Swing-JTable检测单元格数据变更事件

Posted 2020-06-09

在JTable的初级教程中往往会提到，使用TableModel的 addTableModelListener方法可以监听单元格数据的变更，在其事件处理函，数tableChanged中，可以通过e.getColumn()，e.getFirstRow()，e.getLastRow()，e.getType()来获取变更发生的位置和变更的类型（插入、更新或删除）。然而该方法存在2个致命的问题：

1.双击单元格使其处于可编辑状态后，即使没有做出任何修改，当单元格失去焦点时，该事件将被激活。

2.通过该事件你可以获取单元格最新的数据，却无法获取原有数据。

经过一番搜索发现该文章已经解决了这个问题Table Cell Listener，作者自己实现了一个单元格监听器TableCellListener，它订阅了指定table的addPropertyChangeListener，根据e.getPropertyName()来识别单元格编辑事件，根据table.isEditing()方法来判断单元格正在编辑还是编辑完毕。如果是正在编辑，则记录单元格位置和原因数据；如果已经编辑完毕，则记录新数据并与原有数据进行比对，如果不一致则说明单元格数据发生了变更，则激活指定响应函数。

测试用例如下：

TableDemo.java

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 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
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 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */ 

package TableCellListenerTest;

/*
 * TableDemo.java requires no other files.
 */

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;

import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;

/** 
 * TableDemo is just like SimpleTableDemo, except that it
 * uses a custom TableModel.
 */
public class TableDemo extends JPanel {
    private boolean DEBUG = false;

    public TableDemo() {
        super(new GridLayout(1,0));

        JTable table = new JTable(new MyTableModel());
        table.setPreferredScrollableViewportSize(new Dimension(500, 70));
        table.setFillsViewportHeight(true);

        //Create the scroll pane and add the table to it.
        JScrollPane scrollPane = new JScrollPane(table);

        //Add the scroll pane to this panel.
        add(scrollPane);
        Action action = new AbstractAction()
        {
            public void actionPerformed(ActionEvent e)
            {
                TableCellListener tcl = (TableCellListener)e.getSource();
                System.out.printf("cell changed%n");
                System.out.println("Row   : " + tcl.getRow());
                System.out.println("Column: " + tcl.getColumn());
                System.out.println("Old   : " + tcl.getOldValue());
                System.out.println("New   : " + tcl.getNewValue());
            }
        };
        TableCellListener tcl = new TableCellListener(table, action);
    }

    class MyTableModel extends AbstractTableModel {
        private String[] columnNames = {"First Name",
                                        "Last Name",
                                        "Sport",
                                        "# of Years",
                                        "Vegetarian"};
        private Object[][] data = {
        {"Kathy", "Smith",
         "Snowboarding", new Integer(5), new Boolean(false)},
        {"John", "Doe",
         "Rowing", new Integer(3), new Boolean(true)},
        {"Sue", "Black",
         "Knitting", new Integer(2), new Boolean(false)},
        {"Jane", "White",
         "Speed reading", new Integer(20), new Boolean(true)},
        {"Joe", "Brown",
         "Pool", new Integer(10), new Boolean(false)}
        };

        public int getColumnCount() {
            return columnNames.length;
        }

        public int getRowCount() {
            return data.length;
        }

        public String getColumnName(int col) {
            return columnNames[col];
        }

        public Object getValueAt(int row, int col) {
            return data[row][col];
        }

        /*
         * JTable uses this method to determine the default renderer/
         * editor for each cell.  If we didn‘t implement this method,
         * then the last column would contain text ("true"/"false"),
         * rather than a check box.
         */
        public Class getColumnClass(int c) {
            return getValueAt(0, c).getClass();
        }

        /*
         * Don‘t need to implement this method unless your table‘s
         * editable.
         */
        public boolean isCellEditable(int row, int col) {
            //Note that the data/cell address is constant,
            //no matter where the cell appears onscreen.
            if (col < 2) {
                return false;
            } else {
                return true;
            }
        }

