cocos-js button点击事件

/**
 * Created by Tomas on 2017/4/5.
 */
var  MyLayer=cc.Layer.extend({
    _topDisplayLabel:null,
    ctor:function()
    {
        this._super();
        var button =new ccui.Button();
        button.x=size.width/2;
        button.y=size.height/2;
        button.loadTextures(res.HelloWorld_png,res.HelloWorld_png);
        button.addTouchEventListener(this.touchEvent, this);
        this.addChild(button);

        this._topDisplayLabel=new cc.LabelTTF("this is a button test","Arial",32);
        this._topDisplayLabel.x=size.width/2;
        this._topDisplayLabel.y=size.height/2+50;
        this.addChild(this._topDisplayLabel,5);
    },
    touchEvent: function (sender, type) {
        switch (type) {
            case ccui.Widget.TOUCH_BEGAN:
                this._topDisplayLabel.setString("Touch Down");
                break;

            case ccui.Widget.TOUCH_MOVED:
                this._topDisplayLabel.setString("Touch Move");
                break;

            case ccui.Widget.TOUCH_ENDED:
                this._topDisplayLabel.setString("Touch Up");
                break;

            case ccui.Widget.TOUCH_CANCELED:
                this._topDisplayLabel.setString("Touch Cancelled");
                break;
            default:
                break;
        }
    }
});
var myscene=cc.Scene.extend({
    onEnter:function () {
        this._super();
        var layer=new MyLayer();
        this.addChild(layer);
    }
});