vaadin-framework/documentation/components/components-calendar.asciidoc

---
title: Calendar
order: 30
layout: page
---

[[components.calendar]]
= [classname]#Calendar#

ifdef::web[]
[.sampler]
image:{live-demo-image}[alt="Live Demo", link="http://demo.vaadin.com/sampler/#ui/data-input/dates/dates-calendar"]
endif::web[]

The [classname]#Calendar# component allows organizing and displaying calendar
events. The main features of the calendar include:

* Monthly, weekly, and daily views
* Two types of events: all-day events and events with a time range
* Add events directly, from a [classname]#Container#, or with an event provider
* Control the range of the visible dates
* Selecting and editing date or time range by dragging
* Drag and drop events to calendar
* Support for localization and timezones

User interaction with the calendar elements, such as date and week captions as
well as events, is handled with event listeners. Also date/time range
selections, event dragging, and event resizing can be listened by the server.
The weekly view has navigation buttons to navigate forward and backward in time.
These actions are also listened by the server. Custom navigation can be
implemented using event handlers

ifdef::web[]
, as described in
<<components.calendar.customizing>>
endif::web[]
.

The data source of a calendar can be practically anything, as its events are
queried dynamically by the component. You can bind the calendar to a Vaadin
container, or to any other data source by implementing an __event provider__.

The [classname]#Calendar# has undefined size by default and you usually want to
give it a fixed or relative size, for example as follows.


[source, java]
----
Calendar cal = new Calendar("My Calendar");
cal.setWidth("600px");
cal.setHeight("300px");
----

After creating the calendar, you need to set a time range for it, which also
controls the view mode, and set up the data source for calendar events.

[[components.calendar.daterange]]
== Date Range and View Mode

The Vaadin Calendar has two types of views that are shown depending on the date
range of the calendar. The __weekly view__ displays a week by default. It can
show anything between one to seven days a week, and is also used as a single-day
view. The view mode is determined from the __date range__ of the calendar,
defined by a start and an end date. Calendar will be shown in a __monthly view__
when the date range is over than one week (seven days) long. The date range is
always calculated in an accuracy of one millisecond.

[[figure.components.calendar.daterange.monthly]]
.Monthly view with All-Day and Normal Events
image::img/calendar-monthly.png[]

The monthly view, shown in <<figure.components.calendar.daterange.monthly>>, can
easily be used to control all types of events, but it is best suited for events
that last for one or more days. You can drag the events to move them. In the
figure, you can see two longer events that are highlighted with a blue and green
background color. Other markings are shorter day events that last less than a 24
hours. These events can not be moved by dragging in the monthly view.

[[figure.components.calendar.daterange.weekly]]
.Weekly View
image::img/calendar-weekly.png[]

In <<figure.components.calendar.daterange.weekly>>, you can see four normal day
events and also all-day events at the top of the time line grid.

In the following, we set the calendar to show only one day, which is the current
day.


[source, java]
----
cal.setStartDate(new Date());
cal.setEndDate(new Date());
----

Notice that although the range we set above is actually zero time long, the
calendar still renders the time from 00:00 to 23:59. This is normal, as the
Vaadin Calendar is guaranteed to render at least the date range provided, but
may expand it. This behaviour is important to notice when we implement our own
event providers.


[[components.calendar.events]]
== Calendar Events

All occurrences in a calendar are represented as __events__. You have three ways
to manage the calendar events:

* Add events directly to the [classname]#Calendar# object using the [methodname]#addEvent()#
* Use a [interfacename]#Container# as a data source
* Use the __event provider__ mechanism

You can add events with [methodname]#addEvent()# and remove them with the
[methodname]#removeEvent()#. These methods will use the underlying event
provider to write the modifications to the data source.

[[components.calendar.events.types]]
=== Event Interfaces and Providers

Events are handled though the [interfacename]#CalendarEvent# interface. The
concrete class of the event depends on the specific
[classname]#CalendarEventProvider# used in the calendar.

By default, [classname]#Calendar# uses a [classname]#BasicEventProvider# to
provide events, which uses [classname]#BasicEvent# instances.

Calendar does not depend on any particular data source implementation. Events
are queried by the [classname]#Calendar# from the provider that just has to
implement the [interfacename]#CalendarEventProvider# interface. It is up to the
event provider that [classname]#Calendar# gets the correct events.

You can bind any Vaadin [classname]#Container# to a calendar, in which case a
[classname]#ContainerEventProvider# is used transparently. The container must be
ordered by start date and time of the events. See
<<dummy/../../../framework/datamodel/datamodel-container#datamodel.container,"Collecting
Items in Containers">> for basic information about containers.


