4.5.2.4. XML-Attributes of Components
align

Defines the component position relative to the parent container. Possible values are:

  • TOP_RIGHT

  • TOP_LEFT

  • TOP_CENTER

  • MIDDLE_RIGHT

  • MIDDLE_LEFT

  • MIDDLE_CENTER

  • BOTTOM_RIGHT

  • BOTTOM_LEFT

  • BOTTOM_CENTER

caption

Sets the component’s caption.

The attribute value can either be a message or a key in a message pack. In case of a key, the value should begin with the msg:// prefix.

There are two ways of setting a key:

  • A short key – in this case the message will be searched in the package of the current screen:

    caption="msg://infoFieldCaption"

  • Full key including package name:

    caption="msg://com.company.sample.gui.screen/infoFieldCaption"
captionProperty

Defines the name of an entity attribute which is displayed by a component. captionProperty can only be used for entities contained in a datasource (for example, defined by the optionsDatasource property of the LookupField component).

If captionProperty is not defined, instance name is shown.

colspan

Sets the number of grid columns that the component should occupy (default is 1).

This attribute can be defined for any component located immediately within a GridLayout container.

datasource

Sets a data source defined in the dsContext section of the screen XML descriptor.

When setting the datasource attribute for a component implementing the DatasourceComponent interface, the property attribute should also be set.

description

Defines a hint which is displayed in a popup when a user hovers the mouse cursor over the component.

editable

Indicates that the component’s content can be edited (do not confuse with enable).

Possible values − true, false. Default value is true.

Ability to edit content of a component bound to data (inheritor of DatasourceComponent or ListComponent) is also influenced by the security subsystem. If the security subsystem information indicates that the component should not be editable, the value of its editable attribute is ignored.

enable

Defines the component’s enabled/disabled state.

If a component is disabled, it does not accept input focus. Disabling a container disables all of its components as well. Possible values are true, false. By default all components are enabled.

expand

Defines a component within the container that should be expanded to use all available space in the direction of component placement. For a container with vertical placement, this attribute sets 100% height to a component; for the containers with horizontal placement - 100% width. Additionally, resizing a container will resize the expanded component.

height

Sets the component’s height. Can be set in pixels or in percents of the parent container height. For example: 100px, 100%, 50. If it is specified without units, pixels are assumed.

Setting a value in % means that the component will occupy the corresponding height within an area provided by the parent container.

When set to AUTO or -1px, a default value will be used for the component height. For a container, default height is defined by the content: it is the sum of the heights of all nested components.

icon

Sets a component icon.

The attribute value should contain a path to an icon file relative to the themes folder. For example:

icon="icons/create.png"

If different icons should be displayed depending on the user’s language, you can set paths to the icons in the message pack and specify a message key in the icon attribute, for example:

icon="msg://addIcon"

Font elements of Font Awesome can be used instead of files in web client with Halo theme (or derived from it). For this, specify the name of the required constant of the com.vaadin.server.FontAwesome class in the icon property with the font-icon: prefix, for example:

icon="font-icon:BOOK"
id

Sets an identifier of the component.

It is recommended to create identifiers according to the rules for Java-identifiers and use camelСase, for example: userGrid, filterPanel. The id attribute can be specified for any component and should be unique within a screen.

inputPrompt

Defines a string which is displayed in the field when its value is null.

The attribute is used for TextField, LookupField, LookupPickerField, SearchPickerField components in web client only.

margin

Defines indentation between the outer borders and the container content.

It can take value of two types:

  • margin="true" − enables margins for all sides.

  • margin="true,false,true,false" − enables only the top and the bottom margin (the value format is "top,right,bottom,left").

By default margins are disabled.

nullName

Selection of the option defined in the nullName attribute is equal to setting the null value to the component.

The attribute is used for LookupField, LookupPickerField, and SearchPickerField components.

Example of setting an attribute value in an XML-descriptor:

<lookupField datasource="orderDs"
             property="customer"
             nullName="(none)"
             optionsDatasource="customersDs" width="200px"/>

Example of setting an attribute value in a controller:

<lookupField id="customerLookupField" optionsDatasource="customersDs"
             width="200px" datasource="orderDs" property="customer"/>
customerLookupField.setNullOption("<null>");
openType

Defines how a related screen will be opened. Corresponds to the WindowManager.OpenType enumeration with the values NEW_TAB, THIS_TAB, NEW_WINDOW, DIALOG. Default value is THIS_TAB.

optionsDatasource

Sets the name of a data source which contains a list of options.

captionProperty attribute can be used together with optionsDatasource.

property

Sets the name of an entity attribute which value will be displayed and edited by this visual component.

property is always used together with the datasource attribute.

required

Indicates that this field requires a value.

Possible values − true, false. Default is false.

The requiredMessage attribute can be used together with required.

requiredMessage

Used together with the required attribute. It sets a message that will be displayed to a user when the component has no value.

The attribute can contain a message or a key from a message pack, for example: requiredMessage="msg://infoTextField.requiredMessage"

responsive

Indicates that the component should react on change in the available space. Reaction can be customized with the help of styles.

Possible values − true, false. Default is false.

rowspan

Sets the number of grid lines that the component should occupy (default is 1).

This attribute can be set for any component located immediately within a GridLayout container.

settingsEnabled

Defines if user settings of the component should be saved/restored.

Possible values − true, false. Default is true.

spacing

Sets spacing between components within a container.

Possible values − true, false.

By default spacing is disabled.

stylename

Defines a style name for a component. See Themes for details.

tabIndex

Specifies whether the component is focusable and sets the relative order of the component in the sequence of focusable components on the screen.

It can can take integer values of positive or negative range:

  • negative value means that the component should be focusable, but should not be reachable via sequential keyboard navigation;

  • 0 means that the component should be focusable and reachable via sequential keyboard navigation, but its relative order follows its relative position on the screen;

  • positive value means the component should be focusable and reachable via sequential keyboard navigation; its relative order is defined by the value of the attribute: the sequential follows the increasing number of the tabIndex. If several components share the same tabIndex value, their relative order follows their relative position on the screen.

visible

Sets visibility of the component. Possible values − true, false.

If a container is invisible all its components are invisible. By default all components are visible.

width

Defines component’s width.

The value can be set in pixels or in percents of the width of the parent container. For example: 100px, 100%, 50. If specified without units, pixels are assumed. Setting a value in % means that the component will occupy the corresponding width within an area provided by the parent container.

When set to AUTO or -1px, a default value will be used for a component width. For a container, the default width is defined by the content: it is the sum of the widths of all nested components.