org.vaadin.miki.superfields.lazyload

Class ComponentObserver

java.lang.Object

com.vaadin.flow.component.Component

org.vaadin.miki.superfields.lazyload.ComponentObserver

All Implemented Interfaces:

com.vaadin.flow.component.AttachNotifier, com.vaadin.flow.component.DetachNotifier, com.vaadin.flow.component.HasElement, Serializable, HasId, WithIdMixin<ComponentObserver>

Direct Known Subclasses:

ObservedField.ObservedFieldElement

@JsModule(value="./component-observer.js")
 @Tag(value="component-observer")
public class ComponentObserver
extends com.vaadin.flow.component.Component
implements WithIdMixin<ComponentObserver>

A component that wraps Intersection Observer on the client-side to notify server-side about visibility changes. Note: Intersection Observer API is experimental and not all browsers implement it.

Since:

2020-04-28

Author:

miki

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ComponentObserver(com.vaadin.flow.component.Component viewportRoot, String rootMargin, double... visibilityRanges) Creates the observer using provided document as viewport root and provided root margins.
ComponentObserver(double... visibilityRanges) Creates the observer using entire document as viewport.

Method Summary

Modifier and Type	Method and Description
com.vaadin.flow.shared.Registration	addComponentObservationListener(ComponentObservationListener listener) Adds a listener that will be informed about changes in observed components.
protected void	fireComponentObservationEvent(ComponentObservationEvent event) Broadcasts the event using Component.getEventBus().
double[]	getVisibilityRanges() Returns an array with visibility ranges registered for this component.
protected void	initClient()
boolean	isObserving(com.vaadin.flow.component.Component component) Checks whether or not given Component is being observed by this object.
void	observe(com.vaadin.flow.component.Component... components) Starts observation of given components.
protected void	observe(String indexString, com.vaadin.flow.component.Component component) Observes the given component with given index.
protected void	onAttach(com.vaadin.flow.component.AttachEvent attachEvent)
protected void	onDetach(com.vaadin.flow.component.DetachEvent detachEvent)
void	unobserve(com.vaadin.flow.component.Component... components) Stops observation of given components.

Methods inherited from class com.vaadin.flow.component.Component

addListener, fireEvent, from, get, getChildren, getElement, getEventBus, getId, getLocale, getParent, getTranslation, getTranslation, getTranslation, getTranslation, getUI, hasListener, isAttached, isTemplateMapped, isVisible, onEnabledStateChanged, set, setElement, setId, setVisible

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.vaadin.miki.markers.WithIdMixin

withId

Methods inherited from interface org.vaadin.miki.markers.HasId

getId, setId

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

addAttachListener

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

addDetachListener

Constructor Detail

ComponentObserver

public ComponentObserver(double... visibilityRanges)

Creates the observer using entire document as viewport.

Parameters:

visibilityRanges - Ranges at which to trigger visibility change events. If not specified, [0.0, 1.0] will be used.

ComponentObserver

public ComponentObserver(com.vaadin.flow.component.Component viewportRoot,
                         String rootMargin,
                         double... visibilityRanges)

Creates the observer using provided document as viewport root and provided root margins.

Parameters:

viewportRoot - Component to use as viewport root.

rootMargin - Root margin (CSS-like expression).

visibilityRanges - Ranges at which to trigger visibility change events. If not specified, [0.0, 1.0] will be used.

Method Detail

initClient

protected void initClient()

onDetach

protected void onDetach(com.vaadin.flow.component.DetachEvent detachEvent)

Overrides:

onDetach in class com.vaadin.flow.component.Component

onAttach

protected void onAttach(com.vaadin.flow.component.AttachEvent attachEvent)

Overrides:

onAttach in class com.vaadin.flow.component.Component

fireComponentObservationEvent

protected void fireComponentObservationEvent(ComponentObservationEvent event)

Broadcasts the event using Component.getEventBus().

Parameters:

event - Event with relevant information about what happened.

observe

protected void observe(String indexString,
                       com.vaadin.flow.component.Component component)

Observes the given component with given index. Will override the component currently associated with given index, if the was any.

Parameters:

indexString - Index string to register the component with.

component - Component to observe.

observe

public void observe(com.vaadin.flow.component.Component... components)

Starts observation of given components. If a given component is already being observed, it will not be observed an additional time. Given component will stop being observed when it gets detached or when unobserve(Component...) method is called.

Parameters:

components - Components to observe.

unobserve

public void unobserve(com.vaadin.flow.component.Component... components)

Stops observation of given components. If a given component has not been registered with observe(Component...), nothing will happen.

Parameters:

components - Components to stop observing.

addComponentObservationListener

public com.vaadin.flow.shared.Registration addComponentObservationListener(ComponentObservationListener listener)

Adds a listener that will be informed about changes in observed components.

Parameters:

listener - Listener to add.

Returns:

Registration that can be used to stop listening.

isObserving

public boolean isObserving(com.vaadin.flow.component.Component component)

Checks whether or not given Component is being observed by this object.

Parameters:

component - A Component.

Returns:

true when the component has been added through observe(Component...) and not removed with unobserve(Component...).

getVisibilityRanges

public double[] getVisibilityRanges()

Returns an array with visibility ranges registered for this component. Modifying the resulting array has no effect on this object.

Returns:

A non-empty array with visibility ranges.