Question

我通过Java查询MySQL数据库，从结果集中提取数据并将其放入DefaultTableModel中，然后将其放入JTable中，然后放入JScrollPane中进行显示。

在JTable中，我通过

启用表格中的排序

table.setAutoCreateRowSorter(true);

但是，如果我要排序的行中的单元格不是String类，那么我会得到一个java.lang.ClassCastException。我表中的数据包含以下类：

java.sql.Date
java.sql.Time
java.lang.Double
java.lang.Boolean
java.lang.String

下面是我尝试对java.lang.Double类的列进行排序时出现的错误，后面是将结果集作为输入输出的类输出JTable。如果有人对如何解决我的排序问题有任何想法，我将不胜感激。

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.Double `enter code here`cannot be cast to java.lang.String
    at java.text.Collator.compare(Collator.java:327)
    at javax.swing.DefaultRowSorter.compare(DefaultRowSorter.java:968)
    at javax.swing.DefaultRowSorter.access$100(DefaultRowSorter.java:112)
    at javax.swing.DefaultRowSorter$Row.compareTo(DefaultRowSorter.java:1376)
    at javax.swing.DefaultRowSorter$Row.compareTo(DefaultRowSorter.java:1366)
    at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:290)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:157)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)
    at java.util.Arrays.sort(Arrays.java:472)
    at javax.swing.DefaultRowSorter.sort(DefaultRowSorter.java:607)
    at javax.swing.DefaultRowSorter.setSortKeys(DefaultRowSorter.java:319)
    at javax.swing.DefaultRowSorter.toggleSortOrder(DefaultRowSorter.java:480)
    at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseClicked(BasicTableHeaderUI.java:112)
    at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
    at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:269)
    at java.awt.Component.processMouseEvent(Component.java:6508)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4501)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

以下是该课程的来源：

import java.awt.Component;
import java.awt.Dimension;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JTable;
import javax.swing.JToggleButton;
import javax.swing.UIManager;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;
import javax.swing.table.*;


public class ResultSetToCheckBoxTable {
    private int numberOfColumns;
    private DefaultTableModel model;
    private ResultSetMetaData metaData;
    private JTable table;
    private ResultSet rs;
    private TableColumn tc;

    public JTable getTable() {
        return table;
    }
    public ResultSetToCheckBoxTable(ResultSet rs) {
        try {
            this.rs = rs;
            //overrides getColumnClass method in DefaultTableModel to help make checkbox
            model = new DefaultTableModel() {
                @Override
                public Class<?> getColumnClass(int columnIndex) {
                    if (columnIndex == numberOfColumns) {
                        return Boolean.class;
                    } else {
                        //return getValueAt(0, columnIndex).getClass();
                        return String.class;
                    }
                }
            };
            // Get the column names
            metaData = this.rs.getMetaData();
            numberOfColumns = metaData.getColumnCount();
            for (int column = 1; column <= numberOfColumns; column++) {
                model.addColumn(metaData.getColumnLabel(column));
            }
            model.addColumn("");
            // Get the table info
            while (rs.next()) {
                Vector tableRow = new Vector();
                for (int i = 1; i <= numberOfColumns; i++) {
                    tableRow.addElement(rs.getObject(i));
                }
                tableRow.addElement(true);
                model.addRow(tableRow);
            }
            //Create JTable using the model & set options
            table = new JTable(model) {
                @Override
                public boolean isCellEditable(int row, int column) {                
                return false;               
                };
            };
            table.setAutoCreateRowSorter(true);
            table.setPreferredScrollableViewportSize(new Dimension(320, 160));
            //Rest of the stuff
            tc = table.getColumnModel().getColumn(numberOfColumns);
            tc.setHeaderRenderer(new SelectAllHeader(table, numberOfColumns));
        }
        catch (SQLException ex) {
            Logger.getLogger(ResultSetToCheckBoxTable.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public static void main(String[] args) {
    }
}
/**
* A TableCellRenderer that selects all or none of a Boolean column.
* 
* @param numberOfColumns the Boolean column to manage
*/
class SelectAllHeader extends JToggleButton implements TableCellRenderer {

