Question

我在JScrollPane中有一个JTable，并且我重写了getPreferredScrollableViewportSize以使JScrollPane适合固定数量的表行，允许滚动条在需要时出现。我还使用在SO上找到的代码部分来调整表格列的大小以适应它们的内容。

我遇到的问题是，当我在表中添加更宽的行时，水平JScrollBar不会显示。我尝试了不同的方法来强制JTable，JViewport和JScrollPane正确更新，调用revalidate（）或repaint（），doLayout（）等，但我没有成功。

当然我可以回想起JFrame上的pack（）方法，但是它会导致整个滚动条的宽度增加，而水平滚动条仍然不会出现。

我缺少什么？

这里有一个MVCE，它只是一个丑陋的玩具示例，但它应该足以复制不需要的行为。

感谢您的帮助！

代码：

import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.table.*;
public class Main
{
    public static void main (String [] a) {
        SwingUtilities.invokeLater (new Runnable () {
            public void run () {
                initGUI ();
            }
        });
    }
    private static void initGUI () {
        final DataTable table = new DataTable ();
        JPanel container = new JPanel (new BorderLayout (0, 20));
        container.add (new JScrollPane (table));
        container.add (new JButton (new AbstractAction ("Add wider row") {
            public void actionPerformed (ActionEvent e) {
                table.addRow ();
                // some of many useless attempts ...
                // table.resizeColumnWidth ();
                // table.revalidate ();
            }
        }), BorderLayout.SOUTH);
        container.setBorder (new EmptyBorder (10, 10, 10, 10));
        JFrame frame = new JFrame ("Test");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        frame.setResizable (false);
        frame.setContentPane (container);
        frame.setLocationRelativeTo (null);
        frame.pack ();
        frame.setVisible (true);
    }
}
class DataTable extends JTable
{
    private static final int VISIBLE_ROWS = 5;

    DataTable () {
        String [][] data = new String [][] {
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"}
        };
        setModel (new DefaultTableModel (data, new String [] {"", ""}) {
            @Override public boolean isCellEditable (int row, int column) {
               return false;
            }
        });
        columnModel.setColumnMargin (20);
        setBorder (null);
        setFocusable (false);
        setRowSelectionAllowed (false);
        setShowGrid (false);
        setTableHeader (null);
        resizeColumnWidth ();
    }
    public void addRow () {
        ((DefaultTableModel) getModel ()).addRow (new String [] {"SomeLongerText", "SomeLongerText"});
    }
    private int calculateColumnWidth (int column) {
        TableColumn tableColumn = columnModel.getColumn (column);
        int width = 0;
        for (int row=0; row<getRowCount(); row++) width = Math.max (prepareRenderer (getCellRenderer (row, column), row, column).getPreferredSize ().width, width);
        return width + getIntercellSpacing ().width;
    }
    @Override public Dimension getPreferredScrollableViewportSize () {
        int columnsWidth = 0;
        for (int column=0; column<getColumnCount (); column++) columnsWidth += calculateColumnWidth (column);
        return new Dimension (columnsWidth, VISIBLE_ROWS * getRowHeight ());
    }
    protected void resizeColumnWidth () {
        for (int column=0; column<getColumnCount (); column++) columnModel.getColumn (column).setPreferredWidth (calculateColumnWidth (column));
    }
}

编辑：

感谢@camickr，我解决了这个问题，设置了所需的自动调整大小模式，并在每次添加行时调用resizeColumnWidth方法。我已经分开试过了，我不敢相信我没有同时使用它们。）

Hovewer，我发布了更新后的代码，现在效果很好：

import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.table.*;
public class Main
{
    public static void main (String [] a) {
        SwingUtilities.invokeLater (new Runnable () {
            public void run () {
                initGUI ();
            }
        });
    }
    private static void initGUI () {
        final DataTable table = new DataTable ();
        JPanel container = new JPanel (new BorderLayout (0, 20));
        container.add (new JScrollPane (table));
        container.add (new JButton (new AbstractAction ("Add wider row") {
            public void actionPerformed (ActionEvent e) {
                table.addRow ();
            }
        }), BorderLayout.SOUTH);
        container.setBorder (new EmptyBorder (10, 10, 10, 10));
        JFrame frame = new JFrame ("Test");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        frame.setResizable (false);
        frame.setContentPane (container);
        frame.setLocationRelativeTo (null);
        frame.pack ();
        frame.setVisible (true);
    }
}
class DataTable extends JTable
{
    private static final int VISIBLE_ROWS = 5;

    DataTable () {
        String [][] data = new String [][] {
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"},
            {"SomeText", "SomeText"}
        };
        setModel (new DefaultTableModel (data, new String [] {"", ""}) {
            @Override public boolean isCellEditable (int row, int column) {
               return false;
            }
        });
        columnModel.setColumnMargin (20);
        setAutoResizeMode (AUTO_RESIZE_OFF);
        setBorder (null);
        setFocusable (false);
        setRowSelectionAllowed (false);
        setShowGrid (false);
        setTableHeader (null);
        resizeColumnWidth ();
    }
    public void addRow () {
        ((DefaultTableModel) getModel ()).addRow (new String [] {"SomeLongerText", "SomeLongerText"});
        resizeColumnWidth ();
    }
    private int calculateColumnWidth (int column) {
        TableColumn tableColumn = columnModel.getColumn (column);
        int width = 0;
        for (int row=0; row<getRowCount(); row++) width = Math.max (prepareRenderer (getCellRenderer (row, column), row, column).getPreferredSize ().width, width);
        return width + getIntercellSpacing ().width;
    }
    @Override public Dimension getPreferredScrollableViewportSize () {
        int columnsWidth = 0;
        for (int column=0; column<getColumnCount (); column++) columnsWidth += calculateColumnWidth (column);
        return new Dimension (columnsWidth, VISIBLE_ROWS * getRowHeight ());
    }
    protected void resizeColumnWidth () {
        for (int column=0; column<getColumnCount (); column++) columnModel.getColumn (column).setPreferredWidth (calculateColumnWidth (column));
    }
}

Answer 1

当我在表格中添加更宽的行时，水平的JScrollBar不会显示。

只有在使用时才会出现水平滚动条：

setAutoResizeMode( JTable.AUTO_RESIZE_OFF );

所有列都将以其优先大小显示。它们可能小于视口，在这种情况下，您将看到空白区域，或者它们可能更大，在这种情况下您将看到滚动条。

您需要在resizeColumnWidth()中调用ActionListener方法才能显示滚动条。

在TableModel中添加/更改数据时，您还可以查看支持动态列大小计算的Table Column Adjuster。

正确覆盖getPreferredScrollableViewportSize

1 个答案: