使用AsyncTask进行RecyclerView分页制作重复页面?

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问题描述

我有一个图库应用程序，该应用程序正在解析Reddit API并用图像填充recyclerview列表.每页包含该subreddit中的25张图片.但是，此代码正在进行重复的数据调用，当您滚动2或3次才能将相同的页面放入图库时，它们才会到达下一页.我将如何解决此问题?

I have a gallery application that is parsing the Reddit API and populating a recyclerview list with images. Each page contains 25 pictures from that subreddit. But this code is making duplicate data calls which puts the same pages in the gallery when you scroll 2 or 3 times before it get the next page. How would I be able to fix this problem?

 public class DesktopGalleryFragment extends Fragment{
    private int count;
    private RecyclerView mDesktopRecyclerView;
    private List<DesktopItems> mList = new ArrayList<>();
    private String after, nullString;
    private Parcelable recyclerViewState;

    public String getAfter(String s){
        return this.after = s;
    }

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
        new FetchItemsTask().execute(nullString);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        mDesktopRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener(){
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState){

                PhotoAdapter adapter = (PhotoAdapter) recyclerView.getAdapter();
                int lastPostion = adapter.getLastBoundPosition();
                GridLayoutManager layoutManager = (GridLayoutManager) recyclerView.getLayoutManager();
                int loadBufferPosition = 1;
                if (lastPostion >= adapter.getItemCount() - layoutManager.getSpanCount() - loadBufferPosition){
                    new FetchItemsTask().execute(after);
                }
            }
        });

        return v;
    }

    private class FetchItemsTask extends AsyncTask<String, Void, List<DesktopItems>>{
        @Override
        protected List<DesktopItems> doInBackground(String... params){
            return new RedditParser().fetchItems(params[0]);
        }

        @Override
        protected void onPostExecute(List<DesktopItems> items){
            if (count > 1){
                getAfter(DesktopItems.getAfter());
                mList.addAll(items);
                mDesktopRecyclerView.getAdapter().notifyDataSetChanged();
            } else{
                mList = items;
                recyclerViewState = mDesktopRecyclerView.getLayoutManager().onSaveInstanceState();
                mDesktopRecyclerView.getLayoutManager().onRestoreInstanceState(recyclerViewState);
                setupAdapter();
            }
            count++;
        }
    }
}

RedditParser.java

public List<DesktopItems> fetchItems(String after)
{
    List<DesktopItems> items = new ArrayList<>();
    int count = 0;
    int counter = count + 25;

    try
    {
        String url = Uri.parse("https://www.reddit.com/r/battlestations/hot.json")
                .buildUpon()
                .appendQueryParameter("after", after)
                .build()
                .toString();
        String jsonString = getUrlString(url);
        Log.i(TAG, "Received JSON: " + jsonString);
        JSONObject jsonBody = new JSONObject(jsonString);
        parseItems(items, jsonBody);
    return items;
}

onScrollStateChanged

使用AsyncTask进行RecyclerView分页制作重复页面?

问题描述

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