    private static final String ALL = "✓ Select all";
    private static final String NONE = "✓ Select none";
    private JTable table;
    private TableModel tableModel;
    private JTableHeader header;
    private TableColumnModel tcm;
    private int targetColumn;
    private int viewColumn;

    public SelectAllHeader(JTable table, int targetColumn) {
        super(ALL);
        this.table = table;
        this.tableModel = table.getModel();
        if (tableModel.getColumnClass(targetColumn) != Boolean.class) {
            throw new IllegalArgumentException("Boolean column required.");
        }
        this.targetColumn = targetColumn;
        this.header = table.getTableHeader();
        this.tcm = table.getColumnModel();
        this.applyUI();
        this.addItemListener(new ItemHandler());
        header.addMouseListener(new MouseHandler());
        tableModel.addTableModelListener(new ModelHandler());
    }

    @Override
    public Component getTableCellRendererComponent(
        JTable table, Object value, boolean isSelected,
        boolean hasFocus, int row, int column) {
        return this;
    }

    private class ItemHandler implements ItemListener {

        @Override
        public void itemStateChanged(ItemEvent e) {
            boolean state = e.getStateChange() == ItemEvent.SELECTED;
            setText((state) ? NONE : ALL);
            for (int r = 0; r < table.getRowCount(); r++) {
                table.setValueAt(state, r, viewColumn);
            }
        }
    }

    @Override
    public void updateUI() {
        super.updateUI();
        applyUI();
    }

    private void applyUI() {
        this.setFont(UIManager.getFont("TableHeader.font"));
        this.setBorder(UIManager.getBorder("TableHeader.cellBorder"));
        this.setBackground(UIManager.getColor("TableHeader.background"));
        this.setForeground(UIManager.getColor("TableHeader.foreground"));
    }

    private class MouseHandler extends MouseAdapter {

        @Override
        public void mouseClicked(MouseEvent e) {
            viewColumn = header.columnAtPoint(e.getPoint());
            int modelColumn = tcm.getColumn(viewColumn).getModelIndex();
            if (modelColumn == targetColumn) {
                doClick();
            }
        }
    }

    private class ModelHandler implements TableModelListener {

        @Override
        public void tableChanged(TableModelEvent e) {
            if (needsToggle()) {
                doClick();
                header.repaint();
            }
        }
    }

    // Return true if this toggle needs to match the model.
    private boolean needsToggle() {
        boolean allTrue = true;
        boolean allFalse = true;
        for (int r = 0; r < tableModel.getRowCount(); r++) {
            boolean b = (Boolean) tableModel.getValueAt(r, targetColumn);
            allTrue &= b;
            allFalse &= !b;
        }
        return allTrue && !isSelected() || allFalse && isSelected();
    }
}

Answer 1

问题是你告诉JTable你的所有列都包含字符串（escpt是最后一个），这不是真的：

public Class<?> getColumnClass(int columnIndex) {
    if (columnIndex == numberOfColumns) {
        return Boolean.class;
    } else {
        //return getValueAt(0, columnIndex).getClass();
        return String.class;
    }
}

向JTable说实话，它会很高兴。

Answer 2

这是因为在一列中的某些数据是两个类型的类型，如String和Integer或Double和Date ....等等此代码可以解决您的问题：

private void Change_Table_Data_Class (ArrayList<ArrayList<Object>> table) {
    for (int rowIndex = 0; rowIndex < table.size(); rowIndex++) {
        for (int columnIndex = 0; columnIndex < table.get(rowIndex).size(); columnIndex++) {
            Object cellDataType = table.get(0).get(columnIndex);
            Object cellData = table.get(rowIndex ).get(columnIndex);
                if (!(cellDataType instanceof Double)) {
                    DecimalFormat df = new DecimalFormat("#.##");                                
                        String formattedMerging = df.format(cellData);
                            table.get(rowIndex).set(columnIndex, Double.valueOf(formattedMerging));
                } else if (!(cellDataType instanceof String)) {
                         table.get(rowIndex).set(columnIndex, String.valueOf(cellData));
                }
        }
    }
}

使用JTable中的setAutoCreateRowSorter对不同的数据类型进行排序

2 个答案: