未处理的异常NoSuchMethodError：方法'[]'在flutter中被调用为null答案

【问题标题】：Unhandled Exception NoSuchMethodError: The method '[]' was called on null in flutter未处理的异常NoSuchMethodError：方法'[]'在flutter中被调用为null
【发布时间】：2020-12-26 12:14:51
【问题描述】：

Code根据控制台指出的行表示有错误的代码行

错误显示在三个部分。第一个：

新的 FlickrPhotoList.fromJson (package:flutter_app_new_flutter/flickerPhotoList.dart:22:26)

 import 'package:flutter_app_new_flutter/model.dart';

class FlickrPhotoList {
  int page;
  int pages;
  int perpage;
  int total;
  List<FlickrPhoto> photo;

  FlickrPhotoList({
    this.page,
    this.pages,
    this.perpage,
    this.total,
    this.photo
  });

  factory FlickrPhotoList.fromJson(Map<String, dynamic> parsedJson) {

    var list = parsedJson['photo'] as List;
    List<FlickrPhoto> photoList = list.map((i) => FlickrPhoto.fromJson(i)).toList();

    return FlickrPhotoList(
        page: parsedJson['page'],
        pages: parsedJson['pages'],
        perpage: parsedJson['perpage'],
        total: parsedJson['total'],
        photo: photoList);
  }
}

第二个错误如下所示：

新的 FlickrResult.fromJson (package:flutter_app_new_flutter/flickerResult.dart:15:37)

import 'package:flutter_app_new_flutter/flickerPhotoList.dart';

    class FlickrResult {
      FlickrPhotoList photos;
      String stat;
    
      FlickrResult({
        this.photos,
        this.stat
      });
    
      factory FlickrResult.fromJson(Map<dynamic, dynamic> parsedJson) {
    
        var photoList = FlickrPhotoList.fromJson(parsedJson['photos']);
    
        return FlickrResult(
            photos: photoList,
            stat: parsedJson['stat']
        );
      }
    }

这是第三个错误：

_SearchState.getSearchWallpapers。（包：flutter_app_new_flutter/search.dart:47:33）

getSearchWallpapers(String query) async{

    String requestUrl = "https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=b099758ce0d1e1bf8697f8491f7fb5fc&format=json&nojsoncallback=1&safe_search=1&text=$query";
    var file = await DefaultCacheManager().getSingleFile(requestUrl);
    http.Response response = await http.get(requestUrl);
    String lines = await file.readAsString();


    setState(() {
      Map userMap = jsonDecode(lines);
      flickrData = FlickrResult.fromJson(userMap);
      resultsCount = flickrData.photos.photo.length;
    });
  }

【问题讨论】：

标签： flutter dart

【解决方案1】：

昨天发生在我身上的不是某个网站，我通过返回带有标题的响应来修复它。 No such Method 错误的错误是当您的模型与网站的 API 响应不匹配或服务器未提供您的请求示例时，这是错误

return FlickrPhotoList(
        page: parsedJson['page'],

检查 parsedJson 是否提供“页面”；所以首先向邮递员或任何人提出请求并阅读您的 API 响应。

当我们改进时，第二个将起作用对于第三个，请同时发布 search.dart

【讨论】：