如果处理后台消息，firebase_messaging flutter插件在启动时崩溃 [英] firebase_messaging flutter plugin crashing on startup if handling background messages
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问题描述
我将 firebase_messaging v5.1.6 与我的flutter应用程序集成在一起，如README中提到的处理背景"邮件"选项.
I integrated firebase_messaging v5.1.6 with my flutter app as mentioned in README with "handling of background messages" option.
这是我的文件的外观.
MyApplication.kt
MyApplication.kt
class MyApplication : FlutterApplication(), PluginRegistrantCallback {
override fun onCreate() {
super.onCreate()
FlutterFirebaseMessagingService.setPluginRegistrant(this)
}
override fun registerWith(registry: PluginRegistry) {
GeneratedPluginRegistrant.registerWith(registry)
}
}
firebase_util.dart
firebase_util.dart
import 'package:firebase_analytics/firebase_analytics.dart';
import 'package:firebase_analytics/observer.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
final kFirebaseAnalyticsObserver =
FirebaseAnalyticsObserver(analytics: FirebaseUtil().analytics);
Future<dynamic> kFirebaseMessagingBackgroundMessageHandler(
Map<String, dynamic> message) async {
if (message.containsKey('data')) {
// Handle data message
final dynamic data = message['data'];
}
if (message.containsKey('notification')) {
// Handle notification message
final dynamic notification = message['notification'];
}
}
class FirebaseUtil {
static final FirebaseUtil _firebaseUtil = FirebaseUtil._internal();
factory FirebaseUtil() {
return _firebaseUtil;
}
FirebaseUtil._internal();
final analytics = FirebaseAnalytics();
final messaging = FirebaseMessaging();
void messagingInit() {
messaging.requestNotificationPermissions();
messaging.configure(
onMessage: (Map<String, dynamic> message) async {
print("onMessage: $message");
},
onBackgroundMessage: kFirebaseMessagingBackgroundMessageHandler,
onLaunch: (Map<String, dynamic> message) async {
print("onLaunch: $message");
},
onResume: (Map<String, dynamic> message) async {
print("onResume: $message");
},
);
}
}
我在根应用程序小部件的initState中调用FirebaseUtil().messagingInit().
I call FirebaseUtil().messagingInit() in initState of the root App widget.
这是启动应用程序时收到的错误日志.
Here is the error log I get when the app is starting up.
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): Failed to handle method call
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.app.Activity.getApplicationContext()' on a null object reference
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at com.alternadom.wifiiot.WifiIotPlugin.<init>(WifiIotPlugin.java:65)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at com.alternadom.wifiiot.WifiIotPlugin.registerWith(WifiIotPlugin.java:76)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.plugins.GeneratedPluginRegistrant.registerWith(GeneratedPluginRegistrant.java:40)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at <<package_name>>.MyApplication.registerWith(MyApplication.kt:18)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService.startBackgroundIsolate(FlutterFirebaseMessagingService.java:164)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin.onMethodCall(FirebaseMessagingPlugin.java:134)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:222)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:96)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:656)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at android.os.MessageQueue.next(MessageQueue.java:326)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at android.os.Looper.loop(Looper.java:160)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at android.app.ActivityThread.main(ActivityThread.java:6669)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
E/MethodChannel#plugins.flutter.io/firebase_messaging( 6252): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
...
