Question

我想从https://jsonplaceholder.typicode.com/posts调用json api，但是我的输出是“未来的实例”。

我显然希望正确的输出为1。检查链接以了解为什么应为1

getJson（）与输出位于不同的.dart文件（但相同的项目）中。我相信它工作正常（因为有输出）

import 'package:http/http.dart' as http;
import 'dart:convert';

Future<List> getJson() async {
  String apiURL = "https://jsonplaceholder.typicode.com/posts";

  http.Response response = await http.get(apiURL);
  return json.decode(response.body);
}

Future getData(int i, String place) async {
  List _data = await getJson();

  return _data[i][place];

}

那么输出是

Text("This is the output ${getData(0, "id")}"

这导致 "Instance of 'Future<dynamic>'"

Answer 1

您需要等待回复所以代替：

<div class="product_quantity_container">
                            <div class="product_quantity clearfix">
                                <span>Qty</span>
                                <input id="quantity_input" type="text" pattern="[0-9]*" value="1" name="quantity">
                                <div class="quantity_buttons">
                                    <div id="quantity_inc_button" class="quantity_inc quantity_control"><i class="fa fa-chevron-up" aria-hidden="true"></i></div>
                                    <div id="quantity_dec_button" class="quantity_dec quantity_control"><i class="fa fa-chevron-down" aria-hidden="true"></i></div>
                                </div>
                            </div>
                            <div class="button cart_button"><a type="submit" href="{% url 'online:cartitemcreate' pk=prod.pk %}">Add to cart</a></div>
                    </div

您需要这样做：

Text("This is the output ${getData(0, "id")}"

Answer 2

您可以将Text包裹在FutureBuilder内-这样：

FutureBuilder(builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
  if (snapshot.hasData) return Text("This is the output ${snapshot.data}");
  else return Text("There is no output yet");
}, future: getData(0, 'id'),);

不断从JSON输出中获取“'Future <dynamic>'的实例”

2 个答案: