addScrollHandler : function(target){
    let isDrag = false; //判断是否滑动的标识
    let startY , endY , startTime , endTime;
    const box = target.getByName('box');
    box.inputEnabled = true;
    box.input.enableDrag();
    box.input.allowHorizontalDrag = false;  //禁止横向拖拽
    box.input.allowVerticalDrag = true;     //允许纵向拖拽
    box.ignoreChildInput = true;            //忽略子元素事件
    box.input.dragDistanceThreshold = 10;       //滑动阈值
    //允许滑动到底部的最高值
    const maxBoxY = -(box.height - 350);       
    //给父元素添加物理引擎
    customGame.physics.arcade.enable(box);

    box.events.onDragUpdate.add(function(){
        //滑到顶部，禁止继续往下滑
        if(box.y > 100){
            box.y = 100;
        }else if(box.y < maxBoxY - 100){
            //滑到底部，禁止继续往上滑
            box.y = maxBoxY - 100;
        }
        endY = arguments[3];
        endTime = +new Date();
    } , this);
    box.events.onDragStart.add(function(){
        isDrag = true;
        startY = arguments[3];
        startTime = +new Date();
        if(this.currentScrollBox){
            //如果当前有其他正在滑动的元素，取消滑动
            this.currentScrollBox.body.velocity.y = 0;
            this.currentScrollBox = null;
        }
        
    } , this);
    box.events.onDragStop.add(function(){
        isDrag = false;
        //指定可以点击滑动的区域
        box.hitArea = new Phaser.Rectangle(0,-box.y,box.width,box.height + box.y);
        //向下滑动到极限，给极限到最值位置动画
        if(box.y > 0){
            box.hitArea = new Phaser.Rectangle(0, 0 , box.width , box.height);
            customGame.add.tween(box).to({ y : 0} , 100 , Phaser.Easing.Linear.None, true , 0 , 0);
            return;
        }
        //向上滑动到极限，给极限到最值位置动画
        if(box.y < maxBoxY){
            box.hitArea = new Phaser.Rectangle(0, -maxBoxY , box.width , box.height - maxBoxY);
            customGame.add.tween(box).to({ y : maxBoxY} , 100 , Phaser.Easing.Linear.None , true , 0, 0);
            return;
        }
        //模拟滑动停止父元素仍滑动到停止的惯性
        //根据用户的滑动距离和滑动事件计算元素的惯性滑动速度
        const velocity = (Math.abs(Math.abs(endY) - Math.abs(startY)) / (endTime - startTime)) * 40;
        //scrollFlag标识父元素是向上滑动还是向下滑动
        if(endY > startY){// 向下
            box.body.velocity.y = velocity;
            box.scrollFlag = 'down';
        }else if(endY < startY){ //向上
            box.body.velocity.y = -velocity;
            box.scrollFlag = 'up';
        }   
        this.currentScrollBox = box;         
    } , this);
    box.events.onInputUp.add(function(e , p ){
        if(isDrag) return;

        const curX = p.position.x - e.previousPosition.x;
        const curY = p.position.y - e.previousPosition.y;
        //根据点击区域，判断用户点击的是哪个元素
        const idx = e.wrapData.findIndex((val , index , arr) => {
            return curX >= val.minX && curX <= val.maxX && curY >= val.minY && curY <= val.maxY;
        })
        if(idx == -1) return;
        const children = e.children[idx];
        //添加新元素到画面
        this.addNewMobilityObject(children.key , children._frame.name);
    } , this);
},
dealScrollObject : function(){
    if(this.currentScrollBox && this.currentScrollBox.body.velocity.y !== 0){
        const currentScrollBox = this.currentScrollBox,
                height = currentScrollBox.height,
                width = currentScrollBox.width;