E/flutter ( 6252): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: PlatformException(error, Attempt to invoke virtual method 'android.content.Context android.app.Activity.getApplicationContext()' on a null object reference, null)
E/flutter ( 6252): #0 StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:569:7)
E/flutter ( 6252): #1 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:316:33)
E/flutter ( 6252): <asynchronous suspension>
E/flutter ( 6252): #2 FirebaseMessaging.configure (package:firebase_messaging/firebase_messaging.dart:118:16)
E/flutter ( 6252): #3 FirebaseUtil.messagingInit (package:<<package_name>>/util/firebase_util.dart:37:15)
E/flutter ( 6252): #4 _MainPageState.initState (package:<<package_name>>/pages/main.dart:29:20)
E/flutter ( 6252): #5 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4068:58)
E/flutter ( 6252): #6 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3919:5)
E/flutter ( 6252): #7 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3101:14)
E/flutter ( 6252): #8 Element.updateChild (package:flutter/src/widgets/framework.dart:2904:12)
E/flutter ( 6252): #9 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3961:16)
E/flutter ( 6252): #10 Element.rebuild (package:flutter/src/widgets/framework.dart:3738:5)
E/flutter ( 6252): #11 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2348:33)
E/flutter ( 6252): #12 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:760:20)
E/flutter ( 6252): #13 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:280:5)
E/flutter ( 6252): #14 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1033:15)
E/flutter ( 6252): #15 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:975:9)
E/flutter ( 6252): #16 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:891:5)
E/flutter ( 6252): #17 _rootRun (dart:async/zone.dart:1124:13)
E/flutter ( 6252): #18 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 6252): #19 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 6252): #20 _invoke (dart:ui/hooks.dart:249:10)
E/flutter ( 6252): #21 _drawFrame (dart:ui/hooks.dart:207:3)
$扑医生-v
[✓] Flutter (Channel stable, v1.9.1+hotfix.2, on Linux, locale en_IN)
• Flutter version 1.9.1+hotfix.2 at /home/harsh/flutter
• Framework revision 2d2a1ffec9 (3 weeks ago), 2019-09-06 18:39:49 -0700
• Engine revision b863200c37
• Dart version 2.5.0
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /home/harsh/Android/Sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-28, build-tools 28.0.3
• Java binary at: /home/harsh/android-studio/jre/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
• All Android licenses accepted.
[✓] Android Studio (version 3.5)
• Android Studio at /home/harsh/android-studio
• Flutter plugin version 39.0.3
• Dart plugin version 191.8423
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
[✓] Connected device (1 available)
• Android SDK built for x86 • emulator-5554 • android-x86 • Android 9 (API 28) (emulator)
• No issues found!
我仔细检查了自述文件并检查了实现.对我来说看起来不错.不知道出什么事了吗?插件中是否有任何错误?
I checked the README carefully and checked the implementation. It looks good to me. Don't know what is wrong? Is there any bug in the plugin?
如果我没有在FirebaseMessaging.configure方法中传递onBackgroundMessage参数，则此确切的代码有效.
This exact code works if I don't pass onBackgroundMessage argument in FirebaseMessaging.configure method.
推荐答案
您正在使用的一个插件(在本例中为WifiIoTPlugin)引发了null异常.通常，因为该插件是为仅前景方案而设计的. firebase_messaging是一个也在后台运行的插件，因此就是冲突.
One of the plugins you are using (in this case WifiIoTPlugin) is throwing a null exception. Mostly, because the plugin is designed for foreground only scenario. firebase_messaging is a plugin that also working in the background, hence that is the conflict.
当同时使用android_alarm_manager和google_maps_flutter时，引起了类似的问题为android_alarm_manager.
A similar issue was caused when using android_alarm_manager and google_maps_flutter together as android_alarm_manager.
可以通过在没有活动的情况下不注册插件来快速解决此问题.选中用于解决上述问题的拉请求.
This issue can be quickly fixed by not registering the plugin when there is no activity. Check this Pull Request which was used to fix the above mentioned issue.
引起问题的插件(仅适用于前景的插件)代码应如下所示:
The plugin that is causing the issue (foreground only plugin) code should look something like this:
public static void registerWith(Registrar registrar) {
if (registrar.activity() == null) {
// When a background flutter view tries to register the plugin, the registrar has no activity.
// We stop the registration process as this plugin is foreground only.
return;
}
final ForegroundPlugin foregroundPlugin = new ForegroundPlugin(registrar.activity());
...
}
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