[LayaAir2]多指触摸在电脑上检测不出来，理论上要检测出来才对的！

import Input3D = Laya.Input3D;

import Vector2 = Laya.Vector2;



/**

 * 手指。

 */

export class Finger {

    public id: number = 0;  

    public position: Vector2 = new Vector2();

    public deltaPosition: Vector2 = new Vector2();



    constructor(id?: number) {

        if (id != undefined) {

            this.id = id;

        }

    }

}



/**

 * 触摸监听者接口。

 */

export interface ITouchListener {

    onTouchDown(finger: Finger);

    onTouchSwipe(finger: Finger);

    onTouchUp(finger: Finger);

}



/**

 * 多点触摸。

 */

export class Touch {



    private input: Input3D;



    private touchCount: number = 0;



    private touches: Map<number, Laya.Touch> = new Map<number, Laya.Touch>();

    private oldTouches: Map<number, Laya.Touch> = new Map<number, Laya.Touch>();

    private fingers: Map<number, Finger> = new Map<number, Finger>();



    private listener: ITouchListener;



    constructor(input: Input3D) {

        this.input = input;



        if (Laya.Browser.onPC) {



        }

    }



    dispose() {

        if (Laya.Browser.onPC) {

            

        }

    }



    public setListener(listener: ITouchListener) {

        this.listener = listener;

    }



    /** 帧更新函数中调用。 */

    public update() {

        this.touchCount = this.input.touchCount();   // 这个在 PC 上永远是 0。



        // copy touches.

        if (this.oldTouches.size > 0) {

            this.oldTouches.clear();

        }

        for (let [key, value] of this.touches) {

            this.oldTouches.set(key, value);

        }



        // reset touches.

        if (this.touches.size > 0) {

            this.touches.clear();

        }



        // get touches.

        for (let i = 0; i < this.touchCount; ++i) {

            let touch = this.input.getTouch(i);

            // this.touches.set(touch.identifier, touch); // iOS 上是一个不确定的很小的负数，并不是0开始的，且每点击一次都会-1，所以有问题。

            this.touches.set(i, touch);

        }



        // fingers gesture.

        for (let [key, value] of this.touches) {

            // get finger.

            let finger = this.fingers.get(key)

            if (finger == undefined) {

                finger = new Finger();

                finger.id = key;

                this.fingers.set(key, finger);

            }



            if (this.oldTouches.has(key)) {

                // downing.

                finger.deltaPosition.x = value.position.x - finger.position.x;

                finger.deltaPosition.y = value.position.y - finger.position.y;

                finger.position.x = value.position.x;

                finger.position.y = value.position.y;



                if (finger.deltaPosition.x != 0 || finger.deltaPosition.y != 0) {

                    // console.log("Swipe", key, Date.now());

                    if (this.listener) this.listener.onTouchSwipe(finger);

                }

            }

            else {

                // down start.               

                finger.deltaPosition.x = 0;

                finger.deltaPosition.y = 0;

                finger.position.x = value.position.x;

                finger.position.y = value.position.y;



                // console.log("Down", key);

                if (this.listener) this.listener.onTouchDown(finger);

            }

        }



        for (let key of this.oldTouches.keys()) {

            if (!this.touches.has(key)) {

                // up.

                // console.log("Up", key); 

                if (this.listener) this.listener.onTouchUp(this.fingers.get(key));

            }

        }

    }



}