Add a pigeon sample that demonstrates a "realistic" integration scenario with middleware and business logic (#465)

add_to_app/README.md

@@ -10,11 +10,13 @@ standalone Flutter module.
   - Whether to build the Flutter module from source each time the app builds or
     rely on a separately pre-built module.
   - Whether plugins are needed by the Flutter module used in the app.
+* Show Flutter being integrated ergonomically with applications with existing
+  middleware and business logic data classes.
 
 ## Installing Cocoapods
 
 The iOS samples in this repo require the latest version of Cocoapods. To install
-it, run the following command on a MacOS machine:
+it, run the following command on a macOS machine:
 
 ```bash
 sudo gem install cocoapods
@@ -26,20 +28,26 @@ See https://guides.cocoapods.org/using/getting-started.html for more details.
 
 ### Flutter modules
 
-There are two Flutter modules included in the codebase:
+There are three Flutter modules included in the codebase:
 
 * `flutter_module` displays the dimensions of the screen, a button that
   increments a simple counter, and an optional exit button.
 * `flutter_module_using_plugin` does everything `flutter_module` does and adds
   another button that will open the Flutter documentation in a browser using the
   [`url_launcher`](https://pub.dev/packages/url_launcher) Flutter plugin.
+* `flutter_module_books` simulates an integration scenario with existing
+  platform business logic and middleware. It uses the [`pigeon`](https://pub.dev/packages/pigeon)
+  plugin to make integration easier by generating the platform channel
+  interop inside wrapper API and data classes that are shared between the
+  platform and Flutter.
+
 
 Before using them, you need to resolve the Flutter modules' dependencies. Do so
 by running this command from within the `flutter_module` and
 `flutter_module_using_plugin` directories:
 
 ```bash
-flutter packages get
+flutter pub get
 ```
 
 ### Android and iOS applications
@@ -139,6 +147,50 @@ Flutter frameworks, see this article in the Flutter GitHub wiki:
 
 https://flutter.dev/docs/development/add-to-app/ios/project-setup
 
+### `android_books` and `ios_books (TODO)`
+
+These apps integrate the `flutter_books` module using the simpler build-together
+project setup. They simulate a mock scenario where an existing book catalog
+list app already exists. Flutter is used to implement an additional book details
+page.
+
+* Similar to `android_fullscreen` and `ios_fullscreen`.
+* An existing books catalog app is already implemented in Kotlin and Swift.
+* The platform-side app has existing middleware constraints that should also
+  be the middleware foundation for the additional Flutter screen.
+    * On Android, the Kotlin app already uses GSON and OkHttp for networking and
+      references the Google Books API as a data source. These same libraries
+      also underpin the data fetched and shown in the Flutter screen.
+    * iOS TODO.
+* The platform application interfaces with the Flutter book details page using
+  idiomatic platform API conventions rather than Flutter conventions.
+    * On Android, the Flutter activity receives the book to show via activity
+      intent and returns the edited book by setting the result intent on the
+      activity. No Flutter concepts are leaked into the consumer activity.
+    * iOS TODO.
+* The [pigeon](https://pub.dev/packages/pigeon) plugin is used to generate
+  interop APIs and data classes. The same `Book` model class is used within the
+  Kotlin/Swift program, the Dart program and in the interop between Kotlin/Swift
+  and Dart. No manual platform channel plumbing needed for interop.
+    * The `api.dart/java/mm` files generated from the
+      `flutter_module_books/pigeon/schema.dart` file are checked into source
+      control. Therefore `pigeon` is only a dev dependency with no runtime
+      requirements.
+    * If the `schema.dart` is modified, the generated classes can be updated with
+
+        ```shell
+        flutter pub run pigeon \
+            --input pigeon/schema.dart \
+            --java_out ../android_books/app/src/main/java/dev/flutter/example/books/Api.java \
+            --java_package "dev.flutter.example.books"
+        ```
+
+      in the `flutter_module_books` directory.
+
+Once you've understood the basics of add-to-app with `android_fullscreen` and
+`ios_fullscreen`, this is a good sample to demonstrate how to integrate Flutter
+in a slightly more realistic setting with existing business logic.
+
 ## Questions/issues
 
 If you have a general question about incorporating Flutter into an existing

add_to_app/android_books/.gitignore

@@ -0,0 +1,14 @@
+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild
+.cxx

add_to_app/android_books/app/.gitignore

@@ -0,0 +1 @@
+/build

add_to_app/android_books/app/build.gradle

@@ -0,0 +1,49 @@
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
+
+android {
+    compileSdkVersion 29
+    buildToolsVersion "29.0.3"
+
+    defaultConfig {
+        applicationId "dev.flutter.example.books"
+        minSdkVersion 16
+        targetSdkVersion 29
+        versionCode 1
+        versionName "1.0"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: "libs", include: ["*.jar"])
+    implementation "com.squareup.okhttp3:okhttp:4.7.2"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+    implementation 'androidx.core:core-ktx:1.3.0'
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation "androidx.activity:activity-ktx:1.1.0"
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    implementation 'com.google.android.material:material:1.1.0'
+    implementation 'com.google.code.gson:gson:2.8.6'
+    implementation project(path: ':flutter')
+    testImplementation 'junit:junit:4.13'
+    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
+
+}

add_to_app/android_books/app/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

add_to_app/android_books/app/src/androidTest/java/dev/flutter/example/books/ExampleInstrumentedTest.kt

@@ -0,0 +1,27 @@
+package dev.flutter.example.books
+
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.ext.junit.runners.AndroidJUnit4
+
+import org.junit.Test
+import org.junit.runner.RunWith
+
+import org.junit.Assert.*
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+@RunWith(AndroidJUnit4::class)
+class MainActivityTest {
+    @Test
+    fun useAppContext() {
+        // Context of the app under test.
+        val appContext = InstrumentationRegistry.getInstrumentation().targetContext
+        assertEquals("dev.flutter.example.books", appContext.packageName)
+    }
+
+    // The app should be hermetic (with offline books JSON) before adding
+    // more tests.
