Advanced Object Composition

Table of Contents

Markup Tutorial

Interfacing with Java™

Web Services

Object Composition

Advanced Table Features

Calendar

Note: Compared to other examples presented so far, this is a fairly advanced example of object composition. To follow it, you must have a good understanding of Model-View-Controller Pattern and Object Composition.

We now show you how to build a fully functioning calendar using many of the pieces we have already developed. We will later use this example to demonstrate advanced table features, and show how you can radically alter the view of the calendar using markup alone.

Calendar Structure

The structure of a calendar is shown below. The notation is the same as in earlier examples — red boxes represent models, purple boxes represent controllers, and green circles represent events. To reduce clutter, not all of the connections between event sources and event listeners are shown. See numeric spinner and month picker for details on how the year entry field and the month picker are implemented.

The most significant addition to this composition is the scroll pane containing a table that serves as the date view for the calendar. The table gets its data from the table model which can be manipulated by the calendar controller represented by the large purple box on the right.

Calendar Controller

The calendar controller is defined by the class com.enode.calendar.Calendar. As shown below, it implements the interfaces javax.swing.event.TableModelListener and com.enode.xalt.SequenceChangeListener.

package com.enode.calendar;

import com.enode.xalt.Sequence;
import com.enode.calendar.MonthSequence;
import com.enode.calendar.CalendarModel;

public class Calendar implements javax.swing.event.TableModelListener,
                                com.enode.xalt.SequenceChangeListener {

    public Calendar() {
        // Java beans must have a zero-argument constructor
    }

    public void setMonthModel(Sequence model) {
        monthModel = model;
        synchronizeMonth();
    }

    public void setYearModel(Sequence model) {
        yearModel = model;
        synchronizeYear();
    }

    public void setCalendarModel(CalendarModel model) {
        calendarModel = model;
        synchronizeMonth();
        synchronizeYear();
    }

    public void tableChanged(javax.swing.event.TableModelEvent event) {
        synchronizeMonth();
        synchronizeYear();
    }

    public void sequenceChanged(com.enode.xalt.SequenceChangeEvent event) {
        if (calendarModel == null)
            return;

        final Sequence    sequence = (Sequence) event.getSource();
        if (sequence instanceof MonthSequence) {
            switch (event.getChangeType()) {
                case Sequence.INCREMENT: {
                    calendarModel.adjustMonth(1);
                    break;
                }
                case Sequence.DECREMENT: {
                    calendarModel.adjustMonth(-1);
                    break;
                }
                default: {
                    calendarModel.setMonth(((Integer)sequence.getValue()).intValue());
                    break;
                }
            }
        }
        else {
            calendarModel.setYear(((Integer)sequence.getValue()).intValue());
        }
    }

    private void synchronizeMonth() {
        if ((monthModel != null) && (calendarModel != null)) {
            final int month = ((Number) monthModel.getValue()).intValue();
            final int calendarMonth = calendarModel.getCalendar().get(java.util.Calendar.MONTH);
            if (month != calendarMonth) { // synchronize monthModel and calendarModel
                monthModel.setValue(new Integer(calendarMonth));
                calendarModel.setMonth(((Number) monthModel.getValue()).intValue());
            }
        }
    }

    private void synchronizeYear() {
        if ((yearModel != null) && (calendarModel != null)) {
            final int year = ((Number) yearModel.getValue()).intValue();
            final int calendarYear = calendarModel.getCalendar().get(java.util.Calendar.YEAR);
            if (year != calendarYear) { // synchronize yearModel and calendarModel
                yearModel.setValue(new Integer(calendarYear));
                calendarModel.setYear(((Number) yearModel.getValue()).intValue());
            }
        }
    }

    private CalendarModel   calendarModel = null;
    private Sequence        monthModel = null;
    private Sequence        yearModel = null;
}

Calendar Model

To implement the communication protocol between the various objects in this example, we establish bi-directional associations between the calendar controller and each of the three models depicted above. The combo box model and the text model are unchanged from the month picker and numeric spinner examples, respectively. The listing for the table model is shown below.

package com.enode.calendar;
import java.util.Calendar;
import java.util.Date;

public class CalendarModel extends javax.swing.table.DefaultTableModel {
    public CalendarModel() {
        calendar.setTime(new Date());   // use current date
        calendar.set(Calendar.DATE, 1); // start with 1st of the month
        updateCalendar();
    }

    public void setMonth(int month) {   // zero-based month index
        if (month != getMonth()) {
            calendar.set(Calendar.MONTH, month);
            updateCalendar();
        }
    }

    public int getMonth() { // zero-based month index
        return calendar.get(Calendar.MONTH);
    }

    public void setYear(int year) {
        if (year != getYear()) {
            calendar.set(Calendar.YEAR, year);
            updateCalendar();
        }
    }

    public int getYear() {
        return calendar.get(Calendar.YEAR);
    }

    public void adjustMonth(int amount) {
        calendar.add(Calendar.MONTH, amount);
        updateCalendar();
    }

    public void adjustYear(int amount) {
        calendar.add(Calendar.YEAR, amount);
        updateCalendar();
    }