[[components.calendar.events.details]]
=== Event Types

A calendar event requires a start time and an end time. These are the only
mandatory properties. In addition, an event can also be set as an all-day event
by setting the [literal]#++all-day++# property of the event. You can also set
the [literal]#++description++# of an event, which is displayed as a tooltip in
the user interface.

If the [literal]#++all-day++# field of the event is [literal]#++true++#, then
the event is always rendered as an all-day event. In the monthly view, this
means that no start time is displayed in the user interface and the event has an
colored background. In the weekly view, all-day events are displayed in the
upper part of the screen, and rendered similarly to the monthly view. In
addition, when the time range of an event is 24 hours or longer, it is rendered
as an all-day event in the monthly view.

When the time range of an event is equal or less than 24 hours, with the
accuracy of one millisecond, the event is considered as a normal day event.
Normal event has a start and end times that may be on different days.


[[components.calendar.events.basic]]
=== Basic Events

The easiest way to add and manage events in a calendar is to use the __basic
event__ management API. Calendar uses by default a
[classname]#BasicEventProvider#, which keeps the events in memory in an internal
reprensetation.

For example, the following adds a two-hour event starting from the current time.
The standard Java [classname]#GregorianCalendar# provides various ways to
manipulate date and time.


[source, java]
----
// Add a two-hour event
GregorianCalendar start = new GregorianCalendar();
GregorianCalendar end   = new GregorianCalendar();
end.add(java.util.Calendar.HOUR, 2);
calendar.addEvent(new BasicEvent("Calendar study",
        "Learning how to use Vaadin Calendar",
        start.getTime(), end.getTime()));
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#calendar.monthlyview[on-line example, window="_blank"].

This adds a new event that lasts for 3 hours. As the BasicEventProvider and
BasicEvent implement some optional event interfaces provided by the calendar
package, there is no need to refresh the calendar. Just create events, set their
properties and add them to the Event Provider.



[[components.calendar.container]]
== Getting Events from a Container

You can use any Vaadin [interfacename]#Container# that implements the
[interfacename]#Indexed# interface as the data source for calendar events. The
[classname]#Calendar# will listen to change events from the container as well as
write changes to the container. You can attach a container to a
[classname]#Calendar# with [methodname]#setContainerDataSource()#.

In the following example, we bind a [classname]#BeanItemContainer# that contains
built-in [classname]#BasicEvent# events to a calendar.


[source, java]
----
// Create the calendar
Calendar calendar = new Calendar("Bound Calendar");

// Use a container of built-in BasicEvents
final BeanItemContainer<BasicEvent> container =
    new BeanItemContainer<BasicEvent>(BasicEvent.class);

// Create a meeting in the container
container.addBean(new BasicEvent("The Event", "Single Event",
            new GregorianCalendar(2012,1,14,12,00).getTime(),
            new GregorianCalendar(2012,1,14,14,00).getTime()));

// The container must be ordered by the start time. You
// have to sort the BIC every time after you have added
// or modified events.
container.sort(new Object[]{"start"}, new boolean[]{true});

calendar.setContainerDataSource(container, "caption",
    "description", "start", "end", "styleName");
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#calendar.beanitemcontainer[on-line example, window="_blank"].

The container must either use the default property IDs for event data, as
defined in the [interfacename]#CalendarEvent# interface, or provide them as
parameters for the [methodname]#setContainerDataSource()# method, as we did in
the example above.

[[components.calendar.container.sorting]]
=== Keeping the Container Ordered

The events in the container __must__ be kept ordered by their start date/time.
Failing to do so may and will result in the events not showing in the calendar
properly.

Ordering depends on the container. With some containers, such as
[classname]#BeanItemContainer#, you have to sort the container explicitly every
time after you have added or modified events, usually with the
[methodname]#sort()# method, as we did in the example above. Some container,
such as [classname]#JPAContainer#, keep the in container automatically order if
you provide a sorting rule.

For example, you could order a [classname]#JPAContainer# by the following rule,
assuming that the start date/time is held in the [literal]#++startDate++#
property:


[source, java]
----
// The container must be ordered by start date. For JPAContainer
// we can just set up sorting once and it will stay ordered.
container.sort(new String[]{"startDate"}, new boolean[]{true});
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#calendar.jpacontainer[on-line example, window="_blank"].


ifdef::web[]
[[components.calendar.container.customization]]
=== Delegation of Event Management

Setting a container as the calendar data source with
[methodname]#setContainerDataSource()# automatically switches to
[classname]#ContainerEventProvider#. You can manipulate the event data through
the API in [classname]#Calendar# and the user can move and resize event through
the user interface. The event provider delegates all such calendar operations to
the container.