+}

add_to_app/android_books/app/src/main/AndroidManifest.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="dev.flutter.example.books">
+
+    <application
+        android:name=".BookApplication"
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+        <activity
+            android:name=".FlutterBookActivity"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize" />
+    </application>
+    <uses-permission android:name="android.permission.INTERNET" />
+
+</manifest>

add_to_app/android_books/app/src/main/java/dev/flutter/example/books/Api.java

@@ -0,0 +1,143 @@
+// Autogenerated from Pigeon (v0.1.0), do not edit directly.
+// See also: https://pub.dev/packages/pigeon
+
+package dev.flutter.example.books;
+
+import java.util.HashMap;
+
+import io.flutter.plugin.common.BasicMessageChannel;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.StandardMessageCodec;
+
+/** Generated class from Pigeon. */
+public class Api {
+
+  /** Generated class from Pigeon that represents data sent in messages. */
+  public static class Book {
+    private String title;
+    public String getTitle() { return title; }
+    public void setTitle(String setterArg) { this.title = setterArg; }
+
+    private String subtitle;
+    public String getSubtitle() { return subtitle; }
+    public void setSubtitle(String setterArg) { this.subtitle = setterArg; }
+
+    private String author;
+    public String getAuthor() { return author; }
+    public void setAuthor(String setterArg) { this.author = setterArg; }
+
+    private String description;
+    public String getDescription() { return description; }
+    public void setDescription(String setterArg) { this.description = setterArg; }
+
+    private String publishDate;
+    public String getPublishDate() { return publishDate; }
+    public void setPublishDate(String setterArg) { this.publishDate = setterArg; }
+
+    private Long pageCount;
+    public Long getPageCount() { return pageCount; }
+    public void setPageCount(Long setterArg) { this.pageCount = setterArg; }
+
+    HashMap toMap() {
+      HashMap<String, Object> toMapResult = new HashMap<String, Object>();
+      toMapResult.put("title", title);
+      toMapResult.put("subtitle", subtitle);
+      toMapResult.put("author", author);
+      toMapResult.put("description", description);
+      toMapResult.put("publishDate", publishDate);
+      toMapResult.put("pageCount", pageCount);
+      return toMapResult;
+    }
+    static Book fromMap(HashMap map) {
+      Book fromMapResult = new Book();
+      fromMapResult.title = (String)map.get("title");
+      fromMapResult.subtitle = (String)map.get("subtitle");
+      fromMapResult.author = (String)map.get("author");
+      fromMapResult.description = (String)map.get("description");
+      fromMapResult.publishDate = (String)map.get("publishDate");
+      fromMapResult.pageCount = (map.get("pageCount") instanceof Integer) ? (Integer)map.get("pageCount") : (Long)map.get("pageCount");
+      return fromMapResult;
+    }
+  }
+
+  /** Generated class from Pigeon that represents Flutter messages that can be called from Java.*/
+  public static class FlutterBookApi {
+    private BinaryMessenger binaryMessenger;
+    public FlutterBookApi(BinaryMessenger argBinaryMessenger){
+      this.binaryMessenger = argBinaryMessenger;
+    }
+    public interface Reply<T> {
+      void reply(T reply);
+    }
+    public void displayBookDetails(Book argInput, Reply<Void> callback) {
+      BasicMessageChannel<Object> channel =
+          new BasicMessageChannel<Object>(binaryMessenger, "dev.flutter.pigeon.FlutterBookApi.displayBookDetails", new StandardMessageCodec());
+      HashMap inputMap = argInput.toMap();
+      channel.send(inputMap, new BasicMessageChannel.Reply<Object>() {
+        public void reply(Object channelReply) {
+          callback.reply(null);
+        }
+      });
+    }
+  }
+
+  /** Generated interface from Pigeon that represents a handler of messages from Flutter.*/
+  public interface HostBookApi {
+    void cancel();
+    void finishEditingBook(Book arg);
+
+    /** Sets up an instance of `HostBookApi` to handle messages through the `binaryMessenger` */
+    static void setup(BinaryMessenger binaryMessenger, HostBookApi api) {
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<Object>(binaryMessenger, "dev.flutter.pigeon.HostBookApi.cancel", new StandardMessageCodec());
+        if (api != null) {
+          channel.setMessageHandler(new BasicMessageChannel.MessageHandler<Object>() {
+            public void onMessage(Object message, BasicMessageChannel.Reply<Object> reply) {
+              HashMap<String, HashMap> wrapped = new HashMap<String, HashMap>();
+              try {
+                api.cancel();
+                wrapped.put("result", null);
+              }
+              catch (Exception exception) {
+                wrapped.put("error", wrapError(exception));
+              }
+              reply.reply(wrapped);
+            }
+          });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<Object>(binaryMessenger, "dev.flutter.pigeon.HostBookApi.finishEditingBook", new StandardMessageCodec());
+        if (api != null) {
+          channel.setMessageHandler(new BasicMessageChannel.MessageHandler<Object>() {
+            public void onMessage(Object message, BasicMessageChannel.Reply<Object> reply) {
+              Book input = Book.fromMap((HashMap)message);
+              HashMap<String, HashMap> wrapped = new HashMap<String, HashMap>();
+              try {
+                api.finishEditingBook(input);
+                wrapped.put("result", null);
+              }
+              catch (Exception exception) {
+                wrapped.put("error", wrapError(exception));
+              }
+              reply.reply(wrapped);
+            }
+          });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+    }
+  }
+  private static HashMap wrapError(Exception exception) {
+    HashMap<String, Object> errorMap = new HashMap<String, Object>();
+    errorMap.put("message", exception.toString());
+    errorMap.put("code", null);
+    errorMap.put("details", null);
+    return errorMap;
+  }
+}

add_to_app/android_books/app/src/main/java/dev/flutter/example/books/BookApplication.kt

@@ -0,0 +1,28 @@
+// 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.
