Admob原生广告未显示

Question

我想在我的应用中使用原生高级广告。我研究了许多资料，并按照他们所说的做了。我开始播放广告，但没有任何显示。我检查一下；给出onFailedLoad错误。在Toast消息中显示3。 （其他广告类型正在投放；横幅广告，插页式等）。请帮助我。下面的代码

此处所有代码：https://github.com/theoyuncu8/nativetest/

public void onAdFailedToLoad(int errorCode) {
  Toast.makeText(context, "code " + errorCode, Toast.LENGTH_SHORT).show(); // out : 3
 }

MainActiviy：

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);



        MobileAds.initialize(this, new OnInitializationCompleteListener() {
            @Override
            public void onInitializationComplete(InitializationStatus initializationStatus) {
            }
        });

        AdLoader adLoader = new AdLoader.Builder(context, "ca-app-pub-3940256099942544/2247696110")
                .forUnifiedNativeAd(new UnifiedNativeAd.OnUnifiedNativeAdLoadedListener() {
                    @Override
                    public void onUnifiedNativeAdLoaded(UnifiedNativeAd unifiedNativeAd) {
                        FrameLayout frameLayout = findViewById(R.id.frame_layout);
                        @SuppressLint("InflateParams") UnifiedNativeAdView adView = (UnifiedNativeAdView) getLayoutInflater().inflate(R.layout.ad_unified, null);
                        populateUnifiedNativeAdView(unifiedNativeAd, adView);
                        frameLayout.removeAllViews();
                        frameLayout.addView(adView);
                    }
                })
                .withAdListener(new AdListener() {
                    @Override
                    public void onAdFailedToLoad(int errorCode) {
                        Toast.makeText(context, "code " + errorCode, Toast.LENGTH_SHORT).show();
                    }
                })
                .build();

        adLoader.loadAd(new AdRequest.Builder().build());
    }


private void populateUnifiedNativeAdView(UnifiedNativeAd nativeAd, UnifiedNativeAdView adView) {
        adView.setMediaView((MediaView) adView.findViewById(R.id.ad_media));
        adView.setHeadlineView(adView.findViewById(R.id.ad_headline));
        adView.setBodyView(adView.findViewById(R.id.ad_body));
        adView.setCallToActionView(adView.findViewById(R.id.ad_call_to_action));
        adView.setIconView(adView.findViewById(R.id.ad_icon));
        adView.setPriceView(adView.findViewById(R.id.ad_price));
        adView.setStarRatingView(adView.findViewById(R.id.ad_stars));
        adView.setStoreView(adView.findViewById(R.id.ad_store));
        adView.setAdvertiserView(adView.findViewById(R.id.ad_advertiser));

        ((TextView) adView.getHeadlineView()).setText(nativeAd.getHeadline());
        adView.getMediaView().setMediaContent(nativeAd.getMediaContent());


        if (nativeAd.getBody() == null) {
            adView.getBodyView().setVisibility(View.INVISIBLE);
        } else {
            adView.getBodyView().setVisibility(View.VISIBLE);
            ((TextView) adView.getBodyView()).setText(nativeAd.getBody());
        }

        if (nativeAd.getCallToAction() == null) {
            adView.getCallToActionView().setVisibility(View.INVISIBLE);
        } else {
            adView.getCallToActionView().setVisibility(View.VISIBLE);
            ((Button) adView.getCallToActionView()).setText(nativeAd.getCallToAction());
        }

        if (nativeAd.getIcon() == null) {
            adView.getIconView().setVisibility(View.GONE);
        } else {
            ((ImageView) adView.getIconView()).setImageDrawable(
                    nativeAd.getIcon().getDrawable());
            adView.getIconView().setVisibility(View.VISIBLE);
        }

        if (nativeAd.getPrice() == null) {
            adView.getPriceView().setVisibility(View.INVISIBLE);
        } else {
            adView.getPriceView().setVisibility(View.VISIBLE);
            ((TextView) adView.getPriceView()).setText(nativeAd.getPrice());
        }

        if (nativeAd.getStore() == null) {
            adView.getStoreView().setVisibility(View.INVISIBLE);
        } else {
            adView.getStoreView().setVisibility(View.VISIBLE);
            ((TextView) adView.getStoreView()).setText(nativeAd.getStore());
        }

        if (nativeAd.getStarRating() == null) {
            adView.getStarRatingView().setVisibility(View.INVISIBLE);
        } else {
            ((RatingBar) adView.getStarRatingView())
                    .setRating(nativeAd.getStarRating().floatValue());
            adView.getStarRatingView().setVisibility(View.VISIBLE);
        }

        if (nativeAd.getAdvertiser() == null) {
            adView.getAdvertiserView().setVisibility(View.INVISIBLE);
        } else {
            ((TextView) adView.getAdvertiserView()).setText(nativeAd.getAdvertiser());
            adView.getAdvertiserView().setVisibility(View.VISIBLE);
        }
        adView.setNativeAd(nativeAd);

    }