Firebase RecyclerView无法加载新数据

本文介绍了Firebase RecyclerView无法加载新数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 每当用户将某个项目添加到Firebase中的某个数据库引用时，我正试图创建一个实时RecyclerView。这是我的模型类： $ $ p $ code $ @ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $私人字符串题; 私人字符串image_URL; $ b $ public Poll（）{} public Poll（String Question，String Image_URL）{ this.question = Question; this.image_URL = Image_URL; } public String getQuestion（）{ return question; } public void setQuestion（String question）{ question = question; } public String getImage_URL（）{ return image_URL; public void setImage_URL（String image_URL）{ image_URL = image_URL; } @Exclude public Map< String，Object> toMap（）{ HashMap< String，Object> result = new HashMap<>（）; result.put（问题，问题）; result.put（image_URL，image_URL）; 返回结果; $ b 这里是我将数据保存到Firebase的类。它实际上是写给Firebase的，所以我可以确认我写的是正确的： $ p $ public void setQuestion（String question）{ this.question = question; public void setImage_URL（String image_URL）{ this.image_URL = image_URL; $ / code> 并替换此代码： 映射< String，Object> pollMap = poll.toMap（）; String key = mBaseRef.child（Polls）。push（）。getKey（）; 地图< String，Object> childUpdates = new HashMap< String，Object>（）; childUpdates.put（/ Polls /+ key，pollMap）; mBaseRef.updateChildren（childUpdates）; ： @Override $ b $ public void onComplete（DatabaseError databaseError，DatabaseReference databaseReference）{ if（databaseError == null）{ Log.i（Poll，onComplete：SUCCESS）; } else { Log.w（Poll， onComplete：，databaseError.toException（））; } } }）; 同时移动创建 mFireAdapter 的代码，将它设置在 mRecyclerview 从 onStart（）到的结尾onCreateView（） // ... mRecyclerview.setLayoutManager（mLayoutManager）; mFireAdapter = ...; mRecyclerview.setAdapter（mFireAdapter）; return v; 文档 bI am trying to create a real-time RecyclerView every time a user adds an item to a certain Database reference in Firebase. Here is my model class:@IgnoreExtraPropertiespublic class Poll {private String question;private String image_URL;public Poll() {}public Poll(String Question, String Image_URL){ this.question = Question; this.image_URL = Image_URL;}public String getQuestion() { return question;}public void setQuestion(String question) { question = question;}public String getImage_URL() { return image_URL;}public void setImage_URL(String image_URL) { image_URL = image_URL;}@Excludepublic Map<String, Object> toMap(){ HashMap<String, Object> result = new HashMap<>(); result.put("question", question); result.put("image_URL", image_URL); return result;}Here is the class where I save data to Firebase. It is actually being written to Firebase, so I can confirm that I am writing it correctly: mSubmitPollCreation.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //TODO: Need to check if poll requirements are added, i.e. Question, Answer, ...... //check if image has been loaded first if (resultImageURL == null){ Toast.makeText(getApplicationContext(),getResources().getString(R.string.no_image_selected),Toast.LENGTH_LONG).show(); return; } Poll poll = new Poll(mCreatePollQuestion.getText().toString(), resultImageURL); Map <String, Object> pollMap = poll.toMap(); String key = mBaseRef.child("Polls").push().getKey(); Map<String, Object> childUpdates = new HashMap<String, Object>(); childUpdates.put("/Polls/" + key, pollMap); mBaseRef.updateChildren(childUpdates); Intent toHomeActivity = new Intent(CreateActivity.this, HomeActivity.class); toHomeActivity.putExtra("viewpager_position", 2); startActivity(toHomeActivity); } });I want the recyclerview to live update on all devices as an item is added. Here is the fragment I use to populate the RecyclerView using the Firebase UI library. As I add data/write to Firebase as listed in the previous code snippet, I am not seeing any live updates on any devices:public class LiveFragment extends Fragment {// TODO: Rename parameter arguments, choose names that match// the fragment initialization parameters, e.g. ARG_ITEM_NUMBERprivate static final String ARG_PARAM1 = "param1";private static final String ARG_PARAM2 = "param2";private RecyclerView mRecyclerview;private DatabaseReference mBaseRef;private DatabaseReference mPollsRef;private LinearLayoutManager mLayoutManager;private FirebaseRecyclerAdapter <Poll, PollHolder> mFireAdapter;// TODO: Rename and change types of parametersprivate String mParam1;private String mParam2;private OnFragmentInteractionListener mListener;public LiveFragment() { // Required empty public constructor}/** * Use