+
+package dev.flutter.example.books
+
+import android.app.Application
+import io.flutter.embedding.engine.FlutterEngine
+import io.flutter.embedding.engine.FlutterEngineCache
+import io.flutter.embedding.engine.dart.DartExecutor
+
+class BookApplication: Application() {
+    companion object {
+        const val ENGINE_ID = "book_engine"
+    }
+
+    private lateinit var flutterEngine: FlutterEngine
+
+    override fun onCreate() {
+        super.onCreate()
+        // This application reuses a single FlutterEngine instance throughout.
+        // Create the FlutterEngine on application start.
+        flutterEngine = FlutterEngine(this).apply{
+            dartExecutor.executeDartEntrypoint(DartExecutor.DartEntrypoint.createDefault())
+        }
+        FlutterEngineCache.getInstance().put(ENGINE_ID, flutterEngine)
+    }
+}

add_to_app/android_books/app/src/main/java/dev/flutter/example/books/FlutterBookActivity.kt

@@ -0,0 +1,101 @@
+// 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.
+
+package dev.flutter.example.books
+
+import android.app.Activity
+import android.content.Context
+import android.content.Intent
+import dev.flutter.example.books.BookApplication.Companion.ENGINE_ID
+import io.flutter.embedding.android.FlutterActivity
+import io.flutter.embedding.engine.FlutterEngine
+import java.util.HashMap
+
+/**
+ * This {@link FlutterActivity} class repackages Kotlin-Dart interop using the Pigeon IPC mechanism.
+ * It repackages Flutter/Dart-side functionalities in standard Android API style, passing
+ * arguments in and out of the activity using 'startActivityForResult' intents and
+ * 'onActivityResult' intents.
+ */
+class FlutterBookActivity: FlutterActivity() {
+    companion object {
+        const val EXTRA_BOOK = "book"
+
+        /**
+         * Static intent factory to start {@link FlutterBookActivity} with the singleton
+         * {@link FlutterEngine} the application started.
+         *
+         * The activity launched from this intent shows the details of the {@link Api.Book}
+         * supplied.
+         */
+        fun withBook(context: Context, book: Api.Book): Intent {
+            // In a more realistic app, there should be some dependency injection mechanism to
+            // determine which engine to use.
+            return CachedEngineBookIntentBuilder(ENGINE_ID)
+                .build(context)
+                .putExtra(
+                    // The Pigeon data class is useful not only between Kotlin/Java and Dart
+                    // but also within Kotlin/Java where activities must communicate with
+                    // each other via serializable data. The Pigeon data class is a
+                    // serializable class by definition.
+                    EXTRA_BOOK,
+                    // TODO(gaaclarke): the Pigeon generated data class should just implement
+                    // Serializable so we won't need 'toMap()' here
+                    // https://github.com/flutter/flutter/issues/58909
+                    book.toMap()
+                )
+        }
+
+        /**
+         *  A static helper method to parse a result intent from this activity into a {@link Book}.
+         *
+         * @param resultIntent an {@link Intent} that must be the data intent returned by this
+         *                     activity's {@code onActivityResult}.
+         */
+        fun getBookFromResultIntent(resultIntent: Intent): Api.Book {
+            return Api.Book.fromMap(resultIntent.getSerializableExtra(FlutterBookActivity.EXTRA_BOOK) as HashMap<*, *>);
+        }
+    }
+
+    // Intent builder class to build a FlutterBookActivity instance instead of the default FlutterActivity.
+    class CachedEngineBookIntentBuilder(engineId: String): CachedEngineIntentBuilder(FlutterBookActivity::class.java, engineId) { }
+
+    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
+        // Called shortly after the activity is created, when the activity is bound to a
+        // FlutterEngine responsible for rendering the Flutter activity's content.
+        super.configureFlutterEngine(flutterEngine)
+
+        // The book to give to Flutter is passed in from the MainActivity via this activity's
+        // source intent getter. The intent contains the book serialized as on extra.
+        val bookToShow = Api.Book.fromMap(intent.getSerializableExtra(EXTRA_BOOK) as HashMap<*, *>)
+
+        // Register the HostBookApiHandler callback class to get results from Flutter.
+        Api.HostBookApi.setup(flutterEngine.dartExecutor, HostBookApiHandler())
+
+        // Send in the book instance to Flutter.
+        Api.FlutterBookApi(flutterEngine.dartExecutor).displayBookDetails(bookToShow) {
+            // We don't care about the callback
+        }
+    }
+
+    // This {@link Api.HostBookApi} subclass will be called by Pigeon when the corresponding
+    // APIs are invoked on the Dart side.
+    inner class HostBookApiHandler: Api.HostBookApi {
+        override fun cancel() {
+            // Flutter called cancel. Finish the activity with a cancel result.
+            setResult(Activity.RESULT_CANCELED)
+            finish()
+        }
+
+        override fun finishEditingBook(book: Api.Book?) {
+            if (book == null) {
+                throw IllegalArgumentException("finishedEditingBook cannot be called with a null argument")
+            }
+            // Flutter returned an edited book instance. Return it to the MainActivity via the
+            // standard Android Activity set result mechanism.
+            setResult(Activity.RESULT_OK, Intent().putExtra(EXTRA_BOOK, book.toMap()))
+            finish()
+        }
+    }
+}

add_to_app/android_books/app/src/main/java/dev/flutter/example/books/MainActivity.kt

@@ -0,0 +1,166 @@
+// 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.
