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, ComboBoxBase, CustomField, DatePicker, DateTimePicker, EmailField, GeneratedVaadinCheckbox, GeneratedVaadinCheckboxGroup, GeneratedVaadinDatePicker, GeneratedVaadinEmailField, GeneratedVaadinNumberField, GeneratedVaadinPasswordField, GeneratedVaadinRadioGroup, GeneratedVaadinRichTextEditor, GeneratedVaadinSelect, GeneratedVaadinTextArea, GeneratedVaadinTextField, GeneratedVaadinTimePicker, Input, IntegerField, ListBox, ListBoxBase, MultiSelectComboBox, 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	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

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	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

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

Nested Class Summary

Method Summary

Method Detail

setValue

getValue

addValueChangeListener

getEmptyValue

getOptionalValue

isEmpty

clear

setReadOnly

isReadOnly

setRequiredIndicatorVisible

isRequiredIndicatorVisible

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