阅读时Firebase数据库数据返回空
我不知道为什么，我已经探索了.setValue()和.updateChildren()方法，但无论出于何种原因，当我从.updateChildren()读取数据时，它返回null。 以下是我写给Firebase的方式：
模特投票类：
@IgnoreExtraProperties public 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) { this.question = question; } public String getImage_URL() { return image_URL; } public void setImage_URL(String image_URL) { this.image_URL = image_URL; } @Exclude public Map toMap(){ HashMap result = new HashMap(); result.put("question", question); result.put("image_URL", image_URL); return result; } }
*我在这里使用我的.toMap()方法并使用.updateChildren()
这是我创建Firebase引用并写入数据库的位置：
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_create); mStorage = FirebaseStorage.getInstance(); mStorageRef = mStorage.getReferenceFromUrl("gs://firebase-fan-polls.appspot.com"); mBaseRef = FirebaseDatabase.getInstance().getReference(); mPollsRef = mBaseRef.child("Polls"); mAddImageButton = (FloatingActionButton) findViewById(R.id.add_image_button); mAddAnswersButton = (ImageView) findViewById(R.id.add_answers_button); mImagePreview = (ImageView) findViewById(R.id.preview_image); mCreatePollQuestion = (EditText) findViewById(R.id.create_poll_question_editText); mCreatePollAnswerCounter = (TextView) findViewById(R.id.create_poll_answer_counter_TextView); mEditTextAnswerLayout = (ViewGroup) findViewById(R.id.create_poll_questions_answer_layout); mSubmitPollCreation = (FloatingActionButton) findViewById(R.id.submit_poll_FAB); mNumberOfPollAnswersCreatedByUser = 2; mAnswerChoices = new ArrayList(); mCreatePollAnswerCounter.setText(String.valueOf(mNumberOfPollAnswersCreatedByUser)); for (int i = 0; i 5) { Toast.makeText(getApplicationContext(), R.string.max_create_answers, Toast.LENGTH_SHORT).show(); return; } createAnswerChoice(mNumberOfPollAnswersCreatedByUser); mCreatePollAnswerCounter.setText(String.valueOf(mNumberOfPollAnswersCreatedByUser)); } }); mSubmitPollCreation.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //TODO: Need to check if poll requirements are added, ie 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 pollMap = poll.toMap(); String key = mBaseRef.child("Polls").push().getKey(); Map childUpdates = new HashMap(); childUpdates.put("/Polls/" + key, pollMap); mBaseRef.updateChildren(childUpdates); if (mNumberOfPollAnswersCreatedByUser > 5) { Toast.makeText(getApplicationContext(), getResources().getText(R.string.poll_answers_greater_than_five), Toast.LENGTH_LONG).show(); mNumberOfPollAnswersCreatedByUser = 5; } Intent toHomeActivity = new Intent(CreateActivity.this, HomeActivity.class); toHomeActivity.putExtra("viewpager_position", 2); startActivity(toHomeActivity); } });
一切都正确写入Firebase，因为我可以在我的控制台的数据库中看到它。 我尝试从这个活动中读取它：public class PollFragment extends Fragment {
@Bind(R.id.comment_label_counter) TextView mCommentCounter; @Bind(R.id.comments_label_icon) ImageView mCommentsLabelIcon; private DatabaseReference mBaseRef; private DatabaseReference mPollsRef; private DatabaseReference mSelectedPollRef; private RadioGroup mPollQuestionRadioGroup; private RadioGroup.LayoutParams mParams; //static private TextView mCommentsLabel; private TextView mTotalVoteCounter; private TextView mSelectedVote; private TextView mYourVotelabel; private ViewPager mViewPager; private int mPagerCurrentPosition; private static final String VOTE_COUNT_LABEL = "Vote_Count"; private static final String QUESTION_LABEL = "question"; private static final String ANSWERS_LABEL = "Answers"; private static final String POLL_LABEL = "Poll"; private static final String IMAGE_URL = "image_URL"; //all date items; dynamic private DateFormat mDateFormat; private Date mDate; private String mCurrentDateString; private TextView mPollQuestion; private ArrayList mPollAnswerArrayList; private HorizontalBarChart mPollResults; ArrayList pollResultChartValues; private BarDataSet data; private ArrayList dataSets; private ValueEventListener valueEventListener; private String pollID; private int mPollIndex; private ProgressBar mProgressBar; private OnFragmentInteractionListener mListener; public PollFragment() { // Required empty public constructor } /** * Use this factory method to create a new instance of * this fragment using the provided parameters. * * @return A new instance of fragment PollFragment. */ // TODO: Rename and change types and number of parameters // TODO: Decide where to add comments button; public static PollFragment newInstance(String pollIndex) { PollFragment fragment = new PollFragment(); Bundle args = new Bundle(); args.putString("POLL_ID", pollIndex); fragment.setArguments(args); return fragment; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //TODO: check navigation to see if there are different ID's being generated from trending, following, and new fragments Bundle args = getArguments(); String pollID = args.getString("POLL_ID"); Log.v("TAG", "THE PASSED ID Is " + pollID); mBaseRef = FirebaseDatabase.getInstance().getReference(); mPollsRef = mBaseRef.child(POLL_LABEL); mSelectedPollRef = mPollsRef.child(pollID); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // TODO: Add Fragment Code to check if savedInstanceState == null; add at Activity Level? // Inflate the layout for this fragment final ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_poll, container, false); ButterKnife.bind(this, rootView); getActivity().setTitle(R.string.todays_polls_title); //Initialize Poll Results Bar Chart and set to Invisible mPollResults = (HorizontalBarChart) rootView.findViewById(R.id.poll_results_chart); mPollResults.setBackgroundColor(getResources().getColor(R.color.white)); mPollResults.setNoDataTextDescription(getResources().getString(R.string.no_results_description)); mPollResults.setVisibility(View.INVISIBLE); mTotalVoteCounter = (TextView) rootView.findViewById(R.id.total_vote_counter); mCommentCounter = (TextView) rootView.findViewById(R.id.comment_label_counter); mCommentCounter = (TextView) rootView.findViewById(R.id.comment_label_counter); mProgressBar = (ProgressBar) rootView.findViewById(R.id.progress_bar_white); mPollQuestion = (TextView) rootView.findViewById(R.id.poll_question); mPollQuestion.setTextSize(TypedValue.COMPLEX_UNIT_PX, getResources().getDimension(R.dimen.poll_question_text_size)); mPollQuestionRadioGroup = (RadioGroup) rootView.findViewById(R.id.poll_question_group); mSelectedPollRef.addListenerForSingleValueEvent(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { Log.v("TAG", dataSnapshot.getKey()); //add question String pollQuestion = (String) dataSnapshot.child(QUESTION_LABEL).getValue(); Log.v("TAG", "THE POLL QUESTION IS " + pollQuestion); mPollQuestion.setText(pollQuestion); mPollQuestion.setTypeface(null, Typeface.BOLD); //add image String pollImageURL = (String) dataSnapshot.child(IMAGE_URL).getValue(); Log.v("TAG", "THE POLL IMAGE URL IS" + pollImageURL); Picasso.with(getActivity()) .load(pollImageURL) .fit() .placeholder(R.drawable.loading_spinner_white) .into((ImageView) rootView.findViewById(R.id.poll_image));
最后，这是我的Firebase数据库：
粗心的错误：
private static final String POLL_LABEL = "Poll";
应该：
private static final String POLL_LABEL = "Polls";
第一个选择不是正确的Firebase引用，从而导致错误。