+
+package dev.flutter.example.books
+
+import android.app.Activity
+import android.content.Intent
+import androidx.appcompat.app.AppCompatActivity
+import android.os.Bundle
+import android.view.View
+import android.widget.LinearLayout
+import android.widget.ProgressBar
+import android.widget.TextView
+import com.google.android.material.button.MaterialButton
+import com.google.gson.GsonBuilder
+import com.google.gson.JsonParser
+import okhttp3.Call
+import okhttp3.Callback
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okhttp3.Response
+import java.io.IOException
+import java.lang.Exception
+import java.lang.RuntimeException
+
+class MainActivity : AppCompatActivity() {
+    companion object {
+        const val BOOKS_QUERY = "https://www.googleapis.com/books/v1/volumes?q=greenwood+tulsa&maxResults=15"
+    }
+
+    private lateinit var books: MutableList<Api.Book>
+    private lateinit var list: LinearLayout
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+        list = findViewById<LinearLayout>(R.id.list)
+
+        // OkHttp is arbitrarily chosen here to represent an existing middleware constraint that's
+        // already present in an existing application's infrastructure.
+        val httpClient = OkHttpClient()
+        val bookRequest = Request.Builder()
+            // Retrieve data from Google Books API (arbitrarily chosen). This represents existing
+            // data sources that an existing application is already interfacing with.
+            .url(BOOKS_QUERY)
+            .build()
+
+        httpClient.newCall(bookRequest).enqueue(object : Callback {
+            override fun onFailure(call: Call, e: IOException) {
+                throw e
+            }
+
+            override fun onResponse(call: Call, response: Response) {
+                response.use {
+                    if (!response.isSuccessful) throw IOException("Unexpected code $response")
+                    books = parseGoogleBooksJsonToBooks(response.body!!.string())
+
+                    val spinner = findViewById<ProgressBar>(R.id.spinner)
+
+                    runOnUiThread {
+                        // Showed a spinner while network call is in progress. Remove it when
+                        // response is received.
+                        spinner.visibility = View.GONE
+                        populateBookCards()
+                    }
+                }
+            }
+        })
+    }
+
+    // Take a top level Google Books query's response JSON and create a list of Book Pigeon data
+    // classes that will be used both as a model here on the Kotlin side and also in the IPCs
+    // to Dart.
+    private fun parseGoogleBooksJsonToBooks(jsonBody: String): MutableList<Api.Book> {
+        // Here we're arbitrarily using GSON to represent another existing middleware constraint
+        // that already exists in your existing application's infrastructure.
+        val jsonBooks = JsonParser.parseString(jsonBody).asJsonObject.getAsJsonArray("items")
+        val books = mutableListOf<Api.Book>()
+        for (jsonBook in jsonBooks.map { it.asJsonObject }) {
+            try {
+                // Here we're using GSON to populate a Pigeon data class directly. The Pigeon data
+                // class can be used not just as part of your IPC API's signature but also as a
+                // normal data class in your existing application.
+                //
+                // We could either push the Pigeon data class usage higher into the existing GSON
+                // "middleware" or lower, closer to the IPC.
+                val book = Api.Book()
+                val volumeInfoJson = jsonBook.getAsJsonObject("volumeInfo")
+                book.title = volumeInfoJson.get("title").asString
+                book.subtitle = volumeInfoJson.get("subtitle")?.asString
+                // Sorry co-authors, we're trying to keep this simple.
+                book.author = volumeInfoJson.getAsJsonArray("authors")[0].asString
+                book.description = volumeInfoJson.get("description").asString
+                book.publishDate = volumeInfoJson.get("publishedDate").asString
+                book.pageCount = volumeInfoJson.get("pageCount").asLong
+                books.add(book)
+            } catch (e: Exception) {
+                println("Failed to parse book:")
+                println(GsonBuilder().setPrettyPrinting().create().toJson(jsonBook))
+                println("Parsing error:")
+                println(e)
+            }
+        }
+        return books
+    }
+
+    // Given a populated books list, create a Material Design card in a scroll view for each book.
+    private fun populateBookCards() {
+        for ((index, book) in books.withIndex()) {
+            val card = layoutInflater.inflate(R.layout.book_card, null)
+            updateCardWithBook(card, book)
+            card.findViewById<MaterialButton>(R.id.edit).setOnClickListener {
+                // When the edit button is clicked in a book's card, launch a Flutter activity
+                // showing the details of the book.
+                startActivityForResult(
+                    // We're using our own 'FlutterActivity' subclass which wraps Pigeon API usages
+                    // into an idiomatic Android activity interface with intent extras as input and
+                    // with activity 'setResult' as output.
+                    //
+                    // This lets activity-level feature developers abstract their Flutter usage
+                    // and present a standard Android API to their upstream application developers.
+                    //
+                    // No Flutter-specific concepts are leaked outside the Flutter activity itself
+                    // into the consuming class.
+                    FlutterBookActivity
+                        // Re-read from the 'books' list rather than just capturing the iterated
+                        // 'book' instance since we change it when Dart updates it in onActivityResult.
+                        .withBook(this, books[index]),
+                    // The index lets us know which book we're returning the result for when we
+                    // return from the Flutter activity.
+                    index)
+            }
+            list.addView(card)
+        }
+    }
+
+    // Given a Material Design card and a book, update the card content to reflect the book model.
+    private fun updateCardWithBook(card: View, book: Api.Book) {
+        card.findViewById<TextView>(R.id.title).text = book.title
+        card.findViewById<TextView>(R.id.subtitle).text = book.subtitle
+        card.findViewById<TextView>(R.id.author).text = resources.getString(R.string.author_prefix, book.author)
+    }
+
+    // Callback when the Flutter activity started with 'startActivityForResult' above returns.
+    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
+        super.onActivityResult(requestCode, resultCode, data)
+
+        // The Flutter activity may cancel the edit. If so, don't update anything.
+        if (resultCode == Activity.RESULT_OK) {
+            if (data == null) {
+                throw RuntimeException("The FlutterBookActivity returning RESULT_OK should always have a return data intent")
+            }
+
+            // If the book was edited in Flutter, the Flutter activity finishes and returns an
+            // activity result in an intent (the 'data' argument). The intent has an extra which is
+            // the edited book in serialized form.
+            val returnedBook = FlutterBookActivity.getBookFromResultIntent(data)
+            // Update our book model list.