        /*
         * Don‘t need to implement this method unless your table‘s
         * data can change.
         */
        public void setValueAt(Object value, int row, int col) {
            if (DEBUG) {
                System.out.println("Setting value at " + row + "," + col
                                   + " to " + value
                                   + " (an instance of "
                                   + value.getClass() + ")");
            }

            data[row][col] = value;
            fireTableCellUpdated(row, col);

            if (DEBUG) {
                System.out.println("New value of data:");
                printDebugData();
            }
        }

        private void printDebugData() {
            int numRows = getRowCount();
            int numCols = getColumnCount();

            for (int i=0; i < numRows; i++) {
                System.out.print("    row " + i + ":");
                for (int j=0; j < numCols; j++) {
                    System.out.print("  " + data[i][j]);
                }
                System.out.println();
            }
            System.out.println("--------------------------");
        }
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("TableDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        TableDemo newContentPane = new TableDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application‘s GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

 

TableCellListener.java

package TableCellListenerTest;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*;

/*
 *  This class listens for changes made to the data in the table via the
 *  TableCellEditor. When editing is started, the value of the cell is saved
 *  When editing is stopped the new value is saved. When the oold and new
 *  values are different, then the provided Action is invoked.
 *
 *  The source of the Action is a TableCellListener instance.
 */
public class TableCellListener implements PropertyChangeListener, Runnable
{
    private JTable table;
    private Action action;

    private int row;
    private int column;
    private Object oldValue;
    private Object newValue;

    /**
     *  Create a TableCellListener.
     *
     *  @param table   the table to be monitored for data changes
     *  @param action  the Action to invoke when cell data is changed
     */
    
    public TableCellListener(JTable table, Action action)
    {
        this.table = table;
        this.action = action;
        this.table.addPropertyChangeListener( this );
    }

    /**
     *  Create a TableCellListener with a copy of all the data relevant to
     *  the change of data for a given cell.
     *
     *  @param row  the row of the changed cell
     *  @param column  the column of the changed cell
     *  @param oldValue  the old data of the changed cell
     *  @param newValue  the new data of the changed cell
     */
    private TableCellListener(JTable table, int row, int column, Object oldValue, Object newValue)
    {
        this.table = table;
        this.row = row;
        this.column = column;
        this.oldValue = oldValue;
        this.newValue = newValue;
    }

    /**
     *  Get the column that was last edited
     *
     *  @return the column that was edited
     */
    public int getColumn()
    {
        return column;
    }

    /**
     *  Get the new value in the cell
     *
     *  @return the new value in the cell
     */
    public Object getNewValue()
    {
        return newValue;
    }

    /**
     *  Get the old value of the cell
     *
     *  @return the old value of the cell
     */
    public Object getOldValue()
    {
        return oldValue;
    }

    /**
     *  Get the row that was last edited
     *
     *  @return the row that was edited
     */
    public int getRow()
    {
        return row;
    }

    /**
     *  Get the table of the cell that was changed
     *
     *  @return the table of the cell that was changed
     */
    public JTable getTable()
    {
        return table;
    }
//
//  Implement the PropertyChangeListener interface
//
    @Override
    public void propertyChange(PropertyChangeEvent e)
    {
        //  A cell has started/stopped editing

        if ("tableCellEditor".equals(e.getPropertyName()))
        {
            if (table.isEditing()){
                System.out.printf("tableCellEditor is editing..%n");
                processEditingStarted();
            }
            else{
                System.out.printf("tableCellEditor editing stopped..%n");
                processEditingStopped();
            }
                
        }
    }

    /*
     *  Save information of the cell about to be edited
     */
    private void processEditingStarted()
    {
        //  The invokeLater is necessary because the editing row and editing
        //  column of the table have not been set when the "tableCellEditor"
        //  PropertyChangeEvent is fired.
        //  This results in the "run" method being invoked

        SwingUtilities.invokeLater( this );
    }
    /*
     *  See above.
     */
    @Override
    public void run()
    {
        row = table.convertRowIndexToModel( table.getEditingRow() );
        column = table.convertColumnIndexToModel( table.getEditingColumn() );
        oldValue = table.getModel().getValueAt(row, column);
        newValue = null;
    }

    /*
     *    Update the Cell history when necessary
     */
    private void processEditingStopped()
    {
        newValue = table.getModel().getValueAt(row, column);

        //  The data has changed, invoke the supplied Action
        if (! newValue.equals(oldValue))
        {
            //  Make a copy of the data in case another cell starts editing
            //  while processing this change

            
            TableCellListener tcl = new TableCellListener(
                getTable(), getRow(), getColumn(), getOldValue(), getNewValue());

            ActionEvent event = new ActionEvent(
                tcl,
                ActionEvent.ACTION_PERFORMED,
                "");        
            action.actionPerformed(event);
        }
    }
}