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Swing Chapter 18. (Advanced topics) Tables. Easy for reading, Click here!

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Swing Chapter 18. (Advanced topics) Tables. Easy for reading, Click here!

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Page: 7/9 



Previous Page Previous Page (6/9) - Next Page (8/9) Next Page
Subpages: 1. JTable  
2.
Stocks Table: part I - Basic JTable example 
3.
Stocks Table: part II - Custom renderers 
4. Stocks Table: part III - Data formatting 
5. Stocks Table: part IV - Sorting columns 
6.
Stocks Table: part V - JDBC
7.
Stocks Table: part VI - Column addition and removal
8.
Expense report application
9.
JavaBeans property editor

18.7  Stocks Table: part VI - column addition and removal

JTable allows us to dynamically add and remove TableColumns on the fly. Recall that the TableColumnModel interface provides the methods addColumn() and removeColumn() to programmatically add or remove a TableColumn respectively. In this section we add dynamic column addition and removal to our StocksTable application.

Figure 18.6 JTable with dynamic column addition and removal.

<<file figure18-6.gif>>

The Code: StocksTable.java

see \Chapter18\6

import java.awt.*;

import java.awt.event.*;

import java.util.*;

import java.io.*;

import java.text.*;

import java.sql.*;

import javax.swing.*;

import javax.swing.border.*;

import javax.swing.event.*;

import javax.swing.table.*;

public class StocksTable extends JFrame

{

  // Unchanged code from section 18.5

  public StocksTable() {

    // Unchanged code from section 18.5

    header.setReorderingAllowed(true);

    m_table.getColumnModel().addColumnModelListener(

      m_data.new ColumnMovementListener());

    // Unchanged code from section 18.5

  } 

  protected JMenuBar createMenuBar() {

    // Unchanged code from section 18.5

    JMenu mView = new JMenu("View");

    mView.setMnemonic('v');

    TableColumnModel model = m_table.getColumnModel();

    for (int k = 0; k < StockTableData.m_columns.length; k++) {

      JCheckBoxMenuItem item = new JCheckBoxMenuItem(

        StockTableData.m_columns[k].m_title);

      item.setSelected(true);

      TableColumn column = model.getColumn(k);

      item.addActionListener(new ColumnKeeper(column,

        StockTableData.m_columns[k]));

      mView.add(item);

    }

    menuBar.add(mView);

    return menuBar;

  }

  // Unchanged code from section 18.5

  class ColumnKeeper implements ActionListener

  {

    protected TableColumn m_column;

    protected ColumnData  m_colData;

    public ColumnKeeper(TableColumn column, ColumnData  colData) {

      m_column = column;

      m_colData = colData;

    }

    public void actionPerformed(ActionEvent e) {

      JCheckBoxMenuItem item = (JCheckBoxMenuItem)e.getSource();

      TableColumnModel model = m_table.getColumnModel();

      if (item.isSelected()) {

        model.addColumn(m_column);

      }

      else {

        model.removeColumn(m_column);

      }

      m_table.tableChanged(new TableModelEvent(m_data));

      m_table.repaint();

    }

  }

  public static void main(String argv[]) {

    new StocksTable();

  }

}

// Unchanged code from section 18.5

class StockTableData extends AbstractTableModel

{

  // Unchanged code from section 18.5

  protected SimpleDateFormat m_frm;

  protected Vector m_vector;

  protected java.util.Date m_date;

  protected int m_columnsCount = m_columns.length;

  // Unchanged code from section 18.5

  public int getColumnCount() {

    return m_columnsCount;

  }

  // Unchanged code from section 18.5

  class ColumnListener extends MouseAdapter

  {

    // Unchanged code from section 18.4

    public void mouseClicked(MouseEvent e) {

      // Unchanged code from section 18.4

      for (int i=0; i < m_columnsCount; i++) {

        TableColumn column = colModel.getColumn(i);

        column.setHeaderValue(getColumnName(column.getModelIndex()));    

      }

      m_table.getTableHeader().repaint(); 

      // Unchanged code from section 18.4

    }

  }

  class ColumnMovementListener implements TableColumnModelListener

  {

    public void columnAdded(TableColumnModelEvent e) {

      m_columnsCount++;

    }

    public void columnRemoved(TableColumnModelEvent e) {

      m_columnsCount--;

    }

    public void columnMarginChanged(ChangeEvent e) {}

    public void columnMoved(TableColumnModelEvent e) {}

    public void columnSelectionChanged(ListSelectionEvent e) {}

  }

  // Unchanged code from section 18.5

}

// Class StockComparator unchanged from section 18.4

Understanding the Code

Class StocksTable

The StocksTable constructor now adds an instance of StockTableData.ColumnMovementListener (see below) to our table's TableColumnModel to listen for column additions and removals.

Our createMenuBar() method  now adds several checkbox menu items to a new "View" menu -- one for each column.  Each of these check box menu items recieves a ColumnKeeper instance (see below) as ActionListener.

Class StocksTable.ColumnKeeper

This inner class implements the ActionListener interface and serves to keep track of when the user removes and adds columns to the table. The constructor receives a TableColumn instance and a ColumnData object. The actionPerformed() method adds this column to the model with the addColumn() method if the corresponding menu item is checked, and removes this column from the model with removeColumn() if it is unchecked. To update the table to properly reflect these changes, we call its tableChanged() method followed by a repaint() request.

Class StockTableData

StockTableData now contains instance variable m_columnsCount to keep track of the current column count. This variable is decremented and incremented in the columnRemoved() and columnAdded() methods of inner class ColumnMovementListener. It is also used in the StockTableData.ColumnListener class's mouseClicked() method for properly setting header values for the visible columns only.

Class StockTableData.ColumnMovementListener

This class implements TableColumnModelListener to increment and decrement StockTableData's m_columnsCount variable when a column addition or removal occurs, respectively. An instance of this inner class is added to our table's TableColumnModel in the StocksTable constructor.

Running the Code

Figure 18.7 shows the new "View" menu with an unchecked "Change %" menu item, and the corresponding column hidden. Reselecting this menu item will place the column back in the table at the end position. Verify that each menu item functions similarly.



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