+            books[requestCode] = returnedBook
+
+            // Refresh the UI here on the Kotlin side.
+            updateCardWithBook(list.getChildAt(requestCode), returnedBook)
+        }
+    }
+}

add_to_app/android_books/app/src/main/res/drawable-v24/ic_launcher_foreground.xml

@@ -0,0 +1,30 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path android:pathData="M31,63.928c0,0 6.4,-11 12.1,-13.1c7.2,-2.6 26,-1.4 26,-1.4l38.1,38.1L107,108.928l-32,-1L31,63.928z">
+        <aapt:attr name="android:fillColor">
+            <gradient
+                android:endX="85.84757"
+                android:endY="92.4963"
+                android:startX="42.9492"
+                android:startY="49.59793"
+                android:type="linear">
+                <item
+                    android:color="#44000000"
+                    android:offset="0.0" />
+                <item
+                    android:color="#00000000"
+                    android:offset="1.0" />
+            </gradient>
+        </aapt:attr>
+    </path>
+    <path
+        android:fillColor="#FFFFFF"
+        android:fillType="nonZero"
+        android:pathData="M65.3,45.828l3.8,-6.6c0.2,-0.4 0.1,-0.9 -0.3,-1.1c-0.4,-0.2 -0.9,-0.1 -1.1,0.3l-3.9,6.7c-6.3,-2.8 -13.4,-2.8 -19.7,0l-3.9,-6.7c-0.2,-0.4 -0.7,-0.5 -1.1,-0.3C38.8,38.328 38.7,38.828 38.9,39.228l3.8,6.6C36.2,49.428 31.7,56.028 31,63.928h46C76.3,56.028 71.8,49.428 65.3,45.828zM43.4,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2c-0.3,-0.7 -0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C45.3,56.528 44.5,57.328 43.4,57.328L43.4,57.328zM64.6,57.328c-0.8,0 -1.5,-0.5 -1.8,-1.2s-0.1,-1.5 0.4,-2.1c0.5,-0.5 1.4,-0.7 2.1,-0.4c0.7,0.3 1.2,1 1.2,1.8C66.5,56.528 65.6,57.328 64.6,57.328L64.6,57.328z"
+        android:strokeWidth="1"
+        android:strokeColor="#00000000" />
+</vector>

add_to_app/android_books/app/src/main/res/drawable/ic_launcher_background.xml

@@ -0,0 +1,170 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#3DDC84"
+        android:pathData="M0,0h108v108h-108z" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M9,0L9,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,0L19,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,0L29,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,0L39,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,0L49,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,0L59,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,0L69,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,0L79,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M89,0L89,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M99,0L99,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,9L108,9"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,19L108,19"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,29L108,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,39L108,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,49L108,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,59L108,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,69L108,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,79L108,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,89L108,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,99L108,99"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,29L89,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,39L89,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,49L89,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,59L89,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,69L89,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,79L89,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,19L29,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,19L39,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,19L49,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,19L59,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,19L69,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,19L79,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+</vector>

add_to_app/android_books/app/src/main/res/layout/activity_main.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <com.google.android.material.appbar.AppBarLayout
+        android:id="@+id/appbar"
+        app:liftOnScroll="true"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content">
+
+    </com.google.android.material.appbar.AppBarLayout>
+
+    <androidx.core.widget.NestedScrollView
+        android:id="@+id/nestedScrollView"
+        android:layout_width="match_parent"
+
+
+        android:layout_height="match_parent"
+        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior">
+
+        <LinearLayout
+            android:id="@+id/list"
+            android:orientation="vertical"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            tools:context=".MainActivity" />
+
+    </androidx.core.widget.NestedScrollView>
+
+    <ProgressBar
+        android:id="@+id/spinner"
+        style="?android:attr/progressBarStyle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:indeterminate="true"
+        app:layout_anchor="@+id/nestedScrollView"
+        app:layout_anchorGravity="center" />
+
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

add_to_app/android_books/app/src/main/res/layout/book_card.xml

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<FrameLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    >
+
+    <com.google.android.material.card.MaterialCardView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="21dp"
+        android:layout_marginStart="21dp"
+        android:layout_marginEnd="21dp"
+        android:layout_marginBottom="2dp">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical"
+            android:padding="16dp">
+
+            <TextView
+                android:id="@+id/title"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:textAppearance="?attr/textAppearanceHeadline5"
+                tools:text="Title" />
+
+            <TextView
+                android:id="@+id/subtitle"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:textAppearance="?attr/textAppearanceSubtitle1"
+                android:textColor="?android:attr/textColorSecondary"
+                tools:text="subtitle" />
+
+            <TextView
+                android:id="@+id/author"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="16dp"
+                android:textAppearance="?attr/textAppearanceBody1"
+                android:textColor="?android:attr/textColorSecondary"
+                tools:text="Author" />
+
+            <LinearLayout
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_margin="8dp"
+                android:orientation="horizontal"
+                android:layout_gravity="end">
+                <com.google.android.material.button.MaterialButton
+                    android:id="@+id/edit"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="@string/edit"
+                    style="?attr/borderlessButtonStyle"
+                    />
+            </LinearLayout>
+
+        </LinearLayout>
+
+    </com.google.android.material.card.MaterialCardView>
+
+</FrameLayout>
+

add_to_app/android_books/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

add_to_app/android_books/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

add_to_app/android_books/app/src/main/res/values/colors.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#6200EE</color>
+    <color name="colorPrimaryDark">#3700B3</color>
+    <color name="colorAccent">#03DAC5</color>
+</resources>

add_to_app/android_books/app/src/main/res/values/strings.xml

@@ -0,0 +1,5 @@
+<resources>
+    <string name="app_name">Books</string>
+    <string name="edit">Edit</string>
+    <string name="author_prefix">By: %1$s</string>
+</resources>

add_to_app/android_books/app/src/main/res/values/styles.xml

@@ -0,0 +1,10 @@
+<resources>
+    <!-- Base application theme. -->
+    <style name="AppTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+        <!-- Customize your theme here. -->
+        <item name="colorPrimary">@color/colorPrimary</item>
+        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
+        <item name="colorAccent">@color/colorAccent</item>
+    </style>
+
+</resources>

add_to_app/android_books/build.gradle

@@ -0,0 +1,26 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+buildscript {
+    ext.kotlin_version = "1.3.72"
+    repositories {
+        google()
+        jcenter()
+    }
+    dependencies {
+        classpath "com.android.tools.build:gradle:4.0.0"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}

add_to_app/android_books/gradle.properties

@@ -0,0 +1,21 @@
+# Project-wide Gradle settings.
