240, 255);

    public TextAreaCellRenderer() {
        super();
        setLineWrap(true);
        setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2));
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
        if (isSelected) {
            setForeground(table.getSelectionForeground());
            setBackground(table.getSelectionBackground());
        } else {
            setForeground(table.getForeground());
            setBackground(table.getBackground());
            setBackground((row % 2 == 0) ? evenColor : getBackground());
        }
        setFont(table.getFont());
        setText((value == null) ? "" : value.toString());
        return this;
    }
}

Answer 2

要从TableCellRenderer 中获得最大性能，请确保您没有在每次调用getTableCellRenderer 时都创建组件的新实例。制作一次组件并将它们保存为类的字段。

此外，您需要确保您使用的每个组件都覆盖了以下方法以不执行任何操作：

• 验证
• 无效
• 重新验证
• 重绘
• firePropertyChange

（你可能想硬编码isOpaque）。

欲了解更多信息，请参阅：http://docs.oracle.com/javase/6/docs/api/javax/swing/tree/DefaultTreeCellRenderer.html

Answer 3

问题似乎源于将 JTable 的 setRowHeight() 放在自定义单元格渲染器中，因为它调用自定义单元格渲染器，将其抛入无限循环。

我必须添加检查以查看当前行高是否与计算的换行行高匹配。如果是这样，我没有尝试再次 setRowHeight()。

更正的代码：

import java.awt.Component;

import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.table.TableCellRenderer;

//custom cell renderer for word wrapping, but if you use, you have to
//implement zebra striping functionality which the default renderer has
public class LineWrapCellRenderer extends JTextArea implements TableCellRenderer
{
    private int numOfTimesCalled;
    @Override
    public Component getTableCellRendererComponent(
            JTable table,
            Object value,
            boolean isSelected,
            boolean hasFocus,
            int row,
            int column)
    {
        System.out.println("Line Wrap Cell Renderer Called: " + numOfTimesCalled++);
        System.out.println("row:"+ row + ", col:" + column);
//set up the row size based on the number of newlines in the text in the cell
        int fontHeight = this.getFontMetrics(this.getFont()).getHeight();
        int numWraps = value.toString().split("\r\n|\r|\n").length;
        int rowHeight = fontHeight * numWraps;
//if the calculated rowHeight is the same as the row height of row,
// then don't call setRowHeight again, as doing so will throw us into
// an infinite loop
        if(rowHeight != table.getRowHeight(row))
        {
            table.setRowHeight(row, rowHeight);

//configure word wrapping
            setWrapStyleWord(true);
            setLineWrap(true);
//use the table's font
            setFont(table.getFont());
        }
//zebra striping, because whatever cell uses this renderer loses the
//default cell renderer zebra striping
        if(isSelected)
        {
            setBackground(table.getSelectionBackground());
        }
        else
        {
            if(row%2 == 1)
            {
                setBackground(UIManager.getColor("Table.alternateRowColor"));
            }
            else
            {
                setBackground(table.getBackground());
            }
        }
        this.setText(value.toString());
        return this;
    }
}