Class CallbackEventHandler

Interface for classes capable of having callbacks to handle events.

Inheritance

Object

CallbackEventHandler

Focusable

Namespace: UnityEngine.UIElements

Syntax

public abstract class CallbackEventHandler : object, IEventHandler

Methods

ExecuteDefaultAction(EventBase)

Executes logic after the callbacks registered on the event target have executed, unless the event has been marked to prevent its default behaviour. .

Declaration

protected virtual void ExecuteDefaultAction(EventBase evt)

Parameters

Type	Name	Description
EventBase	evt	The event instance.

Remarks

This method is designed to be overriden by subclasses. Use it to implement event handling without registering callbacks which guarantees precedences of callbacks registered by users of the subclass. Unlike ExecuteDefaultActionAtTarget(EventBase), this method is called after both the callbacks registered on the element and callbacks registered on its ancestors with NoTrickleDown.

ExecuteDefaultActionAtTarget(EventBase)

Executes logic after the callbacks registered on the event target have executed, unless the event is marked to prevent its default behaviour. .

Declaration

protected virtual void ExecuteDefaultActionAtTarget(EventBase evt)

Parameters

Type	Name	Description
EventBase	evt	The event instance.

Remarks

This method is designed to be overriden by subclasses. Use it to implement event handling without registering callbacks, which guarantees precedences of callbacks registered by users of the subclass. Unlike ExecuteDefaultAction(EventBase), this method is called after the callbacks registered on the element but before callbacks registered on its ancestors with NoTrickleDown.

HandleEvent(EventBase)

Handle an event, most often by executing the callbacks associated with the event.

Declaration

public virtual void HandleEvent(EventBase evt)

Parameters

Type	Name	Description
EventBase	evt	The event to handle.

Implements

IEventHandler.HandleEvent(EventBase)

HasBubbleUpHandlers()

Return true if event handlers for the event propagation BubbleUp phase have been attached on this object.

Declaration

public bool HasBubbleUpHandlers()

Returns

Type	Description
Boolean	True if object has event handlers for the BubbleUp phase.

Implements

IEventHandler.HasBubbleUpHandlers()

HasTrickleDownHandlers()

Returns true if event handlers, for the event propagation TrickleDown phase, are attached to this object.

Declaration

public bool HasTrickleDownHandlers()

Returns

Type	Description
Boolean	True if object has event handlers for the TrickleDown phase.

Implements

IEventHandler.HasTrickleDownHandlers()

RegisterCallback<TEventType>(EventCallback<TEventType>, TrickleDown)

Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect.

Declaration

public void RegisterCallback<TEventType>(EventCallback<TEventType> callback, TrickleDown useTrickleDown = default(TrickleDown))
    where TEventType : EventBase<TEventType>, new()

Parameters

Type	Name	Description
EventCallback<TEventType>	callback	The event handler to add.
TrickleDown	useTrickleDown	By default, this callback is called during the BubbleUp phase. Pass TrickleDown.TrickleDown to call this callback during the TrickleDown phase.

Type Parameters

Name	Description
TEventType

RegisterCallback<TEventType, TUserArgsType>(EventCallback<TEventType, TUserArgsType>, TUserArgsType, TrickleDown)

Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect.

Declaration

public void RegisterCallback<TEventType, TUserArgsType>(EventCallback<TEventType, TUserArgsType> callback, TUserArgsType userArgs, TrickleDown useTrickleDown = default(TrickleDown))
    where TEventType : EventBase<TEventType>, new()

Parameters

Type	Name	Description
EventCallback<TEventType, TUserArgsType>	callback	The event handler to add.
TUserArgsType	userArgs	Data to pass to the callback.
TrickleDown	useTrickleDown	By default, this callback is called during the BubbleUp phase. Pass TrickleDown.TrickleDown to call this callback during the TrickleDown phase.

Type Parameters

Name	Description
TEventType
TUserArgsType

SendEvent(EventBase)

Sends an event to the event handler.

Declaration

public abstract void SendEvent(EventBase e)

Parameters

Type	Name	Description
EventBase	e	The event to send.

Implements

IEventHandler.SendEvent(EventBase)

UnregisterCallback<TEventType>(EventCallback<TEventType>, TrickleDown)

Remove callback from the instance.

Declaration

public void UnregisterCallback<TEventType>(EventCallback<TEventType> callback, TrickleDown useTrickleDown = default(TrickleDown))
    where TEventType : EventBase<TEventType>, new()

Parameters

Type	Name	Description
EventCallback<TEventType>	callback	The callback to remove.
TrickleDown	useTrickleDown	Set this parameter to true to remove the callback from the TrickleDown phase. Set this parameter to false to remove the callback from the BubbleUp phase.

Type Parameters

Name	Description
TEventType

UnregisterCallback<TEventType, TUserArgsType>(EventCallback<TEventType, TUserArgsType>, TrickleDown)

Remove callback from the instance.

Declaration

public void UnregisterCallback<TEventType, TUserArgsType>(EventCallback<TEventType, TUserArgsType> callback, TrickleDown useTrickleDown = default(TrickleDown))
    where TEventType : EventBase<TEventType>, new()

Parameters

Type	Name	Description
EventCallback<TEventType, TUserArgsType>	callback	The callback to remove.
TrickleDown	useTrickleDown	Set this parameter to true to remove the callback from the TrickleDown phase. Set this parameter to false to remove the callback from the BubbleUp phase.

Type Parameters

Name	Description
TEventType
TUserArgsType