If you add events through the [classname]#Calendar# API, notice that you may be
unable to create events of the type held in the container or adding them
requires some container-specific operations. In such case, you may need to
customize the [methodname]#addEvent()# method.

For example, [classname]#JPAContainer# requires adding new items with
[methodname]#addEntity()#. You could first add the entity to the container or
entity manager directly and then pass it to the [methodname]#addEvent()#. That
does not, however, work if the entity class does not implement
[interfacename]#CalendarEvent#. This is actually the case always if the property
names differ from the ones defined in the interface. You could handle creating
the underlying entity objects in the [methodname]#addEvent()# as follows:


[source, java]
----
// Create a JPAContainer
final JPAContainer<MyCalendarEvent> container =
    JPAContainerFactory.make(MyCalendarEvent.class,
                             "book-examples");

// Customize the event provider for adding events
// as entities
ContainerEventProvider cep =
        new ContainerEventProvider(container) {
    @Override
    public void addEvent(CalendarEvent event) {
        MyCalendarEvent entity = new MyCalendarEvent(
            event.getCaption(), event.getDescription(),
            event.getStart(), event.getEnd(),
            event.getStyleName());
        container.addEntity(entity);
    }
}

// Set the container as the data source
calendar.setEventProvider(cep);

// Now we can add events to the database through the calendar
BasicEvent event = new BasicEvent("The Event", "Single Event",
    new GregorianCalendar(2012,1,15,12,00).getTime(),
    new GregorianCalendar(2012,1,15,14,00).getTime());
calendar.addEvent(event);
----

endif::web[]


ifdef::web[]
[[components.calendar.eventprovider]]
== Implementing an Event Provider

If the two simple ways of storing and managing events for a calendar are not
enough, you may need to implement a custom event provider. It is the most
flexible way of providing events. You need to attach the event provider to the
[classname]#Calendar# using the [methodname]#setEventProvider()# method.

Event queries are done by asking the event provider for all the events between
two given dates. The range of these dates is guaranteed to be at least as long
as the start and end dates set for the component. The component can, however,
ask for a longer range to ensure correct rendering. In particular, all start
dates are expanded to the start of the day, and all end dates are expanded to
the end of the day.

[[components.calendar.eventprovider.customevents]]
=== Custom Events

An event provider could use the built-in [classname]#BasicEvent#, but it is
usually more proper to define a custom event type that is bound directly to the
data source. Custom events may be useful for some other purposes as well, such
as when you need to add extra information to an event or customize how it is
acquired.

Custom events must implement the [interfacename]#CalendarEvent# interface or
extend an existing event class. The built-in [classname]#BasicEvent# class
should serve as a good example of implementing simple events. It keeps the data
in member variables.


[source, java]
----
public class BasicEvent
       implements CalendarEventEditor, EventChangeNotifier {
   ...

   public String getCaption() {
        return caption;
    }

    public String getDescription() {
        return description;
    }

    public Date getEnd() {
        return end;
    }

    public Date getStart() {
        return start;
    }

    public String getStyleName() {
        return styleName;
    }

    public boolean isAllDay() {
        return isAllDay;
    }

    public void setCaption(String caption) {
        this.caption = caption;
        fireEventChange();
    }

    public void setDescription(String description) {
        this.description = description;
        fireEventChange();
    }

    public void setEnd(Date end) {
        this.end = end;
        fireEventChange();
    }

    public void setStart(Date start) {
        this.start = start;
        fireEventChange();
    }

    public void setStyleName(String styleName) {
        this.styleName = styleName;
        fireEventChange();
    }

    public void setAllDay(boolean isAllDay) {
        this.isAllDay = isAllDay;
        fireEventChange();
    }

    public void addEventChangeListener(
            EventChangeListener listener) {
        ...
    }

    public void removeListener(EventChangeListener listener) {
        ...
    }

    protected void fireEventChange() {...}
}
----

You may have noticed that there was some additional code in the
[classname]#BasicEvent# that was not in the [interfacename]#CalendarEvent#
interface. Namely [classname]#BasicEvent# also implements two additional
interfaces:

[interfacename]#CalendarEditor#:: This interface defines setters for all the fields, and is required for some of
the default handlers to work.

[interfacename]#EventChangeNotifier#:: This interface adds the possibility to listen for changes in the event, and
enables the [classname]#Calendar# to render the changes immediately.



The start time and end time are mandatory, but caption, description, and style
name are not. The style name is used as a part of the CSS class name for the
HTML DOM element of the event.

