Flutter：加载时显示rewardedAd

Question

为了展示广告，我这样做：

await adState.showRewardedAd();
await adState.rewardedAd!.show(onUserEarnedReward: (RewardedAd ad, RewardItem reward) {
// reward
});

和：

Future createRewardedAd([bool showVideo = false]) async {
    await RewardedAd.load(
      adUnitId: rewardeUnitAdId,
      request: request,
      rewardedAdLoadCallback: RewardedAdLoadCallback(
        onAdLoaded: (RewardedAd ad) async {
          adState.rewardedAd = ad;
          _numRewardedLoadAttempts = 0;
          if (showVideo) {
            showRewardedAd();
          }
        },
        onAdFailedToLoad: (LoadAdError error) async {
          adState.rewardedAd = null;
          _numRewardedLoadAttempts += 1;
          if (_numRewardedLoadAttempts <= maxFailedLoadAttempts) {
            await createRewardedAd();
          }
        },
      ),
    );
  }

  Future<void> showRewardedAd() async {
    if (adState.rewardedAd == null) {
      return await createRewardedAd(true);
    }

    adState.rewardedAd!.fullScreenContentCallback =
        await FullScreenContentCallback(
      onAdShowedFullScreenContent: (RewardedAd ad) => {},
      onAdDismissedFullScreenContent: (RewardedAd ad) async {
        ad.dispose();
        await createRewardedAd();
      },
      onAdFailedToShowFullScreenContent: (RewardedAd ad, AdError error) async {
        ad.dispose();
        await createRewardedAd();
      },
    );
  }

因此，每次我们关闭奖励广告时，我们都会再次创建/加载它，以便为下次做好准备。直到这里一切都很好。

---

当我们点击再次显示它的速度太快时，问题就出现了。当我们这样做时：

if (adState.rewardedAd == null) {
      return await createRewardedAd(true);
    }

我强制加载它并等待，await RewardedAd.load()但尽管我等待，该onAdLoaded事件仍然需要一些时间，并且异步函数不知道它尚未准备好。

所以，当我这样做时，await adState.rewardedAd!它可以为空。

我怎样才能让这个更安全？谷歌的文档没有涵盖这一点