        const maxBoxY = -(height - 350);
        if(currentScrollBox.y > 0){
            currentScrollBox.hitArea = new Phaser.Rectangle(0, 0 , width , height);
            customGame.add.tween(currentScrollBox).to({ y : 0} , 100 , Phaser.Easing.Linear.None, true , 0 , 0);
            currentScrollBox.body.velocity.y = 0;
            return;
        }
        if(currentScrollBox.y < maxBoxY){
            currentScrollBox.hitArea = new Phaser.Rectangle(0, -maxBoxY , width , height - maxBoxY);
            customGame.add.tween(currentScrollBox).to({ y : maxBoxY} , 100 , Phaser.Easing.Linear.None , true , 0, 0);
            currentScrollBox.body.velocity.y = 0;
            return;
        }
        currentScrollBox.hitArea = new Phaser.Rectangle(0,-currentScrollBox.y,width,height + currentScrollBox.y);
        if(currentScrollBox.scrollFlag == 'up'){
            currentScrollBox.body.velocity.y += 1.5;
            if(currentScrollBox.body.velocity.y >= 0){
                currentScrollBox.body.velocity.y = 0;
            }
        }else if(currentScrollBox.scrollFlag == 'down'){
            currentScrollBox.body.velocity.y -= 1.5;
            if(currentScrollBox.body.velocity.y <= 0){
                currentScrollBox.body.velocity.y = 0;
            }
        }
    }
},
update : function(){
    this.dealScrollObject();
}

addNewMobilityObject : function(){
    ...
    //绑定选中元素
    this.bindObjectSelected(newOne);
    //让新建元素成为当前选中元素
    this.objectSelected(newOne);
},
bindObjectSelected : function(target){
    target.inputEnabled = true;
    target.input.enableDrag(false , true);
    //绘制编辑框
    target.events.onDragStart.add(this.objectSelected , this ); 
},
objectSelected : function(e, p){
    if(e.name == 'wall' || e.name == this.selectedObject) return;
    //如果点击的元素是当前选中元素，则不进行任何操作
    if(this.selectWrap && e.keyNum == this.selectWrap.keyNum) return;
    //去掉当前选中元素状态
    this.deleteCurrentWrap();

    const offsetNum = 10 , 
            width = e.width,
            height = e.height, 
            offsetX = -width/2 ,
            offsetY = -height / 2,
            boxWidth = width + 2*offsetNum , 
            boxHeight = height + 2*offsetNum; 
    
    const dashLine = customGame.add.bitmapData(width + 2*offsetNum , height + 2*offsetNum);
    const wrap = customGame.add.image(e.x + offsetX - offsetNum, e.y + offsetY - offsetNum, dashLine)
    wrap.name = 'wrap';
    wrap.keyNum = e.keyNum;

    //绘制虚线
    dashLine.ctx.shadowColor = '#a93e26';
    dashLine.ctx.shadowBlur = 20;
    dashLine.ctx.beginPath();
    dashLine.ctx.lineWidth = 6;
    dashLine.ctx.strokeStyle = 'white';
    dashLine.ctx.setLineDash([12 , 12]);
    dashLine.ctx.moveTo(0,0);
    dashLine.ctx.lineTo(boxWidth , 0);
    dashLine.ctx.lineTo(boxWidth , boxHeight);
    dashLine.ctx.lineTo(0 , boxHeight);
    dashLine.ctx.lineTo(0,0);
    dashLine.ctx.stroke();
    dashLine.ctx.closePath();
    wrap.bitmapDatas = dashLine;

    //删除按钮
    const close = customGame.add.sprite(- 27, -23,'objects','close.png');
    close.inputEnabled = true;
    close.events.onInputDown.add(this.deleteObject , this , null , e , e._frame.name);
    wrap.addChild(close);
    //放大按钮
    const scale = customGame.add.sprite(boxWidth - 27 , -23 , 'objects' , 'scale.png');
    scale.inputEnabled = true;
    scale.events.onInputDown.add(function(ev , pt){
        //判断用户是否要缩放元素
        this.isOnTarget = true;
        this.onScaleTarget = e;
        this.onScaleTargetValue = e.scale.x;
    } , this);
    
    wrap.addChild(scale);
    this.selectWrap = wrap;
},