Package com.vaadin.flow.component

Class Component

    • Constructor Detail

      • Component

        protected Component()
        Creates a component instance with an element created based on the Tag annotation of the sub class.

        If this is invoked through from(Element, Class) or Element.as(Class), uses the element defined in those methods instead of creating a new element.

      • Component

        protected Component​(Element element)
        Creates a component instance based on the given element.

        For nearly all cases you want to pass an element reference but it is possible to pass null to this method. If you pass null you must ensure that the element is initialized using setElement(Component, Element) before getElement() is used.

        Parameters:
        element - the root element for the component

    • Method Detail

      • getElement

        public Element getElement()
        Gets the root element of this component.

        Each component must have exactly one root element. When the component is attached to a parent component, this element is attached to the parent component's element hierarchy.

        Specified by:
        getElement in interface HasElement
        Returns:
        the root element of this component

      • setElement

        protected static void setElement​(Component component,
                                 Element element)
        Initializes the root element of a component.

        Each component must have a root element and it must be set before the component is attached to a parent. The root element of a component cannot be changed once it has been set.

        Typically you do not want to call this method but define the element through Component(Element) instead.

        Parameters:
        component - the component to set the root element to
        element - the root element of the component

      • getParent

        public Optional<Component> getParent()
        Gets the parent component of this component.

        A component can only have one parent.

        Returns:
        an optional parent component, or an empty optional if the component is not attached to a parent

      • getChildren

        public Stream<Component> getChildren()
        Gets the child components of this component.

        The default implementation finds child components by traversing each child Element tree.

        If the component is injected to a PolymerTemplate using the @Id annotation the getChildren method will only return children added from the server side and will not return any children declared in the template file.

        Returns:
        the child components of this component
        See Also:
        Id

      • getEventBus

        protected ComponentEventBus getEventBus()
        Gets the event bus for this component.

        This method will create the event bus if it has not yet been created.

        Returns:
        the event bus for this component

      • addListener

        protected <T extends ComponentEvent<?>> Registration addListener​(Class<T> eventType,
                                                                 ComponentEventListener<T> listener)
        Adds a listener for an event of the given type.
        Type Parameters:
        T - the component event type
        Parameters:
        eventType - the component event type, not null
        listener - the listener to add, not null
        Returns:
        a handle that can be used for removing the listener

      • hasListener

        protected boolean hasListener​(Class<? extends ComponentEvent> eventType)
        Checks if there is at least one listener registered for the given event type for this component.
        Parameters:
        eventType - the component event type
        Returns:
        true if at least one listener is registered, false otherwise

      • getListeners

        protected Collection<?> getListeners​(Class<? extends ComponentEvent> eventType)
        Returns all listeners that match or extend the given event type.
        Parameters:
        eventType - the component event type
        Returns:
        A collection with all registered listeners for a given event type. Empty if no listeners are found.

      • getUI

        public Optional<UI> getUI()
        Gets the UI this component is attached to.
        Returns:
        an optional UI component, or an empty optional if this component is not attached to a UI

      • setId

        public void setId​(String id)
        Sets the id of the root element of this component. The id is used with various APIs to identify the element, and it should be unique on the page.
        Parameters:
        id - the id to set, or "" to remove any previously set id

      • getId

        public Optional<String> getId()
        Gets the id of the root element of this component.
        Returns:
        the id, or and empty optional if no id has been set
        See Also:
        setId(String)

      • onAttach

        protected void onAttach​(AttachEvent attachEvent)
        Called when the component is attached to a UI.

        The default implementation does nothing.

        This method is invoked before the AttachEvent is fired for the component.

        Parameters:
        attachEvent - the attach event

      • onDetach

        protected void onDetach​(DetachEvent detachEvent)
        Called when the component is detached from a UI.

        The default implementation does nothing.

        This method is invoked before the DetachEvent is fired for the component.

        Parameters:
        detachEvent - the detach event

      • isAttached

        public boolean isAttached()
        Checks whether this component is currently attached to a UI.

        When UI.close() is called, the UI and the components are not detached immediately; the UI cleanup is performed at the end of the current request which also detaches the UI and its components.

        Returns:
        true if the component is attached to an active UI.

      • set

        protected <T> void set​(PropertyDescriptor<T,​?> descriptor,
                       T value)
        Sets the value of the given component property.
        Type Parameters:
        T - type of the value to set
        Parameters:
        descriptor - the descriptor for the property to set, not null
        value - the new property value to set
        See Also:
        PropertyDescriptor

      • get

        protected <T> T get​(PropertyDescriptor<?,​T> descriptor)
        Gets the value of the given component property.
        Type Parameters:
        T - type of the value to get
        Parameters:
        descriptor - the descriptor for the property to set, not null
        Returns:
        the property value
        See Also:
        PropertyDescriptor

      • from

        public static <T extends Component> T from​(Element element,
                                           Class<T> componentType)
        Creates a new component instance using the given element.

        You can use this method when you have an element instance and want to use it through the API of a Component class.

        This method attaches the component instance to the element so that Element.getComponent() returns the component instance. This means that getParent(), getChildren() and other methods which rely on Element -> Component mappings will work correctly.

        Note that only one Component can be mapped to any given Element.

        Type Parameters:
        T - the component type to create
        Parameters:
        element - the element to wrap
        componentType - the component type
        Returns:
        the component instance connected to the given element
        See Also:
        Element.as(Class)

      • setVisible

        public void setVisible​(boolean visible)
        Sets the component visibility value.

        When a component is set as invisible, all the updates of the component from the server to the client are blocked until the component is set as visible again.

        Invisible components don't receive any updates from the client-side. Unlike the server-side updates, client-side updates, if any, are discarded while the component is invisible, and are not transmitted to the server when the component is made visible.

        Parameters:
        visible - the component visibility value

      • isVisible

        public boolean isVisible()
        Gets the component visibility value.
        Returns:
        true if the component is visible, false otherwise

      • onEnabledStateChanged

        public void onEnabledStateChanged​(boolean enabled)
        Handle component enable state when the enabled state changes.

        By default this sets or removes the 'disabled' attribute from the element. This can be overridden to have custom handling.

        Parameters:
        enabled - the new enabled state of the component

      • isTemplateMapped

        protected boolean isTemplateMapped()
        Gets whether this component was attached as part of a template (by being mapped by an Id annotation), or if it was created directly.
        Returns:
        true when it was mapped inside a template, false otherwise

      • getTranslation

        public String getTranslation​(String key,
                             Object... params)
        Get the translation for the component locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        key - translation key
        params - parameters used in translation string
        Returns:
        translation for key if found (implementation should not return null)
        See Also:
        getLocale()

      • getTranslation

        public String getTranslation​(Object key,
                             Object... params)
        Get the translation for the component locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        key - translation key
        params - parameters used in translation string
        Returns:
        translation for key if found (implementation should not return null)
        See Also:
        getLocale()

      • getTranslation

        @Deprecated
public String getTranslation​(String key,
                             Locale locale,
                             Object... params)
        Deprecated.
        Use getTranslation(Locale, String, Object...) instead
        Get the translation for key with given locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        key - translation key
        locale - locale to use
        params - parameters used in translation string
        Returns:
        translation for key if found

      • getTranslation

        @Deprecated
public String getTranslation​(Object key,
                             Locale locale,
                             Object... params)
        Deprecated.
        Use getTranslation(Locale, String, Object...) instead
        Get the translation for key with given locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        key - translation key
        locale - locale to use
        params - parameters used in translation string
        Returns:
        translation for key if found

      • getTranslation

        public String getTranslation​(Locale locale,
                             String key,
                             Object... params)
        Get the translation for key with given locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        locale - locale to use
        key - translation key
        params - parameters used in translation string
        Returns:
        translation for key if found

      • getTranslation

        public String getTranslation​(Locale locale,
                             Object key,
                             Object... params)
        Get the translation for key with given locale.

        The method never returns a null. If there is no I18NProvider available or no translation for the key it returns an exception string e.g. '!{key}!'.

        Parameters:
        locale - locale to use
        key - translation key
        params - parameters used in translation string
        Returns:
        translation for key if found

      • getLocale

        protected Locale getLocale()
        Gets the locale for this component.

        It returns the UI locale if it has been set. If there is no UI locale available then it tries to use the first locale provided by the I18NProvider. If there is no any provided locale then the default locale is used.

        Returns:
        the component locale

      • scrollIntoView

        public void scrollIntoView()
        Scrolls the current component into the visible area of the browser window.

      • findAncestor

        public <T> T findAncestor​(Class<T> componentType)
        Traverses the component tree up and returns the first ancestor component that matches the given type.
        Type Parameters:
        T - the type of the ancestor component to return
        Parameters:
        componentType - the class of the ancestor component to search for
        Returns:
        The first ancestor that can be assigned to the given class. Null if no ancestor with the correct type could be found.