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx2048m
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+# org.gradle.parallel=true
+# AndroidX package structure to make it clearer which packages are bundled with the
+# Android operating system, and which are packaged with your app"s APK
+# https://developer.android.com/topic/libraries/support-library/androidx-rn
+android.useAndroidX=true
+# Automatically convert third-party libraries to use AndroidX
+android.enableJetifier=true
+# Kotlin code style for this project: "official" or "obsolete":
+kotlin.code.style=official

add_to_app/android_books/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Sat Jun 06 17:49:00 PDT 2020
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip

add_to_app/android_books/gradlew

@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

add_to_app/android_books/gradlew.bat

@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

add_to_app/android_books/settings.gradle

@@ -0,0 +1,10 @@
+include ':app'
+setBinding(new Binding([gradle: this]))
+evaluate(new File(
+  settingsDir,
+  '../flutter_module_books/.android/include_flutter.groovy'
+))
+rootProject.name = "Android Books"
+
+include ':flutter_module_books'
+project(':flutter_module_books').projectDir = new File('../flutter_module_books')

add_to_app/flutter_module_books/.gitignore

@@ -0,0 +1,48 @@
+.DS_Store
+.dart_tool/
+
+.packages
+.pub/
+
+.idea/
+.vagrant/
+.sconsign.dblite
+.svn/
+
+*.swp
+profile
+
+DerivedData/
+
+.generated/
+
+*.pbxuser
+*.mode1v3
+*.mode2v3
+*.perspectivev3
+
+!default.pbxuser
+!default.mode1v3
+!default.mode2v3
+!default.perspectivev3
+
+xcuserdata
+
+*.moved-aside
+
+*.pyc
+*sync/
+Icon?
+.tags*
+
+build/
+.android/
+.ios/
+.flutter-plugins
+.flutter-plugins-dependencies
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json

add_to_app/flutter_module_books/.metadata

@@ -0,0 +1,10 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: c0091b289e9966b6da99647b2f18dcb93de1f207
+  channel: master
+
+project_type: module

add_to_app/flutter_module_books/README.md

@@ -0,0 +1,42 @@
+# Books add-to-app sample
+
+This application simulates a mock scenario where an existing app with
+business logic and middleware already exists. This sample demonstrates how to
+do an add-to-app Flutter integration into existing conventions.
+
+This application also utilizes the [Pigeon](https://pub.dev/packages/pigeon)
+plugin to avoid manual platform channel wiring. Pigeon autogenerates the
+platform channel code in Dart/Java/Objective-C to allow interop using higher
+order functions and data classes instead of string-encoded methods and
+serialized primitives.
+
+The Pigeon autogenerated code is checked-in and ready to use. If the schema
+in `pigeon/schema.dart` is updated, the generated classes can also be re-
+generated using:
+
+```shell
+flutter pub run pigeon \
+    --input pigeon/schema.dart \
+    --java_out ../android_books/app/src/main/java/dev/flutter/example/books/Api.java \
+    --java_package "dev.flutter.example.books"
+```
+
+## Demonstrated concepts
+
+* An existing books catalog app is already implemented in Kotlin and Swift.
+* The platform-side app has existing middleware constraints that should also
+  be the middleware foundation for the additional Flutter screen.
+    * On Android, the Kotlin app already uses GSON and OkHttp for networking and
+      references the Google Books API as a data source. These same libraries
+      also underpin the data fetched and shown in the Flutter screen.
+    * iOS TODO.
+* The platform application interfaces with the Flutter book details page using
+  idiomatic platform API conventions rather than Flutter conventions.
+    * On Android, the Flutter activity receives the book to show via activity
+      intent and returns the edited book by setting the result intent on the
+      activity. No Flutter concepts are leaked into the consumer activity.
+    * iOS TODO.
+* The [pigeon](https://pub.dev/packages/pigeon) plugin is used to generate
+  interop APIs and data classes. The same `Book` model class is used within the
+  Kotlin/Swift program, the Dart program and in the interop between Kotlin/Swift
+  and Dart.

add_to_app/flutter_module_books/lib/api.dart

@@ -0,0 +1,100 @@
+// Autogenerated from Pigeon (v0.1.0), do not edit directly.
