flutter - 将 API 中的数据设置为变量 - Flutter

Question

所以我目前正在从模拟 api 获取一组数据，我试图将这些数据放入我创建的对象中，然后将其呈现在屏幕上。目前我已经从 API 获取数据，但是当我尝试将数据放入变量并打印结果时，它不起作用，但是当我在函数内部打印数据时它确实起作用调用数据（如下所示）。它还在页面的初始化（或状态，我不确定）上调用 Future 函数 (getUserFeed) - 这是当前代码：

class SocialPage extends StatefulWidget {
  final String argument;
  const SocialPage({Key key, this.argument}) : super(key: key);

  @override
  _SocialPageState createState() => _SocialPageState(argument);
}

  Future getUserFeed() async {
  final response = await http.get(
      'https://cartalkio-mock-api.s3.eu-west-2.amazonaws.com/textfeed.json');

  print(response.statusCode);

  if (response.statusCode == 200) {
    print(json.decode(response.body));
    return json.decode(response.body);
  } else {
    throw Exception('Failed to load album');
  }
}

class _SocialPageState extends State<SocialPage> {
  String argument;
  _SocialPageState(this.argument);
  Future feedData;

  setFeedData() {
    setState(() {
      feedData = getUserFeed();
    });
  }

  checkFeedData() {
    print(feedData);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: (FloatingActionButton(onPressed: () async {
        Navigator.pushNamed(context, SectionSelectRoute, arguments: argument);
      })),
      body: SafeArea(
        child: Column(
          children: <Widget>[
            FlatButton(
              onPressed: setFeedData,
              child: (Text('Set data')),
            ),
            FlatButton(
              onPressed: checkFeedData,
              child: (Text('Check data')),
            ),
          ],
        ),
      ),
    );
  }
}

这是我调用“checkFeedData”函数时返回的内容：

Instance of 'Future<dynamic>'

[编辑]

根据 P4yam 提供的答案，将其更改为：

Future<Map<String,dynamic>> getUserFeed() async {
  final response = await http.get(
      'https://cartalkio-mock-api.s3.eu-west-2.amazonaws.com/textfeed.json');

  if (response.statusCode == 200) {
    print(json.decode(response.body));
    return json.decode(response.body);
  } else {
    throw Exception('Failed to load album');
  }
}

class _SocialPageState extends State<SocialPage> {
  String argument;
  _SocialPageState(this.argument);
  Map<String,dynamic> feedData;

 setFeedData() async{
    feedData = await getUserFeed();
  }

  checkFeedData() {
    print(feedData);
  }

调用函数的按钮

        FlatButton(
          onPressed: setFeedData,
          child: (Text('Set data')),
        ),
        FlatButton(
          onPressed: checkFeedData,
          child: (Text('Check data')),
        ),

getUserFeed 函数打印来自 API 的实际数据，但是当我调用 checkFeedData 函数时，它打印 null。

[编辑 2]

功能

  setFeedData() async{
    feedData = await getUserFeed();
    print('-----------'); // It's not running this print function 
    print(feedData); // Dont think its running this function
  }

安慰

I/flutter ( 6245): 200
I/flutter ( 6245): [{id: 2, photoUrl: https://cartalkio-image-storage-dev.s3.eu-west-2.amazonaws.com/o85DvOaTXXE.jpg, description: Magna duis consectetur sit ut commodo non eiusmod., dateAdded: 0001-01-01T00:00:00, isMain: false, publicId: null, isImage: true, mainImage: https://randomuser.me/api/portraits/men/76.jpg, userId: 9, likers: null, username: Larsen, thumbnail: null, likes: 0}, {id: 4, photoUrl: https://cartalkio-image-storage-dev.s3.eu-west-2.amazonaws.com/lXR833PRh3g.jpg, description: Magna duis consectetur sit ut commodo non eiusmod., dateAdded: 0001-01-01T00:00:00, isMain: false, publicId: null, isImage: true, mainImage: https://randomuser.me/api/portraits/men/4.jpg, userId: 8, likers: null, username: Lloyd, thumbnail: null, likes: 0}, {id: 6, photoUrl: https://cartalkio-image-storage-dev.s3.eu-west-2.amazonaws.com/geTFl8b0m9M.jpg, description: Magna duis consectetur sit ut commodo non eiusmod., dateAdded: 0001-01-01T00:00:00, isMain: false, publicId: null, isImage: true, mainImage: https://randomuser.me/api/port
E/flutter ( 6245): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'FutureOr<Map<String, dynamic>>'
E/flutter ( 6245): #0      getUserFeed (package:TCS/social.dart:29:5)
E/flutter ( 6245): <asynchronous suspension>
E/flutter ( 6245): #1      _SocialPageState.setFeedData (package:TCS/social.dart:48:22)
E/flutter ( 6245): #2      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:779:19)
E/flutter ( 6245): #3      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:862:36)
E/flutter ( 6245): #4      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
E/flutter ( 6245): #5      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:504:11)
E/flutter ( 6245): #6      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:282:5)
E/flutter ( 6245): #7      BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:217:7)
E/flutter ( 6245): #8      PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:475:9)
E/flutter ( 6245): #9      PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:76:12)
E/flutter ( 6245): #10     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:122:9)
E/flutter ( 6245): #11     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8)
E/flutter ( 6245): #12     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:120:18)
E/flutter ( 6245): #13     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:106:7)
E/flutter ( 6245): #14     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:218:19)
E/flutter ( 6245): #15     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22)
E/flutter ( 6245): #16     GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
E/flutter ( 6245): #17     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
E/flutter ( 6245): #18     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
E/flutter ( 6245): #19     _rootRunUnary (dart:async/zone.dart:1196:13)
E/flutter ( 6245): #20     _CustomZone.runUnary (dart:async/zone.dart:1085:19)
E/flutter ( 6245): #21     _CustomZone.runUnaryGuarded (dart:async/zone.dart:987:7)
E/flutter ( 6245): #22     _invoke1 (dart:ui/hooks.dart:275:10)
E/flutter ( 6245): #23     _dispatchPointerDataPacket (dart:ui/hooks.dart:184:5)
E/flutter ( 6245): 

标签： flutterdart

Answer 1

首先更改feedData为：

List<dynamic> feedData;

然后更改Future getUserFeed()为：

Future<List<dynamic>> getUserFeed(){
...

并更改setFeedData为：

  setFeedData() async{
      feedData = await getUserFeed();
  }