samples/add_to_app/books/flutter_module_books/lib/main.dart

// Copyright 2020 The Flutter team. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter_module_books/api.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primaryColor: const Color(0xff6200ee),
        useMaterial3: true,
      ),
      home: const BookDetail(),
    );
  }
}

typedef BookReceived = void Function(Book book);

class FlutterBookApiHandler extends FlutterBookApi {
  FlutterBookApiHandler(this.callback);

  final BookReceived callback;

  @override
  void displayBookDetails(Book book) {
    callback(book);
  }
}

class BookDetail extends StatefulWidget {
  const BookDetail({super.key, this.hostApi, this.flutterApi, this.book});

  // These are the outgoing and incoming APIs that are here for injection for
  // tests.
  final HostBookApi? hostApi;
  final FlutterBookApi? flutterApi;
  final Book? book;

  @override
  State<BookDetail> createState() => _BookDetailState();
}

class _BookDetailState extends State<BookDetail> {
  Book? book;

  late HostBookApi hostApi;

  FocusNode textFocusNode = FocusNode();
  TextEditingController titleTextController = TextEditingController();
  TextEditingController subtitleTextController = TextEditingController();
  TextEditingController authorTextController = TextEditingController();

  @override
  void initState() {
    super.initState();
    book = widget.book;

    // This `HostBookApi` class instance lets us make outgoing calls to the
    // platform.
    hostApi = widget.hostApi ?? HostBookApi();

    // Registering this `FlutterBookApiHandler` class lets us receive incoming
    // calls from the platform.
    // TODO(gaaclarke): make the setup method an instance method so it's
    // injectable https://github.com/flutter/flutter/issues/59119.
    FlutterBookApi.setup(FlutterBookApiHandler(
        // The `FlutterBookApi` just has one method. Just give a closure for that
        // method to the handler class.
        (book) {
      setState(() {
        // This book model is what we're going to return to Kotlin eventually.
        // Keep it bound to the UI.
        this.book = book;
        titleTextController.text = book.title ?? '';
        titleTextController.addListener(() {
          this.book!.title = titleTextController.text;
        });
        // Subtitle could be null.
        // TODO(gaaclarke): https://github.com/flutter/flutter/issues/59118.
        subtitleTextController.text = book.subtitle ?? '';
        subtitleTextController.addListener(() {
          this.book!.subtitle = subtitleTextController.text;
        });
        authorTextController.text = book.author ?? '';
        authorTextController.addListener(() {
          this.book!.author = authorTextController.text;
        });
      });
    }));
  }

  // Not overriding didUpdateWidget because the Android program can't change
  // the book given to Flutter on the Android side.

  void clear() {
    book = null;
    // Keep focus if going to the home screen but unfocus if leaving
    // the activity.
    textFocusNode.unfocus();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Book Details'),
        leading: IconButton(
          icon: const Icon(Icons.clear),
          // Pressing clear cancels the edit and leaves the activity without
          // modification.
          onPressed: () {
            hostApi.cancel();
            clear();
          },
        ),
        actions: [
          IconButton(
            icon: const Icon(Icons.check),
            // Pressing save sends the updated book to the platform.
            onPressed: book != null
                ? () {
                    hostApi.finishEditingBook(book!);
                    clear();
                  }
                : null,
          ),
        ],
      ),
      body: book == null
          // Draw a spinner until the platform gives us the book to show details
          // for.
          ? const Center(child: CircularProgressIndicator())
          : BookForm(
              book: book!,
              focusNode: textFocusNode,
              authorTextController: authorTextController,
              subtitleTextController: subtitleTextController,
              titleTextController: titleTextController,
            ),
    );
  }
}

class BookForm extends StatelessWidget {
  const BookForm({
    super.key,
    required this.book,
    required this.focusNode,
    required this.authorTextController,
    required this.subtitleTextController,
    required this.titleTextController,
  });

  final Book book;
  final FocusNode focusNode;
  final TextEditingController titleTextController;
  final TextEditingController subtitleTextController;
  final TextEditingController authorTextController;

  @override
  Widget build(BuildContext context) {
    return Focus(
      focusNode: focusNode,
      child: ListView(
        padding: const EdgeInsets.all(24),
        children: [
          TextField(
            controller: titleTextController,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              filled: true,
              hintText: "Title",
              labelText: "Title",
            ),
          ),
          const SizedBox(height: 24),
          TextField(
            controller: subtitleTextController,
            maxLines: 2,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              filled: true,
              hintText: "Subtitle",
              labelText: "Subtitle",
            ),
          ),
          const SizedBox(height: 24),
          TextField(
            controller: authorTextController,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              filled: true,
              hintText: "Author",
              labelText: "Author",
            ),
          ),
          const SizedBox(height: 32),
          const Divider(),
          Center(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Text(
                  '${book.pageCount} pages  ~  published ${book.publishDate}'),
            ),
          ),
          const Divider(),
          const SizedBox(height: 32),
          if (book.thumbnail?.url != null) ...[
            Center(
              child: Image.network(book.thumbnail!.url!),
            ),
            const SizedBox(height: 32),
          ],
          if (book.summary != null) ...[
            const Center(
              child: Text(
                'BOOK DESCRIPTION',
                style: TextStyle(
                  fontSize: 15,
                  fontWeight: FontWeight.bold,
                  decoration: TextDecoration.underline,
                ),
              ),
            ),
            const SizedBox(height: 12),
            Text(
              book.summary ?? '',
              style: TextStyle(color: Colors.grey.shade600, height: 1.24),
            ),
          ]
        ],
      ),
    );
  }
}