Question

可编辑的来源可在以下网址找到：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来为每个收到的消息显示一行（它接收到的消息每20秒一次）。其中一个表列可以包含大量的文本，所以我创建了一个自定义单元格渲染器，单词包装并设置行相应的高度。

所有这些都按预期工作，除非表格显示第一行，它每秒调用单元格渲染器大约十次......直到用户关闭表

一旦我在那里得到大约20排，桌子就会变得相当迟钝，拿下2-8 秒调整列的大小，向上或向下scoll，或使用。渲染选定的行选定的背景颜色。

我在渲染器中插入了一个print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功能。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。

应该每秒多次调用getTableCellRendererComponent方法当我只是在观看屏幕（不接触鼠标或键盘）时？

TIA

Answer 1

aaaaach
您需要doLayout()，
下一级:-)，然后您可以轻松地为Maximum visible row设置JTextComponents

enter image description here

的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中获得最佳性能，请确保每次调用getTableCellRenderer时都不创建组件的新实例。制作一次组件并将其保存为类的字段。

此外，您需要确保使用的每个组件都覆盖以下方法，以便不执行任何操作：

验证
无效
重新验证
重绘
的firePropertyChange

（你可能想要硬编码isOpaque）。

有关详细信息，请参阅：http://docs.oracle.com/javase/6/docs/api/javax/swing/tree/DefaultTreeCellRenderer.html

Answer 3

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

我必须添加一个检查以查看当前行高是否与计算出的字包裹行高相匹配。如果是的话，我没有再次尝试setRowHeight（）。

更正代码：

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;
    }
}

JTable调用自定义单元格渲染器方法......连续

3 个答案: