Package com.vaadin.flow.component

Interface HasHelper

All Superinterfaces:

HasElement, Serializable

All Known Subinterfaces:

InputField<E,V>

All Known Implementing Classes:

AbstractNumberField, BigDecimalField, Checkbox, CheckboxGroup, ComboBox, ComboBoxBase, CustomField, DatePicker, DateTimePicker, EmailField, IntegerField, MultiSelectComboBox, NumberField, PasswordField, RadioButtonGroup, RangeSlider, Select, Slider, TextArea, TextField, TextFieldBase, TimePicker

public interface HasHelper
extends HasElement

Mixin interface for field components that have helper text as property and slots for inserting components.

Root element should be a web component that uses slot for example in the following way:

     <field-with-helper>
         <shadow-root>
             ...
             <slot name="helper"></slot>
             ...
         </shadow-root>
         <span slot="helper">${helperText}</span>
     </field-with-helper>
 

Since:

2.4

Author:

Vaadin Ltd

Method Summary

Modifier and Type	Method	Description
default void	bindHelperText(Signal<String> helperTextSignal)	Binds a signal's value to the component's helper text so that the helper text is updated when the signal's value is updated.
default Component	getHelperComponent()	Gets the component in the helper slot of this field.
default String	getHelperText()	String used for the helper text.
default void	setHelperComponent(Component component)	Adds the given component into helper slot of component, replacing any existing helper component.
default void	setHelperText(String helperText)	String used for the helper text.

Methods inherited from interface com.vaadin.flow.component.HasElement

getElement

Method Details

getHelperText

default String getHelperText()

String used for the helper text.

Returns:

the helperText property from the web component

setHelperText

default void setHelperText(String helperText)

String used for the helper text. It shows a text adjacent to the field that can be used, e.g., to inform to the users which values it expects. Example: a text "The password must contain numbers" for the PasswordField.

In case both setHelperText(String) and setHelperComponent(Component) are used, only the element defined by setHelperComponent(Component) will be visible, regardless of the order on which they are defined.

Parameters:

helperText - the String value to set

bindHelperText

default void bindHelperText(Signal<String> helperTextSignal)

Binds a signal's value to the component's helper text so that the helper text is updated when the signal's value is updated.

Passing null as the signal removes any existing binding for the given helper text. When unbinding, the current helper text is left unchanged.

While a binding for the helper text is active, any attempt to set the text manually throws BindingActiveException. The same happens when trying to bind a new Signal while one is already bound.

Bindings are lifecycle-aware and only active while this component is in the attached state; they are deactivated while the component is in the detached state.

Parameters:

helperTextSignal - the signal to bind, not null

Throws:

BindingActiveException - thrown when there is already an existing binding

Since:

25.1

See Also:

• setHelperText(String)
• Element.bindProperty(String, Signal)

setHelperComponent

default void setHelperComponent(Component component)

Adds the given component into helper slot of component, replacing any existing helper component. It adds the component adjacent to the field that can be used, e.g., to inform to the users which values it expects. Example: a component that shows the password strength for the PasswordField.

Parameters:

component - the component to set, can be null to remove existing helper component

See Also:

• setHelperText(String)

getHelperComponent

default Component getHelperComponent()

Gets the component in the helper slot of this field.

Returns:

the helper component of this field, or null if no helper component has been set

See Also:

• setHelperComponent(Component)