In addition to the basic event interfaces, you can enhance the functionality of
your event and event provider classes by using the [classname]#EventChange# and
[classname]#EventSetChange# events. They let the [classname]#Calendar# component
to know about changes in events and update itself accordingly. The
[classname]#BasicEvent# and [classname]#BasicEventProvider# examples given
earlier include a simple implementation of these interfaces.


[[components.calendar.eventprovider.eventprovider]]
=== Implementing the Event Provider

An event provider needs to implement the [interfacename]#CalendarEventProvider#
interface. It has only one method to be implemented. Whenever the calendar is
painted, [methodname]#getEvents(Date, Date)# method is called and it must return
a list of events between the given start and end time.

The following example implementation returns only one example event. The event
starts from the current time and is five hours long.


[source, java]
----
public class MyEventProvider implements CalendarEventProvider{
    public List<Event> getEvents(Date startDate, Date endDate){
        List<Event> events = new ArrayList<Event>();
        GregorianCalendar cal = new GregorianCalendar();
        cal.setTime(new Date());

        Date start = cal.getTime();
        cal.add(GregorianCalendar.HOUR, 5);
        Date end = cal.getTime();
        BasicEvent event = new BasicEvent();
        event.setCaption("My Event");
        event.setDescription("My Event Description");
        event.setStart(start);
        event.setEnd(end);
        events.add(event);

        return events;
    }
}
----

It is important to notice that the [classname]#Calendar# may query for dates
beyond the range defined by start date and end date. Particularly, it may expand
the date range to make sure the user interface is rendered correctly.


endif::web[]

ifdef::web[]
[[components.calendar.appearance]]
== Styling a Calendar

Configuring the appearance of the Vaadin Calendar component is one of the basic
tasks. At the least, you need to consider its sizing in your user interface. You
also quite probably want to use some color or colors for events.

[[components.calendar.appearance.sizing]]
=== Sizing

The Calendar supports component sizing as usual for defined (fixed or relative)
sizes. When using an undefined size for the calendar, all the sizes come from
CSS. In addition, when the height is undefined, a scrollbar is displayed in the
weekly view to better fit the cells to the user interface.

Below is a list of style rules that define the size of a Calendar with undefined
size (these are the defaults):


[source, css]
----
.v-calendar-month-sizedheight .v-calendar-month-day {
	height: 100px;
}

.v-calendar-month-sizedwidth .v-calendar-month-day {
	width: 100px;
}

.v-calendar-header-month-Hsized .v-calendar-header-day {
	width: 101px;
}

/* for IE */
.v-ie6 .v-calendar-header-month-Hsized .v-calendar-header-day {
	width: 104px;
}

/* for others */
.v-calendar-header-month-Hsized td:first-child {
	padding-left: 21px;
}

.v-calendar-header-day-Hsized {
	width: 200px;
}

.v-calendar-week-numbers-Vsized .v-calendar-week-number {
	height: 100px;
	line-height: 100px;
}

.v-calendar-week-wrapper-Vsized {
	height: 400px;
	overflow-x: hidden !important;
}

.v-calendar-times-Vsized .v-calendar-time {
	height: 38px;
}

.v-calendar-times-Hsized .v-calendar-time {
	width: 42px;
}

.v-calendar-day-times-Vsized .v-slot,.v-calendar-day-times-Vsized .v-slot-even {
	height: 18px;
}

.v-calendar-day-times-Hsized, .v-calendar-day-times-Hsized .v-slot,.v-calendar-day-times-Hsized .v-slot-even {
	width: 200px;
}
----


[[components.calendar.appearance.event-style]]
=== Event Style

Events can be styled with CSS by setting them a __style name suffix__. The
suffix is retrieved with the [methodname]#getStyleName()# method in
[interfacename]#CalendarEvent#. If you use [classname]#BasicEvent# events, you
can set the suffix with [methodname]#setStyleName()#.


[source, java]
----
BasicEvent event = new BasicEvent("Wednesday Wonder", ... );
event.setStyleName("mycolor");
calendar.addEvent(event);
----

Suffix [literal]#++mycolor++# would create
[literal]#++v-calendar-event-mycolor++# class for regular events and
[literal]#++v-calendar-event-mycolor-add-day++# for all-day events. You could
style the events with the following rules:


[source, css]
----
.v-calendar .v-calendar-event-mycolor {}
.v-calendar .v-calendar-event-mycolor-all-day {}
.v-calendar .v-calendar-event-mycolor .v-calendar-event-caption {}
.v-calendar .v-calendar-event-mycolor .v-calendar-event-content {}
----


endif::web[]

ifdef::web[]
[[components.calendar.visible-hours-days]]
== Visible Hours and Days

As we saw in <<components.calendar.daterange>>, you can set the range of dates
that are shown by the Calendar. But what if you wanted to show the entire month
but hide the weekends? Or show only hours from 8 to 16 in the weekly view? The
[methodname]#setVisibleDays()# and [methodname]#setVisibleHours()# methods allow
you to do that.


