java - 如何在 Xamarin.Android 中实现 RewardedAdLoadCallback？

Question

我正在尝试在 C# 中的 Xamarin.Android 中实现奖励广告。
Android 文档中的代码 fragment 是用 Java 编写的，通常我在 C# 中采用该代码没有太大问题，但现在看来确实是个问题。
要在 Java 中加载 RewardedAd，您必须执行以下操作 (according to the official documentation):

AdRequest adRequest = new AdRequest.Builder().build();

RewardedAd.load(this, "ca-app-pub-3940256099942544/5224354917",
      adRequest, new RewardedAdLoadCallback(){
        @Override
        public void onAdFailedToLoad(@NonNull LoadAdError loadAdError) {
          // Handle the error.
          Log.d(TAG, loadAdError.getMessage());
          mRewardedAd = null
        }

        @Override
        public void onAdLoaded(@NonNull RewardedAd rewardedAd) {
          mRewardedAd = rewardedAd;
          Log.d(TAG, "onAdFailedToLoad");
        }
    });

现在这里的问题是对象 RewardedAdLoadCallback在此代码中传递，还定义了方法实现( onAdFailedToLoad 和 onAdLoaded )，而在 C# 中无法做到这一点。
所以我的解决方案是创建自己的类(class)，MyRewardedAdLoadCallback ，并覆盖方法。

public class MyRewardedAdLoadCallback : RewardedAdLoadCallback
{
    public override void OnAdLoaded(Java.Lang.Object p0)
    {
        base.OnAdLoaded(p0);
    }

    public override void OnAdFailedToLoad(LoadAdError p0)
    {
        base.OnAdFailedToLoad(p0);
    }
}

然后我只需使用以下代码加载奖励广告:

AdRequest adRequest = new AdRequest.Builder().Build();

RewardedAd.Load(this, "ca-app-pub-3940256099942544/5224354917", adRequest, new MyRewardedAdLoadCallback());

现在由于一些奇怪的原因，我在构建项目时遇到了这个错误:

error: name clash: onAdLoaded(Object) in MyRewardedAdLoadCallback and onAdLoaded(AdT) in AdLoadCallback have the same erasure, yet neither overrides the other
    public void onAdLoaded (java.lang.Object p0)
  where AdT is a type-variable:
    AdT extends Object declared in class AdLoadCallback

我尝试在 Internet 上搜索此错误并得出结论，这是一个 Java 错误并且与泛型类型有关(请参阅 this SO 问题)。但是，我在我的代码和关于奖励广告的 Android 文档中都没有看到任何通用类型。关于我正在尝试实现的奖励广告的 Xamarin 文档也为零。
如果有人能帮我解决这个问题，我会很高兴。提前致谢。

Answer 1

这是让插页式广告和奖励广告在 Xamarin.GooglePlayServices.Ads 版本 120.0.0 中工作的技巧。
将以下文件添加到您的项目(需要使用 unsafe 标志构建)并使用 Android.Gms.Ads.Hack命名空间来加载你的广告和子类你的回调。
例如，InterstitialAd.Load变成 global::Android.Gms.Ads.Hack.InterstitialAd.Load和 InterstitialAdLoadCallback变成 global::Android.Gms.Ads.Hack.InterstitialAdLoadCallback .
回调类添加 OnInterstitialAdLoaded()和 OnRewardedAdLoaded()插页式广告和奖励广告加载回调的虚拟方法，分别。

using System;
using System.ComponentModel;
using System.Diagnostics;
using Android.Content;
using Android.Runtime;
using Java.Interop;

namespace Android.Gms.Ads.Hack
{
    public abstract class InterstitialAd : Java.Lang.Object
    {
        private static readonly JniPeerMembers _members = new XAPeerMembers("com/google/android/gms/ads/interstitial/InterstitialAd", typeof(InterstitialAd));

        public unsafe static void Load(Context context, string adUnit, AdRequest request, AdLoadCallback callback)
        {
            IntPtr intPtr = JNIEnv.NewString(adUnit);
            try
            {
                JniArgumentValue* ptr = stackalloc JniArgumentValue[4];
                *ptr = new JniArgumentValue(context?.Handle ?? IntPtr.Zero);
                ptr[1] = new JniArgumentValue(intPtr);
                ptr[2] = new JniArgumentValue(request?.Handle ?? IntPtr.Zero);
                ptr[3] = new JniArgumentValue(callback?.Handle ?? IntPtr.Zero);
                _members.StaticMethods.InvokeVoidMethod("load.(Landroid/content/Context;Ljava/lang/String;Lcom/google/android/gms/ads/AdRequest;Lcom/google/android/gms/ads/interstitial/InterstitialAdLoadCallback;)V", ptr);
            }
            finally
            {
                JNIEnv.DeleteLocalRef(intPtr);
                GC.KeepAlive(context);
                GC.KeepAlive(request);
                GC.KeepAlive(callback);
            }
        }
    }

    [Register("com/google/android/gms/ads/interstitial/InterstitialAdLoadCallback", DoNotGenerateAcw = true)]
    public abstract class InterstitialAdLoadCallback : AdLoadCallback
    {
        private static readonly JniPeerMembers _members = new XAPeerMembers("com/google/android/gms/ads/interstitial/InterstitialAdLoadCallback", typeof(InterstitialAdLoadCallback));

        static IntPtr class_ref => _members.JniPeerType.PeerReference.Handle;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        public override JniPeerMembers JniPeerMembers => _members;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        protected override IntPtr ThresholdClass => _members.JniPeerType.PeerReference.Handle;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        protected override Type ThresholdType => _members.ManagedPeerType;

        protected InterstitialAdLoadCallback(IntPtr javaReference, JniHandleOwnership transfer)
            : base(javaReference, transfer)
        {
        }

