java - 添加 admob 横幅广告时出现 RecyclerView ClassCastException

Question

尝试使用 RecyclerView 添加 Admob 横幅广告时出现 ClassCastException。我正在使用来自 blogger 的 JSON 数据，在添加横幅广告之前它运行良好。我正在使用来自 here 的 GitHub 项目引用.

Error : com.example.abcd.CategoryItem cannot be cast to com.google.android.ads.AdView at com.example.abcd.CategoryAdapter.onBindViewHolder (CategoryAdapter.java:123)

这是我的类别 Activity

public class CategoryActivity extends AppCompatActivity {

public static final int ITEMS_PER_AD=8;
private static final String AD_UNIT_ID="ca-app-pub-3940256099942544/6300978111";

private RecyclerView mRecyclerView;
private CategoryAdapter mCategoryAdapter;
// List of banner ads and MenuItems that populate the RecyclerView.
private List<Object> mCategoryList = new ArrayList<>();

private RequestQueue mRequestQueue;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_category);

    mRecyclerView = findViewById(R.id.recycler_view_category);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

    mRequestQueue = Volley.newRequestQueue(this);

    parseJSON();
    addBannerAds();
    loadBannerAds();

    // Specify an adapter.
    RecyclerView.Adapter<RecyclerView.ViewHolder> adapter = new CategoryAdapter(this, mCategoryList);
    mRecyclerView.setAdapter(adapter);


}
private void parseJSON() {
    String url="http://sambalpurijokeszone.blogspot.com/feeds/posts/summary?alt=json&amp;max-results=0";
    JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    try {
                        JSONObject feed=(JSONObject) response.get("feed");
                        JSONArray category =(JSONArray)feed.get("category");
                        JSONArray sortedCategory=new JSONArray();

                        List<JSONObject> jsonValues=new ArrayList<JSONObject>();
                        for (int i = 0; i < category.length(); i++) {
                            jsonValues.add(category.getJSONObject(i));
                            }
                            //Sorting categories
                        Collections.sort(jsonValues, new Comparator<JSONObject>() {
                            private static final String KEY_NAME="term";

                            @Override
                            public int compare(JSONObject categoryItem, JSONObject t1) {
                                String valA=new String();
                                String valB =new String();
                                try{
                                    valA=(String) categoryItem.get(KEY_NAME);
                                    valB=(String) t1.get(KEY_NAME);
                                }
                                catch (JSONException e){
                                }
                                return valA.compareToIgnoreCase(valB);
                            }
                         });

                        for (int i = 0; i < category.length(); i++) {
                            sortedCategory.put(jsonValues.get(i));
                        }
                        for (int i = 0; i < sortedCategory.length(); i++) {
                            JSONObject hit = sortedCategory.getJSONObject(i);

                            String categoryItem=hit.getString("term");
                            mCategoryList.add(new CategoryItem(categoryItem));
                        }

                      /*mCategoryAdapter = new CategoryAdapter(CategoryActivity.this, mCategoryList);
                        mRecyclerView.setAdapter(mCategoryAdapter);
                        mCategoryAdapter.setOnItemClickListener(CategoryActivity.this);*/

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            error.printStackTrace();
        }
    });

    mRequestQueue.add(request);
}


private void addBannerAds(){
    //Loop through the items array and place a new banner ad in every ith position in the item list
    for(int i=0;i<=mCategoryList.size();i+= ITEMS_PER_AD){
        final AdView adView = new AdView (CategoryActivity.this);
                adView.setAdSize(AdSize.BANNER);
                adView.setAdUnitId(AD_UNIT_ID);
                mCategoryList.add(i,adView);
    }
}

// Sets up and loads the banner ads.
private void loadBannerAds() {
    // Load the first banner ad in the items list (subsequent ads will be loaded automatically
    // in sequence).
    loadBannerAd(0);
}

//Loads the banner ads in the items list.
private void loadBannerAd(final int index) {

    if (index >= mCategoryList.size()) {
        return;
    }

    Object item = mCategoryList.get(index);
    if (!(item instanceof AdView)) {
        throw new ClassCastException("Expected item at index " + index + " to be a banner ad"
                + " ad.");
    }

    final AdView adView = (AdView) item;

