Firebase Data Desc Sorting in Android

Question

I am storing data in Firebase storage.

Object Comment with attribute timestamp. When I push data from device to Firebase I\'m populating

Answer 1

Sort at client side is simple and not require more system resources. Each data snapshot has previousChildkey field. If you want to desc sorting, imagine previousChildkey is nextChildKey. Here are my sample:

class LessonFirebaseArray{

  private ArrayList mItems;
  ...
  public LessonFirebaseArray() {
    mItems = new ArrayList<>();
  }

  public int addItem(ObjectModel item, boolean isReverse){
    int index;
    if (item.getPreviousChildKey() != null) {
      index = getIndexForKey(item.getPreviousChildKey());
      if (index < 0) {
        index = mItems.size();
      }else if(index>0 && !isReverse) {
        index = index + 1;      
      }
    }else{
      index = mItems.size();
    }
    mItems.add(index, item);
    notifyInsertedListeners(index);
    return index;
  }

  private int getIndexForKey(String key) {
    int index = 0;
    for (ObjectModel snapshot : mItems) {
      if (snapshot.getKey().equals(key)) {
         return index;
      } else {
         index++;
      }
    }
    return -1;
  }

  private void notifyInsertedListeners(int index) {
    if (mListener != null) {
      mListener.onInserted(index);
    }
  }
}