EventTarget Class

Defined in: https://github.com/cocos-creator/engine/blob/de46973d0b5edcff4f973186ce89752080cb6b7c/cocos2d/core/event/event-target.js:100

Module: cc

EventTarget is an object to which an event is dispatched when something has occurred. Entity are the most common event targets, but other objects can be event targets too.

Event targets are an important part of the Fireball event model. The event target serves as the focal point for how events flow through the scene graph. When an event such as a mouse click or a keypress occurs, Fireball dispatches an event object into the event flow from the root of the hierarchy. The event object then makes its way through the scene graph until it reaches the event target, at which point it begins its return trip through the scene graph. This round-trip journey to the event target is conceptually divided into three phases:

• The capture phase comprises the journey from the root to the last node before the event target's node
• The target phase comprises only the event target node
• The bubbling phase comprises any subsequent nodes encountered on the return trip to the root of the tree See also: http://www.w3.org/TR/DOM-Level-3-Events/#event-flow

Event targets can implement the following methods:

• _getCapturingTargets
• _getBubblingTargets

Index

Methods

• on Register an callback of a specific event type on the EventTarget.
• off Removes the listeners previously registered with the same type, callback, target and or useCapture,...
• targetOff Removes all callbacks previously registered with the same target (passed as parameter).
• once Register an callback of a specific event type on the EventTarget,...
• dispatchEvent Dispatches an event into the event flow.
• emit Send an event to this object directly, this method will not propagate the event to any other objects.

Details

Methods

on

Register an callback of a specific event type on the EventTarget.

Parameters

• type String A string representing the event type to listen for.
• callback Function The callback that will be invoked when the event is dispatched.

                         The callback is ignored if it is a duplicate (the callbacks are unique).
  

  • event Event event
• target Object The target (this object) to invoke the callback, can be null
• useCapture Boolean When set to true, the capture argument prevents callback

                         from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE.
                         When false, callback will NOT be invoked when event's eventPhase attribute value is CAPTURING_PHASE.
                         Either way, callback will be invoked when event's eventPhase attribute value is AT_TARGET.
  

Examples

node.on(cc.Node.EventType.TOUCH_END, function (event) {
    cc.log("this is callback");
}, node);

off

Removes the listeners previously registered with the same type, callback, target and or useCapture, if only type is passed as parameter, all listeners registered with that type will be removed.

Parameters

• type String A string representing the event type being removed.
• callback Function The callback to remove.
• target Object The target (this object) to invoke the callback, if it's not given, only callback without target will be removed
• useCapture Boolean Specifies whether the callback being removed was registered as a capturing callback or not.

                         If not specified, useCapture defaults to false. If a callback was registered twice,
                         one with capture and one without, each must be removed separately. Removal of a capturing callback
                         does not affect a non-capturing version of the same listener, and vice versa.
  

Examples

// register touchEnd eventListener
var touchEnd = node.on(cc.Node.EventType.TOUCH_END, function (event) {
    cc.log("this is callback");
}, node);
// remove touch end event listener
node.off(cc.Node.EventType.TOUCH_END, touchEnd, node);
// remove all touch end event listeners
node.off(cc.Node.EventType.TOUCH_END);

targetOff

Removes all callbacks previously registered with the same target (passed as parameter). This is not for removing all listeners in the current event target, and this is not for removing all listeners the target parameter have registered. It's only for removing all listeners (callback and target couple) registered on the current event target by the target parameter.

Parameters

• target Object The target to be searched for all related listeners

once

Register an callback of a specific event type on the EventTarget, the callback will remove itself after the first time it is triggered.

Parameters

• type String A string representing the event type to listen for.
• callback Function The callback that will be invoked when the event is dispatched.

                         The callback is ignored if it is a duplicate (the callbacks are unique).
  

  • event Event event
• target Object The target (this object) to invoke the callback, can be null
• useCapture Boolean When set to true, the capture argument prevents callback

                         from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE.
                         When false, callback will NOT be invoked when event's eventPhase attribute value is CAPTURING_PHASE.
                         Either way, callback will be invoked when event's eventPhase attribute value is AT_TARGET.
  

Examples

node.once(cc.Node.EventType.TOUCH_END, function (event) {
    cc.log("this is callback");
}, node);

dispatchEvent

Dispatches an event into the event flow. The event target is the EventTarget object upon which the dispatchEvent() method is called.

Parameters

• event Event The Event object that is dispatched into the event flow

emit

Send an event to this object directly, this method will not propagate the event to any other objects. The event will be created from the supplied message, you can get the "detail" argument from event.detail.

Parameters

• message String the message to send
• detail Any whatever argument the message needs