        [Register(".ctor", "()V", "")]
        public unsafe InterstitialAdLoadCallback()
            : base(IntPtr.Zero, JniHandleOwnership.DoNotTransfer)
        {
            if (!(base.Handle != IntPtr.Zero))
            {
                SetHandle(_members.InstanceMethods.StartCreateInstance("()V", GetType(), null).Handle, JniHandleOwnership.TransferLocalRef);
                _members.InstanceMethods.FinishCreateInstance("()V", this, null);
            }
        }

        private static Delegate cb_onAdLoaded;

        private static Delegate GetOnAdLoadedHandler()
        {
            if (cb_onAdLoaded is null)
            {
                cb_onAdLoaded = JNINativeWrapper.CreateDelegate((Action<IntPtr, IntPtr, IntPtr>)n_onAdLoaded);
            }

            return cb_onAdLoaded;
        }

        private static void n_onAdLoaded(IntPtr jnienv, IntPtr native__this, IntPtr native_p0)
        {
            InterstitialAdLoadCallback? @object = Java.Lang.Object.GetObject<InterstitialAdLoadCallback>(jnienv, native__this, JniHandleOwnership.DoNotTransfer);
            global::Android.Gms.Ads.Interstitial.InterstitialAd object2 = Java.Lang.Object.GetObject<global::Android.Gms.Ads.Interstitial.InterstitialAd>(native_p0, JniHandleOwnership.DoNotTransfer);
            @object!.OnInterstitialAdLoaded(object2);
        }

        [Register("onAdLoaded", "(Lcom/google/android/gms/ads/interstitial/InterstitialAd;)V", "GetOnAdLoadedHandler")]
        public virtual void OnInterstitialAdLoaded(global::Android.Gms.Ads.Interstitial.InterstitialAd interstitialAd)
        {
        }
    }

    public abstract class RewardedAd : Java.Lang.Object
    {
        private static readonly JniPeerMembers _members = new XAPeerMembers("com/google/android/gms/ads/rewarded/RewardedAd", typeof(RewardedAd));

        public unsafe static void Load(Context context, string adUnit, AdRequest request, RewardedAdLoadCallback callback)
        {
            IntPtr intPtr = JNIEnv.NewString(adUnit);
            try
            {
                JniArgumentValue* ptr = stackalloc JniArgumentValue[4];
                *ptr = new JniArgumentValue(context?.Handle ?? IntPtr.Zero);
                ptr[1] = new JniArgumentValue(intPtr);
                ptr[2] = new JniArgumentValue(request?.Handle ?? IntPtr.Zero);
                ptr[3] = new JniArgumentValue(callback?.Handle ?? IntPtr.Zero);
                _members.StaticMethods.InvokeVoidMethod("load.(Landroid/content/Context;Ljava/lang/String;Lcom/google/android/gms/ads/AdRequest;Lcom/google/android/gms/ads/rewarded/RewardedAdLoadCallback;)V", ptr);
            }
            finally
            {
                JNIEnv.DeleteLocalRef(intPtr);
                GC.KeepAlive(context);
                GC.KeepAlive(request);
                GC.KeepAlive(callback);
            }
        }
    }

    [Register("com/google/android/gms/ads/rewarded/RewardedAdLoadCallback", DoNotGenerateAcw = true)]
    public abstract class RewardedAdLoadCallback : AdLoadCallback
    {
        private static readonly JniPeerMembers _members = new XAPeerMembers("com/google/android/gms/ads/rewarded/RewardedAdLoadCallback", typeof(RewardedAdLoadCallback));

        static IntPtr class_ref => _members.JniPeerType.PeerReference.Handle;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        public override JniPeerMembers JniPeerMembers => _members;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        protected override IntPtr ThresholdClass => _members.JniPeerType.PeerReference.Handle;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        protected override Type ThresholdType => _members.ManagedPeerType;

        protected RewardedAdLoadCallback(IntPtr javaReference, JniHandleOwnership transfer)
            : base(javaReference, transfer)
        {
        }

        [Register(".ctor", "()V", "")]
        public unsafe RewardedAdLoadCallback()
            : base(IntPtr.Zero, JniHandleOwnership.DoNotTransfer)
        {
            if (!(base.Handle != IntPtr.Zero))
            {
                SetHandle(_members.InstanceMethods.StartCreateInstance("()V", GetType(), null).Handle, JniHandleOwnership.TransferLocalRef);
                _members.InstanceMethods.FinishCreateInstance("()V", this, null);
            }
        }

        private static Delegate cb_onAdLoaded;

        private static Delegate GetOnAdLoadedHandler()
        {
            if (cb_onAdLoaded is null)
            {
                cb_onAdLoaded = JNINativeWrapper.CreateDelegate((Action<IntPtr, IntPtr, IntPtr>)n_onAdLoaded);
            }

            return cb_onAdLoaded;
        }

        private static void n_onAdLoaded(IntPtr jnienv, IntPtr native__this, IntPtr native_p0)
        {
            RewardedAdLoadCallback? @object = Java.Lang.Object.GetObject<RewardedAdLoadCallback>(jnienv, native__this, JniHandleOwnership.DoNotTransfer);
            global::Android.Gms.Ads.Rewarded.RewardedAd object2 = Java.Lang.Object.GetObject<global::Android.Gms.Ads.Rewarded.RewardedAd>(native_p0, JniHandleOwnership.DoNotTransfer);
            @object!.OnRewardedAdLoaded(object2);
        }

        [Register("onAdLoaded", "(Lcom/google/android/gms/ads/rewarded/RewardedAd;)V", "GetOnAdLoadedHandler")]
        public virtual void OnRewardedAdLoaded(global::Android.Gms.Ads.Rewarded.RewardedAd rewardedAd)
        {
        }
    }
}