dataSnapshot if else 继续循环

Question

The below states that if the month is equal to the value in Firebase , it will add "monthamt" to the existing month. Else it will push a new key for the new month and store "monthamt" into it. But in my case, even thou if(a month is equal to the existing in Firebase , it will still push a new key with the same month).

 ds = mDatabase.getReference().child("Users").child(uid).child("summary");
 ds.orderByKey().addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
        Calendar c = Calendar.getInstance();
        SimpleDateFormat format = new SimpleDateFormat("ddMMyy");
        SimpleDateFormat fm = new SimpleDateFormat("MM");
        String month = (String) dataSnapshot.child("month").getValue();

        double mvalue = Double.valueOf(String.valueOf(dataSnapshot.child("monthamt").getValue()));
            mvalue = roundOff(mvalue);

        if (fm.format(c.getTime()).equals(month)) {
            String key1 = dataSnapshot.getKey();
            ds.child(key1).child("monthamt").setValue(roundOff(mvalue + amt) + "");

        }
        else if(!fm.format(c.getTime()).equals(month)) {
            String key = ds.push().getKey();
            Calendar b = Calendar.getInstance();
            ds.child(key).child("month").setValue(fm.format(b.getTime()));
            ds.child(key).child("monthamt").setValue(amt + "");
            dt.child("Bill").child(k).child("gtranid").setValue("1");
        }
    }

Below is what my Firebase looks like:

Answer 1

Your approach is wrong. Try something like this.

   String key;
   int currentMonth = Calendar.getInstance().get(Calendar.MONTH) + 1;

   ds.addListenerForSingleValueEvent(new ValueEventListener () {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot data: dataSnapshot.getChildren()){
            int month = data.child("month").getValue();
            if (month == currentMonth) {
               // update existing one
               key = data.getKey();
               break;
            }
          }
        }
    });

    if (key != null) {
        double mvalue = data.child("monthamt").getValue();
        mvalue = roundOff(mvalue);
        ds.child(data.getKey()).child("monthamt").setValue(roundOff(mvalue + amt) + "");
    } else {
        key = ds.push().getKey();
        ds.child(key).child("month").setValue(currentMonth);
        ds.child(key).child("monthamt").setValue(amt);
        dt.child("Bill").child(k).child("gtranid").setValue("1");
    }

Answer 2

There's quite a few problems with your code. Some of the first ones that jump out:

1. Why are you storing numeric values as strings? By doing so, you end up converting them repeatedly in your code, which makes that code longer and harder to maintain. I recommend storing numbers as number in the JSON.

2. If the value you want to write to the database depends on a current value in the database, you need to use a transaction .

3. If you want months to be unique in the JSON, you should use them as the key of the node, instead of as a property in there. I'd model your data as:

    "summary": { "month_10": 88, "month_11": 660 }

   This has the advantage that you don't have to query to find the node for the month, as you already know its path:

    DatabaseReference monthRef = ds.child("month_"+mm);

4. Firebase nowadays has a built-in operation for incrementing values, so that you don't even need a transaction for this. It should be as simple as:

    monthRef.setValue(ServerValue.increment(44));

   This even works when the month node doesn't exist yet, as increment will simply assume that it is 0 in that case.

Answer 3

I have figured it out, code as below, instead of using else to loop, I uses if to get month which is different than those in Firebase, and add a break to every if statement to prevent looping:

  Calendar c = Calendar.getInstance();
                    final int currentMonth = c.get(Calendar.MONTH)+1;
                    ds.orderByChild("month").addListenerForSingleValueEvent(new ValueEventListener () {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            if(dataSnapshot.exists()){
                                for (DataSnapshot data: dataSnapshot.getChildren()){
                                    String month = data.child("month").getValue().toString();
                                    String convert1 = String.valueOf(currentMonth);

                                    if (convert1.equals(month)) {
                                        // update existing one
                                        String key = ds.getKey();
                                        double mvalue = Double.valueOf (String.valueOf(data.child("monthamt").getValue()));
                                        mvalue = roundOff(mvalue);
                                        ds.child(data.getKey()).child("monthamt").setValue(roundOff(mvalue + amt) + "");
                                        break;

                                    }
                                    if(!convert1.equals(month)){
                                    String key = ds.push().getKey();
                                    ds.child(key).child("month").setValue(convert1);
                                    ds.child(key).child("monthamt").setValue(amt + "");
                                        break;
                                    }
                                }
                            }
                        }

                        @Override
                        public void onCancelled(@NonNull DatabaseError databaseError) {

                        }
                    });