Firebase Data Desc Sorting in Android
I don't see any option to reverse the data. But One Brute way is to get the data.
List<ModelClass> mList=new ArrayList();
public void onDataChange(DataSnapshot dataSnapshot)
{
mList.clear();
for(DataSnapshot children: dataSnapshot.getChildren()){
ModelClass modelClass=children.getValue(ModelClass.class);
mList.add(modelClass);
}
Collections.reverse(mList);
Adapter.notifyDataSetChanged();
}
Firebase can order the items in ascending order by a given property and then returns either the first N items (limitToFirst()
) or the last N items (limitToLast()
). There is no way to indicate that you want the items in descending order.
There are two options to get the behavior you want:
Use a Firebase query to get the correct data, then re-order it client-side
Add a field that has a descending value to the data
For the latter approach, it is common to have a inverted timestamp.
-1 * new Date().getTime();
one good solution I find if you are using recycler view to render that data...
mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
// And set it to RecyclerView
mRecyclerView.setLayoutManager(mLayoutManager);
it will reverse the data rendering...
private static class ChatMessageViewHolder extends RecyclerView.ViewHolder {
TextView messageText;
TextView nameText;
public ChatMessageViewHolder(View itemView) {
super(itemView);
nameText = (TextView)itemView.findViewById(android.R.id.text1);
messageText = (TextView) itemView.findViewById(android.R.id.text2);
}
}
FirebaseRecyclerViewAdapter<ChatMessage, ChatMessageViewHolder> adapter;
ref = new Firebase("https://<yourapp>.firebaseio.com");
RecyclerView recycler = (RecyclerView)
findViewById(R.id.messages_recycler);
recycler.setHasFixedSize(true);
//////////////////////////////////////////////////////////
mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
recycler.setLayoutManager(mLayoutManager);
/////////////////////////////////////////////////////////
adapter = new FirebaseRecyclerViewAdapter<ChatMessage, ChatMessageViewHolder>(ChatMessage.class, android.R.layout.two_line_list_item, ChatMessageViewHolder.class, mRef) {
public void populateViewHolder(ChatMessageViewHolder chatMessageViewHolder, ChatMessage chatMessage) {
chatMessageViewHolder.nameText.setText(chatMessage.getName());
chatMessageViewHolder.messageText.setText(chatMessage.getMessage());
}
};
recycler.setAdapter(mAdapter);