Swing-JTable检测单元格数据变更事件
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
/* * Copyright (c) 1995, 2008, Oracle and/or its affiliates. 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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, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ 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 DefaultTableModelDemo; 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); //这里应对oldValue为null的情况做处理，否则将导致原值与新值均为空时仍被视为值改变 if(oldValue == null) oldValue = ""; newValue = null; } /* * Update the Cell history when necessary */ private void processEditingStopped() { newValue = table.getModel().getValueAt(row, column); //这里应对newValue为null的情况做处理，否则后面会抛出异常 if(newValue == null) newValue = ""; // 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); } } }