[source, java]
----
calendar.setVisibleDays(1,5);   // Monday to Friday
calendar.setVisibleHours(0,15); // Midnight until 4 pm
----

After the above settings, only weekdays from Monday to Friday would be shown.
And when the calendar is in the weekly view, only the time range from 00:00 to
16:00 would be shown.

Note that the excluded times are never shown so you should take care when
setting the date range. If the date range contains only dates / times that are
excluded, nothing will be displayed. Also note that even if a date is not
rendered because these settings, the event provider may still be queried for
events for that date.

endif::web[]

ifdef::web[]
[[components.calendar.drag-and-drop]]
== Drag and Drop

Vaadin Calendar can act as a drop target for drag and drop, described in
<<dummy/../../../framework/advanced/advanced-dragndrop#advanced.dragndrop,"Drag
and Drop">>. With the functionality, the user could drag events, for example,
from a table to a calendar.

To support dropping, a [classname]#Calendar# must have a drop handler. When the
drop handler is set, the days in the monthly view and the time slots in the
weekly view can receive drops. Other locations, such as day names in the weekly
view, can not currently receive drops.

Calendar uses its own implementation of [interfacename]#TargetDetails#:
[classname]#CalendarTargetdetails#. It holds information about the the drop
location, which in the context of [classname]#Calendar# means the date and time.
The drop target location can be retrieved via the [methodname]#getDropTime()#
method. If the drop is done in the monthly view, the returned date does not have
exact time information. If the drop happened in the weekly view, the returned
date also contains the start time of the slot.

Below is a short example of creating a drop handler and using the drop
information to create a new event:


[source, java]
----
private Calendar createDDCalendar() {
  Calendar calendar = new Calendar();
  calendar.setDropHandler(new DropHandler() {
    public void drop(DragAndDropEvent event) {
      CalendarTargetDetails details =
              (CalendarTargetDetails) event.getTargetDetails();

      TableTransferable transferable =
              (TableTransferable) event.getTransferable();

      createEvent(details, transferable);
      removeTableRow(transferable);
    }

    public AcceptCriterion getAcceptCriterion() {
      return AcceptAll.get();
    }

  });

  return calendar;
}


protected void createEvent(CalendarTargetDetails details,
  TableTransferable transferable) {
  Date dropTime = details.getDropTime();
  java.util.Calendar timeCalendar = details.getTargetCalendar()
                                    .getInternalCalendar();
  timeCalendar.setTime(dropTime);
  timeCalendar.add(java.util.Calendar.MINUTE, 120);
  Date endTime = timeCalendar.getTime();

  Item draggedItem = transferable.getSourceComponent().
                            getItem(transferable.getItemId());

  String eventType = (String)draggedItem.
                            getItemProperty("type").getValue();

  String eventDescription = "Attending: "
             + getParticipantString(
                 (String[]) draggedItem.
                   getItemProperty("participants").getValue());

  BasicEvent newEvent = new BasicEvent();
  newEvent.setAllDay(!details.hasDropTime());
  newEvent.setCaption(eventType);
  newEvent.setDescription(eventDescription);
  newEvent.setStart(dropTime);
  newEvent.setEnd(endTime);

  BasicEventProvider ep = (BasicEventProvider) details
                       .getTargetCalendar().getEventProvider();
  ep.addEvent(newEvent);
}
----

endif::web[]

ifdef::web[]
[[components.calendar.contextmenu]]
== Using the Context Menu

Vaadin Calendar allows the use of context menu (mouse right-click) to manage
events. As in other context menus in Vaadin, the menu items are handled in
Vaadin as __actions__ by an __action handler__. To enable a context menu, you
have to implement a Vaadin [interfacename]#Action.Handler# and add it to the
calendar with [methodname]#addActionHandler()#.

An action handler must implement two methods: [methodname]#getActions()# and
[methodname]#handleAction()#. The [methodname]#getActions()# is called for each
day displayed in the calendar view. It should return a list of allowed actions
for that day, that is, the items of the context menu. The [parameter]#target#
parameter is the context of the click - a [classname]#CalendarDateRange# that
spans over the day. The [parameter]#sender# is the [classname]#Calendar# object.

