[]图集打包后使用Texture不显示啊

{
"frames": {
"sg.png": {
"frame": {
"x": 0,
"y": 0,
"w": 300,
"h": 300,
"idx": 0
},
"spriteSourceSize": {
"x": 0,
"y": 0,
"w": 300,
"h": 300
},
"sourceSize": {
"w": 300,
"h": 300
},
"rotated": false,
"trimed": true
},
"sg2.png": {
"frame": {
"x": 302,
"y": 0,
"w": 290,
"h": 300,
"idx": 0
},
"spriteSourceSize": {
"x": 10,
"y": 0,
"w": 290,
"h": 300
},
"sourceSize": {
"w": 300,
"h": 300
},
"rotated": false,
"trimed": true
},
"sg3.png": {
"frame": {
"x": 0,
"y": 302,
"w": 290,
"h": 258,
"idx": 0
},
"spriteSourceSize": {
"x": 10,
"y": 24,
"w": 290,
"h": 258
},
"sourceSize": {
"w": 300,
"h": 300
},
"rotated": false,
"trimed": true
}
},
"meta": {
"app": "http:\/\/www.layabox.com",
"version": "0.1.0 alpha",
"format": "json",
"scale": 1,
"image": "start.png",
"prefix": "start\/"
}
}

=============================================================

// 程序入口
import Loader = Laya.Loader;
import Texture = Laya.Texture;
import Handler = Laya.Handler;

class GameMain{
constructor()
{
Laya.init(1080,1321);

//设置适配模式
Laya.stage.scaleMode = "showall";
//设置剧中对齐
Laya.stage.alignH = "center";
//设置横竖屏
//Laya.stage.screenMode = "vertical";

var texture:Texture = Laya.loader.getRes("start/sg.png");
var sp = new Laya.Sprite();
sp.graphics.drawTexture(texture,300,300);

Laya.stage.addChild(sp);

var ani: Laya.Animation = new Laya.Animation();
ani.loadAtlas("res/start.json"); // 加载图集动画
ani.interval = 30; // 设置播放间隔（单位：毫秒）
ani.index = 1; // 当前播放索引
ani.play(); // 播放图集动画

//Laya.stage.addChild(ani); //动画正常显示 文件路径都正常
}

private init(): void {
var assets: Array<any> = ;
assets.push({ url: "res/start.json", type: Loader.ATLAS});

Laya.loader.load(assets, Handler.create(this, this.onComplete));
}

private onComplete(): void {

}
}
new GameMain();
 
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json文件和代码都贴上来了