Flutter 本地通知错误：空对象引用上的“int java.lang.Integer.intValue()”

Question

当我激活预定的 Flutter 本地通知时，它崩溃了。我在 drawable 文件夹中有“launcher_icon”，有来自 github 的所有配置。知道是什么导致了错误？我有 2 个带有 Flutter 本地通知的项目——一个在虚拟机上工作，但不在真实设备上（一旦通知被触发就退出），另一个一开始就不起作用。

这是我的代码：

import 'package:coronada_19/models/infection.dart';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:latlong/latlong.dart' as ds;
import 'package:flutter/cupertino.dart';
import 'package:rxdart/subjects.dart';

import 'package:flutter_local_notifications/flutter_local_notifications.dart';

class ReceivedNotification {
  final int id;
  final String title;
  final String body;
  final String payload;

  ReceivedNotification(
      {@required this.id,
      @required this.title,
      @required this.body,
      @required this.payload});
}

final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
    FlutterLocalNotificationsPlugin();

// Streams are created so that app can respond to notification-related events since the plugin is initialised in the `main` function
final BehaviorSubject<ReceivedNotification> didReceiveLocalNotificationSubject =
    BehaviorSubject<ReceivedNotification>();

final BehaviorSubject<String> selectNotificationSubject =
    BehaviorSubject<String>();

var initializationSettingsAndroid =
    AndroidInitializationSettings('launcher_icon');
// Note: permissions aren't requested here just to demonstrate that can be done later using the `requestPermissions()` method
// of the `IOSFlutterLocalNotificationsPlugin` class
var initializationSettingsIOS = IOSInitializationSettings(
    requestAlertPermission: false,
    requestBadgePermission: false,
    requestSoundPermission: false,
    onDidReceiveLocalNotification:
        (int id, String title, String body, String payload) async {
      didReceiveLocalNotificationSubject.add(ReceivedNotification(
          id: id, title: title, body: body, payload: payload));
    });
var initializationSettings = InitializationSettings(
  initializationSettingsAndroid,
  initializationSettingsIOS,
);
var scheduledNotificationDateTime = DateTime.now().add(Duration(seconds: 10));
var iOSPlatformChannelSpecifics = IOSNotificationDetails();
var platformChannelSpecifics = NotificationDetails(
    androidPlatformChannelSpecifics, iOSPlatformChannelSpecifics);

var androidPlatformChannelSpecifics = AndroidNotificationDetails(
    'your channel id', 'your channel name', 'your channel description',
    importance: Importance.Max, priority: Priority.High);

class DisplayMap extends StatefulWidget {
  static const routeName = "/displayMap";
  final List<Infection> infect;
  DisplayMap({Key key, this.infect}) : super(key: key);

  @override
  _DisplayMapState createState() => _DisplayMapState(infect);
}

class _DisplayMapState extends State<DisplayMap> {
  List<Infection> infect;
  _DisplayMapState(this.infect);

  Widget build(BuildContext context) {
    return Stack(children: [
      RaisedButton(
        onPressed: () async {
          await flutterLocalNotificationsPlugin.schedule(
              0,
              'name',
              'plain body',
              scheduledNotificationDateTime,
              platformChannelSpecifics,
              payload: 'item x');
        },
        child: Text("hehe"),
      )
    ]);
  }
}

我的颤振医生：

[?] Flutter (Channel stable, v1.12.13+hotfix.8, on Microsoft Windows [Version 10.0.18362.657], locale ko-KR)
    • Flutter version 1.12.13+hotfix.8 at C:\User\FF\flutter
    • Framework revision 0b8abb4724 (4 weeks ago), 2020-02-11 11:44:36 -0800
    • Engine revision e1e6ced81d
    • Dart version 2.7.0


[?] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at C:\Users\HP\AppData\Local\Android\sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-29, build-tools 29.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)
    • All Android licenses accepted.

[?] Android Studio (version 3.5)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 44.0.1
    • Dart plugin version 191.8593
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)

[?] Connected device (1 available)
    • Android SDK built for x86 64 • emulator-5554 • android-x64 • Android 10 (API 29) (emulator)

这是错误日志：

java.lang.RuntimeException: Unable to start receiver com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
E/AndroidRuntime( 6448):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:3421)
E/AndroidRuntime( 6448):    at android.app.ActivityThread.access$1300(ActivityThread.java:200)
E/AndroidRuntime( 6448):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1684)
E/AndroidRuntime( 6448):    at android.os.Handler.dispatchMessage(Handler.java:106)
E/AndroidRuntime( 6448):    at android.os.Looper.loop(Looper.java:201)
E/AndroidRuntime( 6448):    at android.app.ActivityThread.main(ActivityThread.java:6810)
E/AndroidRuntime( 6448):    at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime( 6448):    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
E/AndroidRuntime( 6448):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
E/AndroidRuntime( 6448): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
E/AndroidRuntime( 6448):    at com.dexterous.flutterlocalnotifications.FlutterLocalNotificationsPlugin.setSmallIcon(FlutterLocalNotificationsPlugin.java:155)
E/AndroidRuntime( 6448):    at com.dexterous.flutterlocalnotifications.FlutterLocalNotificationsPlugin.createNotification(FlutterLocalNotificationsPlugin.java:131)
E/AndroidRuntime( 6448):    at com.dexterous.flutterlocalnotifications.FlutterLocalNotificationsPlugin.showNotification(FlutterLocalNotificationsPlugin.java:586)
E/AndroidRuntime( 6448):    at com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver.onReceive(ScheduledNotificationReceiver.java:45)
E/AndroidRuntime( 6448):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:3412)
E/AndroidRuntime( 6448):    ... 8 more
I/Process ( 6448): Sending signal. PID: 6448 SIG: 9
Lost connection to device.

Answer 1

您似乎从未运行flutterLocalNotificationsPlugin.initialize，这意味着当应用程序尝试显示通知时，您的 android 和 ios 通知设置未初始化。

该问题的另一个常见原因是AndroidInitializationSettingsandroid/app/src/main/res/drawable 文件夹中不存在的应用程序图标（注意：AndroidInitializationSettings仅调用文件名时不需要文件扩展名）。

这是 Github 中正在解决的问题：https : //github.com/MaikuB/flutter_local_notifications/issues/220

我希望这有帮助

Answer 2

这意味着您没有初始化包，因此它没有找到该对象。所以一定要初始化。

await flutterLocalNotificationsPlugin.initialize(initializationSettings);

应该是在之后

  final InitializationSettings initializationSettings = InitializationSettings(
  android: initializationSettingsAndroid,
  iOS: initializationSettingsIOS,
  macOS: initialization SettingsMacOS);

整个初始化代码：

FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

const AndroidInitializationSettings initializationSettingsAndroid =  AndroidInitializationSettings('app_icon');

final IOSInitializationSettings initializationSettingsIOS =  const IOSInitializationSettings(
  requestAlertPermission: true,
  requestBadgePermission: true,
  requestSoundPermission: true,
  onDidReceiveLocalNotification: onDidReceiveLocalNotification);

final MacOSInitializationSettings initializationSettingsMacOS = const MacOSInitializationSettings();

final InitializationSettings initializationSettings = InitializationSettings(
  android: initializationSettingsAndroid,
  iOS: initializationSettingsIOS,
  macOS: initializationSettingsMacOS);

  await flutterLocalNotificationsPlugin.initialize(initializationSettings);