Event

Events are a messaging mechanism used for object interaction within the engine.

Event monitoring

// The event listener will be triggered every time, you need to 
// manually cancel the registration
xxx.on(type, func, target);
Property Description
type the event registration string.
func the callback for performing event monitoring.
target the event receiving object.

Event cancellation

// Cancel all registered events of this type on the object
xxx.off(type);
// Cancel the event of the specified target of the specified 
// callback on the object
xxx.off(type, func, target);

Event distribution

// Dispatch parameters can be specified when the event 
// is dispatched
xxx.emit(type, ...arg);

Note: due to the performance considerations of the underlying event dispatch, only a maximum of 5 event parameters are supported here. Therefore, it is necessary to pay attention to the number of control parameters when passing parameters.

Event descriptions

System events

System events refer to global events, which are monitored and distributed directly from the browser.

cc.systemEvent.on(type, func, target);

Currently supported system events are: touch events, mouse events, gravity events, and key press events. The global event type can be ontained by using cc.SystemEventType.

Event Name Event Type Description
TOUCH_START Finger starts touch event.
TOUCH_MOVE When your finger moves on the screen.
TOUCH_END The finger ends the touch event.
TOUCH_CANCEL When the finger leaves the screen outside the target node area.
MOUSE_DOWN Triggered once when the mouse is pressed.
MOUSE_MOVE When the mouse moves on the target node in the target node area, whether it is pressed or not.
MOUSE_UP Triggered once when the mouse is released from the pressed state.
MOUSE_WHEEL Mouse scroll event.
MOUSE_ENTER When the mouse moves into the target node area, whether it is pressed or not.
MOUSE_EXIT When the mouse moves out of the target node area, whether it is pressed or not.
KEY_DOWN Event triggered when a key is pressed.
KEY_UP Event triggered when the key is released.
DEVICEMOTION Gravity sensing.

The key value list obtained by the KEY event can be used by referring to the API Macro.

UI events

Event processing is done in the node. For components, you can register and listen to events by accessing the node this.node. Monitoring events can be registered using the this.node.on() function as follows:

import { _decorator, Component, Node } from "Cocos3D";
const { ccclass } = _decorator;

@ccclass("example")
export class example extends Component {
    onLoad() {
      this.node.on(Node.EventType.TOUCH_CANCEL, this.callback, this);
    }

    callback(){

    }

    onDestroy(){
      // In general, for data recovery control, we will 
      // specify func, and cancel the event when the component 
      // is destroyed
      this.node.off(Node.EventType.TOUCH_CANCEL);
    }
Event Name Event Type Description
TRANSFORM_CHANGED Node change position, rotation or zoom event.
POSITION_PART Node position change event. Unified monitoring by TRANSFORM_CHANGED, and judge the type after distribution.
ROTATION_PART Node rotation event. Unified monitoring by TRANSFORM_CHANGED, and judge the type after distribution.
SCALE_PART Node zoom event. Unified monitoring by TRANSFORM_CHANGED, and judge the type after distribution.
SIZE_CHANGED Event triggered when the node size changes.
ANCHOR_CHANGED Event triggered when the node anchor changes.
CHILD_ADDED Node subclass added.
CHILD_REMOVED Node subclasses removed.

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