JTable調用自定義單元格渲染器方法......連續

Question

可編輯的源代碼可在以下網址找到： http ： //www.splashcd.com/jtable.tar

我是這門語言的新手，所以我不確定這是否是可接受的行為。

我創建了一個JTable來為每個收到的消息顯示一行（它每20秒接收一次）。 其中一個表列可以包含大量文本，因此我創建了一個自定義單元格渲染器，該單詞渲染器相應地包裝並設置行高。

所有這一切都按預期工作，除了表格顯示第一行后，它每秒調用單元格渲染器大約十次......直到用戶關閉表格。

一旦我在那里得到大約20行，表格變得相當遲緩，需要2-8秒來調整列的大小，向上或向下scoll，或者使用所選的背景顏色渲染選定的行。

我在渲染器中插入了一個print語句，因此我可以看到調用getTableCellRendererComponent方法的次數。

我禁用了工具提示，並禁用了所有單元格編輯。 我有一個監聽器，當添加新行或調整表格大小時，它會將視圖滾動到最后一行。

當我剛剛查看屏幕（不接觸鼠標或鍵盤）時，是否應該每秒調用幾次getTableCellRendererComponent方法？

TIA

Answer 1

• aaaaach

• 你需要doLayout() ，

• 下一級:-)，然后你可以輕松地為JTextComponents設置Maximum visible row

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

要從TableCellRenderer獲得最佳性能，請確保每次調用getTableCellRenderer都不創建組件的新實例。 制作一次組件並將其保存為類的字段。

此外，您還需要確保使用的每個組件都覆蓋以下方法，不執行任何操作：

• 驗證
• 廢止
• 重新驗證
• 重繪
• 中的firePropertyChange

（你可能想要硬代碼isOpaque ）。

有關更多信息，請參閱： http ： //docs.oracle.com/javase/6/docs/api/javax/swing/tree/DefaultTreeCellRenderer.html

Answer 3

問題似乎源於在自定義單元格渲染器中具有JTable的setRowHeight（） ，因為它調用自定義單元格渲染器，將其拋入無限循環。

我必須添加一個檢查，以查看當前行高是否與計算出的字包裹行高相匹配。 如果是這樣，我沒有嘗試再次setRowHeight（）。

更正代碼：

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;
    }
}