Android firebase orderByKey不会改变任何东西

Question

I was searching for two days now, but the firebase topic is really poorly discussed i guess

I want to sort my data from firebase DB to get the weights from the newest to the oldest. I was trying to do it directly with ref.orderByKey and with Query refQuery = ref.orderByKey(); but none seems to work.

The key is a date with yy:MM:dd format, but with that code i'm getting data not sorted in any possible way... Any help?

final Firebase ref = new Firebase("https://myapp.com/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/weight/");

ref.orderByKey().addListenerForSingleValueEvent(new ValueEventListener() {
     @Override
     public void onDataChange(DataSnapshot snapshot) {
        weights = new Double[(int)snapshot.getChildrenCount()];
        dates = new String[(int)snapshot.getChildrenCount()];
        Toast.makeText(getActivity(), "Wczytuje Pierwsze Dane"+snapshot.getValue(), Toast.LENGTH_LONG).show();
        int i = 0;
        for (DataSnapshot child : snapshot.getChildren()) {
            weights[i] = child.getValue(Double.class);
            dates[i] = child.getKey();
            weightMap.put(child.getKey(), child.getValue(Double.class));
            i++;
        }
        testowy.setText(""+weightMap.size());

        if(weightMap.size()>1)
        diffValue.setText(""+(weights[weightMap.size()-1] - weights[weightMap.size()-2]));

        WeightListAdapter weightList = new WeightListAdapter(weightMap);
        ListView weightListView = (ListView) view.findViewById(R.id.weightList);
        weightListView.setAdapter(weightList);
     }

     @Override
     public void onCancelled(FirebaseError firebaseError) {
     }
 });

Edit 1:

 ref.orderByKey().addListenerForSingleValueEvent(new ValueEventListener() {
                                             @Override
                                             public void onDataChange(DataSnapshot snapshot) {
                                                 weights = new Double[(int)snapshot.getChildrenCount()];
                                                 dates = new String[(int)snapshot.getChildrenCount()];

                                                 int i = 0;
                                                 for (DataSnapshot child : snapshot.getChildren()) {
                                                     weights[i] = child.getValue(Double.class);
                                                     dates[i] = dt.format(Long.parseLong(child.getKey()));
                                                     weightMap.put(child.getKey(), child.getValue(Double.class));
                                                     i++;
                                                 }

I stood without converting the date for clarity of the question.The snapshot comes unsorted. Why...?

Edit 2: Is this what you asked me for?

Answer 1

• Try to format your date in milliseconds and then store it to database.
• Its better to convert your date in millisecond and then store it to the database and then convert it back when retrieved from db.

Otherwise,

• If you have set date as your key and can't change it then add time as a child (where data like weight is available) and apply sort on that child. Store millisecond on time.
• And use this :- ref.orderByChild("time").addLis...

Updated :

• Replace this

   final Firebase ref = new Firebase("https://myapp.com/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/weight/"); 

  • with this

      final Firebase ref = new Firebase("https://myapp.com/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/weight/hiper-diet-keeper/UBwsiRUqZrarupNRS/"); 

and use ref.orderByKey()

Answer 2

Ok, i've solved it.

Hashmap doesn't keep order of it's items. I used LinkedHashMap instead and it works now ;)