Question

因此，我正在查询Firebase数据库，并尝试将数据读取到recyclerview中。现在，当我简单地将数据读入文本视图并将文本设置为数据时（即，我有3个文本视图-颜色，高度，名称），一切正常，并且显示了正确的数据。

但是，我一直试图将查询结果加载到回收站视图rvResults中，但它根本无法工作。我将数据添加到arraylists中，然后将包含查询结果的arrayLists（颜色，高度，名称）传递到我的ResultsRecyclerAdapater中。但是，当我运行时，我得到了一个空白屏幕-但没有崩溃。

我不是专家，但这似乎是问题所在。似乎没有将这些添加到arrayLists中。我的“植物”课很好，所以这不是问题。

String name = plant.getName();
                        String bio = plant.getBio();
                        String height = plant.getHeight();
                        String colour = plant.getColour();

                        names.add(name);
                        heights.add(height);
                        colours.add(colour);

任何帮助将不胜感激！

   ArrayList<String> names = new ArrayList<>();
    ArrayList<String> heights = new ArrayList<>();
    ArrayList<String> colours = new ArrayList<>();

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

    Task task1 = plantRef.whereEqualTo("height", "Medium")
            .get();

    Task task2 = plantRef.whereEqualTo("colour", "Red")
            .get();

    Task<List<QuerySnapshot>> allTasks = Tasks.whenAllSuccess(task1, task2);
    allTasks.addOnSuccessListener(new OnSuccessListener<List<QuerySnapshot>>() {
        @Override
        public void onSuccess(List<QuerySnapshot> querySnapshots) {
            String data = "";

            for(QuerySnapshot queryDocumentSnapshots : querySnapshots){
                for (QueryDocumentSnapshot documentSnapshot:queryDocumentSnapshots){
                    Plant plant = documentSnapshot.toObject(Plant.class);
                    plant.setDocumentID(documentSnapshot.getId());

                    String documentId =  plant.getDocumentID();

                    String name = plant.getName();
                    String bio = plant.getBio();
                    String height = plant.getHeight();
                    String colour = plant.getColour();

                    names.add(name);
                    heights.add(height);
                    colours.add(colour);
                }
            }
        }
    });

    //set up the RecyclerView, setting the Layout to Horizontal, and binding the adapter
    RecyclerView recyclerView = findViewById(R.id.rvResults);
    recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
    resultsAdapter = new ResultsRecyclerAdapter(this, names, heights, colours);
    resultsAdapter.setClickListener(this);
    recyclerView.setAdapter(resultsAdapter);
}

这里是我的ResultsRecyclerAdapter类：

public class ResultsRecyclerAdapter extends RecyclerView.Adapter<ResultsRecyclerAdapter.ViewHolder> {

    private List<String> mData;
    private List<String> mHeights;
    private List<String> mColours;
    private LayoutInflater mInflater;
    private ItemClickListener mClickListener;

    public ResultsRecyclerAdapter(Context c, List<String> mData, List<String> mHeights, List <String> mColours) {
        this.mInflater = LayoutInflater.from(c);
        this.mData = mData;
        this.mHeights = mHeights;
        this.mColours = mColours;
    }

    // inflates the row layout from xml when needed
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.recycler_view_second_activity, parent, false);
        return new ViewHolder(view);
    }


    @Override
    public void onBindViewHolder(ViewHolder holder, final int position) {
        String name = mData.get(position);
        String height = mHeights.get(position);
        String colour = mColours.get(position);

        holder.tvName.setText(name);
        holder.tvColour.setText(height);
        holder.tvHeight.setText(colour);
    }

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

    // stores and recycles views as they are scrolled off screen
    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView tvName;
        TextView tvHeight;
        TextView tvColour;

        ViewHolder(View itemView) {
            super(itemView);
            tvName = itemView.findViewById(R.id.tvName);
            tvHeight = itemView.findViewById(R.id.tvHeight);
            tvColour = itemView.findViewById(R.id.tvColour);
            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
        }
    }

    // convenience method for getting data at click position
    String getItem(int id) {
        return mData.get(id);
    }

    // allows clicks events to be caught
    void setClickListener(ResultsRecyclerAdapter.ItemClickListener itemClickListener) {
        this.mClickListener = itemClickListener;
    }

    // parent activity will implement this method to respond to click events
    public interface ItemClickListener {
        void onItemClick(View view, int position);
    }
}

Answer 1

您的查询运行异步，您必须致电

resultAdapter.notifyDataSetChange();

在onSuccess(List<QuerySnapshot> querySnapshots)的末尾，您的数据已准备就绪。

Answer 2

您正在呼叫ResultsRecyclerAdapter，然后在OnSuccessListener中准备数据 onSuccess完成后，尝试更新适配器

回收器视图未显示

2 个答案: