正在下载数据但无法在 RecyclerView 上显示

Question

大家好，我正在尝试使用 RSS 提要创建一个 Flickr 应用程序并从 RecylerView 显示它。 我可以下载数据（我可以在日志猫中看到链接）但在 RecyclerView 中看不到它们我的日志猫没有任何错误。

公共 class MainActivity 扩展 AppCompatActivity 实现 GetFlickrJsonData.OnDataAvailable { private static final String TAG = "MainActivity"; 私人 FlickrRecyclerViewAdapter mFlickrRecyclerViewAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    Log.d(TAG, "onCreate: starts");
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    mFlickrRecyclerViewAdapter = new FlickrRecyclerViewAdapter(this, new ArrayList<>());
    recyclerView.setAdapter(mFlickrRecyclerViewAdapter);

tags=android,nougat,sdk&tagmode=any&format=json&nojsoncallback=1"); Log.d(TAG, "onCreate: 结束");

    Log.d(TAG, "onCreate: ends");
}

@Override
protected void onResume() {
    Log.d(TAG, "onResume: starts");
    super.onResume();
    GetFlickrJsonData getFlickrJsonData = new GetFlickrJsonData("https://api.flickr.com/services/feeds/photos_public.gne","en-us",true,this);
  
    getFlickrJsonData.execute("android, nougat");
    Log.d(TAG, "onResume: ends");
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    
    getMenuInflater().inflate(R.menu.menu_main, menu);
    Log.d(TAG, "onCreateOptionsMenu returned: " + true);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    
    int id = item.getItemId();

 
    if (id == R.id.action_settings) {
        return true;
    }
    Log.d(TAG, "onOptionsItemSelected() returned: returned");

    return super.onOptionsItemSelected(item);
}

@Override

public void onDataAvailable(List<Photo> data, DownloadStatus status) {
Log.d(TAG, "onDataAvailable: starts");
if (status == DownloadStatus.OK) {
    mFlickrRecyclerViewAdapter.loadNewData(data);
} else {
    // download or processing failed
    Log.e(TAG, "onDataAvailable failed with status " + status);
}
Log.d(TAG, "onDataAvailable: ends");

}

}

class FlickrRecyclerViewAdapter 扩展 RecyclerView.Adapter<FlickrRecyclerViewAdapter.FlickrImageViewHolder> { private static final String TAG = "FlickrRecyclerViewAdapt"; 私人列表 mPhotoList； 私有上下文 mContext；在此处输入代码

public FlickrRecyclerViewAdapter(Context context, List<Photo> photoList) {
    mContext = context;
    mPhotoList = photoList;
}

@NonNull
@Override
public FlickrImageViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    //Called by the layout manager when it needs a new view
    Log.d(TAG, "onCreateViewHolder: new view requested");
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.browse, parent, false);
    return new FlickrImageViewHolder(view);

}

@Override
public void onBindViewHolder(@NonNull FlickrImageViewHolder holder, int position) {
    //Called by the layout manager when it wants new data in an existing row
    Photo photoItem = mPhotoList.get(position);
    Log.d(TAG, "onBindViewHolder: " + photoItem.getTitle() + " --> "+position );
    Picasso.get().load(photoItem.getImage())
            .error(R.drawable.placeholder2)
            .placeholder(R.drawable.placeholder2)
            .into(holder.thumbnail);

    holder.title.setText(photoItem.getTitle());

}

@Override
public int getItemCount() {
    Log.d(TAG, "getItemCount: called");
    return ((mPhotoList != null) && (mPhotoList.size() != 0) ? mPhotoList.size() : 0);

}

void loadNewData (List<Photo> newPhotos){
    mPhotoList = newPhotos;
    notifyDataSetChanged();
}

public Photo getPhoto(int position){
    return ((mPhotoList != null) && (mPhotoList.size() != 0) ? mPhotoList.get(position) : null);
}

static class FlickrImageViewHolder extends RecyclerView.ViewHolder {

    private static final String TAG = "FlickrImageViewHolder";

    ImageView thumbnail = null;
    TextView title = null;

    public FlickrImageViewHolder(@NonNull View itemView) {
        super(itemView);
        Log.d(TAG, "FlickrImageViewHolder: starts");
        this.thumbnail =(ImageView) itemView.findViewById(R.id.thumbnail);
        this.title = (TextView) itemView.findViewById(R.id.titleText);
    }
}

}