cocos2djs json导出的动画

[coco4 (coco小菜鸟)]

ani = ccs.load(jsonfile);
ani.action.gotoFrameAndPlay(0,50,false);
ani.node.setPosition(cc.p(50,50));
ani.node.runAction(ani.action);
this.addChild(ani.node);

为啥显示不出动画。。