如何修复'NoSuchMethodError：getter'length'被调用为null'

Question

我该如何解决这个问题 我使用函数从 api 获取数据，但我看到错误 'NoSuchMethodError: The getter 'length' was called on null'

我的代码：

Future getData() async{
http.Response response = await http.get('https://myappres.000webhostapp.com/pubg/api.php?action=getskin');
debugPrint(response.body);

_data = json.decode(response.body);
_list = _data['categorys'];

return _list;                                                               
}

和

 Center(
          child: _list.length != null? ListView.builder(
              itemCount: _list.length,
              padding: const EdgeInsets.all(15.9),
              itemBuilder: (BuildContext context, int position){
                final index = position;
                return ListTile(
                    title: Text('${_list[index]['name']}'),
                    subtitle: Image.network('${_list[index]['image']}',width: 200,)
                );
              }
          ):Container()
        )

这是结果错误：

Answer 1

尝试使用 FutureBuilder 等待 Future：

FutureBuilder(
      future: getData(),
      builder: (BuildContext context,AsyncSnapshot<List> snapshot){
        if(snapshot.hasData){
           return Center(child: snapshot.length)
        } else return Container();
      },

//you can use too:
getData().then((listData){
      Center(child: listData)...
});