+// See also: https://pub.dev/packages/pigeon
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import
+import 'dart:async';
+import 'package:flutter/services.dart';
+
+class Book {
+  String title;
+  String subtitle;
+  String author;
+  String description;
+  String publishDate;
+  int pageCount;
+  // ignore: unused_element
+  Map<dynamic, dynamic> _toMap() {
+    final Map<dynamic, dynamic> pigeonMap = <dynamic, dynamic>{};
+    pigeonMap['title'] = title;
+    pigeonMap['subtitle'] = subtitle;
+    pigeonMap['author'] = author;
+    pigeonMap['description'] = description;
+    pigeonMap['publishDate'] = publishDate;
+    pigeonMap['pageCount'] = pageCount;
+    return pigeonMap;
+  }
+
+  // ignore: unused_element
+  static Book _fromMap(Map<dynamic, dynamic> pigeonMap) {
+    final Book result = Book();
+    result.title = pigeonMap['title'];
+    result.subtitle = pigeonMap['subtitle'];
+    result.author = pigeonMap['author'];
+    result.description = pigeonMap['description'];
+    result.publishDate = pigeonMap['publishDate'];
+    result.pageCount = pigeonMap['pageCount'];
+    return result;
+  }
+}
+
+abstract class FlutterBookApi {
+  void displayBookDetails(Book arg);
+  static void setup(FlutterBookApi api) {
+    {
+      const BasicMessageChannel<dynamic> channel = BasicMessageChannel<dynamic>(
+          'dev.flutter.pigeon.FlutterBookApi.displayBookDetails',
+          StandardMessageCodec());
+      channel.setMessageHandler((dynamic message) async {
+        final Map<dynamic, dynamic> mapMessage =
+            message as Map<dynamic, dynamic>;
+        final Book input = Book._fromMap(mapMessage);
+        api.displayBookDetails(input);
+      });
+    }
+  }
+}
+
+class HostBookApi {
+  Future<void> cancel() async {
+    const BasicMessageChannel<dynamic> channel = BasicMessageChannel<dynamic>(
+        'dev.flutter.pigeon.HostBookApi.cancel', StandardMessageCodec());
+
+    final Map<dynamic, dynamic> replyMap = await channel.send(null);
+    if (replyMap == null) {
+      throw PlatformException(
+          code: 'channel-error',
+          message: 'Unable to establish connection on channel.',
+          details: null);
+    } else if (replyMap['error'] != null) {
+      final Map<dynamic, dynamic> error = replyMap['error'];
+      throw PlatformException(
+          code: error['code'],
+          message: error['message'],
+          details: error['details']);
+    } else {
+      // noop
+    }
+  }
+
+  Future<void> finishEditingBook(Book arg) async {
+    final Map<dynamic, dynamic> requestMap = arg._toMap();
+    const BasicMessageChannel<dynamic> channel = BasicMessageChannel<dynamic>(
+        'dev.flutter.pigeon.HostBookApi.finishEditingBook',
+        StandardMessageCodec());
+
+    final Map<dynamic, dynamic> replyMap = await channel.send(requestMap);
+    if (replyMap == null) {
+      throw PlatformException(
+          code: 'channel-error',
+          message: 'Unable to establish connection on channel.',
+          details: null);
+    } else if (replyMap['error'] != null) {
+      final Map<dynamic, dynamic> error = replyMap['error'];
+      throw PlatformException(
+          code: error['code'],
+          message: error['message'],
+          details: error['details']);
+    } else {
+      // noop
+    }
+  }
+}

add_to_app/flutter_module_books/lib/main.dart

@@ -0,0 +1,201 @@
+// 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(MyApp());
+
+class MyApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      theme: ThemeData(
+        primaryColor: const Color(0xff6200ee),
+      ),
+      home: BookDetail(),
+    );
+  }
+}
+
+typedef BookReceived = void Function(Book book);
+
+class FlutterBookApiHandler extends FlutterBookApi {
+  FlutterBookApiHandler(this.callback);
+
+  final BookReceived callback;
+
+  @override
+  void displayBookDetails(Book book) {
+    assert(
+      book != null,
+      'Non-null book expected from FlutterBookApi.displayBookDetails call.',
+    );
+    callback(book);
+  }
+}
+
+class BookDetail extends StatefulWidget {
+  const BookDetail({this.hostApi, this.flutterApi});
+
+  // These are the outgoing and incoming APIs that are here for injection for
+  // tests.
+  final HostBookApi hostApi;
+  final FlutterBookApi flutterApi;
+
+  @override
+  _BookDetailState createState() => _BookDetailState();
+}
+
+class _BookDetailState extends State<BookDetail> {
+  Book book;
+
+  HostBookApi hostApi;
+
+  FocusNode textFocusNode = FocusNode();
+  TextEditingController titleTextController = TextEditingController();
+  TextEditingController subtitleTextController = TextEditingController();
+  TextEditingController authorTextController = TextEditingController();
+
+  @override
+  void initState() {
+    super.initState();
+
+    // 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 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;
+        });
+      });
+    }));
+  }
+
+  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: Text('Book Details'),
+        leading: IconButton(
+          icon: Icon(Icons.clear),
+          // Pressing clear cancels the edit and leaves the activity without
+          // modification.
+          onPressed: () {
+            hostApi.cancel();
+            clear();
+          },
+        ),
+        actions: [
+          IconButton(
+            icon: Icon(Icons.check),
+            // Pressing save sends the updated book to the platform.
+            onPressed: () {
+              hostApi.finishEditingBook(book);
+              clear();
+            },
+          ),
+        ],
+      ),
+      body: book == null
+          // Draw a spinner until the platform gives us the book to show details
+          // for.
+          ? Center(child: CircularProgressIndicator())
+          : Focus(
+              focusNode: textFocusNode,
+              child: ListView(
+                padding: EdgeInsets.all(24),
+                children: [
+                  TextField(
+                    controller: titleTextController,
+                    decoration: InputDecoration(
+                      border: OutlineInputBorder(),
+                      filled: true,
+                      hintText: "Title",
+                      labelText: "Title",
+                    ),
+                  ),
+                  SizedBox(height: 24),
+                  TextField(
+                    controller: subtitleTextController,
+                    maxLines: 2,
+                    decoration: InputDecoration(
+                      border: OutlineInputBorder(),
+                      filled: true,
+                      hintText: "Subtitle",
+                      labelText: "Subtitle",
+                    ),
+                  ),
+                  SizedBox(height: 24),
+                  TextField(
+                    controller: authorTextController,
+                    decoration: InputDecoration(
+                      border: OutlineInputBorder(),
+                      filled: true,
+                      hintText: "Author",
+                      labelText: "Author",
+                    ),
+                  ),
+                  SizedBox(height: 32),
+                  Divider(),
+                  Center(
+                    child: Padding(
+                      padding: const EdgeInsets.all(8.0),
+                      child: Text(
+                          '${book.pageCount} pages  ~  published ${book.publishDate}'),
+                    ),
+                  ),
+                  Divider(),
+                  SizedBox(height: 32),
+                  Center(
+                    child: Text(
+                      'BOOK DESCRIPTION',
+                      style: TextStyle(
+                        fontSize: 15,
+                        fontWeight: FontWeight.bold,
+                        decoration: TextDecoration.underline,
+                      ),
+                    ),
+                  ),
+                  SizedBox(height: 12),
+                  Text(
+                    book.description,
+                    style: TextStyle(color: Colors.grey.shade600, height: 1.24),
+                  ),
+                ],
+              ),
+            ),
+    );
+  }
+}

add_to_app/flutter_module_books/pigeon/schema.dart

@@ -0,0 +1,32 @@
+// 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:pigeon/pigeon.dart';
+
+class Book {
+  String title;
+  String subtitle;
+  String author;
+  String description;
+  String publishDate;
+  int pageCount;
+  // Thumbnail thumbnail;
+}
+
+// TODO(gaaclarke): add this back when the https://github.com/flutter/flutter/issues/58896
+// crash is resolved.
