e957. creating a text field that mirrors the value in the anchor cell in a jtable component.txt

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In some spreadsheet applications, the value of the current cell (anchor) is mirrored in a separate and conveniently larger text field. Any changes to the current cell are immediately reflected in the text field and vice versa. This example demonstrates how to set up a mirror text field for the anchor cell in a table component. 
In order to detect changes to the anchor cell, a selection-changed listener and a cell-value-changed listener must be added to the table. 

See e944 Getting the Anchor Cell in a JTable Component for more information about the anchor cell. 

    JTable table = new JTable();
    
    // Add data
    
    // Create text field and add action
    JTextField textField = new JTextField();
    textField.setAction(new UpdateAnchorAction(table));
    
    // Add selection listener to table
    SelectionListener listener = new SelectionListener(table, textField);
    table.getSelectionModel().addListSelectionListener(listener);
    table.getColumnModel().getSelectionModel()
        .addListSelectionListener(listener);
    
    // Add value changed listener to table
    table.getModel().addTableModelListener(new MyTableModelListener(table, textField));
    
    // Create a frame and add both components to the frame
    JFrame frame = new JFrame();
    frame.getContentPane().add(new JScrollPane(table), BorderLayout.CENTER);
    frame.getContentPane().add(textField, BorderLayout.NORTH);
    frame.pack();
    frame.setVisible(true);
    
    public class SelectionListener implements ListSelectionListener {
        JTable table;
        JTextField textField;
    
        // It is necessary to keep the table since it is not possible
        // to determine the table from the event's source
        SelectionListener(JTable table, JTextField textField) {
            this.table = table;
            this.textField = textField;
        }
    
        // Update the text field whenever the anchor cell changes
        public void valueChanged(ListSelectionEvent e) {
            int rowIndex = table.getSelectionModel().getAnchorSelectionIndex();
            int vColIndex = table.getColumnModel().getSelectionModel()
                .getAnchorSelectionIndex();
    
            // Get the value and set the text field
            textField.setText((String)table.getValueAt(rowIndex, vColIndex));
        }
    }
    
    public class MyTableModelListener implements TableModelListener {
        JTable table;
        JTextField textField;
    
        // It is necessary to keep the table since it is not possible
        // to determine the table from the event's source
        MyTableModelListener(JTable table, JTextField textField) {
            this.table = table;
            this.textField = textField;
        }
    
        // Update the text field whenever the value in the anchor cell changes
        public void tableChanged(TableModelEvent e) {
            // Get anchor cell location
            int rAnchor = table.getSelectionModel().getAnchorSelectionIndex();
            int vcAnchor = table.getColumnModel().getSelectionModel()
                .getAnchorSelectionIndex();
    
            // This method is defined in
            // e915 Converting a Column Index Between the View and Model in a JTable Component
            int mcAnchor = toModel(table, vcAnchor);
    
            // Get affected rows and columns
            int firstRow = e.getFirstRow();
            int lastRow = e.getLastRow();
            int mColIndex = e.getColumn();
    
            if (firstRow != TableModelEvent.HEADER_ROW
                    && rAnchor >= firstRow
                    && rAnchor <= lastRow
                    && (mColIndex == TableModelEvent.ALL_COLUMNS
                        || mColIndex == mcAnchor)) {
                // Set the text field with the new value
                textField.setText((String)table.getValueAt(rAnchor, vcAnchor));
            }
        }
    }
    
    public class UpdateAnchorAction extends AbstractAction {
        JTable table;
        UpdateAnchorAction(JTable table) {
            super("Set Anchor");
            this.table = table;
        }
    
        // Update the value in the anchor cell whenever the text field changes
        public void actionPerformed(ActionEvent evt) {
            JTextField textField = (JTextField)evt.getSource();
    
            // Get anchor cell location
            int rAnchor = table.getSelectionModel().getAnchorSelectionIndex();
            int vcAnchor = table.getColumnModel().getSelectionModel()
                .getAnchorSelectionIndex();
    
            table.setValueAt(textField.getText(), rAnchor, vcAnchor);
        }
    }
    

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