laya3d 下不能显示UI

漏东西了。对比demo。

 
import Handler = laya.utils.Handler;
import Loader = laya.net.Loader;
import UI_mainwin=BlueSkin.UI_mainwin;
// 程序入口
class LayaAir3D {
    private mainwin2D ;
    constructor() {
        Laya3D.init(0, 0, true);
        laya.utils.Stat.show(0, 0);
        Laya.stage.scaleMode = Laya.Stage.SCALE_FULL;
        Laya.stage.alignH = "left";
        Laya.stage.alignV = "top";
        Laya.stage.screenMode = "horizontal";
        //开启统计信息
        Laya.Stat.show();
        //添加3D场景
         var scene = Laya.Scene.load("res/scene/LayaScene_cz2/cz2.ls");
         Laya.stage.addChild(scene);
         //添加2D UI
         Laya.loader.load([
            { url: "res/BlueSkin@atlas0.png", type: Loader.IMAGE },
            { url: "res/BlueSkin.fui", type: Loader.BUFFER }
        ], Handler.create(this, this.onLoaded));
    }
     onLoaded(): void {
        this.mainwin2D = Laya.stage.addChild(fairygui.GRoot.inst.displayObject);
        this.mainwin2D.pos(0.5, 0.5);
        fairygui.UIPackage.addPackage("res/BlueSkin");
        fairygui.UIConfig.defaultFont = "宋体";
        var mainui=new UI_mainwin();
        Laya.timer.frameLoop(1, this, this.animate);
    }
    private animate(): void {
        this.mainwin2D.pos(0.5, 0.5);
    }
}
new LayaAir3D();
 
我对比了DEMO，应该没有漏啊

如果 把  
Laya.stage.scaleMode = Laya.Stage.SCALE_FULL;
 换成DEMO里面的
Laya.stage.scaleMode = "showall";
就什么都不显示了，白屏