+// class Thumbnail {
+//   String url;
+// }
+
+@FlutterApi()
+abstract class FlutterBookApi {
+  void displayBookDetails(Book book);
+}
+
+@HostApi()
+abstract class HostBookApi {
+  void cancel();
+  void finishEditingBook(Book book);
+}

add_to_app/flutter_module_books/pubspec.lock

@@ -0,0 +1,160 @@
+# Generated by pub
+# See https://dart.dev/tools/pub/glossary#lockfile
+packages:
+  args:
+    dependency: transitive
+    description:
+      name: args
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.6.0"
+  async:
+    dependency: transitive
+    description:
+      name: async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.4.1"
+  boolean_selector:
+    dependency: transitive
+    description:
+      name: boolean_selector
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
+  charcode:
+    dependency: transitive
+    description:
+      name: charcode
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.3"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
+  collection:
+    dependency: transitive
+    description:
+      name: collection
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.14.12"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
+  flutter:
+    dependency: "direct main"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  flutter_test:
+    dependency: "direct dev"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  matcher:
+    dependency: transitive
+    description:
+      name: matcher
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.12.6"
+  meta:
+    dependency: transitive
+    description:
+      name: meta
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.8"
+  mockito:
+    dependency: "direct dev"
+    description:
+      name: mockito
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "4.1.1"
+  path:
+    dependency: transitive
+    description:
+      name: path
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.7.0"
+  pigeon:
+    dependency: "direct dev"
+    description:
+      name: pigeon
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.1.0"
+  sky_engine:
+    dependency: transitive
+    description: flutter
+    source: sdk
+    version: "0.0.99"
+  source_span:
+    dependency: transitive
+    description:
+      name: source_span
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.7.0"
+  stack_trace:
+    dependency: transitive
+    description:
+      name: stack_trace
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.9.3"
+  stream_channel:
+    dependency: transitive
+    description:
+      name: stream_channel
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
+  string_scanner:
+    dependency: transitive
+    description:
+      name: string_scanner
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.5"
+  term_glyph:
+    dependency: transitive
+    description:
+      name: term_glyph
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
+  test_api:
+    dependency: transitive
+    description:
+      name: test_api
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.2.16"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.6"
+  vector_math:
+    dependency: transitive
+    description:
+      name: vector_math
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.8"
+sdks:
+  dart: ">=2.7.0 <3.0.0"

add_to_app/flutter_module_books/pubspec.yaml

@@ -0,0 +1,33 @@
+name: flutter_module_books
+description: A Flutter module using the Pigeon package to demonstrate
+  integrating Flutter in a realistic scenario where the existing platform app
+  already has business logic and middleware constraints.
+
+version: 1.0.0+1
+
+environment:
+  sdk: ">=2.7.0 <3.0.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  pigeon: ^0.1.0
+  mockito: ^4.1.1
+  flutter_test:
+    sdk: flutter
+
+flutter:
+  uses-material-design: true
+
+  # This section identifies your Flutter project as a module meant for
+  # embedding in a native host app.  These identifiers should _not_ ordinarily
+  # be changed after generation - they are used to ensure that the tooling can
+  # maintain consistency when adding or modifying assets and plugins.
+  # They also do not have any bearing on your native host application's
+  # identifiers, which may be completely independent or the same as these.
+  module:
+    androidX: true
+    androidPackage: dev.flutter.example.flutter_module_books
+    iosBundleIdentifier: dev.flutter.example.flutterModuleBooks

add_to_app/flutter_module_books/test/widget_test.dart

@@ -0,0 +1,43 @@
+// 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';
+import 'package:flutter_module_books/main.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+
+void main() {
+  testWidgets('Pressing clear calls the cancel API',
+      (WidgetTester tester) async {
+    MockHostBookApi mockHostApi = MockHostBookApi();
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: BookDetail(hostApi: mockHostApi),
+      ),
+    );
+
+    await tester.tap(find.byIcon(Icons.clear));
+
+    verify(mockHostApi.cancel());
+  });
+
+  testWidgets('Pressing done calls the finish editing API',
+      (WidgetTester tester) async {
+    MockHostBookApi mockHostApi = MockHostBookApi();
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: BookDetail(hostApi: mockHostApi),
+      ),
+    );
+
+    await tester.tap(find.byIcon(Icons.check));
+
+    verify(mockHostApi.finishEditingBook(any));
+  });
+}
+
+class MockHostBookApi extends Mock implements HostBookApi {}

tool/travis_flutter_script.sh

@@ -28,6 +28,7 @@ echo "Flutter SDK found at ${LOCAL_SDK_PATH}"
 declare -ar PROJECT_NAMES=(
     "add_to_app/flutter_module" \
     "add_to_app/flutter_module_using_plugin" \
+    "add_to_app/flutter_module_books" \
     "animations" \
     "flutter_maps_firestore" \
     "infinite_list" \