    // Set an AdListener on the AdView to wait for the previous banner ad
    // to finish loading before loading the next ad in the items list.
    adView.setAdListener(new AdListener() {
        @Override
        public void onAdLoaded() {
            super.onAdLoaded();
            // The previous banner ad loaded successfully, call this method again to
            // load the next ad in the items list.
            loadBannerAd(index + ITEMS_PER_AD);
        }

        @Override
        public void onAdFailedToLoad(int errorCode) {
            // The previous banner ad failed to load. Call this method again to load
            // the next ad in the items list.
            Log.e("MainActivity", "The previous banner ad failed to load. Attempting to"
                    + " load the next banner ad in the items list.");
            loadBannerAd(index + ITEMS_PER_AD);
        }
    });

    // Load the banner ad.
    adView.loadAd(new AdRequest.Builder().build());
}

类别适配器:

public class CategoryAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
// A menu item view type.
private static final int MENU_ITEM_VIEW_TYPE = 0;
// The banner ad view type.
private static final int BANNER_AD_VIEW_TYPE = 1;

private Context mContext;

// The list of banner ads and category items.
private final List<Object> mCategoryList;


public CategoryAdapter(Context context, List<Object> CategoryList) {
    mContext = context;
    mCategoryList = CategoryList;
}

@Override
public int getItemCount() {
    return mCategoryList.size();
}



public class CategoryViewHolder extends RecyclerView.ViewHolder {
    public TextView mTextViewCategory;

    public CategoryViewHolder(View itemView) {
        super(itemView);
        mTextViewCategory = itemView.findViewById(R.id.text_view_category);
    }
}

public class AdViewHolder extends RecyclerView.ViewHolder {

    AdViewHolder(View view) {
        super(view);
    }
}

/* Determines the view type for the given position*/
@Override
public int getItemViewType(int position) {
            if (position % CategoryActivity.ITEMS_PER_AD == 0)
                return BANNER_AD_VIEW_TYPE;
            else
                return MENU_ITEM_VIEW_TYPE;
}


/* Creates a new view for a menu item view or a banner ad view
 * based on the viewType. This method is invoked by the layout manager*/
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {

    switch (viewType) {
        case MENU_ITEM_VIEW_TYPE:
            View menuItemLayoutView = LayoutInflater.from(viewGroup.getContext()).inflate(
                    R.layout.category_item, viewGroup, false);
            return new CategoryViewHolder(menuItemLayoutView);
        case BANNER_AD_VIEW_TYPE:
            // fall through
        default:
            View bannerLayoutView = LayoutInflater.from(
                    viewGroup.getContext()).inflate(R.layout.banner_ad_container,
                    viewGroup, false);
            return new AdViewHolder(bannerLayoutView);
    }
}

/** Replaces the content in the views that make up the menu item view and the
 * * banner ad view. This method is invoked by the layout manager.*/
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    int viewType = getItemViewType(position);
    switch (viewType) {
        case MENU_ITEM_VIEW_TYPE:
            CategoryViewHolder categoryItemHolder = (CategoryViewHolder) holder;
            CategoryItem currentItem = (CategoryItem) mCategoryList.get(position);
            String categoryName=currentItem.getCategoryName();
            categoryItemHolder.mTextViewCategory.setText(categoryName);
            break;
        case BANNER_AD_VIEW_TYPE:
            // fall through
        default:
            AdViewHolder bannerHolder = (AdViewHolder) holder;
            AdView adView = (AdView) mCategoryList.get(position);
            ViewGroup adCardView = (ViewGroup) bannerHolder.itemView;

            if (adCardView.getChildCount() > 0) {
                adCardView.removeAllViews();
            }
            if (adView.getParent() != null) {
                ((ViewGroup) adView.getParent()).removeView(adView);
            }

            // Add the banner ad to the ad view.
            adCardView.addView(adView);
    }

}

请帮我解决这个问题。提前致谢。

Answer 1

@Override public int getItemViewType(int position) { 
    if (mCategoryList.get(position) instanceof AdView) 
        return BANNER_AD_VIEW_TYPE; 
    else return MENU_ITEM_VIEW_TYPE; 
}