The [methodname]#handleActions()# receives the target context in the
[parameter]#target#. If the context menu was opened on an event, the target is
the [interfacename]#Event# object, otherwise it is a
[classname]#CalendarDateRange#.

endif::web[]

ifdef::web[]
[[components.calendar.localization]]
== Localization and Formatting

[[components.calendar.localization.locale]]
=== Setting the Locale and Time Zone

Month and weekday names are shown in the language of the locale setting of the
[classname]#Calendar#. The translations are acquired from the standard Java
locale data. By default, [classname]#Calendar# uses the system default locale
for its internal calendar, but you can change it with
[methodname]#setLocale(Locale locale)#. Setting the locale will update also
other location specific date and time settings, such as the first day of the
week, time zone, and time format. However, time zone and time format can be
overridden by settings in the [classname]#Calendar#.

For example, the following would set the language to US English:


[source, java]
----
cal.setLocale(Locale.US);
----

The locale defines the default time zone. You can change it with the
[methodname]#setTimeZone()# method, which takes a
[classname]#java.util.TimeZone# object as its parameter. Setting timezone to
null will reset timezone to the locale default.

For example, the following would set the Finnish time zone, which is EET


[source, java]
----
cal.setTimeZone(TimeZone.getTimeZone("Europe/Helsinki"));
----


[[components.calendar.localization.datecaption]]
=== Time and Date Caption Format

The time may be shown either in 24 or 12 hour format. The default format is
defined by the locale, but you can change it with the
[methodname]#setTimeFormat()# method. Giving a [literal]#++null++# setting will
reset the time format to the locale default.


[source, java]
----
cal.setTimeFormat(TimeFormat.Format12H);
----

You can change the format of the date captions in the week view with the
[methodname]#setWeeklyCaptionFormat(String dateFormatPattern)# method. The date
format pattern should follow the format of the standard Java
[classname]#java.text.SimpleDateFormat# class.

For example:


[source, java]
----
cal.setWeeklyCaptionFormat("dd-MM-yyyy");
----


endif::web[]

ifdef::web[]
[[components.calendar.customizing]]
== Customizing the Calendar

In this section, we give a tutorial for how to make various basic customizations
of the Vaadin Calendar. The event provider and styling was described earlier, so
now we concentrate on other features of the Calendar API.

[[components.calendar.customizing.overview]]
=== Overview of Handlers

Most of the handlers related to calendar events have sensible default handlers.
These are found in the [package]#com.vaadin.ui.handler# package. The default
handlers and their functionalities are described below.

* [classname]#BasicBackwardHandler#. Handles clicking the back-button of the weekly view so that the viewed month is changed to the previous one.
* [classname]#BasicForwardHandler#. Handles clicking the forward-button of the weekly view so that the viewed month is changed to the next one.
* [classname]#BasicWeekClickHandler#. Handles clicking the week numbers int the monthly view so that the viewable date range is changed to the clicked week.
* [classname]#BasicDateClickHandler#. Handles clicking the dates on both the monthly view and the weekly view. Changes the viewable date range so that only the clicked day is visible.
* [classname]#BasicEventMoveHandler#. Handles moving the events in both monthly view and the weekly view. Events can be moved and their start and end dates are changed correctly, but only if the event implements [classname]#CalendarEventEditor# (implemented by [classname]#BasicEvent#).
* [classname]#BasicEventResizeHandler#. Handles resizing the events in the weekly view. Events can be resized and their start and end dates are changed correctly, but only if the event implements [classname]#CalendarEventEditor# (implemented by the [classname]#BasicEvent#).

All of these handlers are automatically set when creating a new
[classname]#Calendar#. If you wish to disable some of the default functionality,
you can simply set the corresponding handler to [literal]#++null++#. This will
prevent the functionality from ever appearing on the user interface. For
example, if you set the [classname]#EventMoveHandler# to [literal]#++null++#,
the user will be unable to move events in the browser.


[[components.calendar.customizing.creating]]
=== Creating a Calendar

Let us first create a new [classname]#Calendar# instance. Here we use our own
event provider, the [classname]#MyEventProvider# described in
<<components.calendar.eventprovider.eventprovider>>.


[source, java]
----
Calendar cal = new Calendar(new MyEventProvider());
----

This initializes the Calendar. To customize the viewable date range, we must set
a start and end date to it.

There is only one visible event in the timeline, starting from the current time.
That is what our event provider passes to the client.//TODO See the figure
3.

It would be nice to also be able to control the navigation forward and backward.
The default navigation is provided by the default handlers, but perhaps we want
to restrict the users so they can only navigate dates in the current year. Maybe
we also want to pose some other restrictions to the clicking week numbers and
dates.

