com.vaadin.flow.component

Interface HasValue<E extends HasValue.ValueChangeEvent<V>,V>

Type Parameters:

E - the type of the value change event fired by this instance

V - the value type

All Superinterfaces:

Serializable

All Known Subinterfaces:

HasValueAndElement<E,V>, MultiSelect<C,T>, SingleSelect<C,T>

All Known Implementing Classes:

AbstractCompositeField, AbstractField, AbstractNumberField, AbstractSinglePropertyField, BigDecimalField, Checkbox, CheckboxGroup, ComboBox, CustomField, DatePicker, DateTimePicker, EmailField, GeneratedVaadinCheckbox, GeneratedVaadinCheckboxGroup, GeneratedVaadinComboBox, GeneratedVaadinDatePicker, GeneratedVaadinEmailField, GeneratedVaadinNumberField, GeneratedVaadinPasswordField, GeneratedVaadinRadioGroup, GeneratedVaadinRichTextEditor, GeneratedVaadinSelect, GeneratedVaadinTextArea, GeneratedVaadinTextField, GeneratedVaadinTimePicker, Input, IntegerField, ListBox, ListBoxBase, MultiSelectListBox, NumberField, PasswordField, RadioButtonGroup, ReadOnlyHasValue, RichTextEditor, Select, TextArea, TextField, TimePicker

public interface HasValue<E extends HasValue.ValueChangeEvent<V>,V>
extends Serializable

A generic interface for field components and other user interface objects that have a user-editable value. Emits change events whenever the value is changed, either by the user or programmatically.

Since:

1.0.

Author:

Vaadin Ltd

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	HasValue.ValueChangeEvent<V> An event fired when the value of a HasValue changes.
static interface	HasValue.ValueChangeListener<E extends HasValue.ValueChangeEvent<?>> A listener for value change events.

Method Summary

Modifier and Type	Method and Description
Registration	addValueChangeListener(HasValue.ValueChangeListener<? super E> listener) Adds a value change listener.
default void	clear() Resets the value to the empty one.
default V	getEmptyValue() Returns the value that represents an empty value.
default Optional<V>	getOptionalValue() Returns the current value of this object, wrapped in an Optional.
V	getValue() Returns the current value of this object.
default boolean	isEmpty() Returns whether this HasValue is considered to be empty.
boolean	isReadOnly() Returns whether this HasValue is in read-only mode or not.
boolean	isRequiredIndicatorVisible() Checks whether the required indicator is visible.
void	setReadOnly(boolean readOnly) Sets the read-only mode of this HasValue to given mode.
void	setRequiredIndicatorVisible(boolean requiredIndicatorVisible) Sets the required indicator visible or not.
void	setValue(V value) Sets the value of this object.

Method Detail

setValue

void setValue(V value)

Sets the value of this object. If the new value is not equal to getValue(), fires a value change event. May throw IllegalArgumentException if the value is not acceptable.

Implementation note: the implementing class should document whether null values are accepted or not, and override getEmptyValue() if the empty value is not null.

Parameters:

value - the new value

Throws:

IllegalArgumentException - if the value is invalid

getValue

V getValue()

Returns the current value of this object.

Implementation note: the implementing class should document whether null values may be returned or not, and override getEmptyValue() if the empty value is not null.

Returns:

the current value

addValueChangeListener

Registration addValueChangeListener(HasValue.ValueChangeListener<? super E> listener)

Adds a value change listener. The listener is called when the value of this HasValue is changed either by the user or programmatically.

Parameters:

listener - the value change listener, not null

Returns:

a registration for the listener

getEmptyValue

default V getEmptyValue()

Returns the value that represents an empty value.

By default HasValue is expected to support null as empty values. Specific implementations might not support this.

Returns:

empty value

getOptionalValue

default Optional<V> getOptionalValue()

Returns the current value of this object, wrapped in an Optional.

The Optional will be empty if the value is null or isEmpty() returns true.

Returns:

the current value, wrapped in an Optional

isEmpty

default boolean isEmpty()

Returns whether this HasValue is considered to be empty.

By default this is an equality check between current value and empty value.

Returns:

true if considered empty; false if not

clear

default void clear()

Resets the value to the empty one.

This is just a shorthand for resetting the value, see the methods setValue(Object) and getEmptyValue().

See Also:

setValue(Object), getEmptyValue()

setReadOnly

void setReadOnly(boolean readOnly)

Sets the read-only mode of this HasValue to given mode. The user can't change the value when in read-only mode.

A HasValue with a visual component in read-only mode typically looks visually different to signal to the user that the value cannot be edited.

Parameters:

readOnly - a boolean value specifying whether the component is put read-only mode or not

isReadOnly

boolean isReadOnly()

Returns whether this HasValue is in read-only mode or not.

Returns:

false if the user can modify the value, true if not.

setRequiredIndicatorVisible

void setRequiredIndicatorVisible(boolean requiredIndicatorVisible)

Sets the required indicator visible or not.

If set visible, it is visually indicated in the user interface.

The method is intended to be used with Binder which does server-side validation. In case HTML element has its own (client-side) validation it should be disabled when setRequiredIndicatorVisible(true) is called and re-enabled back on setRequiredIndicatorVisible(false). It's responsibility of each component implementation to follow the contract so that the method call doesn't do anything else than show/hide the "required" indication. Usually components provide their own setRequired method which should be called in case the client-side validation is required.

Parameters:

requiredIndicatorVisible - true to make the required indicator visible, false if not

isRequiredIndicatorVisible

boolean isRequiredIndicatorVisible()

Checks whether the required indicator is visible.

Returns:

true if visible, false if not