Android 为以下json建议未来的构建器方法

我获取的API返回的json值如下所示。我编写了以下代码来提取数据，如果我像这样编写代码并构建小部件，它会工作，但在小部件加载之前会出现此错误

{
"totalHits": 500,
"hits": [
{
"largeImageURL": "https://pixabay.com/get/52e3d6414352af14f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_1280.jpg",
"webformatHeight": 424,
"webformatWidth": 640,
"likes": 11,
"imageWidth": 4456,
"id": 4332903,
"user_id": 1151065,
"views": 697,
"comments": 14,
"pageURL": "https://pixabay.com/photos/evangelion-mech-unit-02-robot-4332903/",
"imageHeight": 2958,
"webformatURL": "https://pixabay.com/get/52e3d6414352af14f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_640.jpg",
"type": "photo",
"previewHeight": 99,
"tags": "evangelion mech unit 02, robot, fighter",
"downloads": 311,
"user": "vinsky2002",
"favorites": 0,
"imageSize": 878944,
"previewWidth": 150,
"userImageURL": "https://cdn.pixabay.com/user/2019/05/15/02-40-06-911_250x250.png",
"previewURL": "https://cdn.pixabay.com/photo/2019/07/12/13/44/evangelion-mech-unit-02-4332903_150.jpg"
},
{
"largeImageURL": "https://pixabay.com/get/55e7d54b4d51a514f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_1280.jpg",
"webformatHeight": 359,
"webformatWidth": 640,
"likes": 18,
"imageWidth": 3863,
"id": 3708739,
"user_id": 10248012,
"views": 2696,
"comments": 2,
"pageURL": "https://pixabay.com/photos/sky-dark-night-moon-moonlight-3708739/",
"imageHeight": 2170,
"webformatURL": "https://pixabay.com/get/55e7d54b4d51a514f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_640.jpg",
"type": "photo",
"previewHeight": 84,
"tags": "sky, dark, night",
"downloads": 1036,
"user": "Sritam_kumar_Sethy",
"favorites": 25,
"imageSize": 2027189,
"previewWidth": 150,
"userImageURL": "https://cdn.pixabay.com/user/2019/09/28/19-27-53-806_250x250.jpeg",
"previewURL": "https://cdn.pixabay.com/photo/2018/09/28/08/37/sky-3708739_150.jpg"
},
{
"largeImageURL": "https://pixabay.com/get/57e2dc4a4c5aaf14f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_1280.jpg",
"webformatHeight": 360,
"webformatWidth": 640,
"likes": 14,
"imageWidth": 4608,
"id": 1299683,
"user_id": 1151065,
"views": 2932,
"comments": 3,
"pageURL": "https://pixabay.com/photos/panda-z-panda-toy-children-child-1299683/",
"imageHeight": 2592,
"webformatURL": "https://pixabay.com/get/57e2dc4a4c5aaf14f6da8c7dda79367b153fdee254506c4870277bd3934ec45ebf_640.jpg",
"type": "photo",
"previewHeight": 84,
"tags": "panda-z, panda, toy",
"downloads": 1067,
"user": "vinsky2002",
"favorites": 7,
"imageSize": 1745060,
"previewWidth": 150,
"userImageURL": "https://cdn.pixabay.com/user/2019/05/15/02-40-06-911_250x250.png",
"previewURL": "https://cdn.pixabay.com/photo/2016/04/01/09/56/panda-z-1299683_150.jpg"
},
],
"total": 588
}

Future getJsonData（）异步{
var反应；
对于（int i=1；我向我们展示了您如何为
小部件
构建编写。我认为您正在尝试在数据准备好显示之前循环
项
。@JohnJoe这是小部件的代码@sunku7是。有什么解决方案吗？请尝试将
itemCount:40
值改为
itemCount:item.count
<代码>开关

小部件

Future getJsonData() async{
 var response;
 for(int i=1; i<=5; i++){
  response = await http.get(
   Uri.encodeFull(widget.api+i.toString()),
   headers: {"Accept": "application/json"}
  );
  setState(() {
   var toJsonData = json.decode(response.body);
   item.addAll(toJsonData['hits']);
  });
 }
 print(response.body);
 return item;
}