c# - 在Unity中使用Firebase Cloud Messaging时如何获取当前 Activity ？

要在没有Firebase Cloud Messaging的情况下在Unity中获得当前 Activity ，可以使用以下代码:

var unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
var activity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");

但是，Firebase Cloud Messaging扩展了默认的Unity Activity 。因此，我将AndroidJavaClass更改为:

var unityPlayer = new AndroidJavaClass("com.google.firebase.MessagingUnityPlayerActivity");
var activity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");

但是，我现在在logcat中收到以下错误:

08-01 15:51:31.838 20323 20375 E Unity   : AndroidJavaException: java.lang.NoSuchFieldError: no "Ljava/lang/Object;" field "currentActivity" in class "Lcom/google/firebase/MessagingUnityPlayerActivity;" or its superclasses
08-01 15:51:31.838 20323 20375 E Unity   : java.lang.NoSuchFieldError: no "Ljava/lang/Object;" field "currentActivity" in class "Lcom/google/firebase/MessagingUnityPlayerActivity;" or its superclasses
08-01 15:51:31.838 20323 20375 E Unity   :      at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
08-01 15:51:31.838 20323 20375 E Unity   :      at com.unity3d.player.UnityPlayer.access$300(Unknown Source:0)
08-01 15:51:31.838 20323 20375 E Unity   :      at com.unity3d.player.UnityPlayer$e$1.handleMessage(Unknown Source:83)
08-01 15:51:31.838 20323 20375 E Unity   :      at android.os.Handler.dispatchMessage(Handler.java:103)
08-01 15:51:31.838 20323 20375 E Unity   :      at android.os.Looper.loop(Looper.java:214)
08-01 15:51:31.838 20323 20375 E Unity   :      at com.unity3d.player.UnityPlayer$e.run(Unknown Source:20)
08-01 15:51:31.838 20323 20375 E Unity   :   at UnityEngine.AndroidJNISafe.CheckException () [0x00000] in <00000000000000000000000000000000>:0
08-01 15:51:31.838 20323 20375 E Unity   :   at UnityEngine.AndroidJNISafe.GetStaticFieldID (System.IntPtr clazz, System.String name, System.String sig) [0x00000] in <00000000000000000000000000000000>:0
08-01 15:51:31.838 20323 20375 E Unity   :   at UnityEngine._AndroidJNIHelper.GetFieldID (System.IntPtr jc

我不明白为什么。它说currentActivity甚至不存在于父类(super class)中，但是如果我正确理解Firebase Cloud Messaging，则它应该仍然存在于父类(super class)中。我也尝试过用currentActivity，UnityPlayerActivity，MessagingUnityPlayerActivity和mypackage之类的东西替换com.mypackage，但是存在相同的错误。在使用Firebase Cloud Messaging时在我的AndroidJavaClass中引用com.unity3d.player.UnityPlayer有其自身的问题:https://gamedev.stackexchange.com/questions/183734/how-can-i-use-an-inherited-activity-in-c
如果相关，这是我的AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" package="com.mypackage" android:versionCode="1" android:versionName="1.0">
  <application android:label="@string/app_name" android:icon="@drawable/app_icon">
    <!-- The MessagingUnityPlayerActivity is a class that extends
         UnityPlayerActivity to work around a known issue when receiving
         notification data payloads in the background. -->
    <meta-data
            android:name="com.google.firebase.messaging.default_notification_icon"
            android:resource="@drawable/notification_icon" />
    <activity android:name="com.google.firebase.MessagingUnityPlayerActivity" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen">
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
      <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
    </activity>
    <service android:name="com.google.firebase.messaging.MessageForwardingService" android:exported="false" />
  </application>
</manifest>

使用Firebase Cloud Messaging时如何获得当前 Activity ？为什么代码不能按所示方式工作？

最佳答案

如果您将类改回"com.unity3d.player.UnityPlayer"，则此行为应符合预期。
问题在于，静态方法在Java中的行为与标准方法略有不同。如果看到Java documentation for the JNI。

请注意，这可能与您从标准Ja​​va文档(例如:Are static methods inherited in Java?)中得出的结论相反。