Newsgroup: it.comp.java
Titolo: Ordinare tabella per colonna

Ciao tutti,
sono un newbie e sto facendo prove con mysql/swt.
Praticamente estraggo i dati da un database
mysql poi li inserisco in una table SWT.
E fin qui tutto bene.
Ora vorrei poter ordinare la tabella cliccando
gli header delle colonne.
Ho provato la classe TableViewer di JFace,la classe viene
compilata, ma mi da errore quando clicco l'header della colonna.
Questo e' il codice della classe(provando con la colonna "cognome"):
-----------------------------------------------------------------
public class Tabella {
	private Connection connection;
	private Display display;
	private Shell shell;
	TableViewer viewer;
	Table tabAgenti;
	public Tabella() {
		display = new Display();
		shell = new Shell(display);
		viewer = new TableViewer(shell, SWT.NONE);
		tabAgenti = viewer.getTable();
		shell.setText("Prova tabella Mysql");
		shell.setSize(210, 220);
		connectToDB();
		createGUI();
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
	}
	private void createGUI() {
 
		tabAgenti.setBounds(10, 10, 210, 190);
		tabAgenti.setHeaderVisible(true);
		tabAgenti.setLinesVisible(true);
		TableColumn ID = new TableColumn(tabAgenti, SWT.CENTER);
		ID.setText("ID");
		ID.setWidth(30);
		TableColumn nome = new TableColumn(tabAgenti, SWT.LEFT);
		nome.setText("Nome");
		nome.setWidth(80);
		TableColumn cognome = new TableColumn(tabAgenti, SWT.LEFT);
		cognome.setText("Cognome");
		cognome.setWidth(80);
		cognome.addSelectionListener(new SelectionAdapter() {
			public void widgetSelected(SelectionEvent e) {
				viewer.setSorter(new ViewerSorter());
			}
		});
		popolaTabella();
	}
	public static void main(String[] args) {
		new Tabella();
	}
	public void connectToDB() {...}
	private void displaySQLErrors(SQLException e) {...}
	public void popolaTabella() {...}
}
------------------------------------------------------------------------------
Questi sono gli errori:
org.eclipse.jface.util.Assert$AssertionFailedException: null argument;
	at org.eclipse.jface.util.Assert.isNotNull(Assert.java:143)
	at org.eclipse.jface.util.Assert.isNotNull(Assert.java:119)
	at org.eclipse.jface.viewers.StructuredViewer.disassociate(StructuredViewer.java:285)
	at org.eclipse.jface.viewers.TableViewer.internalRefresh(TableViewer.java:608)
	at org.eclipse.jface.viewers.TableViewer.internalRefresh(TableViewer.java:559)
	at org.eclipse.jface.viewers.StructuredViewer$7.run(StructuredViewer.java:964)
	at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:901)
	at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:962)
	at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:921)
	at org.eclipse.jface.viewers.StructuredViewer.setSorter(StructuredViewer.java:1200)
	at Tabella$1.widgetSelected(Tabella.java:75)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:89)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:82)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:796)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:2783)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2442)
	at Tabella.<init>(Tabella.java:51)
	at Tabella.main(Tabella.java:82)
----------------------------------------------------------------------------

