pkgs/jnigen/example/in_app_java/lib/main.dart

// Copyright (c) 2022, the Dart project authors. Please see the AUTHORS file
// for details. 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/foundation.dart';
import 'package:flutter/material.dart';
import 'package:jni/jni.dart';
import 'package:jni_flutter/jni_flutter.dart';

// The hierarchy created in generated code will mirror the java package
// structure.
import 'android_utils.g.dart';

JObject context = androidApplicationContext;

final hashmap = JHashMap<JString, JString>();

final emojiCompat = EmojiCompat.get();

extension IntX on int {
  JString toJString() {
    return toString().toJString();
  }
}

const sunglassEmoji = "😎";

// snippet-start#show_toast
void showToast() {
  final activity =
      androidActivity(PlatformDispatcher.instance.engineId!)?.as(Activity.type);
  final message = 'This is a native toast shown from a Flutter app via JNI.';
  AndroidUtils.showToast(
    activity,
    message.toJString().as(CharSequence.type),
    0,
  );
}
// snippet-end#show_toast

/// Display device model number and the number of times this was called
/// as Toast.
void showToastFancy() {
  final toastCount = hashmap.getOrDefault(
    "toastCount".toJString(),
    0.toJString(),
  );
  final newToastCount = (int.parse(toastCount!.toDartString()) + 1).toJString();
  hashmap.put("toastCount".toJString(), newToastCount);
  final emoji =
      emojiCompat.hasEmojiGlyph(sunglassEmoji.toJString().as(CharSequence.type))
          ? sunglassEmoji
          : ':cool:';
  final message =
      '${newToastCount.toDartString()} - ${Build.MODEL!.toDartString()} $emoji';
  AndroidUtils.showToast(
    androidActivity(PlatformDispatcher.instance.engineId!)?.as(Activity.type),
    message.toJString().as(CharSequence.type),
    0,
  );
}

void main() {
  EmojiCompat.init(context.as(Context.type));
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(primarySwatch: Colors.teal),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(title)),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              child: const Text('Show Device Model'),
              onPressed: () => showToastFancy(),
            ),
          ],
        ),
      ),
    );
  }
}