These restrictions and other custom logic can be defined with custom handlers.
You can find the handlers in the [package]#com.vaadin.addon.calendar.ui.handler#
package and they can be easily extended. Note that if you don not want to extend
the default handlers, you are free to implement your own. The interfaces are
described in [interfacename]#CalendarComponentEvents#.


endif::web[]

[[components.calendar.navigation]]
== Backward and Forward Navigation

Vaadin Calendar has only limited built-in navigation support. The weekly view
has navigation buttons in the top left and top right
corners.
// TODO See the figure 4.

You can handle backward and forward navigation with a
[interfacename]#BackwardListener# and [interfacename]#ForwardListener#.

[source, java]
----
cal.setHandler(new BasicBackwardHandler() {
  protected void setDates(BackwardEvent event,
                          Date start, Date end) {

      java.util.Calendar calendar = event.getComponent()
                                    .getInternalCalendar();
      if (isThisYear(calendar, end)
           && isThisYear(calendar, start)) {
        super.setDates(event, start, end);
      }
  }});
----

The forward navigation handler can be implemented in the same way. The example
handler restricts the dates to the current year.


ifdef::web[]
[[components.calendar.dateclick]]
== Date Click Handling

By default, clicking a date either in month or week view switches to single-day
view, while clicking on the date header in the day view has no effect. The date
click event is handled by a [interfacename]#DateClickHandler#.

The following example handles click events on the date header in the day view to
zoom out to the week view. For other clicks it applies the default behavior; in
the week view clicking on a day switches to the day view.


[source, java]
----
calendar.setHandler(new BasicDateClickHandler() {
    public void dateClick(DateClickEvent event) {
      Calendar cal = event.getComponent();

      // Check if the current range is already one day long
      long currentCalDateRange = cal.getEndDate().getTime() -
                                 cal.getStartDate().getTime();

      // From one-day view, zoom out to week view
      if (currentCalDateRange <= DateConstants.DAYINMILLIS) {
          // Change the date range to the current week
          GregorianCalendar weekstart = new GregorianCalendar();
          GregorianCalendar weekend   = new GregorianCalendar();
          weekstart.setTime(event.getDate());
          weekend.setTime(event.getDate());
          weekstart.setFirstDayOfWeek(java.util.Calendar.SUNDAY);
          weekstart.set(java.util.Calendar.HOUR_OF_DAY, 0);
          weekstart.set(java.util.Calendar.DAY_OF_WEEK,
                       java.util.Calendar.SUNDAY);
          weekend.set(java.util.Calendar.HOUR_OF_DAY, 23);
          weekend.set(java.util.Calendar.DAY_OF_WEEK,
                       java.util.Calendar.SATURDAY);
          cal.setStartDate(weekstart.getTime());
          cal.setEndDate(weekend.getTime());

          Notification.show("Custom zoom to week");
      } else {
        // Default behavior, change date range to one day
        super.dateClick(event);
      }
    }
  });
----

endif::web[]

ifdef::web[]
[[components.calendar.weekclick]]
== Handling Week Clicks

The monthly view displays week numbers for each week row on the left side of the
date grid. The week number are clickable and you can handle the click events by
setting a [interfacename]#WeekClickHandler# for the [classname]#Calendar#
object. The default handler changes the date range to be the clicked week.

In the following example, we add a week click handler that changes the date
range of the calendar to one week only if the start and end dates of the week
are in the current month.


[source, java]
----
cal.setHandler(new BasicWeekClickHandler() {
    protected void setDates(WeekClick event,
                          Date start, Date end) {
        java.util.Calendar calendar = event.getComponent()
                                  .getInternalCalendar();
        if (isThisMonth(calendar, start)
            && isThisMonth(calendar,  end)) {
            super.setDates(event, start, end);
        }
    }
});
----

endif::web[]

ifdef::web[]
[[components.calendar.eventclick]]
== Handling Event Clicks

The calendar events in all views are are clickable. There is no default handler.
Just like the date and week click handlers, event click handling is enabled by
setting an [interfacename]#EventClickHandler# for the [classname]#Calendar#
object.

You can get hold of the clicked event by the [methodname]#getCalendarEvent()#
method in the [classname]#EventClick# object passed to the handler, as shown in
the following example.


[source, java]
----
cal.setHandler(new EventClickHandler() {
    public void eventClick(EventClick event) {
        BasicEvent e = (BasicEvent) event.getCalendarEvent();

        // Do something with it
        new Notification("Event clicked: " + e.getCaption(),
            e.getDescription()).show(Page.getCurrent());
    }
});
----

endif::web[]

ifdef::web[]
[[components.calendar.eventdrag]]
== Event Dragging

The user can drag an event to change its position in time. The default handler
sets the start and end time of the event accordingly. You can do many things
with a custom move handler, such as restrict moving events.