 gli header delle colonne.
eccoti il codice.
ciao
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;
import javax.swing.table.*;
/**
 * TableSorter is a decorator for TableModels; adding sorting
 * functionality to a supplied TableModel. TableSorter does
 * not store or copy the data in its TableModel; instead it maintains
 * a map from the row indexes of the view to the row indexes of the
 * model. As requests are made of the sorter (like getValueAt(row, col))
 * they are passed to the underlying model after the row numbers
 * have been translated via the internal mapping array. This way,
 * the TableSorter appears to hold another copy of the table
 * with the rows in a different order.
 * <p/>
 * TableSorter registers itself as a listener to the underlying model,
 * just as the JTable itself would. Events recieved from the model
 * are examined, sometimes manipulated (typically widened), and then
 * passed on to the TableSorter's listeners (typically the JTable).
 * If a change to the model has invalidated the order of TableSorter's
 * rows, a note of this is made and the sorter will resort the
 * rows the next time a value is requested.
 * <p/>
 * When the tableHeader property is set, either by using the
 * setTableHeader() method or the two argument constructor, the
 * table header may be used as a complete UI for TableSorter.
 * The default renderer of the tableHeader is decorated with a renderer
 * that indicates the sorting status of each column. In addition,
 * a mouse listener is installed with the following behavior:
 * <ul>
 * <li>
 * Mouse-click: Clears the sorting status of all other columns
 * and advances the sorting status of that column through three
 * values: {NOT_SORTED, ASCENDING, DESCENDING} (then back to
 * NOT_SORTED again).
 * <li>
 * SHIFT-mouse-click: Clears the sorting status of all other columns
 * and cycles the sorting status of the column through the same
 * three values, in the opposite order: {NOT_SORTED, DESCENDING, ASCENDING}.
 * <li>
 * CONTROL-mouse-click and CONTROL-SHIFT-mouse-click: as above except
 * that the changes to the column do not cancel the statuses of columns
 * that are already sorting - giving a way to initiate a compound
 * sort.
 * </ul>
 * <p/>
 * This is a long overdue rewrite of a class of the same name that
 * first appeared in the swing table demos in 1997.
 *
 * @author Philip Milne
 * @author Brendon McLean
 * @author Dan van Enckevort
 * @author Parwinder Sekhon
 * @version 2.0 02/27/04
 */
public class TableSorter extends AbstractTableModel {
    protected TableModel tableModel;
    public static final int DESCENDING = -1;
    public static final int NOT_SORTED = 0;
    public static final int ASCENDING = 1;
    private static Directive EMPTY_DIRECTIVE = new Directive(-1,
NOT_SORTED);
    public static final Comparator COMPARABLE_COMAPRATOR = new Comparator()
{
        public int compare(Object o1, Object o2) {
            return ((Comparable) o1).compareTo(o2);
        }
    };
    public static final Comparator LEXICAL_COMPARATOR = new Comparator() {
        public int compare(Object o1, Object o2) {
            return o1.toString().compareTo(o2.toString());
        }
    };
    private Row[] viewToModel;
    private int[] modelToView;
    private JTableHeader tableHeader;
    private MouseListener mouseListener;
    private TableModelListener tableModelListener;
    private Map columnComparators = new HashMap();
    private List sortingColumns = new ArrayList();
    public TableSorter() {
        this.mouseListener = new MouseHandler();
        this.tableModelListener = new TableModelHandler();
    }
    public TableSorter(TableModel tableModel) {
        this();
        setTableModel(tableModel);
    }
    public TableSorter(TableModel tableModel, JTableHeader tableHeader) {
        this();
        setTableHeader(tableHeader);
        setTableModel(tableModel);
    }
    private void clearSortingState() {
        viewToModel = null;
        modelToView = null;
    }
    public TableModel getTableModel() {
        return tableModel;
    }
    public void setTableModel(TableModel tableModel) {
        if (this.tableModel != null) {
            this.tableModel.removeTableModelListener(tableModelListener);
        }
        this.tableModel = tableModel;
        if (this.tableModel != null) {
            this.tableModel.addTableModelListener(tableModelListener);
        }
        clearSortingState();
        fireTableStructureChanged();
    }
    public JTableHeader getTableHeader() {
        return tableHeader;
    }
    public void setTableHeader(JTableHeader tableHeader) {
        if (this.tableHeader != null) {
            this.tableHeader.removeMouseListener(mouseListener);
            TableCellRenderer defaultRenderer =
this.tableHeader.getDefaultRenderer();
            if (defaultRenderer instanceof SortableHeaderRenderer) {
this.tableHeader.setDefaultRenderer(((SortableHeaderRenderer)
defaultRenderer).tableCellRenderer);
            }
        }
        this.tableHeader = tableHeader;
        if (this.tableHeader != null) {
            this.tableHeader.addMouseListener(mouseListener);
            this.tableHeader.setDefaultRenderer(
                    new
SortableHeaderRenderer(this.tableHeader.getDefaultRenderer()));
        }
    }
    public boolean isSorting() {
        return sortingColumns.size() != 0;
    }
    private Directive getDirective(int column) {
        for (int i = 0; i < sortingColumns.size(); i++) {
            Directive directive = (Directive)sortingColumns.get(i);
            if (directive.column == column) {
                return directive;
            }
        }
        return EMPTY_DIRECTIVE;
    }
    public int getSortingStatus(int column) {
        return getDirective(column).direction;
    }
    private void sortingStatusChanged() {
        clearSortingState();
        fireTableDataChanged();
        if (tableHeader != null) {
            tableHeader.repaint();
        }
    }
    public void setSortingStatus(int column, int status) {
