Package com.vaadin.flow.component

Class ComponentEvent<T extends Component>

java.lang.Object

java.util.EventObject

com.vaadin.flow.component.ComponentEvent<T>

Type Parameters:

T - the event source type

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AbstractAttachDetachEvent, AbstractField.ComponentValueChangeEvent, BlurNotifier.BlurEvent, ClickEvent, CompositionEvent, FocusNotifier.FocusEvent, InputEvent, KeyboardEvent, PollEvent, UI.BrowserLeaveNavigationEvent, UI.BrowserNavigateEvent, UI.BrowserRefreshEvent, UploadCompleteEvent, UploadStartEvent, WebComponentUI.WebComponentConnectEvent

public class ComponentEvent<T extends Component>
extends EventObject

An event whose source is a Component.

Typically used together with ComponentEventBus.

Since:

1.0

Author:

Vaadin Ltd

See Also:

• Serialized Form

Field Summary

Fields inherited from class java.util.EventObject

source

Constructor Summary

Constructors

Constructor	Description
ComponentEvent(T source, boolean fromClient)	Creates a new event using the given source and indicator whether the event originated from the client side or the server side.
ComponentEvent(T source, boolean fromClient, UI ui)	Creates a new event using the given source, indicator whether the event originated from the client side or the server side, and an explicit UI to associate with the event.

Method Summary

Modifier and Type	Method	Description
T	getSource()
UI	getUI()	Gets the UI associated with this event.
boolean	isFromClient()	Checks if this event originated from the client side.
void	unregisterListener()	Unregisters the event listener currently being invoked.

Methods inherited from class java.util.EventObject

toString

Methods inherited from class java.lang.Object

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

Constructor Details

ComponentEvent

public ComponentEvent(T source,
 boolean fromClient)

Creates a new event using the given source and indicator whether the event originated from the client side or the server side.

Parameters:

source - the source component

fromClient - true if the event originated from the client side, false otherwise

ComponentEvent

public ComponentEvent(T source,
 boolean fromClient,
 UI ui)

Creates a new event using the given source, indicator whether the event originated from the client side or the server side, and an explicit UI to associate with the event.

Use this constructor when the source component may not be attached to a UI at the time the event is fired, but the UI is still known (for example, when the event is dispatched from code that has access to the current UI). The supplied UI is then returned by getUI() without relying on the source's attachment state.

Parameters:

source - the source component

fromClient - true if the event originated from the client side, false otherwise

ui - the UI associated with the event, or null if not available

Method Details

getSource

public T getSource()

Overrides:

getSource in class EventObject

getUI

public UI getUI()

Gets the UI associated with this event.

The UI is resolved in the following order:

1. If a UI was explicitly provided at construction time, that instance is returned.
2. If the source component is itself a UI, it is returned directly.
3. Otherwise, the UI is obtained from getSource().getUI().get().

In the common case the source is attached to a UI when the event fires, so this method is a convenient shorthand for getSource().getUI().get().

If none of the above applies and the source component is not currently attached to a UI, this method throws an IllegalStateException. This can happen, for example, when an initial value is set on a field before it is added to the UI and a value-change listener is invoked. If your listener can run while the source is detached, use getSource().getUI() instead, which returns an Optional and lets you handle the detached case explicitly.

Returns:

the UI associated with this event, never null

Throws:

IllegalStateException - if the source component is not currently attached to a UI and no UI was provided at construction time

isFromClient

public boolean isFromClient()

Checks if this event originated from the client side.

Returns:

true if the event originated from the client side, false otherwise

unregisterListener

public void unregisterListener()

Unregisters the event listener currently being invoked.

This method can only be called from within an event listener. Calling it will remove the current event listener so no further events are passed to it.