参数类型 'Future Function(int, String, String, String)' 无法分配给参数类型 'void Function(int, String?, String?, String?)?

Question

import 'package:flutter/foundation.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';

class NotificationManager {
// ignore: prefer_typing_uninitialized_variables
var flutterLocalNotificationsPlugin;

NotificationManager() {
flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
initNotifications();
 }

getNotificationInstance() {
return flutterLocalNotificationsPlugin;
}

void initNotifications() {
// initialise the plugin. app_icon needs to be a added as a drawable resource to the 
Android head project
const initializationSettingsAndroid =
    AndroidInitializationSettings('@mipmap/launcher_icon');
const initializationSettingsIOS = IOSInitializationSettings(

我在这个 onDidReceiveLocalNotification 上遇到错误参数类型 'Future Function(int, String, String, String)' 无法分配给参数类型 'void Function(int, String?, String?, String?)?

  onDidReceiveLocalNotification: onDidReceiveLocalNotification);

const initializationSettings =  InitializationSettings(
    android: initializationSettingsAndroid, iOS: initializationSettingsIOS);

flutterLocalNotificationsPlugin.initialize(initializationSettings,
    onSelectNotification: onSelectNotification);
    }

void showNotificationDaily(
  int id, String title, String body, int hour, int minute) async {
var time = Time(hour, minute, 0);
await flutterLocalNotificationsPlugin.showDailyAtTime(
    id, title, body, time, getPlatformChannelSpecfics());
if (kDebugMode) {
  print('Notification Succesfully Scheduled at ${time.toString()}');
  }
 }

getPlatformChannelSpecfics() {
var androidPlatformChannelSpecifics = const AndroidNotificationDetails(
     'your channel name', 'your channel description',
    importance: Importance.max,
    priority: Priority.high,
    ticker: 'Sickle Cell');
var iOSPlatformChannelSpecifics = const IOSNotificationDetails();
var platformChannelSpecifics = NotificationDetails(
    android: androidPlatformChannelSpecifics, iOS: iOSPlatformChannelSpecifics);

 return platformChannelSpecifics;
 }

Future onSelectNotification(String payload) async {
if (kDebugMode) {
  print('Notification clicked');
  }
  return Future.value(0);
 }

 Future onDidReceiveLocalNotification(
  int id, String title, String body, String payload) async {
  return Future.value(1);
  }

 void removeReminder(int notificationId) {
 flutterLocalNotificationsPlugin.cancel(notificationId);
 }
 }

我已经阅读了 flutter_local_notifications 自述文件，但我还是不明白。

Answer 1

onDidReceiveLocalNotification 中的字符串应该可以为空。尝试更改：

Future onDidReceiveLocalNotification(
  int id, String title, String body, String payload) async {
  return Future.value(1);
}

收件人：

Future onDidReceiveLocalNotification(
      int id, String? title, String? body, String? payload) async {
      return Future.value(1);
}

参数类型 'Future Function(int, String, String, String)' 无法分配给参数类型 'void Function(int, String?, String?, String?)?

argument type 'Future Function(int, String, String, String)' can't be assigned to the parameter type 'void Function(int, String?, String?, String?)?

flutter

dart

notifications

flutter-local-notification