        Directive directive = getDirective(column);
        if (directive != EMPTY_DIRECTIVE) {
            sortingColumns.remove(directive);
        }
        if (status != NOT_SORTED) {
            sortingColumns.add(new Directive(column, status));
        }
        sortingStatusChanged();
    }
    protected Icon getHeaderRendererIcon(int column, int size) {
        Directive directive = getDirective(column);
        if (directive == EMPTY_DIRECTIVE) {
            return null;
        }
        return new Arrow(directive.direction == DESCENDING, size,
sortingColumns.indexOf(directive));
    }
    private void cancelSorting() {
        sortingColumns.clear();
        sortingStatusChanged();
    }
    public void setColumnComparator(Class type, Comparator comparator) {
        if (comparator == null) {
            columnComparators.remove(type);
        } else {
            columnComparators.put(type, comparator);
        }
    }
    protected Comparator getComparator(int column) {
        Class columnType = tableModel.getColumnClass(column);
        Comparator comparator = (Comparator)
columnComparators.get(columnType);
        if (comparator != null) {
            return comparator;
        }
        if (Comparable.class.isAssignableFrom(columnType)) {
            return COMPARABLE_COMAPRATOR;
        }
        return LEXICAL_COMPARATOR;
    }
    private Row[] getViewToModel() {
        if (viewToModel == null) {
            int tableModelRowCount = tableModel.getRowCount();
            viewToModel = new Row[tableModelRowCount];
            for (int row = 0; row < tableModelRowCount; row++) {
                viewToModel[row] = new Row(row);
            }
            if (isSorting()) {
                Arrays.sort(viewToModel);
            }
        }
        return viewToModel;
    }
    public int modelIndex(int viewIndex) {
        return getViewToModel()[viewIndex].modelIndex;
    }
    private int[] getModelToView() {
        if (modelToView == null) {
            int n = getViewToModel().length;
            modelToView = new int[n];
            for (int i = 0; i < n; i++) {
                modelToView[modelIndex(i)] = i;
            }
        }
        return modelToView;
    }
    // TableModel interface methods
    public int getRowCount() {
        return (tableModel == null) ? 0 : tableModel.getRowCount();
    }
    public int getColumnCount() {
        return (tableModel == null) ? 0 : tableModel.getColumnCount();
    }
    public String getColumnName(int column) {
        return tableModel.getColumnName(column);
    }
    public Class getColumnClass(int column) {
        return tableModel.getColumnClass(column);
    }
    public boolean isCellEditable(int row, int column) {
        return tableModel.isCellEditable(modelIndex(row), column);
    }
    public Object getValueAt(int row, int column) {
        return tableModel.getValueAt(modelIndex(row), column);
    }
    public void setValueAt(Object aValue, int row, int column) {
        tableModel.setValueAt(aValue, modelIndex(row), column);
    }
    // Helper classes
    private class Row implements Comparable {
        private int modelIndex;
        public Row(int index) {
            this.modelIndex = index;
        }
        public int compareTo(Object o) {
            int row1 = modelIndex;
            int row2 = ((Row) o).modelIndex;
            for (Iterator it = sortingColumns.iterator(); it.hasNext();) {
                Directive directive = (Directive) it.next();
                int column = directive.column;
                Object o1 = tableModel.getValueAt(row1, column);
                Object o2 = tableModel.getValueAt(row2, column);
                int comparison = 0;
                // Define null less than everything, except null.
                if (o1 == null && o2 == null) {
                    comparison = 0;
                } else if (o1 == null) {
                    comparison = -1;
                } else if (o2 == null) {
                    comparison = 1;
                } else {
                    comparison = getComparator(column).compare(o1, o2);
                }
                if (comparison != 0) {
                    return directive.direction == DESCENDING ? -comparison :
comparison;
                }
            }
            return 0;
        }
    }
    private class TableModelHandler implements TableModelListener {
        public void tableChanged(TableModelEvent e) {
            // If we're not sorting by anything, just pass the event along.
            if (!isSorting()) {
                clearSortingState();
                fireTableChanged(e);
                return;
            }
            // If the table structure has changed, cancel the sorting; the
            // sorting columns may have been either moved or deleted from
            // the model.
            if (e.getFirstRow() == TableModelEvent.HEADER_ROW) {
                cancelSorting();
                fireTableChanged(e);
                return;
            }
            // We can map a cell event through to the view without widening
            // when the following conditions apply:
            //
            // a) all the changes are on one row (e.getFirstRow() ==
e.getLastRow()) and,
            // b) all the changes are in one column (column !=
TableModelEvent.ALL_COLUMNS) and,
            // c) we are not sorting on that column
(getSortingStatus(column) == NOT_SORTED) and,
            // d) a reverse lookup will not trigger a sort (modelToView !=
null)
            //
            // Note: INSERT and DELETE events fail this test as they have
column == ALL_COLUMNS.
            //
            // The last check, for (modelToView != null) is to see if
modelToView
            // is already allocated. If we don't do this check; sorting can
become
            // a performance bottleneck for applications where cells
            // change rapidly in different parts of the table. If cells
            // change alternately in the sorting column and then outside of
            // it this class can end up re-sorting on alternate cell
updates -
            // which can be a performance problem for large tables. The last
            // clause avoids this problem.
            int column = e.getColumn();
            if (e.getFirstRow() == e.getLastRow()
                    && column != TableModelEvent.ALL_COLUMNS
                    && getSortingStatus(column) == NOT_SORTED
                    && modelToView != null) {
                int viewIndex = getModelToView()[e.getFirstRow()];
                fireTableChanged(new TableModelEvent(TableSorter.this,
                                                     viewIndex, viewIndex,
                                                     column, e.getType()));
                return;
            }
            // Something has happened to the data that may have invalidated
the row order.
            clearSortingState();
            fireTableDataChanged();
            return;
        }
    }
    private class MouseHandler extends MouseAdapter {
        public void mouseClicked(MouseEvent e) {
            JTableHeader h = (JTableHeader) e.getSource();
            TableColumnModel columnModel = h.getColumnModel();
            int viewColumn = columnModel.getColumnIndexAtX(e.getX());
            int column = columnModel.getColumn(viewColumn).getModelIndex();
            if (column != -1) {
                int status = getSortingStatus(column);
                if (!e.isControlDown()) {
                    cancelSorting();
                }
                // Cycle the sorting states through {NOT_SORTED, ASCENDING,
DESCENDING} or
                // {NOT_SORTED, DESCENDING, ASCENDING} depending on whether
shift is pressed.
                status = status + (e.isShiftDown() ? -1 : 1);
                status = (status + 4) % 3 - 1; // signed mod, returning {-1,
0, 1}
                setSortingStatus(column, status);
            }
        }
    }
    private static class Arrow implements Icon {
        private boolean descending;
        private int size;
        private int priority;
        public Arrow(boolean descending, int size, int priority) {
            this.descending = descending;
            this.size = size;
            this.priority = priority;
        }
        public void paintIcon(Component c, Graphics g, int x, int y) {
            Color color = c == null ? Color.GRAY : c.getBackground();
            // In a compound sort, make each succesive triangle 20%
            // smaller than the previous one.
            int dx = (int)(size/2*Math.pow(0.8, priority));
            int dy = descending ? dx : -dx;
            // Align icon (roughly) with font baseline.
            y = y + 5*size/6 + (descending ? -dy : 0);
            int shift = descending ? 1 : -1;
            g.translate(x, y);
            // Right diagonal.
            g.setColor(color.darker());
            g.drawLine(dx / 2, dy, 0, 0);
            g.drawLine(dx / 2, dy + shift, 0, shift);
            // Left diagonal.
            g.setColor(color.brighter());
            g.drawLine(dx / 2, dy, dx, 0);
            g.drawLine(dx / 2, dy + shift, dx, shift);
            // Horizontal line.
            if (descending) {
                g.setColor(color.darker().darker());
            } else {
                g.setColor(color.brighter().brighter());
            }
            g.drawLine(dx, 0, 0, 0);
            g.setColor(color);
            g.translate(-x, -y);
        }
        public int getIconWidth() {
            return size;
        }
        public int getIconHeight() {
            return size;
        }
    }
    private class SortableHeaderRenderer implements TableCellRenderer {
        private TableCellRenderer tableCellRenderer;
        public SortableHeaderRenderer(TableCellRenderer tableCellRenderer) {
            this.tableCellRenderer = tableCellRenderer;
        }
        public Component getTableCellRendererComponent(JTable table,
                                                       Object value,
                                                       boolean isSelected,
                                                       boolean hasFocus,
                                                       int row,
                                                       int column) {
            Component c =
tableCellRenderer.getTableCellRendererComponent(table,
                    value, isSelected, hasFocus, row, column);
            if (c instanceof JLabel) {
                JLabel l = (JLabel) c;
                l.setHorizontalTextPosition(JLabel.LEFT);
                int modelColumn = table.convertColumnIndexToModel(column);
                l.setIcon(getHeaderRendererIcon(modelColumn,
l.getFont().getSize()));
            }
            return c;
        }
    }
    private static class Directive {
        private int column;
        private int direction;
        public Directive(int column, int direction) {
            this.column = column;
            this.direction = direction;
        }
    }
}

Grazie della dritta.
Purtroppo pero' uso SWT.
Da quel che ho capito TableViewer/JFace
e' piu' o meno equivalente a TableModel/Swing.



Scusa non avevo notato, non so esserti d'aiuto riguardo SWT mi
spiace, vedi se riesci a cavare qualcosa dal codice che ti ho postato.
ciao

 Purtroppo pero' uso SWT.
posso farti una domanda? perchè usi SWT al posto delle swing ?

 posso farti una domanda? perchè usi SWT al posto delle swing ?
Sono un newbie per quanto riguarda la programmazione e lo sono
ancora di piu' per quanto riguarda la programmazione "con le
finestre". Avevo provato altre "librerie grafiche" con c++ e
non mi piacevano (poco intuitive, complesse). Poi ho scoperto
per caso Eclipse e di conseguenza anche le SWT che ho trovato
molto intuitive da studiare.
Non ho mai provato le Swing, ma so che sono piu' pesanti delle SWT.
Le SWT sono native (le API sono pero' "OS-indipendent) e quindi
sono veloci e dovrebbero esserlo anche sotto Linux.