要使用Android的AlarmManager调用flutterLocalNotificationsPlugin.show()方法显示通知，你需要确保已经正确设置了AlarmManager和通知通道。

以下是一个示例代码，演示了如何在Android中使用AlarmManager调用flutterLocalNotificationsPlugin.show()方法显示通知：

首先，确保在Android的AndroidManifest.xml文件中添加以下权限：

接下来，创建一个名为MyNotificationReceiver的BroadcastReceiver类，继承自FlutterLocalNotificationsPlugin.NotificationReceiver类，并重写onReceive()方法：

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class MyNotificationReceiver extends FlutterLocalNotificationsPlugin.NotificationReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);

        // 在这里调用flutterLocalNotificationsPlugin.show()方法显示通知
        // 示例代码：
        // flutterLocalNotificationsPlugin.show(
        //     0,
        //     "标题",
        //     "内容",
        //     new NotificationDetails(
        //         androidPlatformChannelSpecifics,
        //         null
        //     )
        // );
    }
}

然后，在Android的MainActivity中注册MyNotificationReceiver类：

import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugins.GeneratedPluginRegistrant;

public class MainActivity extends FlutterActivity {
    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        GeneratedPluginRegistrant.registerWith(flutterEngine);

        // 注册MyNotificationReceiver类
        new FlutterLocalNotificationsPlugin().setNotificationReceiver(new MyNotificationReceiver());
    }
}

最后，在你的Flutter代码中使用AlarmManager调用flutterLocalNotificationsPlugin.show()方法：

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:android_alarm_manager/android_alarm_manager.dart';

final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
    FlutterLocalNotificationsPlugin();

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  // 初始化flutterLocalNotificationsPlugin
  const AndroidInitializationSettings initializationSettingsAndroid =
      AndroidInitializationSettings('app_icon');
  final InitializationSettings initializationSettings =
      InitializationSettings(android: initializationSettingsAndroid);
  await flutterLocalNotificationsPlugin.initialize(initializationSettings,
      onSelectNotification: null);

  // 注册AlarmManager
  if (Platform.isAndroid) {
    await AndroidAlarmManager.initialize();
  }

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo Home Page'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('调用AlarmManager显示通知'),
          onPressed: () {
            // 设置AlarmManager
            AndroidAlarmManager.oneShot(
              const Duration(seconds: 5),
              0,
              showNotification,
            );
          },
        ),
      ),
    );
  }

  void showNotification() async {
    const AndroidNotificationDetails androidPlatformChannelSpecifics =
        AndroidNotificationDetails(
      'your channel id',
      'your channel name',
      'your channel description',
      importance: Importance.max,
      priority: Priority.high,
      ticker: 'ticker',
    );
    const NotificationDetails platformChannelSpecifics =
        NotificationDetails(android: androidPlatformChannelSpecifics);

    await flutterLocalNotificationsPlugin.show(
      0,
      '标题',
      '内容',
      platformChannelSpecifics,
    );
  }
}

这样，当你点击按钮后，AlarmManager会在5秒后触发showNotification()方法，然后调用flutterLocalNotificationsPlugin.show()方法显示通知。