In the following example, we add a [interfacename]#EventMoveHandler# to a
[classname]#Calendar#. The event handler updates the new position to the
datasource, but only if the new dates are in the current month. This requires
making some changes to the event provider class.


[source, java]
----
cal.setHandler(new BasicEventMoveHandler() {
  private java.util.Calendar javaCalendar;

  public void eventMove(MoveEvent event) {
    javaCalendar = event.getComponent().getInternalCalendar();
    super.eventMove(event);
  }

  protected void setDates(CalendarEventEditor event,
                          Date start, Date end) {
    if (isThisMonth(javaCalendar, start)
        && isThisMonth(javaCalendar, end)) {
      super.setDates(event, start, end);
    }
  }
});
----

For the above example to work, the example event provider presented earlier
needs to be changed slightly so that it doesn't always create a new event when
[methodname]#getEvents()# is called.


[source, java]
----
public static class MyEventProvider
              implements CalendarEventProvider {
  private List<CalendarEvent> events =
        new ArrayList<CalendarEvent>();

  public MyEventProvider() {
    events = new ArrayList<CalendarEvent>();
    GregorianCalendar cal = new GregorianCalendar();
    cal.setTime(new Date());

    Date start = cal.getTime();
    cal.add(GregorianCalendar.HOUR, 5);
    Date end = cal.getTime();
    BasicEvent event = new BasicEvent();
    event.setCaption("My Event");
    event.setDescription("My Event Description");
    event.setStart(start);
    event.setEnd(end);
    events.add(event);
  }

  public void addEvent(CalendarEvent BasicEvent) {
    events.add(BasicEvent);
  }

  public List<CalendarEvent> getEvents(Date startDate,
                                       Date endDate) {
    return events;
  }
}
----

After these changes, the user can move events around as earlier, but dropping an
event, the start and end dates are checked by the server. Note that as the
server-side must move the event in order for it to render to the place it was
dropped. The server can also reject moves by not doing anything when the event
is received.

endif::web[]

ifdef::web[]
[[components.calendar.dragselection]]
== Handling Drag Selection

Drag selection works both in the monthly and weekly views. To listen for drag
selection, you can add a [interfacename]#RangeSelectListener# to the
[classname]#Calendar#. There is no default handler for range select.

In the code example below, we create an new event when any date range is
selected. Drag selection opens a window where the user is asked for a caption
for the new event. After confirming, the new event is be passed to the event
provider and calendar is updated. Note that as our example event provider and
event classes do not implement the event change interface, we must refresh the
[classname]#Calendar# manually after changing the events.


[source, java]
----
cal.setHandler(new RangeSelectHandler() {
  public void rangeSelect(RangeSelectEvent event) {
    BasicEvent calendarEvent = new BasicEvent();
    calendarEvent.setStart(event.getStart());
    calendarEvent.setEnd(event.getEnd());

    // Create popup window and add a form in it.
    VerticalLayout layout = new VerticalLayout();
    layout.setMargin(true);
    layout.setSpacing(true);

    final Window w = new Window(null, layout);
    ...

    // Wrap the calendar event to a BeanItem
    // and pass it to the form
    final BeanItem<CalendarEvent> item =
                         new BeanItem<CalendarEvent>(myEvent);

    final Form form = new Form();
    form.setItemDataSource(item);
    ...

    layout.addComponent(form);

    HorizontalLayout buttons = new HorizontalLayout();
    buttons.setSpacing(true);
    buttons.addComponent(new Button("OK", new ClickListener() {

        public void buttonClick(ClickEvent event) {
            form.commit();

            // Update event provider's data source
            provider.addEvent(item.getBean());

            UI.getCurrent().removeWindow(w);
        }
    }));

    ...
  }
});
----

endif::web[]

ifdef::web[]
[[components.calendar.eventresizing]]
== Resizing Events

The user can resize an event by dragging from both ends to change its start or
end time. This offers a convenient way to change event times without the need to
type anything. The default resize handler sets the start and end time of the
event according to the resize.

In the example below, we set a custom handler for resize events. The handler
prevents any event to be resized over 12 hours in length. Note that this does
not prevent the user from resizing an event over 12 hours in the client. The
resize will just be corrected by the server.


[source, java]
----
cal.setHandler(new BasicEventResizeHandler() {
  private static final long twelveHoursInMs = 12*60*60*1000;

  protected void setDates(CalendarEventEditor event,
                          Date start, Date end) {
    long eventLength = end.getTime() - start.getTime();
    if (eventLength <= twelveHoursInMs) {
      super.setDates(event, start, end);
    }
  }
});
----

endif::web[]