我无法从 api 获取所有数据

Question

我想以帖子的形式显示我从 Web Api 收到的一些数据，大部分数据正常显示在屏幕上，但突然出现错误，所有剩余的帖子都变成红色。

我得到的错误：

The following NoSuchMethodError was thrown building:
The method '[]' was called on null.
Receiver: null
Tried calling: [](0)

When the exception was thrown, this was the stack
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1      _NewsScreenState.build.<anonymous closure>.<anonymous closure>
#2      SliverChildBuilderDelegate.build
package:flutter/…/widgets/sliver.dart:449
#3      SliverMultiBoxAdaptorElement._build
package:flutter/…/widgets/sliver.dart:1130
#4      SliverMultiBoxAdaptorElement.performRebuild.processElement
package:flutter/…/widgets/sliver.dart:1076

我如何显示帖子的方式：

import 'package:flutter/material.dart';

class NewsFrame extends StatelessWidget {
  final String title;
  final String excerpt;
  final String webUrl;
  final String imageUrl;
  final String publishedDateTime;
  final String sourceName;

  const NewsFrame(
      {this.title,
      this.excerpt,
      this.webUrl,
      this.imageUrl,
      this.publishedDateTime,
      this.sourceName});

  String formatTime(String receivedDate) {
    String date = receivedDate.substring(0, 11);
    return "${date.substring(0, 4)}/${date.substring(5, 7)}/${date.substring(8, date.length-1)}";
  }

  void delayedMomemt() async {
    await Future.delayed(Duration(milliseconds: 200));
    print(this.title);
    print(this.excerpt);
    print(this.webUrl);
    print(this.publishedDateTime);
    print(this.imageUrl);
    print(this.sourceName);
  }

  @override
  Widget build(BuildContext context) {
    this.delayedMomemt();
    return Container(
      decoration: BoxDecoration(color: Colors.green),
      padding: const EdgeInsets.all(8),
      margin: const EdgeInsets.all(8),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Text(this.title),
          this.imageUrl == null
              ? SizedBox(height: 0)
              : Image.network(this.imageUrl),
          Text(this.excerpt),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Text(this.publishedDateTime == null
                  ? "No Date"
                  : this.formatTime(this.publishedDateTime)),
              Text(this.sourceName ?? "Unknown")
            ],
          )
        ],
      ),
    );
  }
}

我如何将数据发送到帖子文件：

class NewsScreen extends StatefulWidget {
  @override
  _NewsScreenState createState() => _NewsScreenState();
}

class _NewsScreenState extends State<NewsScreen> {
  var articalsData;

  @override
  void initState() {
    super.initState();
    GetData getData = GetData();
    this.articalsData = getData.getArticals();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: ThmColors.lightBlueClr,
      body: Stack(
        children: [
          FadedBg(img: "img21"),
          Center(
            child: FutureBuilder(
              future: this.articalsData,
              builder: (context, snapshot) {
                if (snapshot.hasData) {
                  return Column(
                    children: [
                      SizedBox(height: MediaQuery.of(context).size.height / 6),
                      Expanded(
                        child: ListView.builder(
                          itemCount: snapshot.data['news'].length,
                          itemBuilder: (context, index) => NewsFrame(
                            title: snapshot.data['news'][index]['title'],
                            excerpt: snapshot.data['news'][index]['excerpt'],
                            webUrl: snapshot.data['news'][index]['webUrl'],
                            imageUrl: snapshot.data['news'][index]['images'][0]['url'],
                            publishedDateTime: snapshot.data['news'][index]['publishedDateTime'],
                            sourceName: snapshot.data['news'][index]['provider']['name'],
                          ),
                        ),
                      ),
                    ],
                  );
                } else if (snapshot.hasError) {
                  return Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      Text('Oops! something went wrong.',
                          style: TextStyle(
                            fontSize: 20,
                            fontWeight: FontWeight.bold,
                          )),
                      Text('(Check out your: Signal, Internet, WiFi...)',
                          style: TextStyle(
                              fontSize: 15,
                              fontWeight: FontWeight.w500,
                              letterSpacing: -0.5)),
                    ],
                  );
                }
                return LoadingRing();
              },
            ),
          ),
          Positioned(
            top: 0,
            child: UpperBar(titleTxt: "News"),
          ),
        ],
      ),
    );
  }
}

请帮忙！

Answer 1

看起来不是每篇文章都有一个图像数组，在获取第一张图像之前尝试检查它是否为空，如果它提供了某种默认图像。像这样的：

imageUrl: getImage(snapshot.data['news'][index])
...

String getImage(data){
 if (data['images'] == null || data['images'].isEmpty)
    return 'default_image_url'
 return data['images'][0]['url']
}