org.vaadin.miki.superfields.unload

Class UnloadObserver

java.lang.Object

com.vaadin.flow.component.Component

org.vaadin.miki.superfields.unload.UnloadObserver

All Implemented Interfaces:

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

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

Server-side component that listens to beforeunload events. Based on the code by Kaspar Scherrer and Stuart Robinson. This component will broadcast events on beforeunload event in the browser. If isQueryingOnUnload() is true, before the event the user will be prompted about leaving the page. However, there is no way to find out what the user selected. If isQueryingOnUnload() is false, the event on the server will be called just before the page is unloaded. Note that the component must be present in the DOM structure in the browser for the event to be received on the server. Warning: this class is pretty much a UI-scoped singleton; the class is final, the constructors are private and there is at most one global instance per UI.

Since:

2020-04-29

Author:

Kaspar Scherrer, Stuart Robinson; adapted to web-component by miki; bugfixing and enhancements by Jean-François Lamy

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
com.vaadin.flow.shared.Registration	addUnloadListener(UnloadListener listener) Adds an UnloadListener.
protected void	fireUnloadEvent(UnloadEvent event) Fires the UnloadEvent.
static UnloadObserver	get() Returns or creates an instance for current UI.
static UnloadObserver	get(com.vaadin.flow.component.UI ui) Returns or creates an instance for a given UI.
static UnloadObserver	getAttached() Returns or creates an instance for current UI and attaches that instance to the UI, if not yet attached.
static <C extends com.vaadin.flow.component.Component & com.vaadin.flow.component.HasComponents> UnloadObserver	getAttached(C parent) Returns or creates an instance for the UI associated with given parent and attaches that instance to parent.
boolean	isQueryingOnUnload() Returns whether or not querying on document unload will happen.
protected void	onAttach(com.vaadin.flow.component.AttachEvent attachEvent)
protected void	onDetach(com.vaadin.flow.component.DetachEvent detachEvent)
void	setQueryingOnUnload(boolean queryingOnUnload) Controls whether or not there should be querying when the document is going to be unloaded.
UnloadObserver	withoutQueryingOnUnload() Shortcut for withQueryingOnUnload(false).
UnloadObserver	withQueryingOnUnload() Shortcut for withQueryingOnUnload(true).
UnloadObserver	withQueryingOnUnload(boolean value) Chains setQueryingOnUnload(boolean) and returns itself.

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

Method Detail

get

public static UnloadObserver get()

Returns or creates an instance for current UI. The result is associated with the UI, but not added to any of its components.

Returns:

An instance of UnloadObserver.

Throws:

IllegalStateException - if there is no current UI.

get

public static UnloadObserver get(com.vaadin.flow.component.UI ui)

Returns or creates an instance for a given UI. The result is associated with the UI, but not added to any of its components.

Parameters:

ui - A UI to register the instance of UnloadObserver in. Must not be null.

Returns:

An instance of UnloadObserver.

getAttached

public static UnloadObserver getAttached()

Returns or creates an instance for current UI and attaches that instance to the UI, if not yet attached. The result is associated with the UI and added to it directly. Identical to calling getAttached(Component) with UI.getCurrent().

Returns:

An instance of UnloadObserver.

getAttached

public static <C extends com.vaadin.flow.component.Component & com.vaadin.flow.component.HasComponents> UnloadObserver getAttached(C parent)

Returns or creates an instance for the UI associated with given parent and attaches that instance to parent. If the instance was already created and belonged to some other parent and that parent allows removing components, an attempt will be made to remove the instance before adding it to the new parent. If that fails, an IllegalStateException will be thrown. If the UI associated with parent is null, an IllegalArgumentException will be thrown.

Type Parameters:

C - Generic type to ensure the parent can have other components added to it.

Parameters:

parent - A Component to add the UnloadObserver to. Must not be null.

Returns:

An instance of UnloadObserver.

Throws:

IllegalStateException - when an instance of UnloadObserver is attached to a component it cannot be removed from

IllegalArgumentException - when the Component.getUI() for parent is not present

setQueryingOnUnload

public void setQueryingOnUnload(boolean queryingOnUnload)

Controls whether or not there should be querying when the document is going to be unloaded.

Parameters:

queryingOnUnload - When true, UnloadListeners registered through addUnloadListener(UnloadListener) will be notified and document unloading can be prevented. When false, nothing will happen when the document gets unloaded.

isQueryingOnUnload

public boolean isQueryingOnUnload()

Returns whether or not querying on document unload will happen.

Returns:

true when unloading the document from browser window results in showing a browser-native confirmation dialog and notifying UnloadListeners; false otherwise.

withQueryingOnUnload

public UnloadObserver withQueryingOnUnload(boolean value)

Chains setQueryingOnUnload(boolean) and returns itself.

Parameters:

value - Whether or not to query on document unload.

Returns:

This.

See Also:

setQueryingOnUnload(boolean)

withQueryingOnUnload

public UnloadObserver withQueryingOnUnload()

Shortcut for withQueryingOnUnload(true).

Returns:

This.

See Also:

withQueryingOnUnload(boolean)

withoutQueryingOnUnload

public UnloadObserver withoutQueryingOnUnload()

Shortcut for withQueryingOnUnload(false).

Returns:

This.

See Also:

withQueryingOnUnload(boolean)

onAttach

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

Overrides:

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

onDetach

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

Overrides:

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

fireUnloadEvent

protected void fireUnloadEvent(UnloadEvent event)

Fires the UnloadEvent.

Parameters:

event - Event to fire.

addUnloadListener

public com.vaadin.flow.shared.Registration addUnloadListener(UnloadListener listener)

Adds an UnloadListener.

Parameters:

listener - Listener to add.

Returns:

A Registration that can be used to stop listening to the event.