this factory method to create a new instance of * this fragment using the provided parameters. * * @param param1 Parameter 1. * @param param2 Parameter 2. * @return A new instance of fragment LiveFragment. */// TODO: Rename and change types and number of parameterspublic static LiveFragment newInstance(String param1, String param2) { LiveFragment fragment = new LiveFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment;}@Overridepublic void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); }}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment final View v = inflater.inflate(R.layout.fragment_new, container, false); mRecyclerview = (RecyclerView) v.findViewById(R.id.new_RecyclerView); mBaseRef = FirebaseDatabase.getInstance().getReference(); mPollsRef = mBaseRef.child("Polls"); if (mRecyclerview != null){ mRecyclerview.setHasFixedSize(true); } mLayoutManager = new LinearLayoutManager(getActivity().getApplicationContext()); mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL ); mRecyclerview.setLayoutManager(mLayoutManager); return v;}// TODO: Rename method, update argument and hook method into UI eventpublic void onButtonPressed(Uri uri) { if (mListener != null) { mListener.onFragmentInteraction(uri); }}@Overridepublic void onStart() { super.onStart(); mFireAdapter = new FirebaseRecyclerAdapter<Poll, PollHolder>( Poll.class, R.layout.latest_item, PollHolder.class, mPollsRef ){ @Override protected void populateViewHolder(PollHolder viewHolder, Poll model, int position) { viewHolder.mPollQuestion.setText(model.getQuestion()); Picasso.with(getActivity().getApplicationContext()) .load(model.getImage_URL()) .fit() .into(viewHolder.mPollImage); Log.v("QUESTION", model.getQuestion()); Log.v("IMAGE", model.getImage_URL()); } }; mRecyclerview.setAdapter(mFireAdapter);}@Overridepublic void onStop() { super.onStop(); if (mFireAdapter != null){ mFireAdapter.cleanup(); }}@Overridepublic void onAttach(Context context) { super.onAttach(context); if (context instanceof OnFragmentInteractionListener) { mListener = (OnFragmentInteractionListener) context; } else { throw new RuntimeException(context.toString() + " must implement OnFragmentInteractionListener"); }}@Overridepublic void onDetach() { super.onDetach(); mListener = null;}public static class PollHolder extends RecyclerView.ViewHolder { TextView mPollQuestion; ImageView mPollImage; public PollHolder(View itemView) { super(itemView); mPollQuestion = (TextView) itemView.findViewById(R.id.latest_item_question); mPollImage = (ImageView) itemView.findViewById(R.id.pollThumbNailImage); }}/** * This interface must be implemented by activities that contain this * fragment to allow an interaction in this fragment to be communicated * to the activity and potentially other fragments contained in that * activity. * <p> * See the Android Training lesson <a href= * "http://developer.android.com/training/basics/fragments/communicating.html" * >Communicating with Other Fragments</a> for more information. */public interface OnFragmentInteractionListener { // TODO: Update argument type and name void onFragmentInteraction(Uri uri); }}EDIT: I believe the data being written to Firebase is null for some reason, as the Logs for the Question and ImageURL are not returning any data. 解决方案 Your Poll setter methods are missing this:public void setQuestion(String question) { this.question = question;}public void setImage_URL(String image_URL) { this.image_URL = image_URL;}And replace this code: Map <String, Object> pollMap = poll.toMap(); String key = mBaseRef.child("Polls").push().getKey(); Map<String, Object> childUpdates = new HashMap<String, Object>(); childUpdates.put("/Polls/" + key, pollMap); mBaseRef.updateChildren(childUpdates);with:mBaseRef.child("Polls").push().setValue(poll, new DatabaseReference.CompletionListener() { @Override public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) { if (databaseError == null) { Log.i("Poll", "onComplete: SUCCESS"); } else { Log.w("Poll", "onComplete: ", databaseError.toException()); } }});Also move the code that creates mFireAdapter and sets it on mRecyclerview from onStart() to end of onCreateView()://...mRecyclerview.setLayoutManager(mLayoutManager);mFireAdapter = ...;mRecyclerview.setAdapter(mFireAdapter);return v;The documentation provides an example. 这篇关于Firebase RecyclerView无法加载新数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！