    public Calendar getCalendar() {
        return calendar;
    }

    public int getColumnCount() {
        return 7;
    }

    public int getRowCount() {
        return rows;
    }

    public Object getValueAt(int week, int day) {
        // day is zero-based; firstDay is one-based;
        int date = (week * 7) + (day + 1) - (firstDay - 1);
        return (date < 1) || (date > lastDay) ? "" :
                                    Integer.toString(date);
    }

    public String getColumnName(int column) {
        String  columnName;
        try {
            columnName = shortWeekdays[Calendar.SUNDAY + column];
        }
        catch (Exception ex) {
            columnName = "";
        }
        return columnName;
    }

    public boolean isCellEditable(int row, int column) {
        return false;   // none of the cells are editable
    }

    private void updateCalendar() {
        final int   era = calendar.get(Calendar.ERA);
        final int   year = calendar.get(Calendar.YEAR);
        final int   month = calendar.get(Calendar.MONTH);

        // Pin to March 1, 4 AD in the Gregorian Calendar
        if ((year < 4) || (era == java.util.GregorianCalendar.BC) ||
            ((year == 4) && (month < Calendar.MARCH))) {
            calendar.set(Calendar.MONTH, Calendar.MARCH);
            calendar.set(Calendar.YEAR, 4);
        }

        firstDay = calendar.get(Calendar.DAY_OF_WEEK);
        lastDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
        rows = (lastDay + (firstDay - 1)) / 7;
        if (((lastDay + (firstDay - 1)) % 7) > 0)
            rows += 1;

        fireTableChanged(new javax.swing.event.TableModelEvent(this));
    }

    protected Calendar                          calendar = new java.util.GregorianCalendar();
    private final java.text.DateFormatSymbols   dateSymbols = new java.text.DateFormatSymbols();
    private final String[]                      shortWeekdays = dateSymbols.getShortWeekdays();
    private int                                 firstDay, lastDay, rows;
}

Calendar View

The markup for the calendar view is shown below.

<?xml version="1.0"?>
<resource xmlns="http://www.enode.com/xalt" xmlns:xlink="http://www.w3.org/1999/xlink">
    <frame title="Calendar">
        <reserve> <!-- describe objects needed later -->
            <object id="calendar" class="com.enode.calendar.Calendar">
                <property key="calendarModel">
                    <tableModel id="calendarModel" class="com.enode.calendar.CalendarModel">
                        <tableModelListenerRef xlink:href="#calendar"/>
                    </tableModel>
                </property>
                <property key="monthModel">
                    <object id="monthModel" class="com.enode.calendar.MonthModel"/>
                </property>
                <property key="yearModel">
                    <object id="yearModel" class="com.enode.xalt.IntegerTextModel">
                        <property key="maximum">
                            <int value="2030"/>
                        </property>
                        <property key="minimum">
                            <int value="1980"/>
                        </property>
                        <property key="value">
                            <int value="2002"/>
                        </property>
                    </object>
                </property>
            </object>
            <vector id="callParameters">
                <objectRef xlink:href="#calendar"/>
            </vector>
            <call target="#monthModel"
                    method="addSequenceChangeListener" 
                    parameters="#callParameters"/>
            <call target="#yearModel"
                    method="addSequenceChangeListener" 
                    parameters="#callParameters"/>
            <object id="monthController" class="com.enode.xalt.Sequencer">
                <property key="sequence">
                    <objectRef xlink:href="#monthModel"/>
                </property>
            </object>
            <object id="yearController" class="com.enode.xalt.Sequencer">
                <property key="sequence">
                    <objectRef xlink:href="#yearModel"/>
                </property>
            </object>
            <action id="previous" icon="images/arrowLeft.gif" target="#monthController" method="decrement"/>
            <action id="next" icon="images/arrowRight.gif" target="#monthController" method="increment"/>
            <action id="up" icon="images/arrowUpTiny.gif" target="#yearController" method="increment"/>
            <action id="down" icon="images/arrowDownTiny.gif" target="#yearController" method="decrement"/>
            <bevelBorder id="myBorder" type="raised"/>
        </reserve>
        <panel> <!-- Calendar "view", with date picker on top -->
            <borderLayout/>
            <panel constraints="North"> <!-- begin date picker -->
                <flowLayout horizontalGap="20"/>
                <button action="#previous" preferredSize="26 26" border="#myBorder"/>
                <comboBox model="#monthModel"/>
                <panel border="#myBorder"> <!-- begin spinner -->
                    <borderLayout/>
                    <textField columnCount="4" model="#yearModel"/>
                    <panel constraints="East">
                        <borderLayout/>
                        <button action="#up" preferredSize="16 11" constraints="North"/>
                        <button action="#down" preferredSize="16 11" constraints="South"/>
                    </panel>
                </panel> <!-- end spinner -->
                <button action="#next" preferredSize="26 26" border="#myBorder"/>
            </panel> <!-- end date picker -->
            <scrollPane preferredSize="300 180">
                <table model="#calendarModel" rowHeight="32"/>
            </scrollPane>
        </panel>
    </frame>
</resource>

Make this object in eNode Sandbox. The result should be similar to the following:

See Advanced Table Features for some exciting ways to change the appearance of this calendar.