Question

我正在尝试使用FirebaseUI来简化我的recyclerview。我已阅读文档并提供以下代码：

POJO：

public class Polls {

private String Question;
private String user;
private String date;
private String voteCounter;
private String commentCounter;
private String Image_URL;
private String pollID;

public Polls(String Question, String Image_URL){
    this.Question = Question;
    this.Image_URL = Image_URL;
}


public String getPollID(){
    return pollID;
}

public String getQuestion() {
    return Question;
}

public String getUser() {
    return user;
}

public String getDate() {
    return date;
}

public String getVoteCounter() {
    return voteCounter;
}

public String getCommentCounter() {
    return commentCounter;
}

public String getPollImage() {
    return Image_URL;
}

public void setQuestion(String question) {
    this.Question = question;
}

public void setUser(String user) {
    this.user = user;
}

public void setDate(String date) {
    this.date = date;
}

public void setVoteCounter(String voteCounter) {
    this.voteCounter = voteCounter;
}

public void setCommentCounter(String commentCounter) {
    this.commentCounter = commentCounter;
}

public void setPollImage(String pollImage) {
    this.Image_URL = pollImage;
   }
  }

这是我写给Firebase的地方，这是我读到的单独活动：

mSubmitPollCreation.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Calendar c = Calendar.getInstance();
            final String epochTime = String.valueOf(c.getTimeInMillis());
            mEpochRef = mBaseRef.child("Polls").child(epochTime);

            if (resultImageURL != null){
                Map<String, Object> imageURL = new HashMap<String, Object>();
                imageURL.put("Image_URL", resultImageURL);
                mEpochRef.updateChildren(imageURL);
            } else {
                Toast.makeText(getApplicationContext(),getResources().getString(R.string.no_image_selected),Toast.LENGTH_LONG).show();
                return;
            }

            //Add Question
            Map<String, Object> pollQuestion = new HashMap<String, Object>();
            pollQuestion.put("Question", mCreatePollQuestion.getText().toString());
            Log.v("POLL_QUESTION_CREATED", mCreatePollQuestion.getText().toString());
            mEpochRef.child("Polls").updateChildren(pollQuestion);

            //Add Answer Counter defaulted to 0
 //                Map<String, Object> pollAnswerCounter = new      HashMap<String, Object>();
//                pollAnswerCounter.put("Vote_Count", 0);
//                mEpochRef.updateChildren(pollAnswerCounter);



            if (mNumberOfPollAnswersCreatedByUser > 5){
                Toast.makeText(getApplicationContext(),getResources().getText(R.string.poll_answers_greater_than_five),Toast.LENGTH_LONG).show();
                mNumberOfPollAnswersCreatedByUser = 5;
            }
            //add answers to Firebase
 //                for (int i = 0; i <     mNumberOfPollAnswersCreatedByUser; i++){
 //                    EditText editText = (EditText)     mEditTextAnswerLayout.findViewWithTag(getResources().getString(R.string.cre   ated_answer_editText_id)+String.valueOf(i+1));
//                    String editTextInputForAnswer =

    String.valueOf(editText.getText());
   //                    final String answerLabel = "Answer";
   //                    Map<String, Object> answerChoice = new    HashMap<String, Object>();
  //                    answerChoice.put(answerLabel,    editTextInputForAnswer);
  //                          mEpochRef.child("Answers").child(String.valueOf(i+1)).updateChildren(pollAnswerCounter);
//                         mEpochRef.child("Answers").child(String.valueOf(i+1)).updateChildren(answer  Choice);
//                           Toast.makeText(getApplicationContext(),editTextInputForAnswer,Toast.LENGTH_       SHORT).show();
   //                }

                Intent toHomeActivity = new Intent(CreateActivity.this, HomeActivity.class);
                toHomeActivity.putExtra("viewpager_position", 2);
                startActivity(toHomeActivity);
            }
        });

以下是我从Firebase读取的内容，并尝试使用FirebaseUI RecyclerViewAdapter加载RecyclerView：

public class LiveFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private 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;


// TODO: Rename and change types of parameters
private 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 parameters
public 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;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
        mBaseRef = FirebaseDatabase.getInstance().getReference();
        mPollsRef = mBaseRef.child("Polls");
    }
}

@Override
public 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);

    if (mRecyclerview != null){
        mRecyclerview.setHasFixedSize(true);
    }

    mLayoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
    mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL
    );

    mRecyclerview.setLayoutManager(mLayoutManager);

    FirebaseRecyclerAdapter<Polls, PollHolder> mFireAdapter = new FirebaseRecyclerAdapter<Polls, PollHolder>(
            Polls.class,
            R.layout.latest_item,
            PollHolder.class,
            mPollsRef
    ){

        @Override
        protected void populateViewHolder(PollHolder viewHolder, Polls model, int position) {
            viewHolder.mPollQuestion.setText(model.getQuestion());
            Picasso.with(getActivity().getApplicationContext())
                    .load(model.getPollImage())
                    .fit()
                    .into(viewHolder.mPollImage);

        }
    };

    mRecyclerview.setAdapter(mFireAdapter);

    return v;
}

// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}



@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) {
        mListener = (OnFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public 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);
}

}

这是我收到的错误：

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.troychuinard.fanpolls, PID: 11738
              java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database.ChildEventListener com.google.firebase.database.Query.addChildEventListener(com.google.firebase.database.ChildEventListener)' on a null object reference
                  at com.firebase.ui.database.FirebaseArray.<init>(FirebaseArray.java:43)
                  at com.firebase.ui.database.FirebaseRecyclerAdapter.<init>(FirebaseRecyclerAdapter.java:128)
                  at com.troychuinard.fanpolls.Fragment.LiveFragment$1.<init>(LiveFragment.java:103)
                  at com.troychuinard.fanpolls.Fragment.LiveFragment.onCreateView(LiveFragment.java:98)
                  at android.support.v4.app.Fragment.performCreateView(Fragment.java:2087)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1113)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295)
                  at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
                  at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1643)
                  at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679)
                  at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
                  at android.support.v4.view.ViewPager.populate(ViewPager.java:1272)
                  at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:672)
                  at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:634)
                  at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:615)
                  at android.support.design.widget.TabLayout$ViewPagerOnTabSelectedListener.onTabSelected(TabLayout.java:2175)
                  at android.support.design.widget.TabLayout.dispatchTabSelected(TabLayout.java:1154)
                  at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1147)
                  at android.support.design.widget.TabLayout.selectTab(TabLayout.java:1117)
                  at android.support.design.widget.TabLayout$Tab.select(TabLayout.java:1412)
                  at android.support.design.widget.TabLayout$TabView.performClick(TabLayout.java:1520)
                  at android.view.View$PerformClick.run(View.java:21294)
                  at android.os.Handler.handleCallback(Handler.java:739)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5527)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

这可能确实是一个映射问题，但我希望确认。我还附上了Firebase数据库的结构：

FirebaseDatabase引用在适配器中返回Null

0 个答案: