.NET MAUI Firebase 消息传递：针对 Android 12 及更高版本的应用程序需要在意图过滤器时为 `android:exported` 指定显式值答案

【问题标题】：.NET MAUI Firebase Messaging: Apps targeting Android 12 and higher are required to specify an explicit value for `android:exported` when intent filter.NET MAUI Firebase 消息传递：针对 Android 12 及更高版本的应用程序需要在意图过滤器时为 `android:exported` 指定显式值
【发布时间】：2022-08-20 13:48:15
【问题描述】：

我正在尝试设置Xamarin.Firebase.Messaging，它说要指定android:exported，我尝试添加一些活动标签，我也发现了很多类似的问题，但在我的 .NET MAUI 项目中没有任何工作，或者我只是不知道如何请参阅MyFirebaseMessagingService.cs。它引发了这个错误：

Severity    Code    Description Project File    Line    Suppression State
Error   AMM0000 
    android:exported needs to be explicitly specified for element <service#crc64bdb245ab40403d31.MyFirebaseMessagingService>. Apps targeting Android 12 and higher are required to specify an explicit value for `android:exported` when the corresponding component has an intent filter defined. See https://developer.android.com/guide/topics/manifest/activity-element#exported for details.
    FIrebasePushNotoficationsTest2  C:\\Users\\Lukas-PC\\source\\repos\\FIrebasePushNotoficationsTest2\\FIrebasePushNotoficationsTest2\\obj\\Debug\\net6.0-android31.0\\AndroidManifest.xml   28

当我从MyFirebaseMessagingService.cs 中删除[Service] 时，通知工作有效，但不调用方法OnMessageReceived。

MyFirebaseMessagingService.cs：

using Android.App;
using Firebase.Messaging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FIrebasePushNotoficationsTest2.Platforms.Android
{
    [Service]
    [IntentFilter(new[] { \"com.google.firebase.MESSAGING_EVENT\" })]
    public class MyFirebaseMessagingService : FirebaseMessagingService
    {
        public override void OnMessageReceived(RemoteMessage message)
        {
            Log.SendLog($\"Msg:{message.GetNotification().Body}\");
        }
    }
}

AndroidManifest.xml

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<manifest xmlns:android=\"http://schemas.android.com/apk/res/android\">
    <application android:allowBackup=\"true\" android:icon=\"@mipmap/appicon\" android:roundIcon=\"@mipmap/appicon_round\" android:supportsRtl=\"true\">
    <receiver android:name=\"com.google.firebase.iid.FirebaseInstanceIdInternalReceiver\" android:exported=\"false\" />
    <receiver android:name=\"com.google.firebase.iid.FirebaseInstanceIdReceiver\" android:exported=\"true\" android:permission=\"com.google.android.c2dm.permission.SEND\">
      <intent-filter>
        <action android:name=\"com.google.android.c2dm.intent.RECEIVE\" />
        <action android:name=\"com.google.android.c2dm.intent.REGISTRATION\" />
        <category android:name=\"${applicationId}\" />
      </intent-filter>
    </receiver>
  </application>
    <uses-permission android:name=\"android.permission.ACCESS_NETWORK_STATE\" />
    <uses-permission android:name=\"android.permission.INTERNET\" />
</manifest>

MainActivity.cs：

using Android.App;
using Android.Content.PM;
using Android.OS;
using Firebase.Iid;
using Firebase.Messaging;

namespace FIrebasePushNotoficationsTest2;

[Activity(Theme = \"@style/Maui.SplashTheme\", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        FirebaseMessaging.Instance.SubscribeToTopic(\"General\");

        var t = FirebaseInstanceId.Instance.Token;
        Log.SendLog($\"T:{t}\");
    }
}

我的项目：

标签： android firebase xamarin firebase-cloud-messaging .net-maui

【解决方案1】：

我遇到了这个问题，我将 Exported=false 添加到 Service 属性中，如下所示：

[Service(Exported = false)]
[IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
public class MessagingService : FirebaseMessagingService
{
    public override void OnNewToken(string token)
    {
         base.OnNewToken(token);
    }
}

生成的 AndroidManifest.xml 然后包含以下属性：

 <service android:exported="false" android:name="crc641fa5edea34be3b44.MessagingService">
      <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
      </intent-filter>
 </service>

希望这会有所帮助！

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