How to fix the Exception Error in flutter book app? - json

Question

I am creating a Books app in Flutter and I have an Exception in api.dart file which is working fine according to the code. But I am unable to fetch the books and their properties while using the google Books API. I can't figure out why the link is not working. I hope you can help me out. The api key is hidden but I've copied it right. This is the code:
api.dart
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'books.dart';
import 'package:books_app/config.dart';
class BooksApi {
Future<List<Book>> fetchBooks() async {
final response = await http.get(Uri.parse(
'https://www.googleapis.com/books/v1/volumes?key=$apiKey'));
if (response.statusCode == 200) {
// If the call to the API was successful, parse the JSON
List<dynamic> jsonResponse = jsonDecode(response.body)['items'];
return (jsonResponse.map((book) => Book.fromJson(book)).toList());
} else {
throw Exception('Failed to load books');
}
}
}
books.dart
class Book {
final String title;
final String author;
final String description;
final DateTime datePublished;
final String isbn;
final String imageUrl;
Book(
{required this.title,
required this.author,
required this.description,
required this.datePublished,
required this.isbn,
required this.imageUrl});
factory Book.fromJson(Map<String, dynamic> json) {
return Book(
title: json['volumeInfo']['title'],
author: json['volumeInfo']['author'][0],
description: json['volumeInfo']['description'],
datePublished: json['volumeInfo']['datePublished'],
isbn: json['volumeInfo']['ISBN'],
imageUrl: json['volumeInfo']['imageLinks']['thumbnail']);
}
}
main.dart
import 'package:books_app/api.dart';
import 'package:flutter/material.dart';
import 'books.dart';
final booksAPI = BooksApi();
void main() {
runApp(const MyApp());
}
class DisplayBooks extends StatefulWidget {
const DisplayBooks({super.key});
#override
State<DisplayBooks> createState() => _DisplayBooksState();
}
class _DisplayBooksState extends State<DisplayBooks> {
#override
Widget build(BuildContext context) {
return FutureBuilder<List<Book>>(
future: booksAPI.fetchBooks(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return ListView.builder(
itemCount: snapshot.data!.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(snapshot.data![index].title),
subtitle: Text(snapshot.data![index].author),
leading: Image.network(snapshot.data![index].imageUrl),
);
});
} else if (snapshot.hasError) {
return Text("${snapshot.error}");
}
return const CircularProgressIndicator();
},
);
}
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
home: const Scaffold(body: DisplayBooks()),
debugShowCheckedModeBanner: false,
title: 'BooksApp',
theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: Colors.black),
);
}
}
This is the response code:
response code

Answer 1

Your are missing the query in the api call for volumes. Because just calling volumes won't return anything. And your status, 400 is a "Bad Request" and that indicates that the server could not understand the requested call.
?q=query&
https://www.googleapis.com/books/v1/volumes?q=$query&key=$apiKey
So you need to pass in a query for to fetch all the books you want.
Google Books API just won't let you return all of their billions of books, you need to pass a query and narrow it down to languages, genre, etc.
Read more here, for what queries you can do
Google Books api query documentation
Then You need to pass the books into your model and make sure you're not missing any field or if a field can be missing make sure that field is then optional. And your DateTime should be string because the json you receive doesn't contain any DateTime objects so you need to convert that response into datetime in your code.