CocosCreator 根据碰撞法线计算是否在空中

const{ccclass,property}=cc._decorator;

@ccclass
export default class Player extends cc.Component{
	
	private _rigidBody:cc.RigidBody;
	private _onGroundB2Contacts:any[]=[];
	private _isInAir:boolean=true;
	
	protected onLoad():void{
		this._rigidBody=this.node.getComponent(cc.RigidBody);
		this._rigidBody.enabledContactListener=true;//激活接触侦听
	}
	
	private onPreSolve(contact:cc.PhysicsContact,selfCollider:cc.PhysicsCollider,otherCollider:cc.PhysicsCollider):void{
		let b2Contact=contact["_b2contact"];
		
		//所有设置contact.disabled的代码写在此处
		
		//检测落地(不在onBeginContact中写，因为设置contact.disabled时会导致出错)
		let index=this._onGroundB2Contacts.indexOf(b2Contact);
		if(index<0){
			if(!contact.disabled&&!contact.disabledOnce&&!otherCollider.sensor&&contact.isTouching()){
				let ny=-contact.getWorldManifold().normal.y;
				if(ny>0.7){
					this._onGroundB2Contacts.push(b2Contact);
					if(this._isInAir){
						this._isInAir=false;
						//落地时
						this.onDropGround();
					}
				}
			}
		}
	}
	
	private onEndContact(contact:cc.PhysicsContact,selfCollider:cc.PhysicsCollider,otherCollider:cc.PhysicsCollider):void{
		let b2Contact=contact["_b2contact"];
		let index=this._onGroundB2Contacts.indexOf(b2Contact);
		if(index>-1)this._onGroundB2Contacts.splice(index,1);
		if(this._onGroundB2Contacts.length<=0){
			if(!this._isInAir){
				this._isInAir=true;
				//离开地面时
				this.onLeaveGround();
			}
		}

	}
	
	private onDropGround():void{
	
	}
	
	private onLeaveGround():void{
	
	}
}