34.12. Review Questions | Introduction to Java Programming-Comprehensive Version (6th Edition)

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31.7. Table Model Events

JTable does not fire table events. It fires events like MouseEvent , KeyEvent , and ComponentEvent that are inherited from its superclass, JComponent . Table events are fired by table models, table column models, and table-selection models whenever changes are made to these models. Table models fire TableModelEvent when table data is changed. Table column models fire TableColumnModelEvent when columns are added, removed, or moved, or when the column selection changes. Table-selection models fire ListSelectionEvent when the selection changes.

To listen for these events, a listener must be registered with an appropriate model and implement the correct listener interface. Listing 31.10 gives an example that demonstrates how to use these events. The program displays messages on a text area when a row or a column is selected, when a cell is edited, or when a column is removed. Figure 31.15 is a sample run of the program.

Figure 31.15. Table event handlers display table events on a text area.

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Listing 31.10. TableEventsDemo.java

(This item is displayed on pages 1066 - 1068 in the print version)

 1   import   java.awt.*; 2   import   java.awt.event.*; 3   import   javax.swing.*; 4   import   javax.swing.event.*; 5   import   javax.swing.table.*; 6   import   java.util.*; 7 8   public class   TableEventsDemo   extends   JApplet { 9  // Create table column names  10   private   String[] columnNames = 11 {   "Title"   ,   "Copies Needed"   ,   "Publisher"   ,   "Date Published"   , 12   "In-stock"   ,   "Book Photo"   }; 13 14  // Create image icons  15   private   ImageIcon intro1eImageIcon = 16   new   ImageIcon(getClass().getResource(   "image/intro1e.gif"   )); 17   private   ImageIcon intro2eImageIcon = 18   new   ImageIcon(getClass().getResource(   "image/intro2e.gif"   )); 19   private   ImageIcon intro3eImageIcon = 20   new   ImageIcon(getClass().getResource(   "image/intro3e.jpg"   )); 21 22  // Create table data  23   private   Object[][] rowData = { 24 {   "Introduction to Java Programming"   ,   120   , 25   "Que Education & Training"   , 26   new   GregorianCalendar(   1998   ,   1-1   ,   6   ).getTime(), 27   false   , intro1eImageIcon}, 28 {   "Introduction to Java Programming, 2E"   ,   220   , 29   "Que Education & Training"   , 30   new   GregorianCalendar(   1999   ,   1-1   ,   6   ).getTime(), 31   false   , intro2eImageIcon}, 32 {   "Introduction to Java Programming, 3E"   ,   220   , 33   "Prentice Hall"   , 34   new   GregorianCalendar(   2000   ,   12-1   ,     ).getTime(), 35   true   , intro3eImageIcon}, 36 }; 37 38  // Create a table model  39   private   MyTableModel tableModel =   new   MyTableModel( 40 rowData, columnNames); 41 42  // Create a table  43   private   JTable jTable1 =   new   JTable(tableModel); 44 45  // Get table column model  46   private   TableColumnModel tableColumnModel = 47 jTable1.getColumnModel(); 48 49  // Get table selection model  50   private   ListSelectionModel selectionModel = 51 jTable1.getSelectionModel(); 52 53  // Create a text area  54   private   JTextArea jtaMessage =   new   JTextArea(); 55 56  // Create a button  57   private   JButton jbtDeleteColumn = 58   new   JButton(   "Delete Selected Column"   ); 59

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 60   public   TableEventsDemo() { 61  // Set custom renderer for displaying images  62 TableColumn bookCover = jTable1.getColumn(   "Book Photo"   ); 63 bookCover.setCellRenderer(   new   MyImageCellRenderer()); 64 65  // Create a combo box for publishers  66 JComboBox jcboPublishers =   new   JComboBox(); 67 jcboPublishers.addItem(   "Prentice Hall"   ); 68 jcboPublishers.addItem(   "Que Education & Training"   ); 69 jcboPublishers.addItem(   "McGraw-Hill"   ); 70 71  // Set combo box as the editor for the publisher column  72 TableColumn publisherColumn = jTable1.getColumn(   "Publisher"   ); 73 publisherColumn.setCellEditor( 74   new   DefaultCellEditor(jcboPublishers)); 75 76 jTable1.setRowHeight(   60   ); 77 jTable1.setColumnSelectionAllowed(   true   ); 78 79 JSplitPane jSplitPane1 =   new   JSplitPane( 80 JSplitPane.VERTICAL_SPLIT); 81 jSplitPane1.add(   new   JScrollPane(jTable1), JSplitPane.LEFT); 82 jSplitPane1.add(   new   JScrollPane(jtaMessage), JSplitPane.RIGHT); 83 add(jbtDeleteColumn, BorderLayout.NORTH); 84 add(jSplitPane1, BorderLayout.CENTER); 85 86  tableModel.addTableModelListener(   new   TableModelListener()  { 87    public void   tableChanged(TableModelEvent e)  { 88 jtaMessage.append(   "Table changed at row "   + 89 e.getFirstRow() +   " and column "   + e.getColumn() +   "\n"   ); 90 } 91 }); 92 93  tableColumnModel.addColumnModelListener(  94    new   TableColumnModelListener()  { 95    public void   columnRemoved(TableColumnModelEvent e)  { 96 jtaMessage.append(   "Column indexed at "   + e.getFromIndex() + 97   " is deleted \n"   ); 98 } 99   public void   columnAdded(TableColumnModelEvent e) { 100 } 101   public void   columnMoved(TableColumnModelEvent e) { 102 } 103   public void   columnMarginChanged(ChangeEvent e) { 104 } 105   public void   columnSelectionChanged(ListSelectionEvent e) { 106 } 107 }); 108 109 jbtDeleteColumn.addActionListener(   new   ActionListener() { 110   public void   actionPerformed(ActionEvent e) { 111   if   (jTable1.getSelectedColumn() >=     ) { 112 TableColumnModel columnModel = jTable1.getColumnModel(); 113 TableColumn tableColumn = 114 columnModel.getColumn(jTable1.getSelectedColumn()); 115 columnModel.removeColumn(tableColumn); 116 } 117 } 118 }); 119

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 120  selectionModel.addListSelectionListener(  121    new   ListSelectionListener()  { 122    public void   valueChanged(ListSelectionEvent e)  { 123 jtaMessage.append(   "Row "   + jTable1.getSelectedRow() + 124   " and column "   + jTable1.getSelectedColumn() + 125   " selected\n"   ); 126 } 127 }); 128 } 129 }

To respond to the row and column selection events, you need to implement the valueChanged method in ListSelectionListener . To respond to the cell-editing event, you need to implement the tableChanged method in TableModelListener . To respond to the column-deletion event, you need to implement the columnRemoved method in TableColumnModelListener . Let's use the same table from the preceding example, but with a button added for deleting the selected column and a text area for displaying the messages.

A table model is created using MyTableModel (lines 39 “40), which was given in Listing 31.6. When a table is created (line 43), its default column model and selection model are also created. Therefore, you can obtain the table column model and selection model from the table (lines 46 “51).

When a row or a column is selected, a ListSelectionEvent is fired by selectionModel , which invokes the handler to display the selected row and column in the text area (lines 120 “127). When the content or structure of the table is changed, a TableModelEvent is fired by tableModel , which invokes the handler to display the last row and last column of the changed data in the text area (lines 86 “91). When a column is deleted by clicking the Delete Selected Column button, a ColumnModelEvent is fired by tableColumnModel , which invokes the handler to display the index of the deleted column (lines 93 “107).