无法从Firebase下载图像，文本，视频

Question

我无法从Firebase将数据（图像，文本，视频）全部下载到具有多种视图类型的一个回收视图中。屏幕只是空白。

这是我要显示数据的班级

public class Literature extends AppCompatActivity {

private SlidrInterface slidr;
StorageReference storageRef;
String Storage_Path = "All_Uploads/";

// Creating DatabaseReference.
DatabaseReference databaseReference;

// Creating RecyclerView.
RecyclerView recyclerView;

// Creating RecyclerView.Adapter.
RecyclerView.Adapter adapter ;

// Creating Progress dialog
ProgressDialog progressDialog;

// Creating List of ImageUploadInfo class.
ArrayList<Model> list= new ArrayList();

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

    storageRef = FirebaseStorage.getInstance().getReference();
    slidr = Slidr.attach(this);
    recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new LinearLayoutManager(Literature.this));
    progressDialog = new ProgressDialog(Literature.this);
    progressDialog.setMessage("Loading Images From Firebase.");
    progressDialog.show();
    databaseReference = FirebaseDatabase.getInstance().getReference("All_Uploads/Design/" );


    databaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {

            for (DataSnapshot postSnapshot : snapshot.getChildren()) {

                Model model = postSnapshot.getValue(Model.class);

                list.add(model);
            }

            adapter = new MultiViewTypeAdapter(list , getApplicationContext());

            recyclerView.setAdapter(adapter);

            // Hiding the progress dialog.
            progressDialog.dismiss();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

            // Hiding the progress dialog.
            progressDialog.dismiss();

        }
    });

}
}

这是Recycler View的适配器类

public class MultiViewTypeAdapter extends RecyclerView.Adapter {

private ArrayList<Model>dataSet;
Context mContext;
int total_types;
MediaPlayer mPlayer;
private boolean fabStateVolume = false;

public static class TextTypeViewHolder extends RecyclerView.ViewHolder {

    TextView txtType;
    CardView cardView;

    public TextTypeViewHolder(View itemView) {
        super(itemView);

        this.txtType = (TextView) itemView.findViewById(R.id.type);
        this.cardView = (CardView) itemView.findViewById(R.id.card_view);
    }
}

public static class ImageTypeViewHolder extends RecyclerView.ViewHolder {

    TextView txtType;
    ImageView image;

    public ImageTypeViewHolder(View itemView) {
        super(itemView);

        this.txtType = (TextView) itemView.findViewById(R.id.type);
        this.image = (ImageView) itemView.findViewById(R.id.background);
    }
}

public static class VideoTypeViewHolder extends RecyclerView.ViewHolder {

    TextView txtType;
    FloatingActionButton fab;

    public VideoTypeViewHolder(View itemView) {
        super(itemView);

        this.txtType = (TextView) itemView.findViewById(R.id.type);
        this.fab = (FloatingActionButton) itemView.findViewById(R.id.fab);
    }
}

public MultiViewTypeAdapter(ArrayList<Model>data, Context context) {
    this.dataSet = data;
    this.mContext = context;
    total_types = dataSet.size();
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    View view;
    switch (viewType) {
        case Model.TEXT_TYPE:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_type, parent, false);
            return new TextTypeViewHolder(view);
        case Model.IMAGE_TYPE:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.image_type, parent, false);
            return new ImageTypeViewHolder(view);
        case Model.VIDEO_TYPE:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.video_type, parent, false);
            return new VideoTypeViewHolder(view);
    }
    return null;
}

@Override
public int getItemViewType(int position) {

    switch (dataSet.get(position).type) {
        case 0:
            return Model.TEXT_TYPE;
        case 1:
            return Model.IMAGE_TYPE;
        case 2:
        return Model.VIDEO_TYPE;
        default:
            return -1;
    }
}

@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int listPosition) {

    Model object = dataSet.get(listPosition);
    if (object != null) {
        switch (object.type) {
            case Model.TEXT_TYPE:
                ((TextTypeViewHolder) holder).txtType.setText(object.text);

                break;
            case Model.IMAGE_TYPE:
                ((ImageTypeViewHolder) holder).txtType.setText(object.text);
                ((ImageTypeViewHolder) holder).image.setImageResource(object.data);
                break;
            case Model.VIDEO_TYPE:


                break;
        }
    }
}

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

这是Model类

public class Model {

public static final int TEXT_TYPE=0;
public static final int IMAGE_TYPE=1;
public static final int VIDEO_TYPE=2;

public int type;
public int data;
public String text;

public Model(int type, String text, int data)
{
    this.type=type;
    this.data=data;
    this.text=text;
}
}

我的数据库

请帮助我看看我要去哪里